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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 23236
Location: Oklahoma City
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 Posted: Mon Mar 31, 2025 10:24 am Post subject: Re: Brakes heating up and seizing after replacing calipers |
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Lil-Jinx said:
| Quote: |
| you dismiss the idea of the MC being the cause ,because it happened with both MCs,and after repairing the brake spring problem,the brakes still drag with the second mc just as they did with the first mc ,so you are saying that shows that the second mc is also good and the problem must be elsewhere because the return spring didn't fix it |
I am not dissmissing anything...but until someone pulls the MC out, strips it down and compares it to the old MC (oh yeah...thats gone).....nothing is indicating that it is the master cylinder....so MOVE ON...and test/observe/measure the other items.
What you seem to keep forgetting is that the original MC was functioning perfectly with:
1. The original pushod adjustment (supposedly the mechanic did not touch that)
2. The original spring
3. The original calipers
4. The orignal rubber hoses
5. The original booster
6. The original hard lines
7. The original rear wheel cylinders......
.....in short.....the PO only had the CALIPERS changed.
There were "0" braking problems when he took the bus in. He simply had the CALIPERS changed because the external boots were shot.
When he got the bus back it NOW had this problem and STILL HAD THE ORIGINAL MASTER CYLINDER.
When he replaced the rubber lines....THE PROBLEM DID NOT CHANGE.
When he changed to the new master cylinder ....THE PROBLEM DID NOT CHANGE.
When he adjusted the pedal pushrod....THE PROBLEM DID NOT CHANGE.
When he simulateed a new spring with the bungee cord....THE PROBLEM DID NOT CHANGE.
Lil-jinx said:
| Quote: |
.you said it has to be the booster ,and and it unlikely
that both MC are faulty , |
No...I did NOT say that it HAS TO BE THE BOOSTER. I said it is possible...probable. HUGE difference.
Lil Jinx said:
| Quote: |
| I,m saying that the first mc is good ,and the return spring would have fixed the problem at the start if he had not replace a perfectly good MC with a MC that has a too long push rod,which many has corrected by shimming it |
So...do you have any evidence whatsoever.....that the first master cylinder was good...and the second one is bad...considering no one has pulled the new one off and directly, visually compared it to the original MC?
Especially since they both exhibit THE EXACT SAME BEHAVIOR! It either means that they are both broken (then why did the first one work?)...or neother were broken and its something else.
Do you have any evidence whatsoever that the spring was "normal" or broken...either way....with the original master cylinder?
Man, you have got to quit reading into what other people are exactly saying....and inserting what you are thinking. Everyones opinion/hypothesis are welcome....but some of you guys suck at testing systems.
Yes...I write a lot and I type fast. I specifically speak in longer more explanitory sentences so that my meaning is as exact as possible.
There are too many things we do not know here simply because we do not have the old parts to compare to the new parts.
The original calipers are gone
The original master cylinder is gone....and guess what....the original master cylinder exhibited the same problem as the new one anyway!
And no matter what....this is still the same booster....and its showing 3mm of extra pushrod on the MC side....with the new master cylinder....and its creating the same EFFECT as the old master cylinder. So its likely that the same 3mm is there with the old MC.
While we have no way to 100% compare the two MC's to be sure....its most likely that something else has changed....beside the Master cylinder.
And, its not the spring. The bungee cord may not be factory but it has shown that its not the spring.
All I have been saying through this whole insane process is that each segment of the system should be tested and measured....ONE PART AT A TIME.
First thing...first 15 minutes... I would have had a caliper apart measuring and photographing and posting it to ask "does this look normal" ?
After checking lines I would have had the snap ring out of the master cylinder checking the fit on the booster pushrod and looking inside of the booster.
Ray |
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SGKent 
Samba Member
Joined: October 30, 2007
Posts: 42788
Location: at the beach
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| Posted: Mon Mar 31, 2025 10:35 am Post subject: Re: Brakes heating up and seizing after replacing calipers |
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Stop. Please.
Everyone is debating how to fix it when the exact cause has yet to be found. He needs to isolate the cause. It is possible that the booster got tweaked. Or the master has wrong dimensions. Or John has air in the lines and can't feel the correct adjustment. But let's isolate the cause and then deal with it. Please.
| SGKent wrote: |
there is only one thing that John has to do to move this along. John I hope you are listening. With your bungee solution, step on the brakes until you feel pressure and drag, then disconnect the clevis and bar. Hang it with a wire or string etc., move it towards the front of the bus just a tiny bit - you don't want to pull it apart or tug on it, just make 100% sure that there is NO PRELOAD back towards the master cylinder. Then check the brakes to see if they are free.
If yes they are free > then you need to carefully adjust the bar so it is not preloading the master cylinder. If you have air in the lines it will be hard to feel when the master is being pushed by the bar and rod.
If no they are stuck > and there still is pressure and drag - then the master and booster are not compatible, or one is defective or machined differently than the originals. When the booster is at rest it should absolutely not put pressure on the master cylinder. VW designed it so the master and servo could be swapped without a hassle. |
_________________
George Carlin:
"Most people don't know what they're doing, and a lot of them are really good at it."
Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice"  |
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wagen19
Samba Member
Joined: November 16, 2007
Posts: 752
Location: germany
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| Posted: Mon Mar 31, 2025 11:11 am Post subject: Re: Brakes heating up and seizing after replacing calipers |
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| I believe, all my contributions, starting on page 5 are ignored. |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 23236
Location: Oklahoma City
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| Posted: Mon Mar 31, 2025 11:13 am Post subject: Re: Brakes heating up and seizing after replacing calipers |
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| SGKent wrote: |
Stop. Please.
Everyone is debating how to fix it when the exact cause has yet to be found. He needs to isolate the cause. It is possible that the booster got tweaked. Or the master has wrong dimensions. Or John has air in the lines and can't feel the correct adjustment. But let's isolate the cause and then deal with it. Please.
| SGKent wrote: |
there is only one thing that John has to do to move this along. John I hope you are listening. With your bungee solution, step on the brakes until you feel pressure and drag, then disconnect the clevis and bar. Hang it with a wire or string etc., move it towards the front of the bus just a tiny bit - you don't want to pull it apart or tug on it, just make 100% sure that there is NO PRELOAD back towards the master cylinder. Then check the brakes to see if they are free.
If yes they are free > then you need to carefully adjust the bar so it is not preloading the master cylinder. If you have air in the lines it will be hard to feel when the master is being pushed by the bar and rod.
If no they are stuck > and there still is pressure and drag - then the master and booster are not compatible, or one is defective or machined differently than the originals. When the booster is at rest it should absolutely not put pressure on the master cylinder. VW designed it so the master and servo could be swapped without a hassle. |
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Exactly what I have been saying through this whole thread. I have not once said its absolutely X part is the culprit".
Actually most of those posting in this thread have not said X part is ABSOLUTELY for sure the problem. Lots of good suggestions of what COULD BE happening.
Test....measure....each component. It's either normal or suspect. If you find something that is off....either replace it or make note of it and move on to finish testing the rest of the components.
However, we keep having a recurring issue here with one person who keeps saying....."why do you say this?".....when no one said THIS. It just clutters things up.
Ray |
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wagen19
Samba Member
Joined: November 16, 2007
Posts: 752
Location: germany
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| Posted: Mon Mar 31, 2025 11:39 am Post subject: Re: Brakes heating up and seizing after replacing calipers |
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I think, you are quite right here, Ray.
What for me a important question here is, whether the OP has the tools, knowledge and technical feeling, that´s needed here.
When he asks, if it could be also the regulator, imo, that´s alarming.
But why not asking that person, where that overhauled booster comes from, to check that part again? Or a booster as exchange part, maybe with MC?
Is this possible? |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 23236
Location: Oklahoma City
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| Posted: Mon Mar 31, 2025 12:39 pm Post subject: Re: Brakes heating up and seizing after replacing calipers |
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| wagen19 wrote: |
I think, you are quite right here, Ray.
What for me a important question here is, whether the OP has the tools, knowledge and technical feeling, that´s needed here.
When he asks, if it could be also the regulator, imo, that´s alarming.
But why not asking that person, where that overhauled booster comes from, to check that part again? Or a booster as exchange part, maybe with MC?
Is this possible? |
As per your last question, I do not think your advice/suggestions have been ignored.....not completely.....and not on purpose. I think a lot of it is timing. Lots of suggestions and test requests between your posts.
From the start, one of your prime suggestions has been either:
A. Inspect the booster with endoscopy and
B. Remove booster and MC and Inspect and fit on the bench.
I think the OP noted he agreed with A. But cannot locate his endoscopy.
I think B has been suggested by more than one as well and it's just been a matter of time getting around to it while trying other tests.
Whil this has been a slow process.....I think each round of testing has created a "spiral" pattern of results that gets closer and closer to the booster (if that makes sense). As he ticks off what he finds that it.... IS NOT....the best hypothesis gets closer to being a booster issue at best or a fit issue between booster and MC at worst.
I realize not everyone has the same time, tools or knowledge to just dive into it, pull all of the parts of and inspect at one time.....which is what I would have done after a handful of quick tests to cross things like soft lines, hardlines and fluid flow and basic adjustment off the list....which is why I have stuck with this thread.
Ray |
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lil-jinx
Samba Member
Joined: August 14, 2013
Posts: 1654
Location: New Brunswick,Canada
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| Posted: Mon Mar 31, 2025 12:43 pm Post subject: Re: Brakes heating up and seizing after replacing calipers |
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last word you,ll hear about this from me (everyone breath a sign of relief )
yes it is either the mc or the booster, a simple measurement proves the mc one way or another,to test the booster it would have to be disassembled by someone that has the experience and knowledge to inspect it .
i did not know that the old mc was disposed of so he can compare the two,but i beleive the measurement was given in a link that i posted,
ill be back when the repair is completed.
_________________
https://www.thesamba.com/vw/forum/viewtopic.php?t=620186
https://www.thesamba.com/vw/forum/viewtopic.php?t=668799
1974 Bay Westfalia. she likes to be called Ethel.
1968 Dune Buggy sold dec 2024
1974 parts bus
A smart man learns from his mistakes,a very smart man learns from other's mistakes. |
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skills@eurocarsplus
Samba Peckerhead
Joined: January 01, 2007
Posts: 17871
Location: sticksville, ct.
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| Posted: Mon Mar 31, 2025 1:51 pm Post subject: Re: Brakes heating up and seizing after replacing calipers |
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| wagen19 wrote: |
| I believe, all my contributions, starting on page 5 are ignored. |
that's why I deleted my comments a bunch of pages ago. now i'm here to see if we can make it to page 40.
there seems to be a huge lack in any diagnostic strategy and it's like yelling squirrel to someone on the spectrum.
_________________
| gprudenciop wrote: |
my reason for switching to subaru is my german car was turning chinese so i said fuck it and went japanese....... |
| Jake Raby wrote: |
| Thanks for the correction. I used to be a nice guy, then I ruined it by exposing myself to the public. |
| Brian wrote: |
| Also the fact that people are agreeing with Skills, it's a turn of events for samba history |
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 23236
Location: Oklahoma City
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| Posted: Mon Mar 31, 2025 2:28 pm Post subject: Re: Brakes heating up and seizing after replacing calipers |
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| lil-jinx wrote: |
last word you,ll hear about this from me (everyone breath a sign of relief )
yes it is either the mc or the booster, a simple measurement proves the mc one way or another,to test the booster it would have to be disassembled by someone that has the experience and knowledge to inspect it .
i did not know that the old mc was disposed of so he can compare the two,but i beleive the measurement was given in a link that i posted,
ill be back when the repair is completed. |
Don't run off. No one is beating on you. However, read people's responses a bit more carefully before accusing them of saying something they did not.
Yes.....I believe you are correct. The measurement you posted could indicate exactly whether or not there is a booster of MC issue or both.
Ray |
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jtauxe
Samba Member
Joined: September 30, 2004
Posts: 5977
Location: Los Alamos, New Mexico, USA
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| Posted: Tue Apr 01, 2025 6:51 pm Post subject: Re: Brakes heating up and seizing after replacing calipers |
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OK. Time to catch up, which won't be much new information but rather clarification. I left the house for one day and an awful lot of posting and activity has been going on. So, let's all take a breath.  And folks, don't leave the thread out of frustration; I appreciate you. No one is more frustrated than I.
| SGKent wrote: |
Stop. Please.
Everyone is debating how to fix it when the exact cause has yet to be found. He needs to isolate the cause. It is possible that the booster got tweaked. Or the master has wrong dimensions. Or John has air in the lines and can't feel the correct adjustment. But let's isolate the cause and then deal with it. Please. |
I am sure that the bleeding has gone well and that there is not air in the lines.
| SGKent wrote: |
| there is only one thing that John has to do to move this along. John I hope you are listening. With your bungee solution, step on the brakes until you feel pressure and drag, then disconnect the clevis and bar. Hang it with a wire or string etc., move it towards the front of the bus just a tiny bit - you don't want to pull it apart or tug on it, just make 100% sure that there is NO PRELOAD back towards the master cylinder. Then check the brakes to see if they are free. |
Yes, I am listening.
So, about the clevis pin attaching the pedal assembly to the rod for the booster: There is no need to hang it when disconnected, as it runs through a circular opening in a crossmember of the frame and just sits there, still with its forks loose around the pedal, but not attached. Unfortunately, it does not allow sufficient clearance from the pedal to rotate the rod, so my only adjustment is with the jam nuts. Fortunately, that is plenty sufficient to accomplish the proper adjustment.
And note that the clevis is at neutral, and can be wiggled around with the fingers while the pedal is hoisted by the bungee. This assures me that there is no preloading on the booster.
| SGKent wrote: |
| If yes they are free > then you need to carefully adjust the bar so it is not preloading the master cylinder. If you have air in the lines it will be hard to feel when the master is being pushed by the bar and rod. |
As I work the rod by hand, pulling down on the pedal under the truck, I can feel engagement with a couple of things inside the booster/MC system. First, the slack in the clevis is closed. Then there are two "clunks", though I cannot discern where they come from. I am assuming that the first one is the pedal-booster rod contacting the innards of the booster, and the second is maybe the booster rod contacting the MC. But again, I am not sure.
| SGKent wrote: |
| If no they are stuck > and there still is pressure and drag - then the master and booster are not compatible, or one is defective or machined differently than the originals. When the booster is at rest it should absolutely not put pressure on the master cylinder. VW designed it so the master and servo could be swapped without a hassle. |
| wagen19 wrote: |
What for me a important question here is, whether the OP has the tools, knowledge and technical feeling, that´s needed here.
When he asks, if it could be also the regulator, imo, that´s alarming. |
I realize that the pressure regulator is a potential red herring. I was challenged by someone off-line that he could solve the problem for sure, and he is sending me a pressure regulator that I can try as a replacement. If it doesn't work, he'll pay for return shipping. If it does work, then huzzah! He wins the prize! That said, I am skeptical, because I do not see how it figures into the system in such a way that it could be causing some malfunction of the MC, but he is confident. I am willing to try it since he as nice enough to send it as an attempt to fix the problem. So, that is a side quest in all this, and it is not slowing down other work. I will be as surprised as anyone if it fixes the problem.
Here is my plan:
• Replace the brake pedal return spring when I get one, meanwhile using the bungee in the cab to raise the pedal.
• I've been putting it off because it is such a friggin' mess, but I am resigned to removing the MC and checking it. This will involve:
- Poking down the throat of the sleeve that accepts the booster rod to see if there is any crud at the back that is preventing the rod from making complete contact.
- Comparing this depth to that of the previous MC (a Varga unit that has worked for a long time, though not the truck's original MC) which I have not tossed. It is sitting on my bench wrapped in a bag in a rag in a bag but nevertheless may need some cleaning and will need new rubber gaskets for the reservoir before trying it again. I will consider reinstalling the previous MC only after comparing throat depths.
• While the MC is out, I will examine the booster as best I can. I want to look to see if there is the spacer ring behind the tip, and to see if anything looks amiss inside the booster as far as I can see. If in the end, the booster is at fault, I will return it to the folks who rebuilt it and see what they can do for me.
_________________
John
"Travelling in a fried-out Kombi, on a hippie trail, head full of zombie..." - Colin Hay and Ron Strykert
http://vw.tauxe.net
1969 Transporter, 1971 Westfalia, 1976, 1977, 1976, 1977, 1971, 1973, 1977 Westfalias,
1979 Champagne Sunroof, 1974 Westfalia Automatic, 1979 Transporter, 1972 Sportsmobile, 1973 Transporter Wild Westerner, 1974 Westfalia parts bus, 1975 Mexican single cab *FOR SALE*, 1978 Irish 4-door double cab RHD
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 42788
Location: at the beach
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| Posted: Tue Apr 01, 2025 8:50 pm Post subject: Re: Brakes heating up and seizing after replacing calipers |
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John - I need to know if when the clevis is out, and the rod pulled a tiny bit forward the pressure in the brakes goes away. Build pressure in the front brakes, pull the clevis pin, move the rod forward a tiny bit and check to see if that frees the brakes. If it does not then the booster is holding the master partially engaged. If you still have pressure and you loosen the two nuts, and the pressure goes away, that proves that then verifies that the booster and the master are not working together as a team. From that point forward you will have to make decisions how to fix that.
_________________
George Carlin:
"Most people don't know what they're doing, and a lot of them are really good at it."
Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice" |
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jtauxe
Samba Member
Joined: September 30, 2004
Posts: 5977
Location: Los Alamos, New Mexico, USA
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| Posted: Wed Apr 02, 2025 2:20 pm Post subject: Re: Brakes heating up and seizing after replacing calipers |
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Clevis pin in. It is at neutral and moves with the fingers. I know that the cotter pin is supposed to have a washer under it, and reassembled it that way after this photo:
Pressure built up until front wheels do not turn easily, by pumping the pedal about 70 times.
I removed the clevis, still at neutral with respect to the connecting rod, obviously:
Note how it rests in the round cutout in the "frame" crossmember. This is why I cannot rotate the connecting rod without removing it from the booster.
I pulled as hard as I could (in an admittedly awkward position) forward on the brake booster rod. It did not want to move forward at all. The brakes remained tight.
I loosened the MC nuts to back it off a few mm from the booster, and the wheels turn freely. Tightened the MC against the booster again and brakes are tight again.
According to your analysis,
| SGKent wrote: |
| If [moving the pedal-booster rod forward (I could not)] does not [relieve brake pressure (it did not)] then the booster is holding the master partially engaged. If you still have pressure and you loosen the two nuts, and the pressure goes away, that proves that then verifies that the booster and the master are not working together as a team. From that point forward you will have to make decisions how to fix that. |
_________________
John
"Travelling in a fried-out Kombi, on a hippie trail, head full of zombie..." - Colin Hay and Ron Strykert
http://vw.tauxe.net
1969 Transporter, 1971 Westfalia, 1976, 1977, 1976, 1977, 1971, 1973, 1977 Westfalias,
1979 Champagne Sunroof, 1974 Westfalia Automatic, 1979 Transporter, 1972 Sportsmobile, 1973 Transporter Wild Westerner, 1974 Westfalia parts bus, 1975 Mexican single cab *FOR SALE*, 1978 Irish 4-door double cab RHD
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lil-jinx
Samba Member
Joined: August 14, 2013
Posts: 1654
Location: New Brunswick,Canada
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jtauxe
Samba Member
Joined: September 30, 2004
Posts: 5977
Location: Los Alamos, New Mexico, USA
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| Posted: Wed Apr 02, 2025 2:38 pm Post subject: Re: Brakes heating up and seizing after replacing calipers |
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| lil-jinx wrote: |
| if you put the brake pedal to thr floor would the clevis then turn? |
The clevis pin will not move under that condition because it is held tight between the brake pedal assembly and the pedal-booster rod.
But I expect that you are asking, prompted by the photo, is if the pedal assembly will clear the forks on the booster rod if it is brought down all the way, allowing the booster rod to turn. No, it does not clear the rod forks.
This setup may be an oddity on this unique bus, as I have not encountered it on other buses. Note that next to that round cutout there are two holes, as if a master cylinder could be bolted on right there, for trucks without boosters. (See photo of MC on the '78 RHD double cab on p. 15 above, where there is no booster).
_________________
John
"Travelling in a fried-out Kombi, on a hippie trail, head full of zombie..." - Colin Hay and Ron Strykert
http://vw.tauxe.net
1969 Transporter, 1971 Westfalia, 1976, 1977, 1976, 1977, 1971, 1973, 1977 Westfalias,
1979 Champagne Sunroof, 1974 Westfalia Automatic, 1979 Transporter, 1972 Sportsmobile, 1973 Transporter Wild Westerner, 1974 Westfalia parts bus, 1975 Mexican single cab *FOR SALE*, 1978 Irish 4-door double cab RHD
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lil-jinx
Samba Member
Joined: August 14, 2013
Posts: 1654
Location: New Brunswick,Canada
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| Posted: Wed Apr 02, 2025 3:56 pm Post subject: Re: Brakes heating up and seizing after replacing calipers |
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so when you adjust the rod you are turning the part that the rod screws into,I was thinking that that could be a problem,but bentley don,t say not to turn it,which I think they would if it were a problem,
_________________
https://www.thesamba.com/vw/forum/viewtopic.php?t=620186
https://www.thesamba.com/vw/forum/viewtopic.php?t=668799
1974 Bay Westfalia. she likes to be called Ethel.
1968 Dune Buggy sold dec 2024
1974 parts bus
A smart man learns from his mistakes,a very smart man learns from other's mistakes. |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 42788
Location: at the beach
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| Posted: Wed Apr 02, 2025 4:52 pm Post subject: Re: Brakes heating up and seizing after replacing calipers |
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Let me sum up the problem now that we have conclusive evidence.
In the position where the clevis is pulled, the rod and associated parts inside the booster are at rest. At rest there should be no preload on the master cylinder. However John must loosen the master cylinder to relieve the preload on it. The preload is blocking the compensating port. The booster and master are not working as a team. One or both do not function as VW designed the system.
Since John said the problem did not exist before the calipers were changed, we can only guess that "something" happened that day. My suspicion, and it is only a suspicion, is that while bleeding the brakes, a part within the booster changed dimensions, maybe a spring collapsed, or some clip let loose, whatever, and that change is interfering with the booster returning to rest. My only suggestion at this point is if John has another booster at his disposal, he could swap it and see if the issue goes away. All he really needs to know is if another booster is bolted on, does the master cylinder return to rest when the clevis is pulled. If no. then the odds are that the master is not the proper length. If I had a booster to lend him I would.
I guess that it is possible that the problem has always been there since he replaced the booster, and that there was enough movement in the old calipers when the pistons retracted, that the pressure never was high enough to move them out. But that is only a possibility.
I just had a call from a Samba member who has a bad connecting rod on a type IV engine, and he wants to use a brake hone to resize it rather than let the machine shop handle it. I cannot believe the level of stupidity this person is asking about - even after I said don't do it. No wonder VW buses have a bad reputation. I sincerely hope that whatever fix John elects to go with on this brake problem has more class and finesse than the call I just got off. For the record, I have submitted the question about this Ate booster to a shop that rebuilt for me to see if they have seen this before in an Ate booster. Will post when they get back to me.
My vote is to locate and borrow another booster, even if it leaks, and test fit it to see if the problem continues or goes away. I don't know the history of the booster he has on there now, or how close to original it is.
_________________
George Carlin:
"Most people don't know what they're doing, and a lot of them are really good at it."
Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice" |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 52488
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| Posted: Wed Apr 02, 2025 6:00 pm Post subject: Re: Brakes heating up and seizing after replacing calipers |
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| When the calipers were changed where the rotors turned? If so did the brakes throb badly previous to the caliper change? I am thinking that if their was a lot of variance in the thickness of the rotors the pulsations in the hydraulics may have been enough to force more of the fluid back into the master cylinder, overall causing less dragging. |
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jtauxe
Samba Member
Joined: September 30, 2004
Posts: 5977
Location: Los Alamos, New Mexico, USA
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| Posted: Wed Apr 02, 2025 7:29 pm Post subject: Re: Brakes heating up and seizing after replacing calipers |
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| SGKent wrote: |
| My suspicion, and it is only a suspicion, is that while [the shop installing the calipers was] bleeding the brakes, a part within the booster changed dimensions, maybe a spring collapsed, or some clip let loose, whatever, and that change is interfering with the booster returning to rest. |
This is the most plausible hypothesis so far, since it is consistent with all the data gathered so far. Or at least it is not inconsistent.
| Wildthings wrote: |
| When the calipers were changed where the rotors turned? If so did the brakes throb badly previous to the caliper change? I am thinking that if their was a lot of variance in the thickness of the rotors the pulsations in the hydraulics may have been enough to force more of the fluid back into the master cylinder, overall causing less dragging. |
No, the rotors are fine -- no pulsing or vibration. They were also replaced many years but not so many miles ago.
_________________
John
"Travelling in a fried-out Kombi, on a hippie trail, head full of zombie..." - Colin Hay and Ron Strykert
http://vw.tauxe.net
1969 Transporter, 1971 Westfalia, 1976, 1977, 1976, 1977, 1971, 1973, 1977 Westfalias,
1979 Champagne Sunroof, 1974 Westfalia Automatic, 1979 Transporter, 1972 Sportsmobile, 1973 Transporter Wild Westerner, 1974 Westfalia parts bus, 1975 Mexican single cab *FOR SALE*, 1978 Irish 4-door double cab RHD
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 23236
Location: Oklahoma City
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| Posted: Thu Apr 03, 2025 8:22 am Post subject: Re: Brakes heating up and seizing after replacing calipers |
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| Quote: |
Let me sum up the problem now that we have conclusive evidence.
In the position where the clevis is pulled, the rod and associated parts inside the booster are at rest. At rest there should be no preload on the master cylinder. However John must loosen the master cylinder to relieve the preload on it. The preload is blocking the compensating port. The booster and master are not working as a team. One or both do not function as VW designed the system. |
Pretty sure we already had conclusive evidence pages back....(1mm of play at pushrod, no vacuum meaning system at rest, pushrod pulled back with bungeer cord and 3mm of unwanted preload on the MC)....but I agree with the test because it gets rid of any more argument and speculation that the pushrod from the peal had anything to do with it.
Pump the brakes until it locks and remove the pedal pushrod. So now we have double secret evidence that something is bent and/or (as you say)...not working as a team.
My only point....to pointlessly re-point out...is the point that we had this same issue with two MC's in a row....and did not have it before we swapped calipers.
To that point...your point! 
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| Since John said the problem did not exist before the calipers were changed, we can only guess that "something" happened that day. My suspicion, and it is only a suspicion, is that while bleeding the brakes, a part within the booster changed dimensions, maybe a spring collapsed, or some clip let loose, whatever, and that change is interfering with the booster returning to rest. My only suggestion at this point is if John has another booster at his disposal, he could swap it and see if the issue goes away. All he really needs to know is if another booster is bolted on, does the master cylinder return to rest when the clevis is pulled. If no. then the odds are that the master is not the proper length. If I had a booster to lend him I would. |
Yep...yep...agree...and we were here a few pages back as well.
1. either something happened to the booster that day or....
2. some kind of feedback from the new calipers is doing something.
Again...I am making the pointless point to re-point out this point....its done this with two sets of new calipers in a row....right? Different brands....hmmmm.
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| My vote is to locate and borrow another booster, even if it leaks, and test fit it to see if the problem continues or goes away. I don't know the history of the booster he has on there now, or how close to original it is. |
I believe this is a good path forward.
However, through most of this when specualting about the POSSIBLE caliper issues...I have been speculating that if there is an issue with them, that its an oversized bore. This would explain the calipers jacking themselves out by over-adjusting.
However a few posts back....either Lil-Jinx or Wildthings (or both) speculated that the calipers may be too TIGHT (bore too small)....and the pistons are simply just sticking.
I think its also high time to remove a caliper and simply pop out a piston and lets measure what we have.
I still think something is bent in the booster....but lets kill off the caliper speculation once and for all. This is dead easy to remove a piston and boot.
Ray |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 42788
Location: at the beach
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| Posted: Thu Apr 03, 2025 9:27 am Post subject: Re: Brakes heating up and seizing after replacing calipers |
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| but I agree with the test because it gets rid of any more argument and speculation that the pushrod from the peal had anything to do with it. |
It is never good enough to believe evidence points to something as a cause, one must verify that hypothesis if a valid test is available at minimal cost of time and money.
_________________
George Carlin:
"Most people don't know what they're doing, and a lot of them are really good at it."
Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice" |
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