LHM level and misbehaving back end...

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DervDonkey
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LHM level and misbehaving back end...

Post by DervDonkey »

I'm not quite sure of this, perhaps someone can clarify:
Due to a leaky pump (another thread) my LHM level has dropped below minimum and the STOP light stays on. That's not the problem.
Going through the procedure to depressurise the system prior to pump removal, I set the height adjuster lever to minimum after starting the engine at normal height. The rear suspension wouldn't drop. On further investigation, at normal height with running engine, I found that if I sat on the tailgate the rear suspension would behave nomally (drop,wait, rise back) until I hopped off, when it rose but didn't sink again. The car's now sitting with its bum in the air!
Is this due to the operation of the anti-sink valve, considering the low LHM level? Is it safe to depressurise the regulator at the screw with the car like this? Obviously I'd like to avoid adding new LHM at this stage, when I'm about to remove the pump...
Robin
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Post by Robin »

I would go for a stuck HC rear control lever and assembly. The height control valve is working correctly but the link with the in car lever is either siezed or disconnected. Thats my guess anyway.
Remember not to try and free it off with you underneath and nothing to stop it giving you a sqeeze! R.
DervDonkey
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Post by DervDonkey »

Just been out to check it again - same behaviour as before, but some differences in method.
I started the engine with the height lever in the minimum position. The back end promptly dropped and the warning light went out and stayed out. Waited a couple of minutes, and put the lever in normal position. The car took about 40 seconds to rise to normal position and the warning lights came back on. It's not the control lever then - that seems to be working. Of course, when I set it back to minimum, the back end stayed up!
It seems likely that the antisink valve is being triggered by the lack of LHM in the rest of the system, and enough must have leaked back overnight to initially pressurise the system and drop the tail. At least I know how to drop it now without adding more LHM!
Anyone disagree?
RichardW
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Post by RichardW »

That big light with STOP written on it does mean something......
The brakes are fed off the LHM and if it's low you risk not having any brakes! Fix it before it fixes you.
The weird behaviour at the rear is probably caused by the height corrector being seized up.
DervDonkey
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Post by DervDonkey »

I thought the implication was fairly obvious - but I'll state it explicitly: I am NOT driving/using this car at present. I'm trying to fix it so I can - I'm not a total numpty! I don't want to add more LHM because I'm about to remove the leaky HP pump and would prefer to keep it in the bottle rather than pouring it on the ground. It's just too expensive for that.
P.S. I was merely looking for some confirmation that this strange behaviour is due to the low LHM level in the system coupled with the car's antisink system. Before the pump hassle everything worked normally.
nick
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Post by nick »

I think you're right, its the lack of pressure in the rest of the system thats stopping the anti sink valve from opening.
If you just need to lower the car to work on the pump, I would bung the height lever onto the minimum setting with the engine off. I know you're not strictly speaking supposed to do this, and it will probably make an awful groaning noise as it sinks down, but doing this now & again doesn't seem to do any actual damage in my experience.
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