[C5 X7] Friday-evening horror short-story of the mysterious LDS fountain.

[the-termin8r]

Honestly I'm at a loss here. Got my rear right TPMS replaced by Chevronics today. On my way back home I notice some pretty strong vibrations at about 75-80 MPH. I figured they forgot to balance the wheel (no biggie, mistakes happen). So I take a short detour to my local tyre place when I get near home. They kindly offer to balance it for me on the spot. I pull in, drive the car onto the mini lift thing that gives about a foot of height. This is where my potential mistake comes along, I forgot to lift the car. It's been a long day, I'm tired, it slipped my mind, that's on me.

As they start to lift the car, I notice a small puddle growing in front of the front right wheel. The pang of dread immediately hits me as I know exactly what it is: LDS. At this point the car's wheels weren't even actually off the ground but the suspension had travelled a little. I tell them to immediately stop and set the car back down. I open the bonnet expecting the worst, a ruptured tank, but no. Instead I'm greeted by the biggest (and only) LDS fountain I've ever seen. LDS was squirting out of the breather hole in the cap so hard that it was hitting the open bonnet and deflecting off it into the rest of the engine bay.

Not knowing what on Earth was happening and what I was doing I decided to turn the engine over and raise it to max height. The fountain stopped and I got the wheel balanced (and they very kindly gave the engine bay a quick surface clean). Brought the car back to the ground, set it to normal height and everything seemed fine. No complaints from the car, nothing weird with the steering. Drove it back home (couple of miles) and it felt fine. I let the car sit on the driveway for about 3h and went out to it a few minutes ago.

There's a couple of drops of LDS on the ground, but I'm assuming that's just residue from the fountain that eventually found its way down. Lowered the car to check the level and it seems fine. It's close to what is shown in the photo here, but my fluid is much cleaner and I can see the bottom of the strainer (?) in the fill hole. I'm going to scan it with Diagbox tomorrow and see if it throws something up, but I'm honestly not expecting anything.

So, the question: WHAT THE BLOODY HELL HAPPENED?!

Seriously, I can't rationalise this. I don't think the tank was over-filled as the suspension has been cycled many times before without issue. I don't think it was me forgetting to raise it since the concern with not raising it is on the way down from the lift. I had the front struts replaced in March, but I don't think that would cause an issue after several months. I'll ask Chevronics about it on Monday, but until then I'm wondering if the hivemind knows something.

Thanks.

[PaulC5]

I do not fully understand it but by lifting the body the struts were working in reverse taking the car's weight off them. Why this would put more fluid back in to the tank rather than suck some out and then it overflows I do not know.

Did the wheel just need balancing ?

[aerodynamica]

Hi Rob, hope your pulse rate has lowered I think maybe it was simply that the LDS level was a bit high and that when the car lift raised the car the hydractive went mad and said "o no, too high", let off all the pressure to lower height, all the LDS vents, back to the LDS tank and if it's already a bit high, overflows and sprays out all over the place. I think it's quite hard to get the level of LDS right because it seems to vary hugely after you have checked it and then re checked it at a later date.. I always set the fluid level to the bottom of the filler with the suspension at low setting. But on occasion I have supported the car on axle stands at the front and found that the LDS overflows the tank when you lower it. It's worse when you consider that really it's only the rear suspension that goes to minimum height with the front raised on axle stands. So there must be a bunch of LDS remaining in the front struts that doesn't go back to the LDS tank and yet it still overflows..... What the heck

[the-termin8r]

Did the wheel just need balancing ?

Yes, I'm hoping so. When I drove up to work this morning it was fine, then after I got the car back it was vibrating. The wheel was the only part of the car that had been messed with. The bloke at the tyre place even showed me on the machine that there was a significant mismatch between the inner and outer edges of the rim. I think it was something like 35g. I haven't gone back out to try it at motorway speeds, but I'm expecting it to be sorted. I'll find out on Monday either way.

I think maybe it was simply that the LDS level was a bit high and that when the car lift raised the car the hydractive went mad and said "o no, too high", let off all the pressure to lower height, all the LDS vents, back to the LDS tank and if it's already a bit high, overflows and sprays out all over the place.

Perhaps, but if that was the case I don't understand why it wouldn't overflow when dropped to its lowest height.

I wonder if this is linked to it not detecting when it reaches max height. If I set it to lift stage 2 the car will get there and stop moving. But the speedo never acknowledges that they height as been reached and the pump actually keeps going but at a lower intensity until it times out. It only does it on max height. Never caused any issues with normal use. Weird stuff.

[PaulC5]

It's worse when you consider that really it's only the rear suspension that goes to minimum height with the front raised on axle stands. So there must be a bunch of LDS remaining in the front struts that doesn't go back to the LDS tank and yet it still overflows..... What the heck

I have not had a C5 X7 but on our 2007 and 2004 C5s when I have raised the car to max height and then the front jacked up/used axle stands, the rear has remained at max height. Similarly when the rear has been jacked up the front has remained at max height.

[the-termin8r]

I scanned the car earlier, besides the expected speed anomaly there were a couple of errors in the suspension ECU about it not being able to communicate with the BSI. I cleared them, rescanned, and they didn't come back. Admittedly I haven't driven it to see if they crop back up.