Caliper piston seal leak

[Jon Wildsmith]

Inspecting the underside of my 80, I noticed it was wetter than I'd like around the drivers side front axle swivel. Nothing too bad, so I'll use it for now. Fast forward a week and I notice the brakes pulling to the left and I'm suspicious of that oil I saw. Another look underneath and I see some fluid on the brake caliper. Off with the wheel and it's clearly a problem in the brake caliper not the inner axle seal.

Popped the dust boots off and could see fluid the wrong side of the seal around the upper piston but not the lower.

Pushed the piston out and the failure in the rubber seal is easy to see:

These were new seals and pistons fitted 19/12/23 so not very old. Nothing obvious wrong with the piston to have worn the seal, so at the moment I'm assuming there was something abrasive trapped in there somehow to cause that.

Rebuilt with new seals and boots and will keep an eye on it. Fluid looks like it needs flushing through again as well.

 

[felix2566]

Could some of the corrosion from the outer part of the bore have got caught in the seal?

 

[Jon Wildsmith]

There's only light surface corrosion, the camera and being wet are making it look worse than it is. There was also some red vegetable grease under there that's now making it look a lot dirtier.

I'm also wondering if the dirty fluid that was found in the caliper when the piston was out reflects the state of the brake system, or is from external contamination through the leaking seal - It's been through some deep water and lots of dust in recent times, plus there was that veg grease.

 

[felix2566]

The red grease is normal to use under the seals, I've used it plenty of times.

Yea was looking at the dirty oil in the bore and wondering if that was in there before you pulled the piston out. You'd expect the hydraulic pressure in the system to be enough to keep water out. Were the pistons ok?

 

[Shayne]

Red rubber grease is supposed to be kinder to seals and waterproof . Looks to me like that is a manufacturing fault , spider fell in the during molding process or something else 1 in a million daft but not worth overthinking on .

 

[Towpack]

I can't really see that fluid contamination, which looks like rust particles, coming from the system. Some of the OEM pipes on the 80 are steel but I'd expect them to rust from the outside in resulting in leaks elsewhere. Perhaps it's possible if fluid can get past the seal so can water, especially when wading. Either way it looks like it's been caught in time to save the caliper and piston.

 

[Jon Wildsmith]

I packed the boots with grease to slow down the inevitable corrosion on the extended part of the piston.

Probably a one off.

I just thought it might be of interest to others.

 

[kano]

make sure you use brake fluid for assembly and not any other types of grease as it can make the rubber swell

 

[Shayne]

He already said "rebuilt with new seals" ratatatado .

 

[Juddian]

Don't know why but i've never managed to successfully reseal/rebuild calipers, invariably i've taken action on calipers due to a piston seizing too tight to do anything with, kudos to anyone who can DIY refurb, tried it several times and always end up with a leaking seal, so exchange or new calipers every time now.

Re-rubbered hundreds of master cylinders and drum brake slave cyls as well as clutch hydraulics over the years when money was tight and hadn't the funds for replacement cylinders, just can't do calipers right for the life of me.

 

[Shayne]

Bigg Red

A leading UK Brake Caliper remanufacturing and component specialist

www.biggred.co.uk

 

[felix2566]

Used Bigg Red so many times for parts and full strip/rebuilds of my calipers, always done a good job.

Couldnt find any pictures of the LC ones I had done, so have some off my Evo 5!

 

[Juddian]

I would have used Big Redd for the front calipers on the 120 but didn't want the vehicle off the road for a week or more.
I offered the old ones here free in case one of our brethren wanted a pair to send to BR, or a still useable pair to get someone out of the mire, indeed soon had a message and they went off to Oswestry IIRC.
It was the lower inner piston causing trouble which seems to be the case on most.

 

[thelal]

when was last time you changed our the brake oil? (is it DOT 3/4/5?)

 

[Jon Wildsmith]

I've never done a full fluid change as such, but I've pushed a lot of fresh DOT4 fluid through bleeding each calliper after rebuilding those. I'm aware of rumours these only like DOT3 but that seems to be anecdotal, possibly based on old false information from an unrelated vehicle ...

 

[Shayne]

Does it not say DOT3 or higher on the cap or wherever else i read it ?

 

[Jon Wildsmith]

What, you expect me to have read the instructions Shayne. Be reasonable (Joke!) Yes, pretty sure DOT 3 or higher, but it has been suggested (mainly on the internet) that the rubber seals in old Toyotas' don't like DOT4.

 

[Shayne]

When 20 years of crap is flushed out and replaced with new fluid is it any wonder leaks are noticed for the first time .