Technical Front right brake caliper appears to stick

[stevec]

Can anyone help, I'm on my second croma and it's displaying the same symptoms as the first one.

Front right brake caliper appears to stick, it's been replaced but it still does it.

It shakes over 50 mph.

You come up to traffic lights on a small incline and the brakes just hold you there.

My first croma was high miles 150K miles 120 bhp 8v MJet and the front right and rear left used to stick on that one, the new one is 80K miles 150 bhp 16v MJet.

I even checked the new one didn't do it before buying with 59K on the clock.

If you drive along say 40 mph and stamp on the brakes and lift off it doesn't feel like they've released properly has anyone else had these symptoms, if so what causes it?

Thanks

Steve

 

[notorious]

When I did brakes the last time the right side was sticking and the pad on the outer side of the caliper was to the metal. The mechanic worked and lubed the caliper and that was that. I will check the condition when I swap the winter wheels to summer alloys. I dont know what causes calipers sticking but seems slightly more common with Croma.

 

[Doofer]

We had just the same with our rear left one. Nothing to feel but a constant squealing while driving and a very hot disk after. The garage replaced the pads and cleaned and lubricated the caliper and it's been fine ever since.

The bloke said something about the pads being very tight (can't remember whether to the disc edge or caliper). I think he also said he trimmed away a bit of the pad with a knife to make a bit more space.

 

[DoIDon'tI]

Some Croma owners have had issues with the Servo, might be worth having a search on this forum.

 

[bobbyblue]

I seems to me that a sticking caliper should be discounted due to a new one having been fitted, I would look at a hydraulic problem, are you sure it's just your RHS caliper sticking? the left may be sticking as well but that it's is not so noticable, I would clamp the RHS flexi hose and drive up a quiet road to see if you get the same effect on the LHS, it may well be the master cylinder recuperation valve isn't working properly, it could even be a faulty brake servo unit still applying pressure, it really is difficult without physically getting your hands on the car, sorry I can't be of more help.

 

[sludgeguts]

No idea what your calipers look like as I've never worked on a Croma. However, I had a similar situation on an old motor I used to own. The pads were an extremely tight fit in the cradle so when the piston applied pressure, the pads gripped but when you took your foot off the brake, the piston backed off but the pads remained in contact.
I pulled the pads out & ran a file around the edge of the pads' backplate. I took off just enough to get a fag paper between the pad and the cradle, making the pad a snug fit rather than a tight fit.

On another car, the cradle itself was to blame - or at least the bolts holding the cradle in place. These were a long bolt, most of which was simply a pin to allow the cradle to slide along them. Took them out, removed the cradle, cleaned out the holes and went over the pins with fine emery cloth, reassembled with a smear of grease on the pins & everything was fine.

 

[Doofer]

When I was working out which of mine was squealing I went for a motorway drive and back home without touching the brakes at all. It takes some careful driving but it is possible. Then just have a feel of the disks and see if any are hot. A tip though - prod quickly with your finger before touching it properly, they don't half get hot from rubbing.

 

[DoIDon'tI]

Sorry, I meant to include the master cylinder with the servo as being a potential source of problems.

 

[halilson]

I had the same problem on my Coupe. It was down to a twisted pipe. The force of applying the brakes pushed the fluid past the kink in the pipe, but then the fluid got trapped, leaving the the brakes partially applied. Check that the garage didn't do the same when fitting your new caliper.

 

[Granvilleb]

I have the same problem. I have made sure that the pads are free in the calliper. I find that if the pedal is pressed hard it releases the brake. I thought it may be the flexible pipe with a bit of rubber acting as a flap so I have changed the pipe and the problem is still there. Some days it appears only to happen occasionally other days it is every time I stop the car. Has our "man in the know" got an answer?

 

[CromaF]

Hello and sry for my bad english.
I have exactly same problem presented in this thread. Frontleft and Rearright brakes are binding.
I have battled this problem whole my croma ownership, and my car is again at garage (Fiat Service) and even them cannot repair these damned brakes.

They have already changed master cylinder (last summer), brake discs at front, all brake pads, brake hoses at rear, tested ABS unit with bosch - tester, changed brake fluids 3 times and tried to "air" brakes at least 4 times. They have opened all brake calibers at least 5 times and tried clean them, but there seems no problem at there.

Problem is identical as Granville B explained: If pedal is pressed hard it sometimes releases brakes. And brakes wont "bind" if i dont press pedal (sure thing) and maybe even at the first or second braking, but it does it all time after these.

I know lot of about technology and physics and so on, but can somebody explain me what exactly is Brake Servo? My croma is diesel, so i think it has somekind of vacuum pump? Is Brake Servo same thing as brake booster? And do it need a separate vacuum pump or is it inside "Servo"?

I even dont know a synonyme to Brake Servo at my motherlanguage

The Fiat Service thinks that the problem is at ABS unit and that is sure expensive and i even dont think that problem is there. I bet on brake hoses or brake pipes or whatever they are, and all new ones is coming, but they dont think them helps problem.

Sorry for the long message, but i am getting mad with this brake problem. Have somebody of these earlier writers repaired problem? Please HELP!?

PS. I hope this helps because if have already eliminated master cylinder

-Alr

 

[Doofer]

On mine the pad was jamming within the caliper. The mechanic said it was a very tight fit, so he shaved some of the edge of the pads. I think he just used a sharp knife.

It's been perfect ever since (over 1 year).

 

[Radlet6]

We've had this problem too. Mechanic just lubbed the piston and everything ok since. Can't understand why it is the RHS when it is the left wheel which spends it's life sploshing through crud.

 

[CromaF]

Ty for replies. Do you think that if one caliper jamms, it can occur that another caliper on its circle jamms too? Because There are 2 brake "circles" or what you call it, 2 pistons in master cylinder, each drives brakes cross (rear right and front left and so on..)...? and both Frontleft and rearright jamms on my car?

Tomorrow they are changin the brake fluids again and tries to drive abs unit with bosch tester again. I can ask them to lub ALL pistons and ensure that they don't jam...

-Alr

 

[Cote DAzur]

Have you actually inspected the pistons within the calliper assembly for ANY signs of corrosion (rust) or split rubber seals?
I had this on a Renault; the rubber seal was split causing water to get behind it and corrode the surface of the piston, thus causing it to stick!
If there is any sign of corrosion then you need to remove calliper from its carrier and push piston out slowly with break pedal (use adjustable clamp to prevent piston coming all the way out) then carefully clean the piston with fine grade emery paper and replace the split seal (if available) or if badly corroded then you will need a new calliper.

 

[CromaF]

Calipers are inspected few times and today again. I just called to service and the brakes are still binding. They tested abs unit again and valves on it is working propertly.

They said that there is NO CHANCE that problem is in caliper, because system lets pressure on brake lanes, and if they open airing screw (or whatever you call it) the pressure releases from it and also the brakes releases. And brakes releases by itself few minutes after pressing pedal. That is why the consumption havent grown on highway. The brakes releases by itselfs (jeah). So no matter how slippy the piston goes inside the caliper, if the pressure is on, youn know, it brakes!

I told mechanican that someone on this forum have changed braking servo and that was solved problem. He told that it can be possible that brake servo "leaks" pressure to first piston on master cylinder, so that keeps pressure on that circle.

And i told you wrong earlier, it is actually frontright and rearleft brakes wich are binding! So the problem is same and i think it is caused by the servo and the first circle on master cylinder...

My car goes to the service again next week and they are inspecting servo and disassembles some more with better time than today... I can inform you then again, what they have tracked down!

-Alr

 

[GrandeGuy]

I know lot of about technology and physics and so on, but can somebody explain me what exactly is Brake Servo? My croma is diesel, so i think it has somekind of vacuum pump? Is Brake Servo same thing as brake booster? And do it need a separate vacuum pump or is it inside "Servo"?

I even dont know a synonyme to Brake Servo at my motherlanguage

 

[GrandeGuy]

Any one tried using a hub type dyno to sort this problem?
That way you can put it under driving condition, watch the pistons, hit the caliper, watch for smooth application etc.
Just an idea, might be cheaper than taking it to garages/stripping it constantly :shrug:

 

[CromaF]

Ty GrandeGuy. Now I know excactly how the brakes operates.

This video Tandem Master Cylinder 2.mp4 (@ youtube, I am not able to post links, because I have less than 5 posts to forum!!!!)
clearly shows, that when the pedal is pressed, the first piston starts operating significantly before the second. So if the Brake power booster still gives low pressure to master cylinder, the first circuit brakes could operate and the second ciruit could idle?

The ABS system just seems to block the pressure to the calipers, so i think that problem still isn't ABS unit... Next week we are more adviced

 

[Radlet6]

Well well. My Croma has just had it's annual service. THe guy at the garage rings up and says that it needs new rear pads. Ok, bung them in I say.

Picks up car to be shown two sets of old pads. One set about two thirds worn and the other set almost to the metal. Guess where the latter set came from.

You got it the N/S caliper.