Full Rear Caliper Strip down and rebuild. Handbrake issues

[Steve Green]

This guide has already been successfully followed by several forum members. It is not foolproof, I have found calipers that are too badly seized to recover. They can still be used as exchange units for the professionals to repair.

But first a preamble about Handbrake cables.

If your car has just failed its MOT on handbrake efficiency, the MOT tester probably said the handbrake needed adjustment. Proceed with caution, its probably the calipers but he cant tell for certain, without taking the wheels off.

Handbrake cables are frequently adjusted and handbrake cables replaced because the autoadjuster, hidden inside the rear caliper is seized.

Handbrake cables are known to have seized, usually due to water ingress. Don't take an average mechanics advice blindly, We on this forum are the expert amateurs, there are very few expert professionals, and they can be found on this forum too.

To replace the handbrake cables you need to lower the fuel tank. I have not attempted to write that 'How To' thats for someone else to do.

If you are advised that your handbrake is innefective, the first thing to do is to jack up the back of the car, support it on stands, and remove both rear road wheels. This will expose the rear of the caliper. With the handbrake lever off, remove the clips and pins that hold the cable to the caliper crank. Now you can check the cables. both sides must move freely inside their sleeves. If they do, they probably dont need replacing. It is possible but very rare, that a cable will stretch. It is impossible to check unless you remove them or have fully working calipers.

Now to the part of the caliper, where the problems occur. There is no worthwhile half way. Operate the crank on the caliper, it should move by hand and it should move through a minimum of 30 deg. If you remove the pads, it should move through close to 90 deg. To put the pads back, you will have to remove the caliper to wind the piston back in, but you were going to fit new pads whilst youe were checking werent you?

If the crank does not move or is stiff to return it's time to follow the rest of this guide and either get some new or refurbed calipers. Aways do both sides at the same time, the same as you would with any suspension component or tyre. Start with the caliper that moves the easiest, it will be easier to dismantle and you will learn from the process.

Following this guide, that I hope is complete, takes you inside the rear caliper to the problem area.

Whist I have posted several pictures, it is best to take pictures of your own as you go along. That way you will have your own record of the way things looked before dissasembly and perhaps help others with your experience.

Complete strip down requires special tools or adapted standard tools and is probably beyond the average mechanic without them. Consider purchasing new or recon calipers before proceeding if you are in any doubt.

Tool Numbers: Toyota 09719-00020 Caliper rewind tool or Halfrauds or similar


Toyota 09756–00010 Nut, Autoadjuster compressor


You will also need a pair of long nose circlip pliers looking like either of these. They need to get 50mm down inside the caliper so need to be narrow, long and stiff. Buy the best you can afford.



Brake caliper cleaning fluid
Millers Oils Red rubber grease (compatable with rubber, helps fit new seals)
Complete Rear Caliper seal kit and a set of rear brake pads to suit your vehicle.

Proceed generally as if changing the brake pads:
 
•   Using a brake hose compression tool, seal the flexible brake hose.
•   Unscrew the brake hose banjo bolt retaining the gasket for re use, if damaged replace. Catch any spilt fluid for disposal.
•   Remove the caliper by unscrewing the lower bolt to the torque plate and lifting it away. The torque plate can be remove sepaerately if reqd.

Dismantling On a clean work bench:
The caliper will contain trapped brake fluid!

•   Examine the caliper for any external signs of damage or wear, especially on visible seals.
•   Remove the rubber dust boots and sliding bushes.


•   Tap out the main pin boot.


•   Using a caliper piston removal tool 09719-00020 unscrew the piston and remove its outer seal.


•   Pry out the piston seal from the bore of the caliper.

The following is the most difficult part and ideally needs a special tool 09756–00010 .


•   Remove the adjusting bolt assembly using a special tool 09756–00010 or a home adapted tool to compress the auto adjuster internal spring and release pressure on the circlip. Failure to do this will either damage the circlip or allow parts to fly around the workshop.


•   Using circlip pliers release the circlip securing the parking brake auto adjuster assembly from the cylinder.






Back to the easy stuff
This is perhaps the area that causes most problems as the internal parts corrode.

•   Pry the torsion spring from the parking brake crank and unbolt the crank from its shaft.


•   Remove the parking brake boot and its shaft and bearing. This is the most likely location of any corrosion that prevents the correct operation of the handbrake auto adjuster. The bearing may not be supplied with your refurb kit, clean it thoroughly in situ and lubricate sparingly with lithium grease.




•   Clean up the autoadjuster components. Note that the small Oring needs replacement.


•   Remove the brake bleed nipple.
The caliper body can now be cleaned thoroughly and painted if requited. Reassembly using new parts where possible:
•   Install the brake bleed nipple.
•   If available install a new parking brake crank bearing and its shaft and dust boot fully into the caliper.
•   Install the parking brake crank and check there is clearance between the parking brake crank and the caliper.
•   Fit the torsion spring.

Back to the difficult bit

•   Reinstall the auto adjuster assembly complete with a new O ring. It must be aligned correctly and must be securely retained by the circlip.

Easy bits again

•   Check that the parking brake mechanism works correctly by operating the handbrake crank and observing that the internal bolt moves smoothly.
•   Install new piston seal in the cylinder, and fit the piston along with its protective boot.
•   Install new sliding pin boots snugly into the caliper.
•   Install the dust boot with the flanged face inside.



•   Reassemble the caliper onto the torque plate as for changing the brake pads.

•   Re fit the brake hose and bleed the brakes.

Finally

•   With the caliper fitted, attach the handbrake cables and tension them so that there is 1.0mm clearance between the handbrake crank on the caliper and its stop pin.

Sources: various Toyota manuals and those from other car manufacturer's workshop manuals .
Thanks to Alucard7002 from Rover 800 Enthusiasts Forum and Eric Southers for some of the pictures.

[Anonymous]

Spot on   s:wink: :wink: s:wink:  

I nearly replaced.my handbrake cables because of seized callipers, after freeing them off handbrake adjustment and performance returned to as new with plenty of thread left for further adjustment. Unfortunately after freeing off three or four times it became aparent that the callipers required a complete overhaul, I opted for the Big Red re-furb simply because after 35 years in a workshop I had enough of the in depth repairs and also I wanted the polymer coating.

Well done on the guide and I'm sure it will save the more confident, competent members a lot of money.

Les

[Steve Green]

As my post on caliper rebuilding has been moved to How To, I cannot add this to my post.
The tool 09756-00010 is £4,56 + Vat, 2011 price. That makes it £ £5.47 delivered by post from my Toyota dealer. Well worth the investment, but dont loose it as its quite small and black. I keep mine with a large cable tie through its middle.


Perhaps the mods can move this to the How To thread to keep the info together.