rear brake caliper dust boot replacement

[adg1]

Hi

Done a really stupid thing and put a small snick in the rubber piston seal of the rear caliper (dont ask!)

Anyway, where can i get one and how to fit?

 

thanks.

[petrolbloke]

Try Brake Parts for Cars (brakesint.co.uk) or Home - Bigg Red for a replacement seal.

 

As for fitting, I haven't done one before so can't really help there but if I needed to I'd be looking at YouTube videos. I imagine it would be similar for most cars.

[adg1]

Thanks, i was hoping it was an easy job ie pull off dust boot, replace in situ but it seems the caliper has to be rebuilt to replace this seal 😞

[kedambarai]

Done that (manual handbreak). By far easier is to remove brake line and handbreak cable, and replace the boot and seal on the bench instead of swearing under the car. I'm not sure what do you mean by rebuilding (you do not need to take apart the handbrake system), there are only three parts involved beside the caliper itself - the piston, the seal and the boot. You need a tool to wind back the piston and a plug to seal the brake line while the caliper is away. I used angle grinder wrench (one that you use for removing the cutting disc), the notches indeed match VAG rear brake piston cutouts  

 

As I remember the job was to release the boot outside rim from the piston, work handbreak lever until the piston pops out of its thread, remove the boot from the caliper along with the piston, change the seal. To assemble you grease the piston, install the boot into the caliper, force the piston into the boot outer rim halfway and carefully work the piston onto the handbrake thread. Use the tool to screw the piston in. You later fix the boot outer rim to the piston top edge, when it's halfway in.

 

Don't forget to bleed the brakes after reassembly!

 

Good luck!

[adg1]

26 minutes ago, kedambarai said:

Done that (manual handbreak). By far easier is to remove brake line and handbreak cable, and replace the boot and seal on the bench instead of swearing under the car. I'm not sure what do you mean by rebuilding (you do not need to take apart the handbrake system), there are only three parts involved beside the caliper itself - the piston, the seal and the boot. You need a tool to wind back the piston and a plug to seal the brake line while the caliper is away. I used angle grinder wrench (one that you use for removing the cutting disc), the notches indeed match VAG rear brake piston cutouts  

 

As I remember the job was to release the boot outside rim from the piston, work handbreak lever until the piston pops out of its thread, remove the boot from the caliper along with the piston, change the seal. To assemble you grease the piston, install the boot into the caliper, force the piston into the boot outer rim halfway and carefully work the piston onto the handbrake thread. Use the tool to screw the piston in. You later fix the boot outer rim to the piston top edge, when it's halfway in.

 

Don't forget to bleed the brakes after reassembly!

 

Good luck!

Ah thanks for that. I've got the correct wind back tool & have a hydraulic hose clamp or is a plug better? Any issues bleeding the caliper with the ABS set up?  i can't see air could get anywhere the abs pump...  i'm assuming pre filling the caliper would be a good idea?  only other alternative is a refurb caliper from Autodoc, would cost me about £50 if they took back my old caliper.

[xman]

Around 15 years ago, changed the rear pads on my Seat Alhambra thinking I could wind back the pistons using a screwdriver or a pair of grips. Car had done about 85,000 miles from new. After struggling for a few minutes, the screwdriver slipped, caught and tore the rubber boot a few mm. Next day, I bought a wind back tool and finished the job but didn't replace the boot. I ran the car for another 10 years and 65,000 miles without any issue with the rear brakes. The car was always parked in a garage and rarely outside so that may have helped.

 

Wouldn't do that nowadays btw.

 

If the cost of a replacement caliper is only £50, I wouldn't faff about rebuilding it but simply replace it.

 

Edited 4 March by xman

[kedambarai]

21 hours ago, adg1 said:

Ah thanks for that. I've got the correct wind back tool & have a hydraulic hose clamp or is a plug better? Any issues bleeding the caliper with the ABS set up?  i can't see air could get anywhere the abs pump...  i'm assuming pre filling the caliper would be a good idea?  only other alternative is a refurb caliper from Autodoc, would cost me about £50 if they took back my old caliper.

No worries, the air won't get upstream the brake line, unless you leave the brake line open upon removing the caliper (and even then the air will not go upstream). The moment you undo the brake line bolt, it will start dripping and you want to plug the line immediately. The fluid will come from the brake fuel reservoir in the front, make sure it's full before you start the job and check it as frequently as you lose the fluid for some reason. If you leave it unattended, there is a chance of emptying the vessel and subsequently air in the system (another magnitude of bleeding the system, you don't want that).

 

The brake line itself is bolted to the caliper with a banjo fitting, so you can plug it either with a suitable plug (ca 10mm, for instance wind some electrical tape on the pencil) or a bolt, 2 washers and nut. I wouldn't use hose clamp - the line is stiff like a stick and if you have some badass hydraulic clamp, I reckon you can damage the line. It's not super critical to fully close it, few drops a minute is ok (put a tray under it). As long as the front reservoir is full. Perhaps you cah use some rubber blocks to close the banjo fitting from both sides and clamp it, haven't tried that.

 

I didn't see a way to pre fill the caliper as I was doing the job first time and almost danced a voodoo dance to stretch the boot onto the piston... Looking back, it's a 30 min job   Plus when you rewind the piston, it will make the prefilled fluid come out and create a mess.

 

After you reassemble the caliper and reattach the brake line, just use the bleeding valve, it will fill allright. (Naturally, you first rewind the piston and then connect the line, otherwise you will pump the air upstream  ). Can't overstate it - check again the front fluid tank, it will use like quarter of a tank or so to fill the caliper.

 

The seal repair kit on ebay is something like £6,80, you need some brake fluid too, I reckon it's worth DIY to get some tinkering experience.

 

Cheers!

 

[adg1]

Thankyou Kedambarai but i think the best way forward is for you to drive down to sunny Cornwall and do the job for me, that way i can see first hand what you mean!!!! 

 

I ve replaced seals on motor bike calipers, many of which don't even have dust boots, will be first time on a car though.

 

Just ordered a seal kit!  how bad can it be? i mean i ve got AA at Home!!!