ABS pump frequently whirring.

[aclwalker 3]

Hi all, I've got a bit of a strange ABS problem and an imminent MoT coming up. Hopefully someone can help. I've done a few searches but can't find any similar problems.

 

The pump appears to be periodically repressurising itself or something and over the course of a couple of days quickly escalated into doing it several times a minute. I can hear a whirr noise when it happens, and can feel it in the clutch and brake if I happen to be using either at the time. It only seemed to do it when the car was moving, but I didn't sit for ages at rest to check.

 

The ABS light doesn't come on (I know the light works as the self-test is fine on startup). I have no fault code on VAG-COM.

 

I was worried that I was going to burn out the ABS unit or something, so I forced a fault by unplugging one of the front sensors. Since doing that, it fails the startup test, as expected, and disables the ABS and I've not had the whirring noise since. Curiously, I was unable to disable the ABS by removing the fuse marked as "ABS" on the fusebox. So, forcing a deliberate fault was my solution.

 

The only thing I can think is that I maybe have air in the master cylinder/ABS unit or possibly even the clutch. A year or so back I replaced all my brake lines from the ABS unit to each caliper, and I didn't bleed the ABS unit or master cylinder at the time, because I wasn't sure how to do it then. I was never really satisfied with the brakes after this, as I felt they were a bit spongy, but it has passed two MoTs since then. I did minimise fluid loss from the ABS when replacing these lines, by using a plug I made from a union with a proper copper pipe with flare with the pipe hammered down flat. This prevented excessive fluid loss, but clearly some air probably got in. I guessed at the time that it would be forced out of the line anyway, but maybe it's stuck around in the ABS unit.

 

Could this whirring be the ABS unit reacting to air, and trying to maintain the pressure? I see no evidence of fluid loss as the reservoir is still full.

 

Again, no ABS light, no VAG-COM code, and the ABS seemed to operate correctly (before I deliberately disabled it), but just has this constant 'repressurising' feeling and whirring noise.

 

Any ideas greatly appreciated.

 

Edit: Actually, I wonder if I should have VAG-COMed it before I disabled the ABS. I'm not sure if the self-test clears other codes out. Should I reconnect the front sensor I deliberately removed, and re-scan for faults as these whirrs are occuring?

[charly_vrsexy 0]

Hi all, I've got a bit of a strange ABS problem and an imminent MoT coming up. Hopefully someone can help. I've done a few searches but can't find any similar problems.

 

The pump appears to be periodically repressurising itself or something and over the course of a couple of days quickly escalated into doing it several times a minute. I can hear a whirr noise when it happens, and can feel it in the clutch and brake if I happen to be using either at the time. It only seemed to do it when the car was moving, but I didn't sit for ages at rest to check.

 

The ABS light doesn't come on (I know the light works as the self-test is fine on startup). I have no fault code on VAG-COM.

 

I was worried that I was going to burn out the ABS unit or something, so I forced a fault by unplugging one of the front sensors. Since doing that, it fails the startup test, as expected, and disables the ABS and I've not had the whirring noise since. Curiously, I was unable to disable the ABS by removing the fuse marked as "ABS" on the fusebox. So, forcing a deliberate fault was my solution.

 

The only thing I can think is that I maybe have air in the master cylinder/ABS unit or possibly even the clutch. A year or so back I replaced all my brake lines from the ABS unit to each caliper, and I didn't bleed the ABS unit or master cylinder at the time, because I wasn't sure how to do it then. I was never really satisfied with the brakes after this, as I felt they were a bit spongy, but it has passed two MoTs since then. I did minimise fluid loss from the ABS when replacing these lines, by using a plug I made from a union with a proper copper pipe with flare with the pipe hammered down flat. This prevented excessive fluid loss, but clearly some air probably got in. I guessed at the time that it would be forced out of the line anyway, but maybe it's stuck around in the ABS unit.

 

Could this whirring be the ABS unit reacting to air, and trying to maintain the pressure? I see no evidence of fluid loss as the reservoir is still full.

 

Again, no ABS light, no VAG-COM code, and the ABS seemed to operate correctly (before I deliberately disabled it), but just has this constant 'repressurising' feeling and whirring noise.

 

Any ideas greatly appreciated.

 

Edit: Actually, I wonder if I should have VAG-COMed it before I disabled the ABS. I'm not sure if the self-test clears other codes out. Should I reconnect the front sensor I deliberately removed, and re-scan for faults as these whirrs are occuring?

 

Hi, where abouts can you hear the whirring from? i have a whirr in mine and the brakes are playing up, just wondered if same problem or completely unrelated whirr, not to sure where the abs pump is?

[aclwalker 3]

Hi, where abouts can you hear the whirring from? i have a whirr in mine and the brakes are playing up, just wondered if same problem or completely unrelated whirr, not to sure where the abs pump is?

Hi Charly, the whirring was definitely from the ABS unit, i.e. under the bonnet at the passenger side. It only did it after picking away or coasting slowly, not when standing idle. When I deliberately unplugged a front ABS sensor to force a fault, this stopped the whirring noise, which is why I suspected it was trying to pressurise itself.

 

I seem to have sorted the problem now anyway. I went out for a drive and deliberately triggered the ABS about 30 times, which is much easier with baldy tyres! This seemed to drastically reduce the frequency of the problem, but it didn't go away totally.

 

I then bled basically the whole system with and Eezibleed. Excellent piece of kit, by the way. First, I bled the clutch slave cylinder. There were a few bubbles in there. My clutch feels so much better now, much more precise and less 'vague'. I then bled the master cylinder, but no air came out.

 

After reading lots about the ABS and coming to conclusion that the Teves 04 system does NOT require the ignition running when bleeding the rear brakes (like some of the other Teves systems), I bled the two points on the top of the ABS unit, but only after pressing the brake pedal about 40 times with the ignition off, to make sure that I got no nasty surprises when opening them up. I'm not sure I got any air out there, maybe a small bubble or two. However, my deliberate triggering of the ABS in the days before was in an attempt to shift any air OUT of the ABS unit, so perhaps my plan worked.

 

Finally I bled each caliper, starting from furthest from the ABS unit to closest. I got air out of all calipers, and a lot out of the right rear, and some dirt and corrosion too. The other three were clean. I had to replace the front two bleed valves as they were severely corroded (just as well I bought spares a long time ago and had them sitting). I had to use the Irwin bolt grips on one of them, which scared me, but it came out fine.

 

I went for a test drive and no more whirring. I also read that ABS problems CAN be caused by loose battery connections and I did notice one of my connections was not loose, but not as tight as it could be since fitting my headlight loom. I think this is a red herring in my case, but it's worth checking anyway.

 

I've now driven it a fair bit since bleeding and no more whirr, so I guess my initial thoughts were correct, i.e. the ABS was having to repressurise the system due to air pockets. My clutch feels much better, and smoother. My brakes have significantly hardened although they're still not new car standard. I actually suspect that my servo may be leaking vacuum slightly, but I'm not going to worry too much about that. My brakes are definitely much better and the exercise was well worth while.

 

I can thoroughly recommend the Eezibleed. Just make sure you pressure test without fluid first and take great care to disconnect the air supply when not needed, in case you forget the system is pressurised. I took the tyre down to 15psi and it worked fine. It says to use no more than 20psi. One thing to watch out for is that you might have to remove some fluid from the reservoir at the end as it will probably be above the maximum. I actually did this but over the course of the next day some pressure must've gone back the way because it actually leaked out the top a bit. Perhaps I didn't remove enough or forgot to account for the float when putting the original lid back on.