Itinerant Air-Cooled

Hiya All,

I have a bit of a mystery on my hands and I could use another point of view.

A little context..........I was driving my Bug the other day. Put my foot down on the brake. Nice firm stop as usual. Then as I was sitting at the light, the pedal gave way just a bit and then firmed up again.

"Uh-oh", I thought. "That's not so good".

A couple of stops later I noticed that my brake warning light was lighting up as I depressed the pedal and again as I let up on the pedal. The light was off at full pedal. At that point I was thinking that I had a blown brake circuit. Funny thing was the brakes seemed just as responsive as before the light business.

I made it home and checked the brake fluid. Top of the reservoir. So, it looked to me as if I might have master cylinder issues.

I had to use the car again today to run an errand. Now, firm pedal and no brake warning lights whatsoever. Huh? How come? Anybody have an idea as to what might be going on here?

Is this an example of the ultra-rare M-999 self healing option?

your MC guess is probably accurate. Another possibility is a combo of sticky brakes that also need adjustment. Probably the MC.

Do the adjustment on your brake adjusting stars first, then look at the master cylinder if symptoms recur.

Good luck, Tim

Your master cylinder may be going south. Check for general seepage (no not General Seepage, besides he's retired) around the front bulkhead and behind the driver's side wheel at the master cylinder.
How old is it? As I'm sure you know it can be a pain, depending on your lines and floor but I'm sure it'll be easy in your case.

Hiya Bob,

Check and double check!

I took a look and everything around the MC is dry. The brake fluid reservoir is still topped off so I'm not thinking that I'm looking at a leak. I'm guessing a seal is suspect inside the master cylinder. Matter of fact, I stopped in at DIP and grabbed a new MC. I've done the master cylinder thing more than a couple of times so no problem on that end.

But the part of all this that has me puzzled is...........why would the brake light warning system be illuminated one day and not the next? What could (might) account for that? That's the mystery part of all this.

A bad switch or connection? But you felt the pedal drop too.

the light comes on when the MC leaks internally and when the MC doesn't leak the light does not come on. Intermittent failure of the MC is the most likely cause. However, if your drum brakes are sticky, and out of adjustment, you can have similar pedal feel.
Let me explain what happens.

Brake shoes stick because of rust in the hardware, or drag on the backing plate.
Brakes out of adjustment have to travel more distance to contact the drum. Wheel cylinder uses more fluid to travel that distance.
Brakes fail to retract fully after last use due to sticky hardware.
Next time you step on brakes the shoes are closer to the drum and feel normal because they have a false adjustment due to the stickyness.
This time they retract all the way, next time you use them they stick halfway and then break free and go all the way out to the drum. That would give you the pedal feel. This has happened to me in my Bus. The MC failing internally has happened to me as well.

I'm not sure but I think the brake warning light will come on if your brakes are far enough out of adjustment.

Bookwus wrote:I was driving my Bug the other day.
as I was sitting at the light, the pedal gave way just a bit and then firmed up again.
?

You can try to replicate the symptoms. Pump the pedal firmly until you know the shoes have been punched out to the drums all the way.
Now hold the pedal firmly and note the position of the pedal. If it stays there firmly, you have no leaks in the system. Lightly release pressure without actually moving the pedal up. Now go back on the pedal firmly. Do this several times and note if the pedal starts dropping a bit with this pressure/release/pressure/release sequence. If the pedal drops, it is the master cylinder.
Colin

Hiya CK,

So, I tried to replicate the situation using your guide above.

Nada. No light. Everything seemed fine. Just fine.

Took it out on an errand. No problemo with the brakes.

Then, about a block away from the house, as I was stopping to make a turn, the brake pedal gave way again. Just as before. A firm pedal at first, then a little mush, then firm again. And the brake warning light again came on as before.

Looks like that new master cylinder is going in.

But I'd still like to know why this situation with the master cylinder is a "sometimes" kinda thing.

You have some internal rubber seals wearing out and losing pressure. Eventually it will start to leak.
I had a Brazilian MC last 8 months once before doing that. OY.

Hiya All,

I did finally find the problem with the brakes. So, I thought I'd post up with the cause in order to bring a little clozure to the discussion. Might help somebody in the future also.

It turns out that the brake switch was leaking. Not much but under pressure brake fluid worked its way THROUGH the switch and leaked past the three spade connectors and into the brake switch boot. The aggravating facet to this is that this is the second time this has happened to me. The difference this time around was that only the rear (closest to the pedal) switch leaked whereas last time both switches were leakers.

I guess this gets partially filed under the "Replacement Parts Are Crap" rant. And these were VW Audi parts.

For the time being I replaced the leaky (and the other one too) switch with the same VW Audi switches. They were all my local parts house had and I wanted to get the beast back on the road. But I have heard that there are VERY GOOD (as in OEM) quality brake switches out there somewhere. Does anybody have a line on those?

My local parts house sold me switches made by Euromax but have the VW/Audi logo stamped in the black plastic part where the tabs are. Sluggo had horrible luck with Euromax (I think) switches that he bought from AutohausAZ. I bought mine back in March and so far, so good. How long did yours last before leaking again?

Hiya Dick,

Indeed, these little beauties are EuroMax. I had just about six months on this switch before it bellyed-up.

Inasmuch as I had the same problem with the previous two switches I asked the counterguy if he had any complaints about the switches leaking. "No, I haven't heard anything about leaking", says he. Considering my experience, I'm having a little problem believing that when he adds, "I did have a guy come in with a switch in which the center just blew right out of the switch body".

Oh great.............just great.

That's why I'm looking for a better (MUCH better) quality brake switch.

Bookwus wrote:That's why I'm looking for a better (MUCH better) quality brake switch.

Sing out when you find 'em!

http://www.aircooled.net/new-bin/viewpr ... 03&cartid=
Read the blurb.