Sticking Brakes

Hi Gents,

In the past year or so, it seems that when I hit the brakes there is a lag of a few seconds before they release after I've taken my foot off the pedal. It definitely is more prone to occurring in colder weather, less so in warm or hot weather, but it still does.

The pedal returns when I take my foot off of it, but the brakes are still at least lightly applied, just for a couple or few seconds, then they release. I notice it most when I pull up to a traffic light - I slow down until I'm nearly stopped and then feel the brakes still lightly applied or dragging as I come to a complete stop. The car doesn't roll freely on a slight incline or decline for a few seconds.

It used to happen once in a while, then it started to happen more often, and now it's probably 80% of the time. I have had all 4 rotors and pads replaced, and all were normal for wear when they were swapped. The lines were bled and fluid replaced as well. It didn't change the issue for better or worse, it's still the same.

The pedal feels normal, with no noticeable variability in the pedal travel distance or effort and it isn't mushy or anything. The booster hiss sounds normal and goes away during the 2 or so seconds while I apply the pedal. There don't appear to be any leaks around the booster or master cylinder.

Any similar experiences or ideas? Thanks!

 

How old are the rubber brakes lines which feed the calipers?

 

I don't know, but I've had the car 6 years and haven't replaced them.

 

I had that same problem when I first purchased my car. Took it back several times and the dealer couldn't figure it out. Eventually it went away but only after I drove the car daily and drove it hard.

My guess is that there is varnish built up in the calipers that's making the pistons stick. I think the varnish is caused from excessive lack of use. My car was 10 years old and had only 9K miles on it when I bought it.

Take it out on a track and heat those brakes up real good!

 

Thanks for the idea, I certainly appreciate any and all feedback. In my case though, I'm not sure it applies for a couple of reasons. The first is that the issue is getting progressively worse with use, not better, as it has been going on for over a year now. The second is that the car actually gets driven quite a lot and by that I mean well over 10,000kms/year. I bought it with 28,000kms on it and it now has over 96,000kms after 6 years of owning it, including a few 5,000km round trips to Concorso Italiano and back.

When the brakes were changed, the wear on all 4 pads was very even from side to side and if it was a sticking caliper, I'd expect something like uneven wear, glazed pads or heat checks on one or more rotors.

The suspicion is that it's either the Master Cylinder or the booster, but I'm interested to hear more from Fastradio about the rubber lines. I'd never considered that.

 

Over time, the lines become like our own arteries; they become blocked. Easy to get pressure through...hard to get it to release back under little to no pressure. The lines have a serviceable life of about 12 years.

 

Curious to see what you find. My car is doing the same exact thing. My thought (I havent had time to diagnose yet) is the master cylinder. I need to bring it to my shop (the shoemaker never has good shoes ) put it on the lift, apply brakes and release see if all four are sticking or just one. Start cracking fittings open to see where the restriction is.

 

First I would check the calipers to see if they are sticking. The issue you are having leads me to believe that is where to start. Bad lines would make a mushy pedal.. If you have a problem where your pedal is not returning - then that is a different story. If that is the case check the pedal spring to see of its clear and not binding. If all good then I would suspect the master cylinder or brake booster. Always check for leaks as well. I would not overlook the calipers because you recently had a brake service. It takes a small amount of rust and or dirt to get up in the caliper piston and walla.. she sticks.. Maybe when they did the brake job they damaged the piston rubber boots when retracting.. Ahh.. maybe .. just maybe.... then dirt and moisture get in and hence a brake issue.. Master cylinders are known to go.. If brake booster was shot I would guess that the engine would do something funky on occasion as well because of vacuum loss (when pedal is depressed - not all the time in some cases..). In conclusion.. my guess... sticking caliper pistons or brake master cylinder. I would not start to crack fittings.. that can become a cluster f*ck..

R

 

Cracking fittings/bleeders open while the brakes are sticking is the way you isolate system components. That is how you find out if it is a caliper, hose, MC etc. I put a pointer type torque wrench on each wheel, have an assistant apply brakes and release. I then measure the torque required to turn each wheel. When you find the sticking wheel or wheels you begin to open bleeders & fittings, while the brakes are sticking, until you find the pressure restriction.

 

Being that you have flushed the fluid, I highly doubt you have any clogged lines or bad rubber. Mine are original and I've never seen any degradation in them. My fluid is always clean however.

I believe the varnish build up I mentioned is actually in the master. It always seemed that all the brakes were sticking, not just one.

Also, you won't see an uneven wear in the pads because even though it sticks, it does release as you start driving. It's not hanging anything up for more than a couple of seconds.

At least that was my experience.

 

David is absolutely right ...

And ... did YOU check your brakesystem personnally ?

You may even find the rubber hoses dated 1986 or older .... and that is absolutely wrong !!!

Have a check first ...

In my case, with next engine-out, I will renew the whole system...

 

Thanks for all the suggestions, gents. I'll post my findings in the next few days as soon as I have some answers. Cheers.

 

Hello gents, the problem is solved and it was indeed the Master Cylinder.

I pulled it out of the car and when disassembled, the brass rings showed quite uneven wear on them, suggesting that they were sliding back and forth in the cylinder at an angle. The rubber bits were also quite battered and warped as well.

I bought a new Master/Booster assembly, but for now I've only installed the new Master to help isolate whether the problem was with the Master, Booster or both. After installing the Master, the problem is completely gone and 100% fixed, so I'm not sure I'm going to bother replacing the booster for now.

Replacing the Master itself took all of about an hour including bleeding, and when it comes to technical ability on this stuff, I'm not exactly Brian Crall so it's a pretty simple job for the average guy

As an aside, the Master itself is a common Bosch unit that if you order elsewhere is a fraction of the cost compared to what the factory charges.

Thanks for all the input and suggestions, much appreciated.

 

Glad to hear it was resolved easily. Go drive it like you stole it now!

 

I am glad to hear it was so simple. I think that is what is wrong with mine, but it has since stopped sticking....but I know it will act up again sooner or later

 

Can you post the bosch part #

 

Indeed, quite a relief to be rolling again!

Your experience mirrors mine in that the issue was at first rare and intermittent (even disappearing for several weeks), then it became more frequent (and more noticeable as well), then almost all the time and in the end it felt like the car had developed hill-descent control!

I don't have the Bosch number on the invoice, but I'm sure it's easy enough to find and I'll post here and on the cross-reference thread when I do.

 

It sounds as if my car is experiencing this very issue. Any chance of finding that Bosch part number? I didn't find it in the cross-reference thread.

 

Anyone can help Spikef15c on that Bosch part number please ?

Imo it is not strange at all that brakeparts with an age of 20 years or older need service or exchanging one day ... so beware !

 

Thanks, Mel. Based off the research that I have done, the original master cylinder is Benditalia, which is very difficult to source. Flat_Twelve was kind enough to send me a link for the Bosch replacement part from a well known parts supplier. That supplier isn't a sponsor, so I'll hold off on posting that link. I'll be happy to pass it along if someone needs it, just pm me. I haven't decided which to do yet, but if I don't purchase the master cylinder outright, I may have the brake master rebuilt from one of the few places that still do this type of work. Price wise, it may be more cost effective to purchase the bosch replacement. I definitely agree that brakes are something that should not be neglected.

 

Rebuild is a way to go.. Find a reputable rebuilder and she will be like new.. I like to see factory brake components (good or bad)..

R

 

You don't "see" them Robbie as they are hidden under the carpet.....

Most owners would also not even know the difference.

But rebuilding is also FUN: you still have the Original part refurbished back ...

 

When I rebuilt mine I had a hard time finding a replacement. Brakes in the TR can be finiky.. I sent master and booster out to be rebuilt.. Once I replaced it was all good and not very expensive..

R