TheSamba.com :: View topic - Help! I have no brake pedal, but no fluid leaks!

Sat Jan 22, 2011 4:22 pm

I have searched, and done some reading on the forums, and I now have enough information to be dangerous. I apologize in advance for posting another thread about brakes, brake fluid, master cylinders. But I would like some kind soul's help in diagnosing my issue. I believe I have a failed master cylinder, but I figured I'd ask the Vanagon gurus for their advice, before this newbie attempts the http://www.vanagonauts.com/Brake-master-cyclinder190.htm

I have an 85 automatic Westfalia. She sat for 2-3 months in the cold. I go to start her up, and before reversing out of the parking space, I depress the brake pedal, and it goes straight to the floor. No brake pedal resistance. There were no early warning signs. There were no puddles of brake fluid around the vehicle. I pulled the instrument cluster, and the brake fluid reservoir was empty. No fluid around the master cylinder. No fluid on the carpet.

I filled up the reservoir with Dot 3/Dot 4 Valvoline from my FLAPS. Without turning the car on, I pumped on the pedal. The brake fluid level will decrease a tiny amount, but then comes right back up. There is a slightly noticeable "click" in the pedal as it travels back up, about halfway.Again no leaking is evident. Pumped the pedal a good bit, with the car off. Then I pumped, with the car running. The brake pedal seems to have a tiny bit more resistance when the engine is idling, but resistance goes to nothing after the engine is cut off. As far as the vacuum system, depressing the pedal seems to increase the idle speed.

Most people, describe leaks of some sort when trying to diagnose brake issues. Are there anymore diagnostic tests I can run? To me, it just seems like the master cylinder won't take any fluid. Can the master cylinder just fail without any evidence of leaking? The master cylinder is old and rusted, looks like it has never been replaced.

Any alternatives to taking out the master cylinder?

Sat Jan 22, 2011 4:31 pm

Yeah, the brake master can fail internally, but that doesn't mean for sure it's your problem.

Right now I'd suspect you just have air in the system.
You need to bleed all four corners, starting with right rear, then left rear, passenger, and then driver side.

By the way, you can bleed these pretty easily by yourself.

I use a clear hose that fits over the bleeder, that way you can see when air bubbles have stopped coming out, and when the fluid is coming out clear, also it keeps air from being pulled back into the system.

Sat Jan 22, 2011 4:34 pm

Advice from Dad, suggests that their is a leak somewhere, hence the no fluid. And that my brake system is now air locked, so the master cylinder will not take any fluid. The next step is to go to the brakes and bleed out any air in the system. Whoohoo!

Sat Jan 22, 2011 4:35 pm

levi wrote: Yeah, the brake master can fail internally, but that doesn't mean for sure it's your problem.

Right now I'd suspect you just have air in the system.
You need to bleed all four corners, starting with right rear, then left rear, passenger, and then driver side.

Thanks, this seems to be the consensus. Just don't want the leak to be at the m/c, and have to deal with caustic brake fluid all over the carpet and dash wires. Wish me luck.

Sat Jan 22, 2011 4:39 pm

Provided the pedal assembly itself is working properly, if there are no leaks present at the wheel cylinders, hydraulic lines or calipers, then the master cylinder IS at fault. If there is no visible leak and yet fluid is still disappearing, then the master is most likely leaking into the brake booster. I would start with bleeding the system, but if the fluid level continues to descend without any external leaks, the master is at fault. Although I don't share the opinion, the colloquial "wisdom" regarding clutch hydraulics here seems to be that you are asking for trouble if you replace just the clutch master or just the slave. there is no functional difference between the clutch and brake hydraulic components and so by that logic, if you replace brake master cylinder, you should also replace the rear wheel cylinders and both front calipers...

Sat Jan 22, 2011 4:48 pm

Andrew A. Libby wrote: Provided the pedal assembly itself is working properly, if there are no leaks present at the wheel cylinders, hydraulic lines or calipers, then the master cylinder IS at fault. If there is no visible leak and yet fluid is still disappearing, then the mast is most likely leaking into the brake booster.

The slight change in resistance between engine running and not, makes me believe that the pedal assembly is not at fault. Since the reservoir was empty, I'd assume there was a leak in the past, but 2-3 months of sitting in the snow/rain may have washed away any evidence. I was trying to reproduce a leak today.

This thread will probably continue when I attempt to bleed the brakes tomorrow or Monday. When I go to bleed the system, how would I identify if the master cyclinder has failed and leaking fluid into the brake booster? Andrew A. Libby wrote: I would start with bleeding the system, but if the fluid level continues to descend without any external leaks, the master is at fault. Thanks!

Sat Jan 29, 2011 3:40 pm

So, anything happening on this, Runamok?
I'm having similar symptoms ( http://www.thesamba.com/vw/forum/viewtopic.php?t=449239 ; Thanks, Dhaavers) and am also interested in this question of the master cylinder leaking into the brake booster. Is such a leak obvious once you get the master cylinder out?

Sat Jan 29, 2011 6:05 pm

It could be the clutch mater cylinder leaking. Mine is and I am looking for help replacing that and found this question. Pump your clutch pedal and see if there are any drips from the master cylinder mounted to the front of the van at the sering column.

Thank you,

David

Sat Feb 12, 2011 11:21 am

I had issues as well. Went to back the van out and no brake pedal or clutch. Checked things out and found the clutch slave was leaking. Fixed that, bled the clutch and brakes and all seemed good.

However, last spring when I checked the fluid level, the same thing happened, but the fluid level in the master cylinder reservoir was not low enough where it sucked any air in so I just added some to bring it to level.

Then I started the van up, to let it idle and I noticed it was blowing white smoke when i revved it up good. I figure it had to be brake fluid that leaked from the master cylinder into the brake booster and was getting sucked into the engine.

Finally, I just checked my MC level today and it is indeed low again - it was at the top line when I parked it in November and now it is midway between both lines and the van has not been started or moved during this time.

Really blows because I put a new master cylinder and brake booster on 4 years ago.

Fri Mar 04, 2011 11:24 pm

BoneStock67 wrote: So, anything happening on this, Runamok?
I'm having similar symptoms ( http://www.thesamba.com/vw/forum/viewtopic.php?t=449239 ; Thanks, Dhaavers) and am also interested in this question of the master cylinder leaking into the brake booster. Is such a leak obvious once you get the master cylinder out?

UPDATE:

I bled the brakes, and got my pedal back.
This will need a little test driving to see if anything else is wrong..