Problem with Brakes

What does the brake guy have to say about the issue.

Are you certain it's the brakes (plural)? Both sides?

Are you certain it's the brakes and not a bearing issue?

Let me be the first to say, PLEASE don't drive the car until this is resolved.

One thing the mechanic never mentioned was the flex lines. I will get the car back today. Hopefully the problem is fixed. My concern is that the problem started after he put in the new master cylinder after the brake pedal started slowly lowering to the floor board. The problem did not exist until the new master cylinder was put in. Thank you for your response

Martin

Oddly those brake lines can fail at any time regardless of whether anything else in the system was worked on or not.

I had one lock up the left front brake on an older pickup I used to drive. I changed it out and the brakes worked great for about two more days, less than three driving hours around town, and the right side did the same thing.

I have also done replacements on a number of other vehicles for my family and myself. I have learned that if you are doing one do the other. They always seem to go bad in pairs with the second one going just behind the other.

So since you have to re prime the whole system after you take one out you might as well just do the other and save yourself a second system visit to the mechanic. Besides they are usually rather cheap anyway at around $15 - $40 each and most only take 15 - 20 minutes with the right tools to change out.

I just picked up the car. The master cylinder that was previously installed was replaced. The brake lines were flushed out, it does brake like a new car, however the problem I had previously occurred after driving the car for 2000 miles on a new master cylinder. I will keep you posted. Thank you for your comment.

Martin

You are absolutely right.I have had 2 vehicles with that problem.Only one side locked up,however,which is scarey.

If you open the bleeder, and the brake releases,you can bet it is in the flex line.

Sometimes they shed debris inside the line and clog the return port of the master cylinder.This trash could still be in his lines even with the new master cylinder,if it was too big to pass through the bleeder port.And if the bleeding was not done in the proper sequence, it may have been simply pushed debris from one line to another without ever being pushed out.

If both sides are locking up, the trash in on the master cylinder side of the divider.A backflush, with master cylinder disconnected may be in order.

You posted:-

If you open the bleeder, and the brake releases,you can bet it is in the flex line.

Which can be true, but is not a 100% correct statement as I know of at least one more reason when opening (any)one of the bleeders will release (all) the brakes.

For instance, when a Master Cylinder has been incorrectly installed or is incorrectly rebuilt/manufactured.....!!!

EH VOILA! he had a new master cylinder installed at the start of the problem!!!

It can be as small an adjustment as loosening the mounting of the master cylinder and moving the unit slightly away from the foot pedal direction.

The locking up is due to the brake master cylinder not being able to return fully, which should happen to allow excess fluid back to the reservoir, the fluid warming up in usage (normal) and pressure building up cause the brakes to lock up (and overheat!!).

What the OP really needs is a better mechanic, this one is simply a dangerous amateur!!!

I have personally seen and fixed this problem several times on cars where amateurs have made repairs!!!

It has also been seen on CR4 from both amateurs and professionals over the years....

GA to you tcmtech. I had that very problem with my 1965 Humber Vogue when I first put it back on the road.

Ask the present "mechanic" for a refund, and get a new mechanic.

Have the new mechanic replace the flex lines as tcmtech says, and check the front/rear proportioning valve.

Thank you for your quick response. I am getting the car back today. He supposed to have fixed the problem. I will test it over the weekend.

I really hope your problem is repaired and does not recur. if it does, replace the flexible lines at the front and inspect or clean out the brake proportioning valve. Flex line deterioration is more common than a failed proportioning valve, but if you have not changed brake fluid often, there could have been moisture in the system that caused a) the funny braking and b) corrosion in the proportioning valve.

Are breaks locking on? or is wheel grabbing on breaking if so check shocks

Suggest you check brain for engagement. Otherwise, sit on hands.

Sorry you are so upset

The person says breaks locking up this could mean either they locked up & stayed locked on, or locked momenteraly on application.

After 50 years working on vintage,classic, & race cars I feel that I made a suggestion that did not warrant your rather rude comment.

I'm not upset, at all. I can't help it if you took offense.

There was no mention of wheel hop, rough roads, nor anything else that would point to shock failure, which would be more likely to occur at the rear wheels due to weight transfer on braking anyway.

Did the shocks magically cure themselves, for a day, while at the mechanics the first time.

The OP is not a mechanic, and the mention of non-brake, red herrings will only confuse them.

Sadly, he is not alone, your last statement was at best "unhelpful!"

Sorry, Lyn, but its true. I would have kept quiet if you had too.....

The brakes are gradually binding up. Fortunately there is plenty of time to determine if the brakes are going to start binding. So far so good. I've been driving the car since yesterday afternoon and no indication of any problems. I will keep you posted.

Thanks,

Martin

That is a sure indication of what is causing the problem, what I posted 20 minutes ago, the master cylinder.

As the fluid heats up in normal driving, the pressure in the brake circuit(s) increase and slowly (but surely!) put the brakes on, because the master cylinder is either defective or incorrectly adjusted - or both!!

If you did a couple of emergency stops, it will happen quicker as the heat of braking gets into the fluid. The thickness of the pads also affects the speed the problem happens at.....

On a dual brake system, the effects my be more on one circuit than the other theoretically, but in my experience, it was all brakes.

Did you check (with a wet finger and quickly, they get EXTREMELY hot) the temperature of ALL brakes both front and back when it happens?

I will bet that when it happens, either one circuit (either 2 or 3 brakes depending upon how dual circuits are installed on this car, but usually just two, one front and the opposite rear on most cars I believe) is hot or both circuits (4 brakes) are hot....

If only a single brake is affected, go for the flexible lines posted already by others.....but change them all. one being defective means the others will soon be affected.

I have never seen two flex lines, with the same problem, on the same day. If it is so, go and get a lottery ticket, you will get 6 numbers right!!! By a bunch of tickets if all four lines are affected....but remember, changing the lines and fiddling around with other bits may fix the problems, keep careful note, BE THERE!!

Its a classic problem, well understood by good mechanics and misunderstood by the rest of the world....