Suddenly, no brakes!

[Igeo]

Well almost. Brakes had a high solid pedal, and stopped the van well. Until today. Temps in the mid 90's in the central valley and was on the highway for 3 hours, then stopped for gas. Pulling in to the service station, I had a very low pedal and flashing brake light. Pedal was very soft and low, but would get solid near the end of the travel and wouldn't sink from there. Checked the reservoir and it was right at the full mark, just like the last time I checked it. No visible leaking at the wheels.

So I gassed up and turned back for home. By the time I got back to Oakland, temps were in the high 60's and the brake pedal felt high and normal. No flashing light.

I'm thinking the master is leaking internally. No known history on when it was last replaced. Could a hot day do this?
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1987 Westfalia 2.1 WBX Manual

[DanHoug]

you really need to check things over. you could have a line that rusted thru, a flex line that has ruptured, a bad master cyl yes, a wheel cyl leaking, or a caliper seal going.

so. time for car ramps and a strong flashlight. go over every inch of your brake system following all the lines and look for a wet spot. i know your fluid level didn't drop but this is the time for the life-saving inspection. if you find NOTHING, then suspect the master cyl.

depending upon your year, the brake light can flash from either a pressure differential or a low brake fluid level.

i've had to replace brake lines on my vanagon, my truck, a Jetta, and a crappy Buick Century of my in-laws. it's a reality in MN. maybe not where you are.
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-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[Steve M.]

Do not overlook the rubber hoses connected to the calipers that they are not old and expanding under the pressure of the fluid when the pedal is pushed.
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This free advice is worth exactly what you paid for it.

There are seven days in a week. Someday is not one of them.

[Sodo]

[joethebeekeeper01]

This exact problem happened to me and appeared to be an intermittent issue as well, I was stopped for about 45 minutes trying to figure out what was going on and the brakes "magically" came back.

When I got home I looked over the brakes and found a bad rear wheel cylinder. Took the opportunity to replace both and bleed the system. 2 years later so far so good!

[Igeo]

Pulled all 4 wheels. Had a good look. No leaking evident. I did the fronts with a big brake kit with hoses 2 years ago. I did the rears with new cylinders last year. All looks good. The master must blow by internally under the right circumstances. I'm going to replace it, and flush/bleed the system. Don't know what else it could be....
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1987 Westfalia 2.1 WBX Manual

[hardway]

The observed phenomena could be explained by the master cylinder bypassing. Or it could be caused by excess play in the slave cylinders. The wheel bearings could be loose and pushing the caliper pistons back. But if I were betting money I'd say it was vapor in the hydraulic circuit. Boiling brake fluid. A long drive in high ambient temperatures.

If it were me, a new ATE or FTE master cylinder and all new DOT 4 brake fluid would be in the bus in the near future. Pay attention to the boiling point specs in the various DOT 4 fluids. You might be surprised

[Igeo]

Procured an FTE master cylinder yesterday and will install today. Do you guys think the clutch hydraulics need bleeding too when changing the master cylinder? Doesn't really seem like it..
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1987 Westfalia 2.1 WBX Manual

[Steve M.]

[Igeo]

I guess I'll gravity bleed that line. The air is bone dry around here (sadly) but I guess it can't hurt, although it does bring up the old favorite "If it ain't broke, just give me a minute".
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1987 Westfalia 2.1 WBX Manual

[Igeo]

Installed without bench bleeding, just cracked the lines open at the master while pushing on the pedal until I saw fluid. Then power bled and flushed. Good high pedal now. Thing is, I had a good high pedal before too. Guess I'll have to drive up the freeway for 2 hours with temps in the 90's to really test it!
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1987 Westfalia 2.1 WBX Manual

[dgbeatty]

what color was the fluid you bled? Did you flush the entire system?
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Schau in das Buch

[Gnarlodious]

Once my brakes went out pretty quick, over the course of a day. Turned out to be the master cylinder has a plastic intake nipple up behind (frontwards) that had cracked and the fluid had all drained out and gone under the carpet and saturated the fiber submat and ruined it. The cause was that the original braided rubber tube coming down from the reservoir had hardened over the decades and the tight curve pressing against the front steel wall caused force on the plastic nipple whenever I pressed on the pedal. I was able to scrounge a replacement nipple and squeeze it into the hole with some difficulty, but didn’t need to take out the master cylinder. I used a clear vinyl tube from the hardware store and it has been fine for many years. The subfloor mat was ruined, which was a shame because it was in pristine condition because most are wrecked from mud, slush and salt/rust. But once it is soaked in brake fluid it is ruined.
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Vanagon ’83 diesel AAZ w/Giles injection, 5spd 4.57R&P+TBD and a '78 diesel Rabbit

[Igeo]