Morning all,

Once again i find myself seeking your help and opinions with my car.

Last week i took the car down to my workshop, put it in the air, took all the wheels off and removed all the calipers to clean them up and re paint them to give them a nice fresh look. All went well and the brakes were cleaned, sanded and painted with 2 coats of the popular Hammerite "Smooth Green" paint. I fitted the brakes back on last Sunday and was pleased with the fresh look. (I gave the wheels a thorough clean, polish and wax also).

While the brakes were off and the system needed bleeding anyway i took this opportunity to change the fluid for DOT5.1 fluid as i nice upgrade.

I went for a quick drive to ensure all was well. My first thoughts were good, the brakes were very very sensitive, requiring only the tinyest pressure on the peddle to really put the brakes on. After 4 miles i noticed that when ever i let of the throttle the car seemed to stop very very quickly, as if the brakes were on all the time, i assumed the handbrake and pulled over to check. Once out the car i was somewhat suprised to feel quite a lot of heat coming off my O/S/F caliper. It was obvious that this was being locked on. I limped back to the workshop and after quite a wait for the brake to cool down, i took it all apart again and gave it a visual check, nothing was obvious so assumed a partly seized piston (from where it had been off the car for a week) i pushed the brake peddle and watched the piston slowly come out. I the pushed it back in then repeated 4/5 times. The first time it was imensly stiff to get back in but buy the 4th time was moving better, stiff, but better. I put them back together, went for a quick drive and all seemed well. I then put away my tools and drove the 10ish miles home. Again, all seemed well.

Yesterday my girlfriend took the car into work and home again, all seemed well. In the evening we nipped to the local supermarket and while on the way i noticed the "Slowing when not on the throttle" again. We did the shopping and limped the car home again.

Now (after that essay, sorry) my question to you all is, Does anyone have any ideas what may be causing this, is it a simple fix or is it easier just to get a new caliper?

I appreciate this is a long winded post but understand the need for all the facts when looking into a problem. I hope you can help.

If the answer is that i do need a new caliper, are there any "upgrade" options i can use and what is involved? R32 calipers, LCR Brembos etc... I dont have alot to spend but at the same time, now may be an ideal time to upgrade.

I await your thoughts.

Kind Regards

Garry

These problems are usually caused by the caliper rust welding onto the slides. Take it off and clean them up properly. Maybe try some Copaslip on the pins when you put it back on.

Ken, thanks for the reply.

Without sounding ignorant what part is ment by "Slides"?

Thanks in advance.

Garry

I don't have a manual to hand, but IME the problem you describe only happens with sliding calipers. The slides are the 2 pins that the caliper is freeish to move left and right on to compensate for uneven disc and pad wear.

Im with you. Are these the same bolts that attach the caliper to the carrier?

I will take it off tonight and strip down what i can and look for any obvious causes.

Is there anything else in the system that could stop the piston retracting when you lift off the brake pedal? Its most evident in the one caliper but i wonder if it may be something else in the system?

Im open to any thoughts

Kind Regards

Garry

Maybe; it depends on caliper design, and I've never looked at the DS3.

It's also vaguely possible the pad could bind in the caliper, or you get a funny failure mode in the ABS, but any ABS failure should throw a warning light.

Or there's an outside chance of a stone under a disc shield, if your has front disc shields, which mine doesn't.

Okay, little update.

A guy at work suggested i crack off the bleed nipple and see what happens and if the disc was released.

I have just done this and sure enough, a squirt of fluid came out and the caliper released the disc and it now rotates freely.

Does anyone have any further ideas? It would appear now as if the caliper itself is not seized but like there is a one way valve in the system, letting fluid into the caliper, but not out?

I am at a loss. Please help.

Kind Regards

Garry

That was what I meant about a funny ABS failure mode. Unfortunately that has totally exhausted by knowledge of the system was thinking that a failure that trapped pressurised fluid in the caliper might be possible!

Thanks Ken. Im going to re bleed the system again and see how i get on tonight. Im hoping its something nice and simple but we shall see.

Thanks again.

Garry

My money would be on the seized caliper piston. You partly unseized it once and it worked for a bit. Take the caliper off and blow the piston out with compressed air then check piston for rust and scoring. Finally apply new brake fluid to the piston to lubricate and make sure it slides easily and smoothly.

Thanks Martin. Thats what we thought at first.

We cracked of the bleed nipple last night and now the piston appears to be able to move more freely, let go of the disc. Not sure what this means exactly tho.

Jacked car up, took wheel off.

Disc held on tight by caliper, could not turn it by hand.

Cracked off the bleed nipple, seemed to release the presure and allow the piston back in, disc now rotates freely.

Its most odd.

Garry

:iagree:sounds to me like your piston is sticking in the caliper! however i have had a similar problem on a volvo & it turned out to be a faulty brake flexi. i doubt if it is your master cylinder but i have had a similar fault on a chevette rallycar,that was not releasing on the o/s/f & releasing the bleed nipple made no difference,it only freed off when the relavent brake pipe coming out of the master cyl was opened up.hope this is of some use to you!

Thanks Mikey.

I shall continue my investications tonight. It does now appear to point to a blockage or similar in the line. A good bleed session i am hoping will fix it. But failing that i am loathed to change the caliper just to rule it out as the failed component. lol.

I shall keep you all posted.

Kind Regards

Garry

if you remove the piston from the caliper(caliper off car with brake flexi clamped) using compressed air through the hole where the bleed nipple goes you can the check the piston & caliper bore for rust or pitting,if all is spotless & smooth i would fit a new seal,refit piston & i would then rule out a faulty caliper,i agree there is to much"stick a new one on & see what happens" nowadays! how did you clamp the brake flexi,s when you first took the calipers off to paint? im wondering if you may of damaged the flexi pipe & its partly collapsed?

if you remove the piston from the caliper(caliper off car with brake flexi clamped) using compressed air through the hole where the bleed nipple goes you can the check the piston & caliper bore for rust or pitting,if all is spotless & smooth i would fit a new seal,refit piston & i would then rule out a faulty caliper,i agree there is to much"stick a new one on & see what happens" nowadays! how did you clamp the brake flexi,s when you first took the calipers off to paint? im wondering if you may of damaged the flexi pipe & its partly collapsed?

Use low pressure air or even a foot pump.

a foot pump wont be powerfull enough,(esp if the piston is seized) i always put a rag in my hand over the end of the piston & give it a few blast of compressed air until its nearly out then remove it by hand. you can pump it out whilst its on the car but i dont recomend this as you may damage the master cyl seals.

a foot pump wont be powerfull enough,(esp if the piston is seized) i always put a rag in my hand over the end of the piston & give it a few blast of compressed air until its nearly out then remove it by hand. you can pump it out whilst its on the car but i dont recomend this as you may damage the master cyl seals.

Damn lying Haynes manual!!