front brakes heating up

[perelaar]

I have noticed recently my front wheels are heating up, sometimes to the point the hub is too hot to touch. So, after a check here I did the following:
- checked bearings, OK
- checked manual hubs, OK (issue occurs both in 2wd and 4wd anyway)
- checked brake pads and discs: OK (changed last year)
- slider pins on both sides are free, took them out and cleaned them just to be sure
- only thing I can think off is a piston "sticking".

Pistons are not completely stuck though: once they are sticking out a bit (used a piece of plywood to stop them popping out while I pressed the brake pedal) I can move them back inside the caliber. Needs a lot of effort, though.

So, any tips or ideas? Is this something that can be repaired (new pistons, seals?) or should I bite the bullet and buy new calipers? Or am I thinking in a completely wrong direction?

 

[panelbeater]

when wheel up does it turn freely if not piston rubbing so work the piston in and out the full motion untill it goes in freely,use a cleaner to ease the job.

 

[rustic]

when wheel up does it turn freely if not piston rubbing so work the piston in and out the full motion untill it goes in freely,use a cleaner to ease the job.

Sound advice.:thumb2

Are both sides the same? normally one side will start to sieze before the other, unless they have been like this for some time.

I guess it also depends on how often you use the brakes, light braking or heavy braking.

After freeing them up, check the pistons a few days later, to see if you have any fluid leaks, as the seals might be getting worn.

When you think about how the brakes wear, as the pads wear, the pistons are going into the bore that they haven't been in for a very long time, and if the pads are changed early, maybe the piston is going into the bore for the first time since the car was built so there could be corrosion in there...
A cheap fix, replace the pads early...:nenau

 

[Banshee]

I had this and then before I could fix it I lost a pad :doh

 

[perelaar]

Hmm - when I got the car the pads were completely worn, and the disc half the allowed thickness (according to Nissan manual).

I'll work them in and out a few times, could do without the expense of new callipers now. But I know I'll have to change them sometime soon.

 

[perelaar]

Panelbeater, I presume you mean brake cleaner?

 

[rustic]

Hmm - when I got the car the pads were completely worn, and the disc half the allowed thickness (according to Nissan manual)...

Sounds like the pistons have been where they wern't designed to have been.
Have you fitted new discs and pads at some point?
Rustic

 

[solarman216]

you can take the pistons out and clean everything up and fit new rubbers, readily available from break parts superstore, they are a bit fiddly to get back in though, Rick

 

[perelaar]

Yes, new discs and pads last winter. Old ones were very thin, both discs and pads. Unevenly worn as well, slider pins were stuck then.

I'll get a set of rubber seals then.

 

[macabethiel]

Caliper Pistons.

To check the pisons are not sticking have you tried pushing them back in with the bleed nipple open ? They should be easy to push back with your fingers when the nipple is open.

On the few times I have replaced piston O rings mainly on BLMC Minis the bore has been corroded near the dust seal areas. I removed the big rust lumpy bit near the edges with a bearing scraper and then some 400 grit. Obviously if main part of the bore is pitted new calipers are the only way but only ever had to replace one caliper in my life. It was a rear caliper on a Merc 260E and the cast iron caliper was crumbling like a biscuit! Turns out Merc had a bad batch that was not very resistant to cement slurry!

 

[perelaar]

Haven't tried with the bleed nipple open - I was afraid it would shear, following reports here on the forum. I did have the reservoir cap off while pushing pistons back in.

 

[macabethiel]

Brake bleed nips

You really need to open a nipple, one day you are going to want to bleed the brakes or change the fluid.
I have found some prior wire brushing & soaking with plus gas then a tap on the nipple with a hammer usually works. I use a ring spanner of the right size and it is a long time since one broke on me.
Luckily for me an Easyout tool worked last time but it was a good sized front nipple. Jarring the thread often does the trick with a rust thread.

 

[don simon]

Panelbeater, I presume you mean brake cleaner?

A trick I use on disc brakes on the bike is to use brake fluid on the pistons to free them up. You can be safe in the knowledge that the seals aren't going to be corroded. It works on bikes, so no reason not to work on the car.

 

[panelbeater]

all sound advise.

 

[rustic]

Caution:- if you are pressing I the piston with the nipple open watch where it goes...

 

[solarman216]

do not bother with trying to open the nipple, remove the caliper to work on the bench with a brake pipe clamp on the hose, only use brake fluid and nothing else on the pistons and bores and rubbers, once the pistons are in push them fully home and reconnect the pipe, place a lump of wood that = the thickness of the disk and the back plates of the pads into the caliper, remove the clamp and press the brake pedal repeatedly till it goes hard, now with the hose on the caliper at the top push the pistons back (I use a G cramp as you cannot do it by hand) this pushes any air back up to the master cylinder, most times pushing one piston does not have any effect on the other but some times the second pushes out, so this needs to be stopped with a block, (this could be caused by a lack of free play on the brake pedal shaft so not allowing the fluid to return to the cylinder freely, another possible cause of brakes binding) pushing the pistons back this way bleeds it, re assemble the caliper and pads, repeatedly press the brake till hard, job done, Rick

 

[Blocky10]

Sounds like you've done that a few times Rik! [emoji38]
Would the advice be the same on mine do you think?

 

[solarman216]

Sounds like you've done that a few times Rik! [emoji38]
Would the advice be the same on mine do you think?

Yes as basically the same system poss pads and calipers slightly different but operation identical, Rick

 

[Blocky10]

Cheers Rik. [emoji106]

 

[perelaar]

Had the chance this weekend to apply the above advice. Cleaned the pistons as far as possible with brake fluid, and worked them in and out a good few times.

I noticed one piston in both calipers is reacting slower, probably those causing the binding. For now the issue is manageable; I drove 150 miles this weekend and did not have an issue. But made up my mind: if the car passes the homologation check next week (meaning a huge road tax reduction) I'll splurge on new brake lines all around and new brake calipers.