Almost burned my car up on Saturday... need help with brakes...

I've had my local custom car shop work on my brakes over the last month... started out replacing all the metal lines, & adding a new remote res Willwood dual chamber master cylinder, replace the pressure switch to get my brake lights working & hone a wheel cylinder that was leaking...

they have been having trouble getting pedal pressure, & the last job done was adding the "T" for the pressure switch, new, into the front brake line... on some of the jobs in the past, I found as the brakes pumped up as I drove it, some of the brakes would drag... ( one got hot enough in the past to warp the brake drum, giving me flutter on the pedal... I thought we were past that... silly me... I was at the local Eddie Cockran car cruise this weekend, & on a 30 mile cruise through a couple small towns, my passenger rear brake pumped up & got so hot it nearly caught the car on fire ( melted my center cap out of my aluminum wheel, & had what looked like melted rubber dripping out of the brake drum ) I had to dump a jug of water from the trunk on the rear brake drum to cool it, & likely if I had gone as much as a mile further... I'd be doing an insurance settlement...

... this is the same brake that held up before & warped... so at least my car didn't burn up but I'm looking for reasons & a fix

the local shop is known for doing high dollar restorations & customs, & the brakes on my 38 Nash is giving them fits & almost cost me my car...

I bought the car from a broker that did just enough to get it running, & often I've had to re-do things they did 1/2 arsed... ( they originally honed all the wheel cylinders, & I've only been dealing with the one front one that had been leaking ) could the wheel cylinder have been the problem ( it certainly is right now ) or is there something either I or they are not seeing with adding the new dual chamber master cylinder to the old drum brake set up that could be causing the brakes to pump up & not release ??? the shop owner mentioned I might need some sort of line valve that they have put on cars with the under the floor master cylinders ???

looking for eye deers... thanks

 

Oh... & a pic from the car show...

 

Brake hoses ( rubber) can collapse inside acting as check valve and not releasing pressure.

 

if the flexlines werent replaced, they could be defective, trapping pressure and causing a dragging cylinder. thats been a problem mentined several times on here

 

Ouch. Could be a wheel cylinder sticking. Check the brake hoses, they can clog. Ive had problems with low pedal, hard to bleed, etc and found hoses almost totally blocked caused it. Good luck, find another shop.

 

sorry... my post was getting long... but that's one of the things the broker did was installed new rubber hoses a new ( single chamber master cylinder ) & honed & rebuilt the wheel cylinders... the right front was still leaking when I bought the car, & the pedal was very soft, often going to the floor, but the car would stop...

... if the hose were the problem... in the rear, wouldn't both brakes be equally a problem ( I realize they may have had one set up more than the other, but they put it on the lift to spin them to check it, while working on it )

 

Very true, however, the typical system has one flex hose that supplies the rear system. A bad hose would probably make both brakes lock up. If the hydraulics are not causing the lock-up, look for bad return springs, a tapered drum, or wrong brake shoes.

 

I have the same problem with my 59 corvette. It had all new parts. First the right front wheel would lock up then started leaking. Found Condensation ( water ) the synthetic brake fluid, replaced the wheel cylinder. Now the left wheel cylinder is locking up. To make a long story short. CHANGE THE BRAKE FLUID PERIODICALLY. Jim.T.

 

how much free play do you have with your pedal adjustment??? you need to have sufficient to allow for all the pressure from applying the brakes to be relieved when the pedal is released. If not enough free play the lines can be holding more residual pressure than the return spring can work against.

Assumming you hard ware is new, are the return springs providig the proper tension or were they istalled simply on the basis of being a length that fit?

Also in discussio we have had recently on a early mopar board, it was discovered that wheel cylinder pistons and the push pins that move the shoes were different among years and brands of wheel cylinders, having different lengths and different shaped ends where they meet the pistons, some tapered, some rounded, etc. This difference usually lead to problems refitting drums over newly serviced systems, but in several instances provided enough difference that the brakes could not be adjusted to provide sufficient clearence leading to dragging, overheating and eventual locking up of a wheel.

Also is there sufficient venting withthe remote filler to allow fluid return and some possible expasion of fluid from heat.

 

Magnum Wheel guy,
This was my thoughts on it also. Bad brake hardware is real common on old cars, as well as everything else that Big Chuck mentioned.

 

Like was said; There is a rear flex hose that could be bad.

What type of E-brake? a drum type at the trans, or cables going to each rear wheel?


edit; x2 on checking brake pedal freeplay

 

Removed the reservoir and look in the hole. The brake piston is probably covering it. It will keep the brakes engaged while driving.

 

the above answer would be my best guess
if you is gonna keep this remove the bad wheel cylinders and sed them out for brass sleveing which will end a lot of maintence problems for a little used car[ look in Hemmings for a place]
you need to find a old guy with the skills of a machinest to fit your brakes together so they work
they proabbly set the petal up to push piston forward to give residual pressure to give good petal without pumping, when they get hot the pressure applies more untill you get smoke and fire
if you had a bleeder wrech you could of bleed of a little pressure and continued

Fix the car right before driving again

 

cables.. but right now they are set loose enough, that with the parking brake set, they barely hook up...

that's pretty harsh... I've been taking it to one of only 2 shops that work on these kinds of cars, because I wanted to "fix it right" I've installed as many new parts as practical ( I can't find wheel cylinders ) installed the dual chamber master for safety... my goal was as good a working original drums as possible...

anyone care to explain this further ??? this is a brand new Wilwood remote reservoir master ( designed from the start to be remote ) have there been some issues with these not working ???

 

I had a similar problem on a different car. On that car, the pushrod in the master cylinder is held in with a snap ring. One end of the snap ring was twisted and the piston in the MC wasn't fully releasing.

That little bit of pressure would cause the pads to heat up...as they heat up, the fluid in the caliper would expand and engage the brakes even more.

 

Since it sounds like you've done everything that has been suggested already, and it can't be fluid, hoses, etc. as those are all new; my suggestion is the wheel cylinder at that location is the culprit. If the piston is either too tight, or too loose it will bind from not enough clearance, or cock and bind from too much clearance. I'd replace that cylinder, or have it properly bushed to get the clearance perfect.

 

X2 if the brakes are properly adjusted, then the rod and piston in the master would lock all brakes, if the rear hose were bad it should affect both rear brakes, more then likely either the wheel cyl isn't returning or, the springs aren't pulling the shoes back. [notice I said more then likely]

 

I'm certainly no pro, but have been thinking "wheel cylinder" the entire time while reading through your post here.

I have to agree with what 1971BB427 just posted...I know you said you haven't been able to find new wheel cylinders, but maybe you could find a used somewhere to rework.

And glad the hear heat didn't get any further into your ride that it did!

 

1st off... thanks for all the suggestions...

I bought the car as a "fix it while I drive it" car... I understand sometimes things don't work out like ya planned, & knew going in, that original Nash parts would be hard to get... I joined the NCCA to get a line on parts & inside information, but so far no wheel cylinders for me...

... I'm buddys with a very good fabricator / welder / machinist ( you may have noticed my custom stainless bumpers )... if I can get through the summer cruise season, I'll pull all the wheel cylinders & have them lined with stainless over the winter... if I could make it work through the summer without downing the car for a month, I'd be happy

 

In the master cylinder, there is a small hole between the reservoir and the cylinder, which is how the fluid gets from the reservoir to the cylinder. If the piston in the cylinder isn't retracting far enough (due to too long a brake pushrod, or a faulty master cylinder, etc.) then the fluid that is in all of the wheel cylinders, lines, etc cannot flow back to the reservoir as it heats up and expands. The fluid has no choice but to create pressure in the system, which will apply the brakes. I doubt this is the problem, as it would typically cause the brakes on more than one wheel to be applied. In a traditional master cylinder, it's fairly easy to determine if the piston is moving back far enough. Take the cover off the reservoir, and have someone step on the brakes. If it's working properly, you will see a small fountain of fluid pushed up through the hole and into the reservoir. Caution: don't have your head directly above the reservoir when this test is done, as pushing the pedal too quickly can cause "fluid face". I'm not familiar with the Wilwood cylinder you're using, but with a remote reservoir the test is likely not as simple as described above.

 

BTW... the shop ower was very concerned when I called him this morning, & asked me to bring in the car right away...

since it was the same brake that hung up before, & we didn't have that drum off, perhaps it was because of the wonderfull work the broker did before I bought it ???

either way, the wheel cylinder will definately need a kit now...

how about other things that might have been effected... outer axel bearing, break drum, actual axel temper, spring tempers, etc... anything else I might not have thought of ???

 

change the rear flex hose and get another wheel cylinder. Is the master cylinder mounted under the floor...? If so they should have put a residual pressure valve in the brake lines for the drum brakes to help hold the brake shoes up to the drum. Are the rear brakes self adjusting or do you have to manually adjust them...? If they are not self adjusting back off the brake shoes on the drum that is getting hot and see what happens........

 

Assuming that one flex hose feeds both rear brakes, I would assume that you would have the locking/dragging with both rear brakes if that was the cause.

I have two suggestions (that I don't think have been mentioned yet) ... check the STEEL rear brake line that feeds the problem brake. There is a possibility that it has been pinched/squashed allowing pressure to reach the wheel cylinder when the brakes are applied, but then restricting the pressure from bleeding off (might even be worth just changing the steel line that feeds that cyl ...)

My other thought is the rear backing plate. The shoes are meant to rub the backing plate in a couple of spots and I wonder if (over the years) there is now a ridge where the worn rub spot meets the untouched part of the backing plate. If the brakes are applied (and newer shoes have been installed at some point probably before you bought it) the ridge might be restricting the shoes from returning to the correct position (I have seen this before, I simply replaced the worn spots with weld, then ground everything smooth again ... basically "restoring" the backing plate to "new condition" ...)

If either of these is not the cause, I would lean towards the wheel cylinder itself.

 

yes... under the floor... can someone give a better detailed explaination of what the residual pressure valve does... if I understand correctly, it would give me a firmer pedal pressure, but would'nt it actually hide or hinder me finding the problem with the brake hanging up ???

the brakes are manual adjust with an excentric at the bottom of the shoes... & that's what we did last time was just back off the adjustment on that rear wheel...

I guess I didn't give it a thought, since I thought we had that straightened out, before they installed the new pressure switch for the brake lights, which was done on the front circuit... so either they readjusted the rears during bleeding, or backing it off was only a temperary fix ???

 

The only thing I have to contribute is to make sure none of your brake lines are too close to the exhaust pipes.
When I first got my car on the road the exhaust was almost touching one of the rubber brake lines.
If I drove it far enough the fluid heated up and the rear drum started dragging, which of course caused more heating and more dragging. I never went beyond that point but I can see how on a long drive serious heat might have resulted.
In my case the fix was as simple as rerouting one brake line and insulating it with a small heat shield I made from a piece of aluminum sheet.

 

Oooops, just read that all the steel lines had been replaced ... that would suggest that replacing one again would not solve your problem (thinking it could be plugged) BUT BUT BUT there is a chance (as I mentioned earlier) that the new steel line has been pinched/squashed SINCE being replaced.

The shop owner, knowing the lines are new, might not be bothering to take a close look at them. I have had a rear brake line get squashed becuase it was not routed correctly and got hit by the exhaust. Worth looking into.

 

The residual valves hold some pressure in the lines/wheel cylinder so that you dont have the fluid draining completely back into the master. This only applies when the master is under the floor. You need a 10lb valve for drum brakes and a 2lb for disc. When the fluid drains back into the master you have alot more pedal travel, or you may have to pump the brakes to get enough pressure to stop.

It doesnt sound like this is your problem though.

 

Those little (2lb and 10lb) pressure valves prevent the fluid from running back into the master cyl if the master is mounted below the wheel cylinders .... they basically keep a little pressure at each brake. I can't see this being your problem because I don't think you are even running them (although IF you are running them, maybe you've got the wrong ones installed and they are keeping too much pressure at the wheel cylinder).


I still suggest that you take a look at the backing plate and make sure the new steel line feeding that wheel isn't damaged.

 

With an old system like yours I doubt there was a residual check valve in it, it simply wasn't needed, there however is one in the master cylinder that takes care of the problem, all they do is hold a small amount of pressure in the line so that it all doesn't run back to the master, if converted to modern discs and drums then putting one in is sometimes needed, I find it odd that there are no wheel cylinders to be had, have you checked with Kanter,also on the free play on the master to push rod, there needs to be a little clearance between the end of the rod and the cup in the master cly, if you can maybe the linkage just a smidgebefore contact to the cup its ok if there is no clerance then it needs to be adjusted so that there is, this is most likely not your problem cause as stated more than one brake would drag, there is a possibility of a bearing going bad now that things have been hot it would be wise to check the rear axle bearings.

 

thanks for the suggestions guys...