Seized Caliper/Piston Tip

[frank rabbets]

The pistons in my rear calipers seized probably explaining my 2 mpg less fuel consumption. The trick is to take the caliper off, take the disc off, take the pads out of the caliper, bolt the caliper back on and press the piston out with the brake pedal. I was hardly strong enough; it was really stuck solid. I've now stripped them and soaked them in acid to get all the rust off. Also I've refaced the discs on the lathe and all should be as good as new soon.

Frank

 

[adrianr]

Well done Frank.

If you put some red rubber grease under the rubber boots it'll help keep them sliding.

I give mine an inspection and top up every 6 months. BTW - a small syringe (no needle) works really well.

 

[frank rabbets]

Hi

Yes I have some original red girling grease. No rust on the sliders but dry. 16 years old and 130,000 miles so not bad going.

Frank

 

[frank rabbets]

More tips!

The main piston on the last caliper was seized due to rust creeping underneath the dust cover bellows and compressing the piston sideways. I had a job getting the piston out even using the brake pedal! Also the two sliding rods were seized. Upon inspection I was surprised to find that one rod runs inside a rubber lining. This is shaped like a test tube with bellows at the top. The other rod runs directly in a bore in the caliper. When you view the side of the caliper you will see two round rubber bits, one is a plug for the bore in the caliper and pops out. The other is the bottom of the "test tube". This is removed when you have the caliper in two halves on the bench. Using 6mm round bar you can push this end up inside and partially turn the "test tube" inside out. Pulling at the bellows at the same time pops the whole out. Now here's the interesting bit. Rust had crept between the rubber tube and the caliper, compressing the metal rod and seizing it. The bore in the caliper is .5 inch so a quick go with a drill cleans it out. Cleaning all bores and rubbers and assembling everything with rubber grease is the fix.
Another seizure point was the pads. These slide stainless steel spring clips. Rust gets behind the these and seizes the pads. The cure is to take these out and file the rust out of the relevant grooves and faces of the caliper.
That's 3 potential seizure points:-
1. Main piston.
2. Sliding rods.
3. Brake pads.

Frank

 

[Chris]

But, just to check Frank, both top and bottom have rubber bellow. One is part of the test tube or rubber tee-tee and the other stand alone with opposite the removable end plug. I have come across several trucks with the second little rubber bellows missing. That's where the crud creeps into the non rubber slide pin. I know what you mean about test tube slider though. You can take this out and put it back in without taking the caliper apart though, but it's easy to get it twisted i there. If it's not lubed then when you undo the sliding pin it twists the rubber. If this is not straightened out again then it leave a dirt channel. TBH I think that the whole thing is a pretty crap design. I have had Toyota almost since I learned to drive and have worked on them all. The brakes are something that have been consistently poor. Sitting where they do in all the muck, you'd have thought that they would have designed something better. Oh well. I just grease that little tube up well and it slips into the hole in the caliper. I have had many where the PO has filled that tube up with bloody copper slip (not grease in my view) which sets hard and binds the moving pin.



Chris

 

[frank rabbets]

Thanks Chris

Both top and bottom bellows are present on both calipers. I did indeed twist the rubber when I unscrewed the appropriate rod. I thought it felt a bit funny but luckily it didn't tear the rubber. It was completely dry whereas all the other pins had nice clean grease on them. I am sure this was assembled from new without grease. Is it a Girling caliper? It has a G on it.

Frank

 

[Chris]

You were lucky indeed. They tend to twizzle the bellows off the end of the tube. I keep spares in as I have done so many I know what to expect.

I occasionally give my brakes a work out. I pull the pad one one side and slip it back in longways to block off one piston then pump the pedal so that the other piston comes out. I do this for all four pots. Part of the problem for brakes as they they don't get out much!!! Keeping them active helps. And as several have said, keeping some strawberry grease in there is a good idea.

No idea if it's a Girling caliper. Never thought about that. I guess someone has to make them. I have a full used set sitting here awaiting a rebuild as spares or sale.

Chris

 

[frank rabbets]

Same thing used to happen with my audi so I used to drive along every so often with the handbrake on hard untill I could smell burning. I never had a problem after this. Doesn't work with LC though!

Does the ABS work in reverse?! See my latest topic.

Frank

 

[adrianr]

Not sure on the reverse + ABS thing

I also now give the brakes a really hard time once a week (whoever said to that thank you!) - that way they are getting hot and used - especially the rears.

 

[frank rabbets]

Just another thought. It does not take much for the any caliper not to work properly. The inner seal is designed so that when you release the brake pedal there is just enough spring in the inner seal to pull back the piston by a whisker thus fully releasing the pad. Just a bit of rust around the outer bellows seal, compressing the rubber, will bind the piston and stop the inner seal from pulling the piston back. Just because it is fairly easy to push the pad and piston up inside the caliper does not mean that the inner seal is working fully.

Frank