New A108 owner with funky brake problem

Hi guys,

Earlier this year I picked up a '68 A108 from a friend of mine.  This thing is very cool.  I race motorcycles so I bought it for the purpose of transporting my race bike and all the crap that goes with it to the track and back.  Also to camp in!

Shortly after I bought it, I noticed the rear right wheel cylinder was leaking pretty bad.  When I opened up the reservoir on the top of the master cylinder (dual circuit), I noticed the rear reservoir was empty so I put fluid in, pumped it up and drove for a month (which means 4 times cause I avg only once a week).  In that time the brakes felt great at the start and would gradually get worse as the fluid leaked out the rear cylinder.

So I finally order a new one through JCwhitney.  I swap it out, bleed it and wow the brakes feel amazing!  I head out to one of the tracks and sit in some pretty terrible traffic, van gets hot, does some vapor locking, and the brake pedal gets really stiff and requires 2-3 times the pressure to get it to stop.  Then they lock up on me, smoke coming from rear right wheel.  I use a couple flat heads and adjust way out then back to normal and make the rest of my drive just fine.  At this point I'm thinking ok I overfilled the reservoir and left no room for expansion so I take some fluid out.  I also adjust both rear brakes to the right amount of drag.  Now, I complete a couple long drives (in heat) with no lock ups but the pedal getting really stiff.  

Then I drive home from the racetrack yesterday (keep in mind the van has been in the sun at the hot racetrack all weekend) and as soon as I start it up, before motor is up to temp even, the pedal is stiff immediately.  I manage most of the drive home without using the brakes.  I get home unload my stuff and start her back up to park and the brakes are locked up.  I adjust the pedal way out and I can hear the creak of the springs pulling the wheel cylinders back.  It definitely resets because leaving the pedal adjusted all the way out, unlocked them and put all the braking action at the floor.

A couple of other things I've noticed.

1. When I was bleeding the brakes (old way, pumping pedal), the first half of the stroke produced what looked like a tiny fountain of brake fluid in the rear port of the reservoir.  My only experience is with single reservoir brake systems so I'm not sure what's happening here.

2. Plenty of meat on the shoe, lining is somewhat damaged from brake fluid.  I used lots of brake clean when I swapped cylinders.

3. Lines are hard lines, fluid does move through them (saw when bleeding)

4. No visible leaks anywhere

5. Pedal adjustment works well and is not tightening or loosening on its own.

Not sure what to do here, new m/c?, new lines?, high temp fluid?  other things to look for?

Any help is greatly appreciated!  I love this van and would love for it to brake consistently....

-Chris

#1-replave master cyl. #2= are u sure the wheel cylinder was absolutely same as one removed?? Check sizes -usually printed on outside ob wheel cyl. itself?
Blow out real brake likes - clean with solvents & blow out again!! Bleed system!Replace brake shoes if wet from fluids too!! 

Fountain is normal.
Time to do a full complete correct brake job.

The shoes are soaked, so replace both sets of rear shoes.
Check the drums carefully. Many this age have been cut oversize.
Check the other wheel cylinder.
Ensure the hardware is in good shape and the same side to side. New can be bought.

Do a full bleed, adjust and then adjust the E brake. That's the rear, check out the front too.

These have been just patched for decades in many cases. Time to go through it and make it all right.

And welcome to VV!

Thanks, Glad to hear fountain is normal. Wheel cylinder has exact same numbers on it as the old one.

You think shoes are sticking to drums? The spring did seem to be in good shape when I put it back on.

Any thoughts on the heat factor?

I think that the saturated shoes are swelling.
I had a similar problem with a 72 Demon. Sat for years, Bought it and started driving it home. Rear brakes got hot and siezed. Had to get a tow. Rebuilt it all and no more problems.
I'd really suggest fixing it rather than puzzling out why a bunch of bad stuff is acting bad.

Welcome to VV!!!!

Forget the heat thingy! likely all due to master cyl being dry & as such coroded inside -REPLACE iT! also do as Rod says on rest -best -shoes in rear . Then u know all's been corrected! 

Oh I'm definitely going to fix it. I just like to know what's happening like having a strategy to throwing parts at the problem. Thanks guys

As a brake mechanic this is what I would do. Either replace the shoes or soak them in alcohol to degrease. Let them air dry. After installing them be certain that the shoe adjustment is correct (just barely making a rubbing noise as you spin them in a forward direction) prior to bleeding. Then bleed as always starting with the farthest wheel cylinder from the master cylinder and work your way to the closest. Keep a close eye on the master cylinder fluid level as you bleed each wheel cylinder. Go around and do that all again.

Ok bit of an update.  I pulled off my wheels and drums and low and behold, the wheel I replaced the cylinder on, these parts fall out.  I have no idea how that happened, if they fell out during adjustment or when I replaced the wheel cylinder and didn't notice (I'm usually better than that, but its possible).

Looking at the other side (pictured), it appears this piece limits the amount the spring can pull the shoe back and the spring is to keep the action smooth?  Anything else?  

The shoes don't look too bad but I'll go ahead and replace them anyway, adjust, then bleed the whole system.  

Any theories on how this translates to issues described above?  Cheers!

you needd to replace the hose from the body to the rear axle. it is failing from the inside out. it is not letting the fluid return.

the part pictured is the park brake equalizer. not used during pedal activation. you could leave it out but then no e-brake working.

The rubber line in the back is my bet but another thing to check is to make sure that the brake lines are not touching or too close to the exhaust.

Update. Replaced rear shoes, blew out the lines, put in new master, checked front shoes (they are good), adjusted everything, and bled the system.  Still got stiff when hot.

Topped off the coolant (not sure why I didn't think to check this).  It was a little low.  Now the motor doesn't get as hot and the brakes stay consistent.  The front brake lines are a bit close to the motor and seeing as I don't have a belly pan or any fans on the radiator, I believe the fluid in the front lines was boiling and expanding.  Now that the motor isn't getting as hot, I haven't had any problems.

Thanks for all the help guys!  

Anyone have an extra belly pan?

Yea, sounds like you were boiling brake fluid. Mine did the same thing in a parade at a car show on a very hot day. Brakes would hang, was a pita.