Caliper Sticking -Front Driver's Side Audi A4, 2009

[audiwaterpump]

Morning,

Car is an Audi A4 2009, 2.0Tdi, 4-door.
The front driver's side caliper seems to be sticking. It was almost impossible to turn the tyre by hand.
Managed to push the caliper piston back, but it was very difficult to begin with, but gradually got relatively easier.

The caliper slider pins (see photo) should they be lightly greased to help movement? - Some say they should be greased and some say they shouldn't.

Thanks

 

[NHN]

I always add some grease to the sliders tbh, but sometimes the caliper piston just needs working back & forth to make it operate normally, however if it's that tight then I'd buy a refurbished unit & swap as doing a removal & repair can leave you stranded if the caliper isn't salvageable when repairing, don't forget to grease the sliders on a refurb unit also before fitting & of course test movement on new unit before removing old & fitting new.

 

[spartacus68]

Yes - if it's sticking, its probably corrosion under the dust sleeve that's the real cause forcing the dust sleeve to stop the piston retracting. You can try a full rebuild, or replace. Add some red grease under the dust sleeve, either way.

Grease for the sliders - light smear of ceramic brake grease.

 

[audiwaterpump]

If the caliper needs to be replaced, is there a diy video on how to replace the brake caliper. I couldn't see a bango bolt on these.

 

[rum4mo]

I tend to use only silicon grease on these guide pins as they move through rubber mountings/dampers, scrub them clean using a green pad for example as that black stuff at the inner end could end up restricting their smooth movement through the mountings/dampers.

 

[JontyMort]

If the caliper needs to be replaced, is there a diy video on how to replace the brake caliper. I couldn't see a bango bolt on these.

There isn’t a banjo bolt. The hose screws into the caliper. This makes it slightly awkward removing the caliper with the hose in situ, as you have to avoid straining the hose, but it can be done. Clamp the hose - using proper hose clamps - then slacken the union at the caliper end while the caliper is still firmly on the bracket. You may have to temporarily re-fit the slide pin bolts for this purpose. Then you have to screw the caliper off the hose - rather than the other way around - while bearing the weight of the caliper. Don‘t forget that means turning the caliper clockwise, so to speak.

An alternative - depending on how old your hoses are - is to take the opportunity of replacing the hose at the same time. If you do that, you don’t need to worry as much about straining the old hose. You’ll still need to clamp it, though. When you’ve fitted the replacement caliper, fit the new hose to the caliper and feed it into the right position - the bracket/grommet arrangement is usually obvious. Then all you have to do is clean up around the top union, slacken it, whip off the old hose, and re-fit the top union. Then bleed the brakes (you should be OK just doing that corner).

 

[audiwaterpump]

Where's the best place to buy a refurbished front caliper, and roughly how much do they cost?
It's a heavy casting and has these characters on it:
750
SP1
GJS

 

[spartacus68]

It's cast-iron. Autodoc have them - ATE version is £108 or Textar £111 plus postage. I'm basing this on 8K2 2.0TDI (163PS/120kw) saloon. Double check with your registration.

 

[audiwaterpump]

"Clamp the hose - using proper hose clamps - then slacken the union at the caliper end "

If you hold down the brake pedal and keep it held down with a prop or false-leg, would that stop the brake fluid leaking out when the brake hose is removed from the caliper?

 

[rum4mo]

I used to remove the brake fluid reservoir cap, place a bit of plastic over the opening then refit the cap, that if done correctly will stop the fluid running out of an open bit of pipework.

Nowadays, since I bought a used 6R Polo brake master cylinder complete with reservoir, I sealed the vent/slit in its reservoir cap, and just fit that to any of our VAG cars when working on the brake fluid lines - and use the reservoir with all fluid openings blanked, as a "test rig" for my many Gunsons Easybleeder as checking them out before using them certainly beats the agro when the Gunsons Easybleeder leaks! That just leaves the hall sensor - just in case my wife's 6C Polo has any issues in that area!

That sealed cap has RED tape on it so that it will never ever stay on a car after it has been put back on the road.

I also finally worked out which of the 2 seals that cap fit the Gunsons cap for modernish VAG cars is the correct one, ie the one that seals properly!

 

[rum4mo]

"Clamp the hose - using proper hose clamps - then slacken the union at the caliper end "

If you hold down the brake pedal and keep it held down with a prop or false-leg, would that stop the brake fluid leaking out when the brake hose is removed from the caliper?

It should do as the fluid reservoir is cut off from the car's fluid lines, but sealing the cap with a bit of poly will save you trying that.

 

[JontyMort]

I used to remove the brake fluid reservoir cap, place a bit of plastic over the opening then refit the cap, that if done correctly will stop the fluid running out of an open bit of pipework.

Nowadays, since I bought a used 6R Polo brake master cylinder complete with reservoir, I sealed the vent/slit in its reservoir cap, and just fit that to any of our VAG cars when working on the brake fluid lines - and use the reservoir with all fluid openings blanked, as a "test rig" for my many Gunsons Easybleeder as checking them out before using them certainly beats the agro when the Gunsons Easybleeder leaks! That just leaves the hall sensor - just in case my wife's 6C Polo has any issues in that area!

That sealed cap has RED tape on it so that it will never ever stay on a car after it has been put back on the road.

I also finally worked out which of the 2 seals that cap fit the Gunsons cap for modernish VAG cars is the correct one, ie the one that seals properly!

Yes, clamping a plastic sheet over the reservoir reduces loss to virtually nil. I’ve moved on from Gunsons to a Sealey kit. It’s one of those that looks like a weed-killer pump . I finally did my fluid change a few weeks back, and it makes a hateful process bearable - worth the expense IMHO.

 

[rum4mo]

Yes, clamping a plastic sheet over the reservoir reduces loss to virtually nil. I’ve moved on from Gunsons to a Sealey kit. It’s one of those that looks like a weed-killer pump . I finally did my fluid change a few weeks back, and it makes a hateful process bearable - worth the expense IMHO.

Many years ago I changed from using a spare wheel with pressure reduced, to an old smallish Hoselock(sp) garden sprayer - then a few years ago I changed again to using a cheaper brand bigger - higher volume garden sprayer and I've even added in a "low pressure range" gauge. Doing all that including being able to dry test everything just prior to use, got rid of the most annoying aspect of the Gunsons kit.

But yes, for anyone who is just about to start doing their own brake fluid changes, the kit you describe is certainly the smart choice, I've even bought in a cheap vacuum bleeder - that works well when modified an old Gunsons metal reservoir cap to allow me to add in an "auto top up" that actually works with the cheap vacuum bleeder kit, for those without an air compressor there is also the MityVac hand pumps which work very well as long as you also buy proper fittings to seal over the bleed nipples and smoother the threads of the bleed nipples with a suitable grease to stop air sneaking in and confusing you with a constant stream of tiny bubbles - all good fun!

I used to dread having to cover the top of the engine with old newspapers and suffer the drip drip of fluid escaping from the leaking connection at the reservoir cap - then needing to finish the job quickly, get the car out of the garage and hose away ALL escaped brake fluid - yes it could be a proper hateful task! And then the disposal of the used fluid - I absorb it into sawdust as that seems to be allowed, and double bag it and put it in the general domestic waste bin - for conversion to energy!

 

[audiwaterpump]

I used to remove the brake fluid reservoir cap, place a bit of plastic over the opening then refit the cap, that if done correctly will stop the fluid running out of an open bit of pipework.

I'm not sure if that can be done on this car as the brake fluid reservoir cap has the fluid level sensor running through the middle of it?
Or maybe I've got that wrong.

 

[rum4mo]

I'm not sure if that can be done on this car as the brake fluid reservoir cap has the fluid level sensor running through the middle of it?
Or maybe I've got that wrong.

Ah, probably correct, so that is where me buying a 6R VW Polo used master cylinder complete with reservoir and brake light switch connector wiring worked for me!

Audi's cap off and placed in an old brake cleaner spray can cap, sealed up VW Polo cap on, sorted.

 

[rum4mo]

Ah, probably correct, so that is where me buying a 6R VW Polo used master cylinder complete with reservoir and brake light switch connector wiring worked for me!

Audi's cap off and placed in an old brake cleaner spray can cap, sealed up VW Polo cap on, sorted.

Sorry, I failed to include that the 6R Polo reservoir cap, while being the same size/diameter, is just a plain cap so can even get used with a thin sheet of poly to seal it - or the seal can be removed and the small slit cut in it, to allow air to get drawn it to replace the drop in fluid, can be cleaned and sealed - and so converting it into a "TEST/REPAIR ONLY" cap which must never get left on the reservoir ideally!

 

[audiwaterpump]

I always add some grease to the sliders tbh, but sometimes the caliper piston just needs working back & forth to make it operate normally,

Update.
I pulled back the piston dust boot, polished a part of the piston that I could see (couldn't see any signs of rust on the piston), applied some silicon grease under the dust boot, and worked the piston back and forth a few times. The caliper piston certainly seems to move a lot better than before.
After a short trip, with minimal braking, the tempreture of the front driver's side disk is about 39 degree Centigrade, which is about 6 degrees more than the other 3 disks.
Not sure if that it normal?

 

[JontyMort]

Update.
I pulled back the piston dust boot, polished a part of the piston that I could see (couldn't see any signs of rust on the piston), applied some silicon grease under the dust boot, and worked the piston back and forth a few times. The caliper piston certainly seems to move a lot better than before.
After a short trip, with minimal braking, the tempreture of the front driver's side disk is about 39 degree Centigrade, which is about 6 degrees more than the other 3 disks.
Not sure if that it normal?

I’d be a bit worried about either (a) having compromised the dust boot or (b) whether the stickiness is being caused by the main piston seal - which of course you’ll never discover without a caliper overhaul. The trouble, of course, is time. A caliper rebuild is a very satisfying DIY job, but the car will be off the road for a weekend. The good news is you haven’t got a completely seized caliper.

 

[audiwaterpump]

I’d be a bit worried about either (a) having compromised the dust boot

It's unlikely that I damaged the dust boot (but is always possible) -I only used a soft cloth and metal polish, and not sandpaper.
Was wondering what temperatures other people are getting with their disks.

 

[audiwaterpump]

"Was wondering what temperatures other people are getting with their disks."

If no infra-red thermometer is available, then the other metric is to see how much the front wheels spin (ideally with both front wheels off the ground).
It is also a good health check of your brakes and should be done regularly anyway.

With the front wheel off the ground, spin the wheel by hand a few time to push back the pads, then with the tyre valve at 12 o'clock, spin the tyre with both hands and see how much it spins.
Repeat on the other front wheel.

How many spins do you get?
Thanks

 

[spartacus 68]

No idea regards temperature, but in my experience a sticky caliper will just get worse. If adding grease under dust boot, then only use red grease. This just buys time.

A caliper exchange or rebuild is normally only option. Have used Budweg parts (Autodoc) before for rebuild and parts are quality.