Another EPB failure

Right car is a 2007 2.0 tdi. It's dad's car and he called me up to say that the rear drivers caliper was stuck on. Smoke was bellowing from it when he got home. He said that the auto release did not work so he kept driving so no surprises why it was smoking. It was only smoking on one caliper though. I plugged in the video and no fault codes present so I did a function test and both calipers rewound wound back in and worked as they should. Took the caliper off just to check the caliper pins were not siezed.

Few days pass and the fault reoccured when he was trying to reverse out a spot. The brake eventually released and he drove on. He reports an intermittent grinding noise along with smoke suggesting sticking caliper.

I did a Vcds scan and there were errors on the abs and epb. Notably was rear right caliper error. I cleared all of the errors and went for a drive and I can't get it to replicate the error. If you release manually it works fine and even tried the auto release but this is fine to.

I know the signs point to a sticking caliper but I want to be sure first. Especially as it does not stick all the time. Additionally he did not try a manual release when it does not auto release. Is there any other issues that could cause this problem? Some posts suggest the switch can be faulty. Is there a way to test this with vcds? Are there any lateral sensors that need adaption or the clutch pedal?

Thanks Mike


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did you replace the discs when the rear pads were changed ??

I think if you don't, the caliper tends to stick as when the pad is wearing down with worn discs, it struggles to rewind when the handbrake is released

when driving the car for say a few miles, feel the wheel nuts for heat right round the car, the rears should marginally be warmer than the front, if the rear right is really hot, its sticking on


please note that replacing the rear nuts are a nightmare, the bolts holding on the brake pad carrier is extremely tight to come out .............................. it is do able, but very tight for space if you have the car on axle stands ........................... might be easier on a ramp, as you could maybe use your body weight to loosen off the nuts. I managed on axle stands ........................ but got good forearm muscles

Quote:

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Originally Posted by niall campbell

did you replace the discs when the rear pads were changed ??

I think if you don't, the caliper tends to stick as when the pad is wearing down with worn discs, it struggles to rewind when the handbrake is released

when driving the car for say a few miles, feel the wheel nuts for heat right round the car, the rears should marginally be warmer than the front, if the rear right is really hot, its sticking on


please note that replacing the rear nuts are a nightmare, the bolts holding on the brake pad carrier is extremely tight to come out .............................. it is do able, but very tight for space if you have the car on axle stands ........................... might be easier on a ramp, as you could maybe use your body weight to loosen off the nuts. I managed on axle stands ........................ but got good forearm muscles

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Bent my extension bar like a banana before the loud crack as the bolts finally released. Bar was close to its yield point and I was grimacing expecting an almighty bang when the bar shattered but fortunately it did not. The bolt ends of the carrier bolts stick through the hub at the back when fully tight exposing them to corrosion which makes them grab tight. Doesn't help that the bolt heads are splined female recesses.

Quote:

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Originally Posted by DMitch16

Bent my extension bar like a banana before the loud crack as the bolts finally released. Bar was close to its yield point and I was grimacing expecting an almighty bang when the bar shattered but fortunately it did not. The bolt ends of the carrier bolts stick through the hub at the back when fully tight exposing them to corrosion which makes them grab tight. Doesn't help that the bolt heads are splined female recesses.

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Aye they are mega tight !!!!!!!!!!!!!!!!!!!

Even getting into them is a pain.

I was thankful I was of farming stock, using a Britool bar that's 50 year old and built for farm use

I have not changed the pads yet as I didn't have the tool to do the discs as well. That's arrived now so I will be able to get them off. The disc on that side was a bit corroded and I did clean it up with the grinder. Getting bolts off won't be an issue as I have access to a ramp so I can get a good big bar on there.

It was the rear drivers side that was smoking but as I have not seen the fault personally I can't say if the other side effects was sticking to.

I have asked him to try pressing the clutch down fully next time it happens. I'd that fails then he should try to manually switching it off. If that doesn't work then try turning the car off and on again.

If it is a faulty caliper why doesn't it stick all the time?


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The bolts are one-time use only torque bolts so they're torqued up not to undo ;)
Triple-square MT14 (aka Spline bit or XZN driver) needed +penetrating fluid if clean, +heat if not

If its the module that's holding on the EPB (I've used this method once and it works)
Forced Reset of EPB Control Module
• Switch ignition OFF.
• Disconnect battery.
• Wait at least 10 seconds and reconnect battery.
• Switch ignition ON.
• While pressing brake pedal, operate electronic parking brake button twice.

Got a help .doc I put together from many an excellent "how-to" posted already.
PM me an email address for return attach

Just adding my tuppence worth, now I don't have an EPB, but have recently changed my pads which I am pretty sure are identical to the EPB ones (if not disregard)
recently put the car in for a full service and te garage came back saying that one of the rear calipers were seized and would require replacing??

cut a long story short, I noticed that while trying to fit the new pads in their carrier, they were extremely tight?? I then took off the guide shims and got a flat screwdriver
and gave the shim seats a knock with screwdriver and hammer, there was quite a lot of rust scale / ***** build up underneath them (red arrows)
refitted the shim guides, after that, I could fit the pads no problem and they were free in the carrier "the caliper was not seized"

maybe you have the same problem? note: it was just one side that was tight, but I cleaned both of slag build up anyway HTH

Attachment 32588

Quote:

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Originally Posted by mike ryan

I have not changed the pads yet as I didn't have the tool to do the discs as well. That's arrived now so I will be able to get them off. The disc on that side was a bit corroded and I did clean it up with the grinder. Getting bolts off won't be an issue as I have access to a ramp so I can get a good big bar on there.

It was the rear drivers side that was smoking but as I have not seen the fault personally I can't say if the other side effects was sticking to.

I have asked him to try pressing the clutch down fully next time it happens. I'd that fails then he should try to manually switching it off. If that doesn't work then try turning the car off and on again.

If it is a faulty caliper why doesn't it stick all the time?


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Put on new discs on both sides, its the thickness of the disc in my mind that doesn't help, I usually put new discs on every set of 3rd of pads if possible; however with my EPB I put on new discs every pad change .................................. every 45,000 miles is a long time and not bad value for a disc

If you don't replace the disc, the pads when wearing down, the piston for pushing the pads are further out than I think are designed for. If the seal is damaged as well, this can allow rust to form.

The discs are not as dear as you may think


A faulty caliper can be sporadic, you could park on a hill for example and the electric motor has to work hard to release the brake; if the motor is on its way out then it will struggle to rewind

a bit like a starter on a cold morning struggling to turn an engine fast enough, okay in mild weather but no use in the winter

its cheaper to replace the disc, clean out & grease the motor than buy new epb

Not forgetting that often the reason for the EPB motor sticking is water ingress and corrosion of the wobble gear inside. As it is a wobble gear moving in an uneven pattern it could be sticking at a certain point in the rotation or is partially corroded inside which would only get worse.

I always thoroughly clean the carrier guides at a pad change and the visible part of the caliper piston with Autosol. Usually 2 pad changes per disc but I get nearly 60k out of each rear disc as I am a use-the-brake-only-when needed type driver and hardly use the brakes on my daily commute. My fronts last a fair while too.