GQ Brake Pistons

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Originally Posted by Robo

what is the replacement bolt in unit, your talking about

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Haven't seen it yet, but I was told that you use a 10mm spanner to undo the brake line, and then 2 more 10mm nuts, and the whole piston unit comes out. Was told this by the mechanic who told me to get it fixed (safety check).

I also agree about using rubber grease. ever seen what happens to inner tube rubber if you use it as a seal for a petrol can etc. ?

I also agree with Robo that the black cake should clean off, and as long as the chrome is not scratched or pitted, the piston is re-useable.

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Originally Posted by Trolatron

Thats probably right to mate as the rim caliper and even the tyre were incredibly hot. Any ideas what caused them to get hot.

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The caliper and thus the pads don't have a lot that pulls them back out of contact with the rotor after you take your foot off the pedal - just the tension in the piston rubber, and the lateral movement in the rotor bumps the caliper back too.

the caliper slides on two bolts - the same two bolts that locate the caliper to the rest of the brake. Crud builds up between the two bolts and the holes in the caliper, to the point where the brake pads stay in contact with the rotor.

Now, the only time I have had a disc brake get anywhere near as hot as you describe, a stick had trapped a rubber brake line, and pinched it closed. Fluid went to the piston, but could not escape and the brake was locked firmly on.

It could be that there is something in your brake hydraulics that is not letting the fluid back to the master cylinder and the pads/caliper to retract from the rotor. It could just be that the slides mentioned above need some Lurve :-).

If it was as hot as all that, might be worth considering regreasing the wheel bearing?

Thanks Silver Ill try cleaning all the parts up grease them up and see if they feel freeyer ( is that a word) and I will have a go at regreasing the bearings too.

The caliper assembly slides bolts should be rubber greased also.
The only time I have seen brakes as hot as I read above have been on a trailer,hand break left on for about 8k,
you don't drive with 1 foot covering the break do you?.
seen, followed this break lights going on/off repeatedly, "driver unaware".
this could lead to hot breaks.
or simply 1 to many hill descents.
recommend drain brakes completely of old fluid, it would simply be fried.
if the brakes are as bad as I think, I'd possibly be replacing everything.
pads, discs, seals, hoses, fluid and wheel bearing grease.
to melt caliper seals is one hellva task.
Anyway Cheers

I would think the heat is pretty normal... I got home from a half hour drive today and all 4 rims were Very hot to touch.. I could feel the radiant heat coming off them in the garage... and thats just normal driving on the bitumen and a 30 deg day.

G'day GQ4200, looking back through the posts, one of the responses was that the black material on the piston was melted seal.

Hi mate,
yeah your right they can give off a bit of heat at times, go back and take a look at the pic our buddy posted and you'll clearly see something has been fried onto the piston, clearly more than a little hot.
recon the have been dragging for sometime and become super hot.
Cheers

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Originally Posted by Trolatron

Thanks Silver Ill try cleaning all the parts up grease them up and see if they feel freeyer ( is that a word) and I will have a go at regreasing the bearings too.

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Be careful what you clean the rubber bits in. I used Kero. Bad move. Maybe less of a problem if you work super fast, don't know, and won't be experimenting to find out. They grew to about 1 1/2 times.

Happily they returned to normal si2e and texture when the dried out and with a little more time :-). You can buy brake cleaner in spray cans. I don't think that spray degreaser upset them either, but kero was bad news!

If you notice splits in the boots that cover the slider bolts - you may be able to buy replacements. I couldn't find any at short notice, and glued them back together with super glue. So far, so good :-)

Yep they were super hot Im talking loose your finger print if you touch it hot. I wasnt resting my foot on the brake pedal Im too lazy to keep my foot up there when crusing the highway
see I was maby 10 minutes from home and I could here a squeel from the brakes so I would dab on the pedal and it would stop then a few ks it would do it again and that happened 5 or 6 times so had a look at home and found all was cooking.

I pulled the other side caliper off today and I would say the piston is pushed out as far as the rubber boot will extend and I cant push it back in by hand...is that normal?
Also opened front caliper on one side and that piston is also unmovable..Ill post up more pics tomorrow.

the rubber bits are disposable once damaged in any fashion.
cleaning product will stuff em completely forget it.
taking chances with your or others lives for way less than $100 dollars !!!.
don't do it bud.
Happy motoring, not condolences.