Rear End Hard And Bouncy

[DrTim]

This is on the new blue one. I didn't notice any sphere replacements when I read thru the partial history, so I guess its due some of those.

I won't be damaging anything back there when it sort of oscillates quite violently after a small bump (but not ALL small bumps) will I?

One of the things that is definitely OK with the old one is the ride (hydraulic leaks and
possibly suspect hydraulic pump notwithstanding) so I have a good reference point.

later

[demag]

Actually sounds quite painful DrTim!

If you open a door and get your head down by a front wheel and then a back wheel, you should be able to hear a distinctive buzz/whistle. Only quiet but definitely audible. If you can't hear anything at the back it could be a duff diode in the rear electrovalve. This will keep the rear centre sphere locked out of the suspension circuit and cause hard suspension.

However, from your description it sounds like your spheres are probably pooped anyway. If you have a duff diode then Roy mackay1 produces a small repair box that simply clips onto a few wires under the bonnet. Then if you're going to do the spheres you could do the diodes at the same time.

As for damage, I think that is more likely at the front where hard suspension can destroy your strut tops in quite spectacular fashion!

[DrTim]

Demaq, yes I did bang my head a couple of times! I noticed it was abit hard but didn't
really appreciate just HOW hard until back in the city with all the potholes.

Looks like this all needs sorting before I do too many miles in it.

I''ll have a listen tomorrow for the electrovalves and maybe look for burns on the ECU
PCB.

[Peter.N.]

The only other option is that the ride height is wrong and its allready hitting the bump stops, but if the suspension rises to the correct height, its got to be the spheres.

Peter.N.

[DrTim]

Update. Not easy to tell with city traffic noise and cooling down noise (check while car is cold!) but I couldn't hear front or back electrovalves with doors open and engine off.

With doors open or closed and engine on all 4 corners quite hard when bouncing, back worse than front, no real change with doors open or closed. Only moves 1 inch or so.

Turning on sports mode with switch does change ride quality somewhat.

Parked it up on the flat and cycled the suspension lo to high and back a few times.
Gives brake pressure warning gong from lo to normal, which goes away when normal achieved. Going from hi to low back end drops like a stone and the "kicks" (I used to have this on the K but not for sometime now) before stabilising.

At least the anti sink works, car was still "up" after standing overnight. I did however notice on first starting back end did drop, then "kick" a bit before stabilizing, as others have mentioned.

Checked LHM level, OK.

Didn't manage to get the top of the ECU, maybe tomorrow, once I have found how to identify the hydractive ECU.

Thanks for any input past or future.

[xmexclusive]

Hi DR Tim

The suspension ECU has 2 separate multi pin electrical connectors on the top. The other ECU's have only one large multi pin plug.

Regards

XMexc

[Peter.N.]

If you cant hear the valves buzzing/whistling, you should hear a 'clonk' as you open a door. Even if they are not working you should have more than an inch of movement, so I would say you certainly need a set of spheres for a start. If the valves are working but the centre spheres are flat, it will give you the same symptoms.

Peter.N.

[DrTim]

OK so I listen for the electrovalves with the engine off, igniition on? Is that correct?
Yesterday I don't think the ignition was on. There is a slight "click" from somewhere under the dash when opening the front doors.

[Peter.N.]

Yes, strange as it may seem the solonoids are energised by opening the doors regardless of the ignition position. You should hear a quiet but discernable 'clonk' from under the car, but you do need a fairly low ambient noise level to hear it, after you have closed the door you should hear another clonk, 30-60 seconds later as they switch off again.

Peter.N.

[Peter.N.]

Just a correction to the previous post. I think turning the ignition also energises the valves, but as you usually have to open the door to swith it on, they are allready energised - so read that 'with the ignition off'.

Peter.N.

[DrTim]

Peter, thanks for clarifying that, I did listen again today but still not sure due to background noise. Now I know what the noise is I know the old one does it, I'd often wondered what it was.

Tried to get at the ECU (looks very clean in there btw, apart from a few bits of thistle and leaves) but gave up trying to disconnect the hydraulic cables (got the engine mgmt cable off and eventually back on again). Is there any way to tell if the mosfets are friend without opening it up? Maybe the Mackay kit is a good solution for me.

One more thing I checked after trawling previous posts. The ride height in the top two suspension positions is identical. Doesn't change perceptibly when switching between them (i did a few cycles). I am assuming this means the ride height selector needs adjusting? And that my ultra bumpy ride ios due at least partially to this?
Had a quick look in Haynes and I don't think I'll be doing that myself.