metallic noise from abs pump after dismantling to clean

[duncmc]

Recently I finished refurbishing my front callipers and fitting new pads/discs. The ABS system still had air in though, so I thought that whilst I was at it, I would take the ABS pump apart and clean it like in the tech archive http://forums.lr4x4....showtopic=50897.

I was unable to get the pressure relief valve out though, so everything was just cleaned with meths, dried and re fitted with fresh brake fluid.

Unfortunately though I did knock ther pressure relief switch off my bench onto the floor!

At first when I started to bleed the ABS system everything was ok, then towards the end a metallic noise developed. Vibration could be felt in the high pressure hose going from the top of the pump to the accumulator, but not in the pump itself. I removed the pump, dismantled it and rebuilt it again to check the the pistons and rotor etc where in the correct place, which they where. However I have still got the noise.

I have taken a video so people can listen to it, here

What is the forum concensus? Is my pressure relief switch broken, or is it something else?

When bleeding at first I did have a good hard pedal, but that has now gone. There is pressure from the pump, as can be seen when I open the bleed screw. And if left the pump will switch off.

Do I need another pressure relief switch? Please help. Range Rover Classic 1993.

Thanks.

[duncmc]

I think that the pump is working properly now even though it is noisier than before.

First thing this morning I had another go at it, and managed to get the pressure relief valve out to clean and check it. That was fine, it is only a spring and ball bearing in a machined housing with an O-ring around it.

I went and got a second hand pump from a scrap LSE for £25, and was going to try that, but the internals of the pump were full of carp. So I just robbed the pressure switch and tried that. Re-bled the accumulator and the two booster screws. Still the same noise! Pumps up to pressure ok, switches of ok, comes back in when the pressure drops, and got my pedal back. So I think it is working.

I can only think that the noise is because I have cleaned the impeller and it is just noisier than before?

Time for a test drive to check now.

[duncmc]

Yes very strange, all working fine now. After about 30 miles the noise started to clear. And within a few more miles all gone. Maybe it was a bit of air in the pump still?

[Snagger]

I have recently replaced my original pump with a second hand unit. My pump was a bit tired (190,000 miles with mostly short trips means a lot of pump cycles) and was taking too long to pressurise the accumulator, so the ECU's system test would time out at 45 seconds after start and the pressure would still be too low, triggering the three amigos. The system was all working - it was just the self test that was failing because it was too soon for the pump. It was a bit noisy too, though just a harsh buzz rather than any metallic sound.

I tested the replacement pump before removing the original because I didn't know its history. I just connected its two plugs to the vehicle's wiring while leaving the old pump fitted and hydraulically connected. It was much quieter on the very short dry test, but once it was fitted and bled, it was as noisy as the original. As best as I can remember, the original pump made the same noise when I bought the vehicle with 80k on the clock.

The pressure switch shouldn't make any noise as there are few moving parts and they only move once under pressure. Any continuous noise must be from the pump itself, either the motor or the hydraulic head.

[Bowie69]

Yes very strange, all working fine now. After about 30 miles the noise started to clear. And within a few more miles all gone. Maybe it was a bit of air in the pump still?

Found this to be the case many times, if only a bit noisey, keep driving and they do eventually self-bleed the air out, where it goes I don't know, but it does