The STOP lamp going on without an obvious reason

BX Tech talk
User avatar
TB2
BXpert
BXpert
Posts: 320
Joined: Sat Apr 28, 2007 3:31 pm
Location: Switzerland

The STOP lamp going on without an obvious reason

Post by TB2 » Tue Aug 12, 2008 5:56 pm

Hi,

so I've done a few test drives and the car is running smoothly. On a longer run on the highway I didn't have any problems, same goes for cities. The other day I was picking someone up and I had to wait at the train station for 20 minutes. I've put the car in low position when I parked it, went away, and when I came back I turned the ignition on and put it in medium. It took a while and then rose to medium without problems. But the STOP lamp was still on. I tried pushing the break hard, tried the power steering... everything running without problems. So I went out, had a look around, and then pushed the rear end down by hand. Right then, the STOP lamp went off.

Later, at the end of the highway, I had to break a bit hard to slow down from 100km/h to a full stop, and just about when I arrived at the white stripe and stopped, the STOP lamp went on again for 2-3 seconds.

Any ideas why this might be happening? I have no idea, the suspension feels fine and it seems like I don't have an internal leak in the doseur valve. At least, the rear isn't dropping when I break hard. Also, there are no external leaks at all. Fluid level is fine. Sometimes, I "feel" like the PAS is a bit weak, but I don't know how it should be, as I've never driven a BX before. It feels okay, but not super-smooth...

What could it be?
Carl

1989 TRD "Entreprise" Turbo Diesel
1989 16 Valve
---
Parts needed:
- One black leather headrest.
- FDV overhaul kit (95.669.034)
Please contact me through PN if you have any of this.

User avatar
Aerodynamica
BXpert
BXpert
Posts: 793
Joined: Sat Jun 07, 2008 11:43 pm
Location: Glasgow

Post by Aerodynamica » Tue Aug 12, 2008 9:36 pm

Have you checked the level of the LHM? it could be that it is running a little low and that driving around causes the LHM to sway in the tank and sometimes makes the low level light come on. If you put the suspension to high position and find that the ight comes on then it's surely a low LHM level. Also look at the yellow float disk on the top of the LHM tank when it's set to high suspension it should sit between the 2 red lines.
Graeme M

CX 2400 Pallas LPG
2CV6 dolly (SORNed)
Mk1 Xantia 1.9TD SX

'c'est hydropneumatique'

jeremy
Over 2k
Posts: 2112
Joined: Fri Jul 01, 2005 2:58 am
Location: Hampshire UK

Post by jeremy » Tue Aug 12, 2008 10:08 pm

The first thing is to check the LHM level (check with the car on MAX height).

The stop light will operate if other failures happen (or sensors send the appropriate signal) The ones that come to mind are the engine oil pressure and the red light of death (temperature warning). Are any others operating?

Is the accumulator sound? To test get the car to normal height and let it idle for a couple of minutes. Turn off the engine and sit in the boot. The back should drop a long way and then after about 30 seconds rise to its original height powered by the accumulator. If it does not the accumulator is probably flat and needs replacing.

Is the hydraulic pump belt tight - it must be VERY TIGHT.

I think the above are forlorn hopes. You mention that the car is slow or difficult to get to rise and this points to a weak pump or flow divider problems. If the pump is weak its generally the power steering which fails first as this takes a large volume of high pressure LHM.

When I got my BX DTR Turbo nearly 9 years ago I had problems with it putting the warning light on at high speed and lower speeds when it was cold - as well as being slow to rise. I changed the pump - steering started to work properly and all was fine for about 3 months - but the light started to come on again - and after prolonged and fruitless investigation I took out the pressure control valve in the FDV and found that it had been assembled incorrectly with the ball bearing valve the wrong side of its support plunger. Correct assembly and refitting to the car - and its still fine many years later. I had overhauled an FDV but it was just the same as before.

I found I could extinguish the light and also get the car to rise by turning the steering wheel so that there was a load on the pinion valve.

mountainmanUK

Post by mountainmanUK » Tue Aug 12, 2008 11:15 pm

I agree with the advice given above 100%, but I would like to add one more thought....

The yellow level marker on the LHM reservoir shouldn't be trusted all the time. They can, and do, stick, usually in the "full" position!
It's worth pulling off the black filler cap (carefully) from the LHM tank and looking in to check that there really IS a reasonable amount of LHM in there.
If the level is low, everything will still work OK, but there is a good chance that the "Stop" light will come on when going around corners or roundabouts, or sometimes up or down hills, or when braking.
To be on the safe side, so long as you can see no obvious leaks under the car, if you carry a 1 litre bottle of LHM with you, you should be OK to cover most journeys (unless you suffer a dramatic burst somewhere!)

Hope this helps,

Dave

User avatar
Aerodynamica
BXpert
BXpert
Posts: 793
Joined: Sat Jun 07, 2008 11:43 pm
Location: Glasgow

Post by Aerodynamica » Tue Aug 12, 2008 11:35 pm

The yellow level marker on the LHM reservoir shouldn't be trusted all the time. They can, and do, stick, usually in the "full" position!
-that's true! and it's exactly what happened in my GSA. The cause was that the little clear dome that goes over it had been bumped by the spare tyre coming in/out of the engine bay and was ever so slightly out of line with the float - nearly invisible to the eye but it had enough of a squint to jam the little disk on MAX..
Graeme M

CX 2400 Pallas LPG
2CV6 dolly (SORNed)
Mk1 Xantia 1.9TD SX

'c'est hydropneumatique'

User avatar
TB2
BXpert
BXpert
Posts: 320
Joined: Sat Apr 28, 2007 3:31 pm
Location: Switzerland

Post by TB2 » Thu Aug 14, 2008 12:18 pm

Ah yes, so the HP belt wasn't tight enough. It was quite obvious once the bonnet was open as it was even squeaking a bit and everytime it kicked in the slack was visible to the eye.
It was a bit tricky to tighten it even more but I used a larg metal rod as a lever to push the pump even further to the back and then tightened it in place.

Also, the LHM meter is in fact stuck on MAX. Doesn't matter if I put the car in high, the meter stays at MAX and if I open the cap to take a look inside there's about 6cm space from the fluid level to the top of the tank. The dome is a bit sparkled from aging. Maybe it'll fix itself after driving the car for a bit.

Apart from that, I ignored the coolant lamp coming on from time to time :oops: The expansion bottle was indeed empty. I don't have any leaks and I was actually wondering why it seemed like I had drained more liquid than what I've put back in when I exchanged the coolant. There was room for another litre or so. Most likely this was the reason for the STOP lamp coming on. So now it should be fine.

I didn't get the chance to properly test it after adjusting the belt but I have a spare 1l bottle of LHM in the boot so I'll top it up a little if I keep having problems. At least, putting the car in high, pressing the brake like hell and steering at the same time didn't do anything to the suspension or the PAS. Seems like it's fine now!

Thanks for your advice!
Carl

1989 TRD "Entreprise" Turbo Diesel
1989 16 Valve
---
Parts needed:
- One black leather headrest.
- FDV overhaul kit (95.669.034)
Please contact me through PN if you have any of this.

User avatar
Way2go
Over 2k
Posts: 7279
Joined: Fri Jan 13, 2006 3:15 pm
Location: RCoBerkshire
x 2

Post by Way2go » Thu Aug 14, 2008 3:53 pm

TB2 wrote: Also, the LHM meter is in fact stuck on MAX. Doesn't matter if I put the car in high, the meter stays at MAX and if I open the cap to take a look inside there's about 6cm space from the fluid level to the top of the tank.
6 cm when on max sounds overfilled to me but as it's too wet outside to check mine I can't be immediately sure. :(

I'm sure that others may have more certain thoughts on this as your lhm meter may not, in fact, be stuck after all. :?
1991 BX19GTi Auto