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Odd rear brake behavior
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Ledbellyhead
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Location: Knoxville TN
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PostPosted: Wed Apr 15, 2015 7:21 am    Post subject: Reply with quote

Called bus depot and they said they would mail the correct ATE, and send RMA for this one... it was drop shipped. Guess I'll be another week.

I did put a new hardware pack in the back with new springs and all.

It's been bled meticulously. I may have to shim it some with the new one, may have needed it with the old, but it was an auto zone replacement and after everyone's input I'm putting the best thing I can on it. I'm also going to do the WW Porsche 944 front disc when time allows.

I'm thinking that this could be the drums being warped like Sean said, but there is absolutely no pulse in the brakes, I can see how that could cause the shoes to shift and drag. I will take them to NAPA and see if they can turn them, they do have a slightly noticeable spot when adjusting them, but not what I would have considered a problem.
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Tcash
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PostPosted: Wed Apr 15, 2015 8:27 am    Post subject: Reply with quote

For Vendor feedback. Please use the Buyer and Seller Feedback Forum.
The Bus Depot
Thank you Tcash
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SGKent Premium Member
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PostPosted: Wed Apr 15, 2015 8:48 am    Post subject: Reply with quote

were it me, I would jack the rear up before and after a trip to see if one or both of the rears are dragging. You can also use an infrared gun to see which is dragging and getting hot. Use the brake bleeder screw to see if releasing pressure causes it to return and stop dragging. If it does then the issue is hydraulic. If it does not then the issue is mechanical.

Also - if you are basing the dragging issue on HEARING a dragging sound, and an IR gun shows it is not getting hot from dragging then it is the drum rubbing on the backing plate and not the shoes. There are several fixes for that.

Typical drum dragging causes that I can think of:

Rubber lines rotted on the inside
weak return springs
return springs not connected correctly
blocked port on brake master
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kreemoweet
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PostPosted: Wed Apr 15, 2015 10:40 am    Post subject: Reply with quote

Ledbellyhead wrote:
I could feel the gap between where it engaged the piston and when it was retracted"


This statement makes me think you are still not understanding that the issue people mention is with the pushrod INSIDE the booster, 'cuz
there is no way to "feel" the gap that should exist between that pushrod and its seat inside the M/C piston. If you have the system
disassembled you can check if the pushrod end sticks out even the tiniest bit past the booster-M/C mounting surface. If it does, then
there will likely be problems with at least some M/C's. Different M/C brands vary somewhat in the criticality of this measurement, and quite
likely there is some variance between the front and rear brake circuits as well. We are talking about fractions of millimeters here that can
make a huge difference in brake system behavior. The better test you can make when your new M/C arrives is to see if it can be set fully onto
the booster, without the o-ring installed, without the slightest indication of "touching" anything except the mounting surface.

I have been burned several times by Bus Depot's annoying practice of dropshipping items with no notice being given, and getting the wrong parts.
Invariably, it would involve getting cheaper substitute parts instead of the part ordered and paid for.
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Tcash
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PostPosted: Wed Apr 15, 2015 5:16 pm    Post subject: Brake Servo (booster) master cylinder pushrod Reply with quote

To link to this post copy and paste
Code:
[url=https://www.thesamba.com/vw/forum/viewtopic.php?p=7636413#7636413]Brake Servo (booster) master cylinder pushrod[/url]



Brake Servo (booster) master cylinder pushrod

Note: this measurement would normally be checked with a gauge. Placed over the brake servo pushrod. Which gives you a side view of the pushrod.
Pushrod gauge


It is easier to check this measurement on the work bench.

Look down the hole in the grommet where the lower brake fluid reservoir attaches to the master cylinder and note where the plunger is located in the Equalization port.
Using a philips screwdriver actuate the plunger while looking down the reservoir hole. Note the action of the piston inside the Equalization port.
With the master cylinder attached to the brake servo. Look down the hole in the grommet and note where the plunger is located. Actuate the plunger with the brake servo connecting rod adapter.
There should be at least 1mm (.040") of free play in the connecting rod adapter before the plunger moves.
If it requires adjustment see:
Brake Servo (booster) master cylinder pushrod

Bench bleed the master cylinder and install it to the servo using a new o-ring, in preparation to install the assembly on the vehicle.

Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.




Hope it helps
Tcash


Last edited by Tcash on Wed Sep 27, 2017 9:11 am; edited 3 times in total
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SGKent Premium Member
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PostPosted: Wed Apr 15, 2015 6:08 pm    Post subject: Reply with quote

on late bays the rod is adjusted between the pedal and booster, unlike many cars with boosters where the rod itself is adjustable. On early models the pushrod has an adjustment. Read Bentley Brakes and Wheels 4.1. Blocking a compensating port will keep the brakes from releasing.
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*You can do it right the first time, or do it over, the choice is yours. It is a free country. As to brakes, steering, tires, axles etc. - you may only get one chance at doing it right.

* VW Buses and VW cars share many of the same systems but if you haven't owned a bus and maintained it for awhile, you really don't know how different it is.
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Ledbellyhead
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PostPosted: Thu Apr 16, 2015 9:42 am    Post subject: Reply with quote

Tcash wrote:
For Vendor feedback. Please use the Buyer and Seller Feedback Forum.
The Bus Depot
Thank you Tcash


Am I being chastised for saying this?
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kreemoweet
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PostPosted: Thu Apr 16, 2015 9:50 am    Post subject: Reply with quote

Ledbellyhead wrote:
Am I being chastised for saying this?


I see not a single word of chastisement there. I am sure the post was meant to be purely informative. Many posters here do not seem to be aware of the
feedback thread, or do not realize how much more effective their remarks would be if posted in there, instead of buried in the middle of some random thread.
I am sure many vendors look at their feedback topic there, and the general samba readership is much more likely to find relevant comments there also.

Generally speaking, posters here are capable of chastizeing without leaving any doubt whatsoever about their intent.
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Ledbellyhead
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PostPosted: Thu Apr 16, 2015 9:54 am    Post subject: Reply with quote

I have checked the clearance that you speak of only by removing and re-installing the master and the feeling I was referring to was almost like you could feel it seat in the piston by pressing on it from the rod, you could feel the gap inside the booster, I studied those pictures hard a year ago. I have also tried to release on the bleeder with no pressure. When the correct master gets here and I install it, we will see. I want to do one thing at a time instead of everything so I know what the problem really was.

Checking with no o-ring and then replacing is a great idea, I did not do that.

Thanks everyone for the help!
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Ledbellyhead
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PostPosted: Thu Apr 16, 2015 9:57 am    Post subject: Reply with quote

kreemoweet wrote:
Ledbellyhead wrote:
Am I being chastised for saying this?


I see not a single word of chastisement there. I am sure the post was meant to be purely informative. Many posters here do not seem to be aware of the
feedback thread, or do not realize how much more effective their remarks would be if posted in there, instead of buried in the middle of some random thread.
I am sure many vendors look at their feedback topic there, and the general samba readership is much more likely to find relevant comments there also.

Generally speaking, posters here are capable of chastizeing without leaving any doubt whatsoever about their intent.


Okay, great, lol, thanks. Yep I've seen some harsh stuff on here.

I was just afraid I wasn't supposed to say anything bad about a vendor or something. It's true and they seem to be straightening "this" issue out in a hurry.

I really mean it, Thanks to everyone!
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Tcash
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PostPosted: Thu Apr 16, 2015 1:07 pm    Post subject: Reply with quote

No chastization here. If that's even a word.
It is only fair to both Buyer and Seller to use the Feedback Forum.
It also gives a prospective Buyer a good resource to use when deciding to do business with a seller.
No worries.

I added some information to my previous post above.^^^

Hope it helps
Tcash
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Ledbellyhead
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PostPosted: Thu Apr 16, 2015 7:53 pm    Post subject: Reply with quote

Thanks so much Tcash, I will check using this method as soon as it gets here, I didn't realize when I installed the other how important it was until it was bled, I may be able to install it upside down without removing the booster to check with a light. Then remove and bench bleed, and install and bleed again...
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DougB
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PostPosted: Fri Apr 17, 2015 10:24 am    Post subject: Reply with quote

Tcash wrote:
No chastization here. If that's even a word.


It is NOW! Smile
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