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Tue Sep 08, 2020 1:52 pm

I was driving I-95 North in CT when, for a split second, the brake pedal sunk almost to the floor before I pumped it once to regain normal braking. I pulled over immediately, checked all brake lines for leaks. I found none. I pulled top off instrument cluster to check fluid level which was a little low. I reluctantly continued the trip, checking brakes often, with no further issues. I took it to a known VW mechanic in CT who saw no leaks around the lines, booster or elsewhere. She filled the reservoir to "max" and told me to keep an eye on it. She suspects master cylinder.

Questions:
1. Will the master cylinder suddenly fail or gradually over time?
2. If there were no leaks around the brake lines, where else should I look? I'm learning now the MC also serves the clutch.
3. Could low fluid cause the issue I experienced?
4. Assuming I replace the MC, I'm seeing a number of them on Amazon. They all look different but "fit my vehicle". Suggestions? I see GW has aftermarket version for $45.
5. Any other culprits beside MC?

Thanks.

(5+ years of ownership and still loving this van).

Tue Sep 08, 2020 1:58 pm

The master can leak into the booster. You really need to unbolt the master to look at the back side and in the booster. If it has been leaking into the booster, the sooner you can flush the booster with soap and water, the better chance of saving the booster. It sounds like the master bypassed internally and allowed the pedal to sink. Don’t take chances with brakes.

Tue Sep 08, 2020 2:25 pm

This thread of a similar experience may be helpful.

https://www.thesamba.com/vw/forum/viewtopic.php?t=741227

Dave

Tue Sep 08, 2020 2:31 pm

Danger Will Roberson!
Something Broke!
Probably you lost the lining of a brake pad. One side of one might be real close to the metal. May start to screech soon.

Tue Sep 08, 2020 2:49 pm

MarkWard wrote: The master can leak into the booster. You really need to unbolt the master to look at the back side and in the booster. If it has been leaking into the booster, the sooner you can flush the booster with soap and water, the better chance of saving the booster. It sounds like the master bypassed internally and allowed the pedal to sink. Don’t take chances with brakes.

x2

and id budget for a replacement booster as ive not seen one that managed to take on fluid and survive, since the leak usually happens slowly and that fluid has been in there working its way through the booster for a long time...

Tue Sep 08, 2020 2:54 pm

A cup in the master cylinder could potentially not seal when the pedal is depressed and then go back to working properly again. If this is what happened the problem will surely reoccur at the very worst time.

Tue Sep 08, 2020 5:13 pm

x3 on the master cylinder internal leak, which can be intermittent as you described. I've had this exact thing happen to me.

I agree that checking for leaking into the booster is important in this process.

Tue Sep 08, 2020 7:04 pm

Check the pads first as that's easy to check and easy to fix too. It happened to my VW Pick-up it was just the pad that needed replacing. Get the best Pads you can find for it when you do a brake job, not stuff from autozone or whatever.

Tue Sep 08, 2020 7:06 pm

If this was my bus I am replacing the master cylinder. As well as checking the pads.

Tue Sep 08, 2020 7:08 pm

Thanks everyone. Looks like I'll be replacing the MC and booster for good measure. Any issues with BD's re-manufactured booster?

I also have new pads, brake lines and rotors that came with the van to replace if necessary.

Looking for someone around here who can do the work. Thanks for any suggestions in Northern NJ.

Tue Sep 08, 2020 7:12 pm

If you are doing the booster it might be a good time to consider the BMW booster upgrade.

Tue Sep 08, 2020 7:13 pm

And check with djkeev for mechanic recommendations in your neck of the woods.

Tue Sep 08, 2020 7:31 pm

I came across the BMW upgrade in my research tonight. Wondering if that increased stopping power puts too much stress on other non-BMW components.

Wed Sep 09, 2020 8:23 am

If your rotors were a little warped and your wheel bearings on the loose side, the pistons can get pushed back into their bores, leading to the scenario you describe.

Wed Sep 09, 2020 9:30 am

HackAl wrote: I came across the BMW upgrade in my research tonight. Wondering if that increased stopping power puts too much stress on other non-BMW components.

Short answer, no.

Wed Sep 09, 2020 9:50 am

?Waldo? wrote: HackAl wrote: I came across the BMW upgrade in my research tonight. Wondering if that increased stopping power puts too much stress on other non-BMW components.

Short answer, no.

The change in the booster would just change the required pressure on the pedal. I personally like the pedal feel of the Vanagon over that of most other cars, not too soft and not to hard. This is a personal thing though, so if you have a 110# wife who drives in high heels her needs are probably very different from mine with my 225# mass.

Wed Sep 09, 2020 11:03 am

Understood. I ordered a Vanagon booster, probably just by default. I could have been sold on the BMW but typically resist change.

I'm hearing the comments that this might just be the pads. It might just be the master cylinder. It might just be rear brake adjustment. My thinking is, as far as I know, the master cylinder and booster have never been replaced. If it's probably the MC, I might as well replace the booster while I'm in there, especially if it may have been damaged by a fluid leak. I already have new pads that came with the van so I will take this opportunity to change them even if there is some life left. Same for the brake lines.

So no, I won't be taking chances with brakes.

I'm going to use my regular mechanic because he's good, even if he's not experienced on Vanagons. From the videos, this does not look like a terribly difficult job. Between the videos and the Bentley, I think he'll be fine. Any special advice for him?

Thanks again. Should have the parts in a few days.

Wed Sep 09, 2020 11:38 am

HackAl wrote: Between the videos and the Bentley, I think he'll be fine. Any special advice for him?

Make sure he understands how fragile everything is on the instrument cluster so you do not get back a few extra pieces...

Wed Sep 09, 2020 12:05 pm

^^^ Alternatively, remove the cluster yourself which will save the mechanic some time and possibly some frustration. I just repaired a cluster tab with an aluminum strap and rivets. It had previously been jb welded (not a great solution) and such a booby trap may be lurking in your van.

Wed Sep 09, 2020 5:36 pm

I would not automatically replace the booster. See what you have when the master is off. I’m running the original booster in our 82 and the 90.

I know there is a lot of internet testimonial for the BMW booster, but I’m at a loss to understand how the brakes are improved. The only affect should be on pedal effort.