GQ Brake Pistons

[Trolatron]

Hi Guys,

I drove home and jumped out of the Trol after hearing the brakes squeeling and the rims were so hot I could not touch them the brakes must of been draging on the discs.
I guess your not supose to pump the brake pelad when there are no pads in there as i done that and the piston poped out.Should I be able to move the piston in and out by hand ( I tried the other side one and I cant ).
If the piston is so tight how does it retract.
Is there some way to adjust the amount of drag on the disc, the Greggory manual talks of using a spring type tool to check the tension and says to adjust the drag...

Here are pics of the parts. Are they stuffed. Am I better of finding some more from a wrecker maby..

http://i279.photobucket.com/albums/kk121/Bendero7/IMAG2180.jpg

http://i279.photobucket.com/albums/kk121/Bendero7/IMAG2184.jpg

Any advice much apreciated.

Ray

[tusman]

I have just put new seal kits through my callipers and the pistons took a little bit of playing around and some high temp grease but got them in by hand. Don't know anything about adjusting the drag sorry

[werafa]

Supacheap/repco/autobarn have a bolt in replacement unit for $50. (for a GQ)
I have located a bloke in cairns selling them for $22 each. at this price, it is not worth the $20 for the rebuild kit.

[Trolatron]

I have just put new seal kits through my callipers and the pistons took a little bit of playing around and some high temp grease but got them in by hand. Don't know anything about adjusting the drag sorry

Thanks mate, I will have to get some of that high temp grease too.
Theres no way mine were going back in easly :(.

[Trolatron]

Supacheap/repco/autobarn have a bolt in replacement unit for $50. (for a GQ)
I have located a bloke in cairns selling them for $22 each. at this price, it is not worth the $20 for the rebuild kit.

I phoned Nissan and they wanted $125 for seal kit both sides, and $154 per piston.
Repco was $18 per side for seal kit and they said pistons wrer not listed at all...

Might take them into local brake joint and see what they say.
Will go into Super cheap too.

Cheers Ray

PS. see what happens I might hit you up for more details on the pistons Werafa.

[werafa]

no worries,

will be doing them in the next two weeks with a bit of luck. this week is the control arm bushes

[Silver]

the usual grease for brake components used to be rubber grease. I've never used HT grease on rubber brake components.

[Robo]

mate it looks like you have simply melted the caliper seal to the piston.
try soaking the piston in gasket stripper or something, thinners take ya pick.
just remember to be sure it's totaly clean of anything once cleaned up.
use rubber grease only going back in.
FYI, your not supposed to use anything but rubber grease and brake fluid to be technical you be the judge.

[Robo]

Supacheap/repco/autobarn have a bolt in replacement unit for $50. (for a GQ)
I have located a bloke in cairns selling them for $22 each. at this price, it is not worth the $20 for the rebuild kit.
what is the replacement bolt in unit, your talking about

[Trolatron]

mate it looks like you have simply melted the caliper seal to the piston.
try soaking the piston in gasket stripper or something, thinners take ya pick.

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

[werafa]

what is the replacement bolt in unit, your talking about

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.

[Silver]

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

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?

[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.

[Robo]

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

[gq4200]

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.

[Silver]

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

[Robo]

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

[Silver]

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.

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 :-)

[Trolatron]

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.

[Robo]

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.

[Robo]

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.

Hi mate, not accusing anyone of any thing just trying to help find a cause for problem, I work on the Rd for buck and see brake light flashing now and then.
From what you write pads and discs past usable spec and due to be replaced, no worries cheap.
slotted rotors, pads, cal kits and fluid approx $300 diy these days, just did mine before chrissy to easy.
Pistons have kicked a little sideways they have ext a long way out, this should be nothing to worry about once rebuilt with new pads etc.
tap carefully to straighten up and it should come out, be careful not to drop it, compressed air and a block of wood to trap it inside cal assembly instead of it flying out breaking fingers ,gently, slowly does it.

[Robo]

this is a messy job air to assist piston out,cover, maybe safety glasses you don't want fluid in ya eyes

[Silver]

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.


The only rubber bits that I cleaned with kero were the slider boots. I would have bought replacements had they been available at the time.

The calipers were fine -no need to do anything with the pistons, so the 'Q got new rotors and pads, and nice slippery slide bolts again.

This was all back in Jan 2011 when I did the front swivel hubs - and that is when I glued the splits. They are still fine, and I check them when under the 'Q.

I am reasonably comfortable taking this approach with the slider boots, Robo. If the slider boots split again they'll let moisture and crud into the slider bolts, which I will pick up while under there for some other reason. As you know they won't cause a major leak of fluid for example.

[Robo]

The only rubber bits that I cleaned with kero were the slider boots. I would have bought replacements had they been available at the time.

The calipers were fine -no need to do anything with the pistons, so the 'Q got new rotors and pads, and nice slippery slide bolts again.

This was all back in Jan 2011 when I did the front swivel hubs - and that is when I glued the splits. They are still fine, and I check them when under the 'Q.

I am reasonably comfortable taking this approach with the slider boots, Robo. If the slider boots split again they'll let moisture and crud into the slider bolts, which I will pick up while under there for some other reason. As you know they won't cause a major leak of fluid for example.

Mate do what ever turns ya on.
No need to make it personal.
This is a help thread isn't it.
Our buddy is about to try something it appears for the first time that is critical life threatening work on his 4x4 .Its more involved work than preformed by yourself, so requires more attention to detail. He may of accidently sprayed cleaner onto components without reading can first and then things would have gone sideways for him.
Simply pointing out brake cleaners and properly every maintance manual ever written, something like not to be used on rubber brake components, so our mate can decide on an approach for himself that's all.
Cheers

[Bigrig]

Call me dumb, but I've sort of missed the point on the 'dangerous' part in all this ...

Please explain?? (quote Pauline Hansen!! lol).

I'm sure both you lads are heading down a certain path and sort of see no head butting at all truth be told (Silver isn't the head butting kind of guy I can assure you).

I'm more than interested (genuinely) in what you're getting at Robo - break it down for a dumb @ss like me and there'll be no room for interpretation (forum speak is a pain sometimes as no body language, tone etc comes through so people can think someone's having a swipe when in fact they are truly just on a different train of thought).

Thanks in advance!!

[Rip'n'Shred]

The dangerous part comes from the fact they are brakes and they play a critical role in doing stopping your 3t truck.

I am ex mechanic and have done many caliper rebuilds in the past. I strongly recommend you either take the calipers or the whole vehicle to a brake expert if you are even slightly not confident in what you are doing with them. Lives depend on your brakes.

Maybe, if your confident enough, get the calipers done professionally and install yourself with new fluid throughout, new pads and as said before regrease your wheel bearings yourself. Get the brake guys to check your rotors too.

And for gods sake, do it in pairs! Both front! Essential! :)

Could be expensive in the end, but worth every penny.

[Silver]

Thanks BigRig and Robo,

I certainly meant no offence Robo, and if I offended, I apologise.

In the meantime, I think Robo and I are singing from the same song sheet, except maybe whether brake cleaner spray or spray degreaser should not be used on rubber brake components. I know that kero is no good for them from personal experience.

We have in common:

Brakes are a critical system with severe consequences if things go wrong.

We noted with interest that some on this thread have used other kinds of grease in contact with rubber brake components, whereas Robo and I were both 'brought up' with the view that it is rubber grease only (or clean new brake fluid) that can be used to lubricate rubber brake components. The experience of the others seems to be different to what Robo and I were taught.

To alert Trolatron to a mistake I had made, I posted that I had incorrectly washed the slider boots in kero which caused them to swell. They subsequently returned to normal si2e. Because the pads on Silver were so worn, the boots were extended and thus split. I was unable to buy replacement boots, so superglued the splits - which has worked for a year + probably because the boots are compressed due to new pads. Both Robo and I agree it would have been better to get new boots - Robo might go so far as to say that this is essential. In my case the consequence of a boot failure is that the caliper would become sticky and wear the pad/s prematurely. I am monitoring same, and all is good so far.

I pointed out that unlike Trolatron, I did not have to work on the piston seals etc - the point being that if I had washed those in kero, and they had grown and shrunk, I would have binned them regardless as I see the consequence of failure as different to boot failure.

Robo gave some information in relation to the benefits and dangers of using compressed air to shift stuck pistons.

All the best with your repairs Trolatron - and don't forget another option is to take the whole caliper to a professional and get them to rebuild it - that's what we did with Bob's caliper, which had a torn piston seal after it was pushed back.

Rick

[Robo]

The dangerous part comes from the fact they are brakes and they play a critical role in doing stopping your 3t truck.

I am ex mechanic and have done many caliper rebuilds in the past. I strongly recommend you either take the calipers or the whole vehicle to a brake expert if you are even slightly not confident in what you are doing with them. Lives depend on your brakes.

Maybe, if your confident enough, get the calipers done professionally and install yourself with new fluid throughout, new pads and as said before regrease your wheel bearings yourself. Get the brake guys to check your rotors too.

And for gods sake, do it in pairs! Both front! Essential! :)

Could be expensive in the end, but worth every penny.

Now I read your post I think I may/should of written similar, but our mate had em already on the bench in bits.

[Trolatron]

Thanks for all your replies guys it's much apreciated, I didnt get to play in the shed today like I had planned, Ill take them into the brake guys tomorrow for inspectoin and see what they say hopefully all is ok and all they need is new seal kits put threw them and new rear pads as the front ones are only half worn ( the rear are down to 1.5mm ) :(.
I know its hard for you guys to diagnose whats going on with them from behind a computer screen and if you could only pick them up and see them in person you could diagnose problems much easyer (and my notes arn't much chop to go on lol ) but its great to get info of this forum as you guys have been there and done that and you know your Patrols where as most mechanical places know general stuff about all cars and 4bys but not all the tricks and traits from an owners day to day living with them like you lot do and it gives us little guys the confidence to have a go at fixing out own trucks and learn how they work or why they dont work:)

Enough dribble and spelling mistakes from me for now.. Ill post back on how I get on.

Cheers Ray

[Trolatron]

Ok guys I made a little video to show progress so far . Should have done it first off at start of thread ill try it next time.


http://www.youtube.com/watch?v=iQsOtYWLpPg

[Silver]

Now I read your post I think I may/should of written similar, but our mate had em already on the bench in bits.

G'day Robo and Rip'n'Shred.

Robo - we got a pretty good answer together in the end, I reckon! Thanks for your major part in it.

There are some gurus on here, I am not one of them in relation to patrol mechanicals, you may well be, Robo.

The gurus touch all the key points right up front all the time - the rest of just contribute what we can, based on experience, and it seems to be appreciated.

Rip'n'Shred - yep, for key safety systems, when in doubt, get expert help. A couple of good mechanics I know seem to forget how much they know from training and experience that helps them to diagnose and deal with problems. And they have manual skills and strength and tips and tricks as well, so they are a pleasure to watch at work.

Trolatron, all the best with your fix - be really interested to know what was holding the brake on, or why otherwise it got so hot

Out of left field, I guess there is a remote possibility that the heat is coming from a wheel bearing problem? I've seen car and trailer wheels depart from the car or trailer because the hub got so hot. Anyway, time and work will tell.

[rockndot]

I had a simalar problem also one day,
towing my Fathers big c/van out of home,(bush hill block)
when braking must have got a stone in behind the pad,
towed the van about 15 k's, noisey brake tap pedal ect, thinking that ford falcon he towes it with is gutsy.
when i stoped i had one hot wheel, one stuffed rotar, and a brake rebuild
But, slow and easy + gregorys manual, no problemo
But have to admit, i have spent plenty of time arround my mechanical mates,
so had seen heaps, but agree with others, if unsure on brakes, leave em for the brain trains.
cheers rock.

[Robo]

Up front, Sorry Rockndot.
Please anything but a Gregory manual.
Way way over priced for what's in em.
made that mistake years back (in my youth young and dumb) gregory very basic manual.
Next to useless for someone with some mech skills
Don't waste your money on gregory. my 2 c w.
There are far better manuals out there, Haynes or similar.
recently got a Max Ellery 1 as a gift for the out law for his tr##py, "opps" did I say that word.
Good manual covered alot of years many models and lots of info, diagnostics codes etc.
looks like recycled paper soft cover but the info in it impressed me. $44 on ebay.
Genuine manual probably best, and get one here.

[Rip'n'Shred]

Well done with the video, I'd never thought of that before.

Very hard to see detail but appears your doing well. Sometimes even minor pitting in the pistons can be bad. There is a lot of pressure behind those suckers.

Definitely replace all rubbers. Use wire brush to remove any build up or rust from slide pins, grease slides with rubber grease. Use clean new brake fluid on pistons to help insert with new seals, but only if you are ready to install straight away as brake fluid is hydroscopic (absorbs moisture in the air), otherwise rubber grease as previously mentioned.

Be sure to remove any excess grease. Does not play well with pads and discs.

Be a good time now to completely drain the brake fluid out of the vehicle if not already done. You don't want dirty old burnt fluid going anywhere near your rebuilt calipers. Refill and bleed very well after fitting all calipers back on. Use clean unopened bottle of correct grade of fluid. Don't mix synthetic and mineral brake fluids, big no no. don't even worry about synthetic, just good quality mineral will be fine.

The stuck piston. Usually use old brake pad against piston and use g clamp to very gently to push piston back in. if it requires force then stop, not good.

Discs. Any lip on the discs isn't good. After doing all this work, may as well get them machined. They will measure them too to ensure not too worn. Check very vigilantly for little cracks in discs, particularly the one that overheated.

Good luck. Feel free to ask any further questions. Thats what forums are for.

Mechanics do tend to forget what they have learnt. :)

[Silver]

Trolatron, your sliders in your video were much more free than mine - where crud had got in through the splits in the boots.

The video was a cracker of an idea, you seem to be a natural, and your camera person did a good job too!

[Trolatron]

:thumbup:
Trolatron, your sliders in your video were much more free than mine - where crud had got in through the splits in the boots.

The video was a cracker of an idea, you seem to be a natural, and your camera person did a good job too!

Thanks Silver, I'll tell her you said she done a good job on the camera might help me get pionts back for swiping her dish washing pad and she missed 10 minutes of her favorite tv show Bones:thumbup:

PS : not bad for a mobile phone vid :smile:

[Robo]

Yes good advise I also have read this somewhere on the mineral and synthetic fluids.
You cant even try and completely drain and replace mineral.
If mineral fluid has been in system at all it's a no go to up grade, it has to be there from brand spanking new.

[werafa]

looking up in the manual - it says to lube the assembly with brake fluid. kinda makes sense too.

[werafa]

the replacement bolt in unit turned out to be for drum brakes. The seal kit was $24 per side

[Trolatron]

Thanks for all your input guys, I have now pulled all 4 calipers apart put new seal kits threw and rubber grease in with fresh brake oil and boy what a difference its made not that I was having problems pulling up in a hurry but it just all feels better threw the pedal and I gained 2 horse power now the brakes ain't dragging:)

Really happy with the results and I now have a much better understanding of how they work.


Cheers
Ray

[Rip'n'Shred]

Well done mate. Good to see it all went well.

Just make sure you check for leaks. Brake fluid washes away with water.

[Robo]

Happy to help out.