awillemsen

awillemsen

Active Member
Last month, I replaced the compressor, air dryer, and exhaust silencer. I also replaced all the seals in the valve block, including the exhaust diaphragm. I had the air bags checked out by an independent, who said that they were fine (well, the rear ones are getting a bit dodgy, but the car stays up overnight).

This weekend, a new noise started, audible in the car, which I've traced to the compressor vibrating like mad, and the lid of the EAS box rattling in sympathy. The noise is mainly down to the base of the compressor hitting the side of the EAS box. This is a new compressor, so the rubber mounts are fine, and the nuts are just pinched down and haven't worked loose.

The compressor doesn't always behave like this - normally, it's fine when the car starts up, and only misbehaves after a mile or so driving. Even then, it's intermittent. And the only time I've caught it "in the act" with the bonnet up, a gentle touch on the top of the compressor put it back into "normal" vibration mode. If this wasn't a coincidence, then it looks to me like some sort of resonance.

The vibrating noise also exposed another problem - the compressor often starts running when I brake. I know that levelling is inhibited when the brake pedal is pushed, and I know that this is working on my car as I've tested it. So why would the pump run - unless there's a pressure drop when I'm braking?
 
Firstly, it sounds like either the compressor or shield is loose - particularly if a gentle touch to the lid stops the noise. I would undo all the mounting bolts and reseat if first before getting too concerned or looking for other problems.

Secondly, you sure it's not the ABS pump you can hear, not the compressor, under braking?
 
MikeV8SE said:
Firstly, it sounds like either the compressor or shield is loose - particularly if a gentle touch to the lid stops the noise. I would undo all the mounting bolts and reseat if first before getting too concerned or looking for other problems.
Click to expand...

Compressor isn't loose - I've checked the nuts (loosened and repinched). And the bad vibration stopped when I touched the top of the compressor, not the top of the lid (the lid was off).

MikeV8SE said:
Secondly, you sure it's not the ABS pump you can hear, not the compressor, under braking?
Click to expand...

I can hear both :) Yes, I know my accumulator needs doing - it's on the shopping list. At first, I thought it was brake vibration, but then it started doing it when stationary as well as when braking - which is when I found out the noise was the compressor.
 
Make sure the mounting rubbers are in the correct way up. Also that the cup washers are orientated correctly.
 
Tightening the mounting nuts made no difference - sorry!

The mounting rubbers are the right way up.

The original washers had been lost (they were missing when I got the car). I found a flat washer in the bottom of the EAS box, so I got two more of the same - from memory, they are about 20mm in diameter (car not here at the moment, so can't check). Is it important that cup washers are used? Should there be washers under the mounts, or just on top?

I've had the flat washers on for two years now, with three different compressors, and only had the noise for the last few days. The compressor seems to have three modes - off, vibrating normally, and vibrating like mad. I can't tell if this is because of resonance or whether the compressor is actually working harder.
 
awillemsen said:
Tightening the mounting nuts made no difference - sorry!

The mounting rubbers are the right way up.

The original washers had been lost (they were missing when I got the car). I found a flat washer in the bottom of the EAS box, so I got two more of the same - from memory, they are about 20mm in diameter (car not here at the moment, so can't check). Is it important that cup washers are used? Should there be washers under the mounts, or just on top?

I've had the flat washers on for two years now, with three different compressors, and only had the noise for the last few days. The compressor seems to have three modes - off, vibrating normally, and vibrating like mad. I can't tell if this is because of resonance or whether the compressor is actually working harder.
Click to expand...


They should be cup washers, one at the bottom and one at the top of each mount. The bottom ones should have the cupped side down and the top ones the cupped side up. The mounts have an open end and a closed end. The closed end should face downwards.
 
wammers said:
They should be cup washers, one at the bottom and one at the top of each mount. The bottom ones should have the cupped side down and the top ones the cupped side up. The mounts have an open end and a closed end. The closed end should face downwards.
Click to expand...

Decided to fit some flat washers as a temporary fix. When I tried to take the compressor off, found that the two rubber mounts at the piston end were "welded" to the plastic of the EAS box. One of them I had to wreck just to get it off. Fortunately, I have some spares off the old compressor. So, washers fitted top and bottom now - wife has taken the old girl shopping with the mother-in-law. If there's a break in the conversation, she will doubtless report whether the vibration is still there.

Does anyone know where I can get some new dished washers from? If not, can someone please kindly give me some measurements? I've tried all my usual places, and don't really want to go to the local dealer - the last time, they thought my car was diesel, even though I gave them the chassis number....

Also, I noticed when taking the rubber mounts off the old compressor that the two on the piston end were noticeably softer then the one on the other end. The mounts on the new compressor are all soft. So, are they supposed to be soft or firm? :)
 
awillemsen said:
If there's a break in the conversation, she will doubtless report whether the vibration is still there.
Click to expand...

Wife reports that the compressor still vibrates like mad. I am trying to get hold of some cup washers, but I'm not convinced that they will stop the problem.

So, I have the following questions, if anyone can help...

If the problem is resonance, and it's not fixed by getting the cup washers, any ideas what causes it or how best to stop it? Could I, for example, put a small block of foam between the bottom of the compressor and the EAS box? Or could something be loose inside the compressor (it's nearly brand new)? Should the rubber mounts be hard or soft?

And why is the compressor running nearly every time I brake, and then usually stops when I come to a standstill? I've done searches, and other people report this problem too. It's not a levelling issue, as I've confirmed that levelling is disabled when the brake pedal is pushed.
 
Try running it without the cover on, see if it is the compressor or the cover that is causing the problem?
 
Check the earth point E0557. ECU is grounded through this. As is compressor. There is a ground link from ABS ECU through BECM to pin 30 on EAS ECU, then out of pin 18 to earth point E0557. If this earth point is not clean to chassis you maybe getting a feed back through ABS when brake is applied upsetting the EAS ECU. See diagram on S1 EAS wiring page 5 electrical trouble shooting manuals.
 
What condition are the four corner mounts in- that are fitted to the feet on the EAS plastic "Box" where it is bolted to the body ??
 
MikeV8SE said:
Try running it without the cover on, see if it is the compressor or the cover that is causing the problem?
Click to expand...

Yep - tried that. It's definitely the compressor vibrating more than it should, and almost definitely (although it's a bit difficult to tell) hitting the side of the EAS box. The one time I managed to catch it doing it with the bonnet up, a slight touch on the top of the compressor body returned it to normal vibration - although this may of couse have been coincidence.
 
wammers said:
Check the earth point E0557. ECU is grounded through this. As is compressor. There is a ground link from ABS ECU through BECM to pin 30 on EAS ECU, then out of pin 18 to earth point E0557. If this earth point is not clean to chassis you maybe getting a feed back through ABS when brake is applied upsetting the EAS ECU. See diagram on S1 EAS wiring page 5 electrical trouble shooting manuals.
Click to expand...

Thanks, wammers. Will check this when I next get to see the car in daylight - wife tends to hog it - don't know why :D
 
Irishrover said:
What condition are the four corner mounts in- that are fitted to the feet on the EAS plastic "Box" where it is bolted to the body ??
Click to expand...

TBH, when I had the valve block out, I didn't check the box feet, so I don't know what state they're in. The box doesn't feel loose, though. When I get a chance, I'll take the box out and take a look.
 
awillemsen said:
Yep - tried that. It's definitely the compressor vibrating more than it should, and almost definitely (although it's a bit difficult to tell) hitting the side of the EAS box. The one time I managed to catch it doing it with the bonnet up, a slight touch on the top of the compressor body returned it to normal vibration - although this may of couse have been coincidence.
Click to expand...

Compressor should never go near side of EAS box. There should not be enough movement in mountings to allow it to. On mine there is not enough movement in mountings to allow compressor to be forced by hand onto side of box. What sort of mountings do you have. The molded ones with the integral boss or the older type with the loose brass bush in them?
 
wammers said:
Compressor should never go near side of EAS box. There should not be enough movement in mountings to allow it to. On mine there is not enough movement in mountings to allow compressor to be forced by hand onto side of box. What sort of mountings do you have. The molded ones with the integral boss or the older type with the loose brass bush in them?
Click to expand...

They're just like the ones in this video:

[ame=http://www.youtube.com/watch?v=ChQklA1fuH0]Range Rover EAS - Replacing Air Compressor Mounts - YouTube[/ame]

Except not broken :)
 
OK and they are the correct way up? Think you checked that before. Can't think why it should vibrate so much. Unless there is a comutator segment not making with the brushes now and again causing the motor to continually hesitate then run. Strange one.
 
wammers said:
OK and they are the correct way up? Think you checked that before. Can't think why it should vibrate so much. Unless there is a comutator segment not making with the brushes now and again causing the motor to continually hesitate then run. Strange one.
Click to expand...

Yep, they're the correct way up. And new washers are on order.

Question - what would happen if the compressor switched on when the system was already up to pressure or even over-pressurized? Is this even possible?
 
awillemsen said:
Yep, they're the correct way up. And new washers are on order.

Question - what would happen if the compressor switched on when the system was already up to pressure or even over-pressurized? Is this even possible?
Click to expand...

Should not be possible, theoretically only thing that can switch compressor on is falling pressure below 120PSI +- 7 psi as detected by pressure sensor. The pressure sensor is not, i believe, an on off switch. It is a device which relies on a resistance measurement. Rather like an oil pressure sender. I think a falling resistance switches the compressor off and a rising resistance switches it back on. Or vise versa. I am not sure of this, but as the switch on is according to RAVE a falling pressure below 120 psi +- 7 psi and the switch off is a rising pressure of 140 psi +- 7 psi. If you take into account the margins the compressor could come on at 127 psi and go off at 133 so the differential could be as low as 6 psi. Or as high as 34 psi. If the pressure sensor was on the blink.
 
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