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Cortland15B
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Joined: March 15, 2011
Posts: 128
Location: Northern Wisconsin
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 Posted: Thu Apr 11, 2013 8:49 am Post subject: Master cylinder problem |
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So I adjusted the brakes earlier this week along with bleeding the brakes. So when we started bleeding the rear passenger side. it had no fluid coming out so we moved to the rear driver side and bled it a little, it had fluid coming out, did the front passenger side and fluid came out but didn't shoot out very fast and was really slow the first time we bled but the 2nd time it came out solid with no air but didn't have the short fast shoot when you loosen it like it usually does, the front driver side shot out like normal and then bled it.
I went back to the rear passenger and bled it, it came out really slow at first then picked up but wasn't really that great but still we did it till no air was coming then did it in all over again in order. The pedal was firm but it became firm really low, like the last 3 inches is when it became firm, and when we let the rear fluid out the pedal went down when we had it held but when we let the front out the pedal didn't move. So we bled it in order 1 more time and tested with the same result. The pedal was not even close to what is normally is it seems that the normal spot where it used to start braking is from the front brakes, then where it is stopping now is for the rear. I am just guessing, I'm new to Vw's. We took it for a test ride down our block and back, the braking force was greatly diminished, we think that the back is working but the front isn't. My dad and I think its the master cylinder. What do you guys think? If it is how do you replace it? Last fall I started to replace the wheel cylinders, shoes, had the drums turned, and replaced the lines up front. What I don't get is why its not working now, last year it worked fine, had it stored in our garage over the winter, and then when we got it out to get her road worthy again it stops working.
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pafree
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Joined: August 16, 2005
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Location: dayton, the one in texas
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| Posted: Thu Apr 11, 2013 9:19 am Post subject: Re: Master cylinder problem |
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first check all lines for leaks. the long line that runs through the cabin along the tunnel. have someone step on the pedal to see if one of the rubber lines leaks under pressure.
when i bleed brakes, i tied a small rope to the brake pedal to pull back up to make sure it comes all the way back up. have you readjusted the brake adjusters after bleeding? adjust, spin the wheel and hit the brakes and then readjust again. it seems to take a couple time for me to get every centered.
if this doesn't help then you have to look at a failed master cylinder.
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Cortland15B
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Joined: March 15, 2011
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Location: Northern Wisconsin
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pafree
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Location: dayton, the one in texas
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| Posted: Tue Apr 16, 2013 6:16 am Post subject: |
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| Cortland15B wrote: | | What has to be done to replace the master cylinder? Is it hard? |
1. remove fuel tank or try to get to everything from under the drivers side wheel well. (removing the tank method is easier)
2. disconnect hard lines leading to wheels from the master cylinder.
3. disconnect plugs for brake lights from the master cylinder.
4. disconnect lines from reservoir from the master cylinder.
5. two bolts hold master cylinder on. they are taking out from behind the pedal assembly.
6. the brake plunger that pushes in on the master cylinder can be left on but if it is crusty then remove the c clip that hold it on the pedal assembly and buff, clean and protect.
7. there might be a rubber boot that goes over the plunger. it helps keep the plunger clean. do you need it? not really but i have seen dirt and mud build up that make the brake not return back up.
extra hints: research bench bleeding and don't over/rough pump a new dry master cylinder. good time to lube the pedal assembly.
new parts to change or have on hand while you are in the area.
1. new brake light pressure sensors if the old ones don't come off nice to go the new master cylinder.
2. new brake reservoir line . fuel line is not brake line and will swell with brake fluid.
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Cortland15B
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Location: Northern Wisconsin
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| Posted: Tue Apr 16, 2013 7:56 am Post subject: |
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then theres 1 thing I could think of that might have happened, one side of the brake reservoir was emptied and I think air was introduced into the master cylinder. We made sure the hose was solid fluid (but only after we bled it for a couple minutes did we notice) then just bled normally, my dad said that it would eventually work its way out through bleeding, is this the right thing to do or is there something else that has to be done?
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pafree
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Joined: August 16, 2005
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Location: dayton, the one in texas
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| Posted: Wed Apr 17, 2013 7:25 pm Post subject: |
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| Cortland15B wrote: | | then theres 1 thing I could think of that might have happened, one side of the brake reservoir was emptied and I think air was introduced into the master cylinder. We made sure the hose was solid fluid (but only after we bled it for a couple minutes did we notice) then just bled normally, my dad said that it would eventually work its way out through bleeding, is this the right thing to do or is there something else that has to be done? |
if you saying the the reservoir went dry while bleeding, then yes it should clear the air with more bleeding but just keep somebody filling the reservoir while bleeding.
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Cortland15B
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pafree
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| Posted: Wed Apr 17, 2013 8:36 pm Post subject: |
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| Cortland15B wrote: | | would it make a difference if it went dry before bleeding, we don't really know when it went dry. |
yes, if it was dry before then it sounds like you have a leak. was the reservoir dry for the front or rear brakes? this will point you in the right direction to help you diagnosis a break in the steel lines, rubber lines (need to be checked under pedal pressure for leaks also), loose line on the back of the wheel cylinder or leaking wheel cylinder. also look where the plunger goes into the master cylinder and reservoir to master cylinder lines.
most of the leaks in the steel lines have been the curve around the pedal assembly and where the line runs next to the seat. i keep reinforcing checking the rubber lines under pressure because i had a almost new rubber line develop a pinhole pressure leak that only found when pressing the pedal.
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Dale M.
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| Posted: Thu Apr 18, 2013 8:17 am Post subject: |
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IF MC went dry during bleeding, you have to start over because you let air into lines....
Also if changing out MC be aware there are two spacer on bolts that hold master cylinder in place... When you pull the bolts out they may drop into channel (if VW pan), you need to keep these spacers in place so you do not crush channel and cause master cylinder to become loose...
Dale
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Cortland15B
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| Posted: Fri Apr 19, 2013 7:43 pm Post subject: |
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| Quote: | | yes, if it was dry before then it sounds like you have a leak. was the reservoir dry for the front or rear brakes? this will point you in the right direction to help you diagnosis a break in the steel lines, rubber lines (need to be checked under pedal pressure for leaks also), loose line on the back of the wheel cylinder or leaking wheel cylinder. also look where the plunger goes into the master cylinder and reservoir to master cylinder lines. |
The half of the reservoir that was empty was the side closest to the driver or rear of the car, I can't tell you for sure if that side hooks to the front or the back and I can't get to that area because it snowed a lot here. Whence I'm able to work on it I will check for leaks on everything you said. Would a leak cause the whole front system to stop working?
Then I have a question, I adjusted the shoes all the way in when I rebuilt the brake system to get the drums back on, so if the shoes were being pushed and the wheel cylinders were working but the shoes weren't able to touch the drum because I adjusted them all the way in and might have not reset them whence I got the drums back on, would this cause the brake pedal not to go stiff because the shoes weren't pushing on anything?
I did have a leak where the rubber line connected to the metal line but I tightened it up before I started bleeding.
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pafree
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Location: dayton, the one in texas
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| Posted: Fri Apr 19, 2013 8:45 pm Post subject: |
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| Cortland15B wrote: |
The half of the reservoir that was empty was the side closest to the driver or rear of the car, I can't tell you for sure if that side hooks to the front or the back and I can't get to that area because it snowed a lot here. Whence I'm able to work on it I will check for leaks on everything you said. Would a leak cause the whole front system to stop working?
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that is why VW switched to a dual system. all that snow and your car is down with a brake problem.
| Cortland15B wrote: | [
Then I have a question, I adjusted the shoes all the way in when I rebuilt the brake system to get the drums back on, so if the shoes were being pushed and the wheel cylinders were working but the shoes weren't able to touch the drum because I adjusted them all the way in and might have not reset them whence I got the drums back on, would this cause the brake pedal not to go stiff because the shoes weren't pushing on anything?
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yes, not having the shoes adjusted will cause a soft brake pedal. it might even cause a wheel cylinder to come apart to much and leak. i adjust and then bleed and then readjust. this helps to make the shoes center and give even pressure.
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Snappy
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| Posted: Fri Apr 19, 2013 10:00 pm Post subject: |
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When you put the drum back on adjust the brakes so they rub a little bit without pressing the pedal. They will wear down to the right spot shortly. You want just a little drag when you turn the drum by hand.
This will decrease the amount of play in your pedal, yes if the brakes aren't adjusted close enough the pedal goes farther down. If you do what I said you should notice a huge difference, when I adjusted my brakes (which worked fine) the difference was night and day.
.-Snappy
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dowha
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Location: St. Helen Michigan
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| Posted: Sat Apr 20, 2013 2:07 pm Post subject: |
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DALE,
You said,
"Also if changing out MC be aware there are two spacer on bolts that hold master cylinder in place... When you pull the bolts out they may drop into channel (if VW pan), you need to keep these spacers in place so you do not crush channel and cause master cylinder to become loose".
Could you clarify?
Is there two walls (Channel) with the spacers between the walls?
Bolts on the MC side to nuts behind the pedals? Spacers Where?
----- OR -----
Bolts on the pedal side to nuts on the MC side? Spacers Where?
How thick are the spacers?
Thanks, John
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Cortland15B
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| Posted: Fri May 03, 2013 9:19 pm Post subject: |
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So I worked on the brakes yesterday, it finally became nice enough to work. I then readjusted the brakes and got them perfect this time, the time before it wasn't the best attempt, I jacked up the car by each wheel, spun it then hit the brakes to see how well they would stop. The front stopped instantly but the back were delayed a little before stopping even with the wheel not spinning as fast.
After that I tightened the rubber lines at the wheel cylinder and the metal line just to be sure there were no leaks, I then tested to see if there were any leaks while under pressure, there were none, it was dry as a bone. I then went on to bleeding it again. It didn't fix the pedal, the brakes did work a little better but its just because we adjusted them better. The only thing I didn't check are the wheel cylinders but they are brand new so they shouldn't be the problem. So is there no other problems you can think of before I go ahead and replace the master cylinder?
Then should I replace the master with a stock replacement or a performance one? If I should get a stock one should I do original german or a reproduction? Here the 2 I've been looking at.
http://www.chircoestore.com/catalog/product_info.p...9dt4i5nks0
http://www.chircoestore.com/catalog/product_info.p...9dt4i5nks0
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pafree
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| Posted: Sat May 04, 2013 4:46 am Post subject: |
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TRW is really a good brand IMO. i use their ball joint and haven't been nice to them and they have done fine.
remember, brakes stop you and they are something you take for granted until you don't them. spending a little more is cheap insurance.
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Cortland15B
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| Posted: Tue May 07, 2013 10:16 pm Post subject: |
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So there are no leaks, there was one that caused the fluid reservoir to empty, probably before I started bleeding, would going dry before bleeding make any difference? I fixed the leak before I bled the brakes but during the first bleeding is when I realized that the reservoir was empty, we filled it then bled more.
When you press the pedal do the front and rear brakes engage at the same time or does one engage before the other? If it is this way which one engages first?
The wheel cylinders all around and the front rubber lines are brand new but the rears I didn't replace. When I preloaded and then later unpreloaded the rear suspension, passenger side, during it I jacked the diagonal arm up as high as it could go and didn't undo the rubber line like some of the instructions said. Say if the rubber line did collapse, what would happen as a result? The rear passenger side brake stream was kind of low on the pressure standpoint.
Just to give you guys all the information when we opened the valve to let the fluid out the pedal dropped dramatically but when we did the front the pedal only went down a little.
Then the rear driver side's pressure was good when we opened the valve, but when we opened the rear passenger side it wasn't as strong as the other side. Then on the front both sides were similar in pressure but the stream didn't shoot out very fast and was more of a steady and longer lasting stream. What would cause this?
Say if there was still air in some of the lines, would having air in them cause the pedal to be stiff, just stiff much lower than usual, or would it make the whole system/pedal be soft? Or say if the was air only in the rear or only in the front, would that cause it to still be stiff just much lower than normal? or would it make the whole system/pedal soft?
Would the brake shoe adjustment effect the effectiveness of the bleeding?
What would cause the brake fluid stream to vary from wheel to wheel like it did on mine?
This is for me getting to understand the brake system better, and to try to fish out ALL of the variables before I go and replace something that might not be broken. I appreciate you guys answering all these questions, even if they sound dumb, this is the first time I've ever worked on any brake system.
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Bashr52
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| Posted: Wed May 08, 2013 5:05 am Post subject: |
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| I may have missed it, but did you replace all the old rubber brake lines? I'd start there if you havnt already |
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Cortland15B
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[email protected]
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| Posted: Wed May 08, 2013 1:19 pm Post subject: |
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One thing that might help you understand how the brakes work is that liquids do not compress but air does.
If all the lines were perfectly bled and did not have any air or leaks or soft hoses or leaking master cylinder, all brakes would engage at the same time.
How much braking they do (front more than back) is built into the proportioning of the MC.
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