hydraulic woes continue

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citroen7
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hydraulic woes continue

Post by citroen7 »

i was having bother a month or so ago with the stop light flickering on and of and the rear suspension going down so after a bit of advice from an earlier post bit the bullet and rebuilt the fdv and swopped the pump for a spare one and hepresto no change ! so heres where we are now car starts up ok and suspension comes up drive of and after going over a few bumps the stop light starts to flicker if you stop the car and restart the suspension comes up and of you go, also if you stop the car leave the engine running and turn the steering to full lock suspension comes back up and of you go the other thing i have noticed is the pump not clicking on and off stroke . so i even changed the pressure regulator and no difference.
Any pointers chaps? i am starting to get a little peeved with this one and i am determined not to be beeten thanks
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Post by tom »

If the height is not correct, then I reckon that you may have a sticky or leaking height corrector. The linkage on the anti-roll bar may have become loose. Check on ramps!
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Post by adamskibx »

Is the steering hard to turn? If not, its not the pump. If it is, it "could" be the pump. A spare pump might not be any better. I havent seen the last post so im just going on what you have said so far. When you turn the steering full lock and the suspension rises, which way are you turning it? If your turning left, then it could be that the fluid level is simply too low, or there is excessive air in the system. A fill up and full bleed of both brakes and main system is a good idea. Other things to check: HP pump drivebelt must be very tight, a long session of going up and down and steering etc (Citrobics) should be completed and so on. Have you successfully managed to drive without problems with the suspension in the higher setting, or with the lever set slightly below normal? Is the ride height generally OK, and what are the spheres like? Lastly, I would replace the spheres (oldest first), and if all this fails I would hyraflush the system and replace the LHM. Others may know more tricks to try than me, but this is ehat I would do.
citroen7
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Post by citroen7 »

before rebuilding the fdv the steering was at times a bit wooly but that has now gone the suspension will come back up when the steering is on full right lock ,bear in mind that the rear only is the problem ,when you turn the steering wheel on full right lock you can hear the pump go on load . The fluid level never drops and i have cleaned tank and filters and refilled with new hlm my gut feeling is that there is air in the system or the rear hight corrector is in some way to blame.
The other symptom to mention is that on start up you can set the suspension to high and up she goes all be it the front struts creak a bit but put her down to low and try to go back up again and nothing , turn the steering wheel to full lock and up she comes confusing i know but IT WILL BE FIXED!
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cauchoiskev
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Post by cauchoiskev »

Have you had a look at your leakage returns into the reservoir ?

The back end going down is often a symptom of a leaky brake valve, if the back end goes down while braking it's a dead cert.
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Post by jeremy »

I used to get something similar when I had a defective FDV. On mine the problem was actually incorrect assembly - in that the pressure control ball bearing (under the middle (screw) cap was the wrong side of its plastic support and so the thing was trying to seal on the plastic support rather than the ball.

In trying to find it I rebuilt another FDV which was no better - and I think I got wrong. Had I not touched it it would probably been fine.

My symptoms were that the steering worked perfectly with a replacement recon pump but gradually other problems started to arise - mainly the thing being very difficult to get to the proper height - (holding the steering wheel against some resistance helped) and a distressing habit of putting on the warning light for the first couple of miles. Strangely lowering the engine speed would improve the pump output and the light would go out - as it would if the wheel was turned.

A drop of new LHM would improve things for a few days and mask the symptoms which made finding the problem more difficult.

So I would say FDV now - and replace it with a known good one. May be worth removing the centre plug which can be done in situ on a TD and making sure thats OK (plug - spring - plunger - ball bearing) or even re-seating this ball (put in hole with a dab of grease and tap smartly onto its seat ONCE with a BRASS punch - then re-assemble)

This job can be done in situ - only strike it ONCE as you want to form one seal not many overlapping ones which will leak nicely and you must use a brass punch as a steel one will put a flat on the ball.

This screw does adjust the ultimate system pressure - and so its relationship with its locking sleeve should be preserved or its position otherwise recorded before dismantling. ( may be possible to measure the position using calipers or something)
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Post by citroen7 »

no back end does not go down under braking in fact brakes work fine
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Post by citroen7 »

jeremy picked up on your reply to the sticky and checked this out and was fine ,did a little test today and sat with the car at idle and constantly hit the brake pedal and after half a dozen pumps the back did go down but only gradualy so where next!!
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Post by jeremy »

Operating the brake should cause minimal fluid flow.

As you know the front brakes and suspension are entirely different circuits, the rear one being fed by the rear suspension circuit - with pipes going to the doseur (brake) valve. So if the rear suspension drops it suggests that large amounts of LHM are being used which suggests that there is a leak somewhere or more likely loads of gas in the system.

How old are the rear spheres and does the rear suspension work properly? Is the accumulator any good?

Thinking about it I don't think my BX goes down even if I do this with the engine off.

If the car is going down with the engine running then the pump must be very feeble.
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Post by tom »

Or a height corrector is leaking.
citroen7
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Post by citroen7 »

right this is were i am now,
on start up the back of the car rises no warning light but pump does not go off stroke ie no hiss and click . Drive off and everything is fine but after 3 miles the back end starts to feel bouncy as per the symptoms of duff spheres when i get to a t junction a further mile down the road i usually have to wait for traffic so i turn the steering wheel to full right lockand the back of the car rises and of you go again
so work carried out so far is fdv rebuilt,lhm change pressure regulator changed (twice) pump swapped (three times)
Other symptoms to chuck in the pot are if you raise the car to max on start up no problem but if you lower to min and then try to go to max it does not move but if you turn to full right lock up it will come.
i am inclined to think that i have rebuilt the fdv wrong but i am not convinced the other thought is toms suggested height corrector leaking as i dont know much about the way they work i can only guess that car rises initially because of some sort of non return valve is working but then is moving and the flow of lhm is just to great for the pump to keep up
with further bits of wisdom would be welcome!!
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Post by DLM »

Height correcters are really some of the simplest components on a hydr-cit: it's stiff, bent, or "sticky" linkages that can often cause problems.

I've got a "back up" problem with my new acquisition at the moment, which I'm more than 90% sure is the linkage or the pivot for the linkage, and the effects of a plentiful helping of mud underneath. On a previous estate where the height control was fitful and unpredictable, I was able to sort out the front quite easily as it was a petrol by reaching down the back of the engine and manually exercising the height corrector linkage. It's little tougher on a diesel (and damn near impossible on a turbodiesel).

The rear, being more difficult to get at, has to be tackled from underneath in a safe position with the car VERY well supported - ramps are good, but you need to watch out for the wheels moving as the car moves up and down. A good cleanup of the area and the pivot with the engine and pressure off will pay dividends, as you can then remove another variable from the diagnosis.

Another point: if a height corrector is failing internally, it'll be delivering back great quantities of lhm via the return pipes: - see the BX DIY site for diagnostic procedures. Be aware though that a height corrector locked in low, by a non-or-partially-moving linkage can cause excess returns.

Good luck!
Back on two wheels and pedal power for the moment.
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Post by tom »

You are honest enought to admit that you don't understand the workings of the height corrector, so let's start there. The job of the height corrector is to correct the ride height, the very thing you have a problem with.
If you read "why the BX" in the homepage, you'll understand a little more but for now, the pump is not cutting out when the car has risen to the normal height so there is clearly a return to the tank. First, check the brake pedal clearance, just to rule it out. now, the linkage to the rear height corrector. It is not moving far enough to cut off the supply until you ask the car to rise further. Fine. That's what I would expect if the linkage is sticky and I would expect the pump to cut out now (Wait for it...) Returning fron high to normal causes the car to work ok but lowering it again repeats the fault cycle. After three miles, the car becomes bouncy. Yes; it is dragging its tail on the bumpstops because all the fluid has leaked away from the rear end.

Height corrector or linkage. 99% certain that that is it. I wouldn't waste any more time on guesswork, Get the axle stands out, wash it all down and get lubricating!
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Post by citroen7 »

tom i have a spare height corrector but have not seen any info on refurbishment ? or is it better to play around with the one on the car i did have trouble with this beasty sticking several months ago but then the problem was simply the car not going to max height for wheel changing,if i can get my sons various bits of motorbike and drum kit moved i will pull her in to the garage and have a play.
tom
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Post by tom »

There are plenty of links on this website to stripping down of height correctors but if you have had similar problems in the past, read my last post and DLM's because you have answered your own question. Clean and lubricate the linkage, then check it is correctly set up. Haynes has all you need for this.