Mystery of the Hydraulic Warning Light

kiwi · Post by **kiwi** » Sat Jan 17, 2009 6:56 am

I thought better start another thread as it seems the other title "Backend wont rise" has railroaded answers.

Heres the problem the warning light comes on for no particular reason if you pump the brake you can get it to come on.

No Leaks evident anywhere

Recently refurbished FDV and replaced accumulator with one from higher mileage model! Had noticed some undescrible audible noise when under load though

Also I used my original sphere.

Tried out the checks to the braking valve described in the other thread "backend wont rise" on both BXs we have and same result.

What did discover is that someone had connected the Return Pipes to the reservior in the wrong place eg to the port nearest the headlight.

nearly 3 years and I didnt notice

Hydraulic fluid a bit tainted so thats obvious needs replacing.

Tried the BX dance! Holding the Brake pedal down from low and it was very slow to respond to any rise. When it did it was as the other BX and typical leap up at the back before settling.

Of course this Damn Light coming on! So now not sure is it the Brake valve but it passes the tests of return flow and not dropping? Rear height corrector can be ruled out I think or is it the Accumulator duff or simply dirt build up?

cauchoiskev · Post by **cauchoiskev** » Sat Jan 17, 2009 10:38 am

Unless there is a massive internal leak, there is no way the height corrector can cause the stop light to come on, even if it is sticking.

So that leaves four possibilities : the pump, the FDV, the pressure regulator and the brake doseur.

From what you describe, I doubt if the doseur is bad enough to cause this problem.

It could be the pump or the FDV, but my bet is on the pressure regulator, especially as you have just changed it and it makes funny noises. Could this be a "re-seating the ball bearing" scenario ? ?

Failing that, I would stick the old leaky PR back on to see what happens.

Geoffrey Gould · Post by **Geoffrey Gould** » Sat Jan 17, 2009 10:40 am

OK so it's war on lights time, a couple of sillies to try, does the pressure regulator control the pressures as it should, IE. cut in and cut out pressures. Are the pressures low? That will play hell with the system.
The security valve also, if I remember rightly (memory not too good at the moment.) the security valve will switch the 'stop' light. If so as a temporary check then disconnect it. see what happens.
I could be talking a load of b0ii0c*s on this one will have to check but have nothing here at the moment.
Cheers.
Geoff.

TB2 · Post by **TB2** » Sat Jan 17, 2009 11:15 am

No idea if it's related, but my stop lamp came on when breaking hard just because the hydraulic pump belt was a wee bit too slack. It was also making funny noises because of that. It needs to sit really tight.

kiwi · Post by **kiwi** » Mon Jan 19, 2009 3:10 am

The mystery deepens

Took it into town today open road running towing a light trailer. That phantom light came on a nd blinked a couple of times for no reason. When I say no reason I mean just random.

Something though became evident on full steering lock and that was noise from somewhere. I can not pin down yep its driving me nuts to now consider that the refurbished FDV or the Regulator that I replaced "could" be the cause.

I am now confident that its not the height corrector or Brake Valve.

All this hassle was a result of a leak of LHM!

kiwi · Post by **kiwi** » Fri Jan 23, 2009 2:07 am

UPDATE

Now spoken to another BX mechanic and gone through a few things with him. Firstly he never heard of Hydraflush before or used it and suggested Kerosene to clean the system.

My reaction to that is not blardy likely matey Kero has a still explosive property.

Beside that he also is saying the pressure valve which he reckopns is easy to clean out alon with the Height Correctors. And the Fileters to the Reservoir. Well I think I found part of my problem!

One of the filters was not fitted properly in the reservoir, the metal clip that holds it in place to the other one was missing. so therefore not doing its job.

Now just waiting for the Total Rep to get back to me for this Hydruncage stuff, unfortunately I forgot its an Anniversery weekend for Auckland

me living in the Wellington area who had theres last weekend. Got to love regional Holidays to confuse you

Two more weeks and waitangi weekend Holiday! Hate this time of year to me damn Holiday weekends.

DavidRutherford · Post by **DavidRutherford** » Fri Jan 23, 2009 8:25 am

kiwi wrote:My reaction to that is not blardy likely matey Kero has a still explosive property.

What, like that big tank of petrol at the back of the car?

Kerosine sounds like a reasonable suggestion. It's mineral based, so shouldn't attack the seals, and is definitely thin enough to rinse out sludge. My only reservation is whether it would hold dirt in suspension like Hydraflush does.

mountainmanUK · Post by **mountainmanUK** » Fri Jan 23, 2009 8:33 am

I don't know if GSF would ship to your Antipodean part of thge planet, but Hydraurincage can be bought from them for around £16 for a 5-litre plastic bottle.
I replaced my disgusting LHM with Hydraurincage, in Monica, in Oct/Nov last year. I have since driven around 1400 miles, and I plan to drain it and refill with nice clean LHM at around 200 miles. The difference in brakes, suspension, and steering has been very noticeable! I can only imagine how much crud must have built up in the system over the years!
I guess that it's quite possible for some accumulation of yucky gunge to have built up somewhere, causing your warning light problem.
Gotta be worth a good flush, eh?

Debelix · Post by **Debelix** » Fri Jan 23, 2009 8:48 am

A friend of mine said that once used petrol for cleaning the suspension system of his Xantia and all was fine. The trick is not to drive with it, but just put it in the LHM tank, start the engine and get the car to do some Citro-"aerobics", which means that he get the car up and down repeatedly for 10-15 times. After that you just get the petrol out, wait for few hours for the petrol to evaporate from the system and pour new LHM in. I never tried it (I used Hydraflush for cleaning) but he said that it had very nice effect on his system and it only takes few hours to do it.

By the way, a suggestion from me - check out all of the pipe fittings for proper tightening - the day before yesterday I was helping a guy with a BX with similar problems - "STOP" light coming on and when pressing the brake the back of the car sinking sometimes (quite randomly) - it turned out that the problem was one of the HP pipes going in the Flow Divider - after tightening up all of a sudden everything was fine. The idea is that because the HP Pump can't provide the pressure because of the weak spot in the system, pressing the pedal causes the doseur to take pressure from the suspension which in turn lights up the "STOP" sign.

kiwi · Post by **kiwi** » Sat Jan 24, 2009 11:10 am

Debelix wrote: By the way, a suggestion from me - check out all of the pipe fittings for proper tightening - the day before yesterday I was helping a guy with a BX with similar problems - "STOP" light coming on and when pressing the brake the back of the car sinking sometimes (quite randomly) - it turned out that the problem was one of the HP pipes going in the Flow Divider - after tightening up all of a sudden everything was fine. The idea is that because the HP Pump can't provide the pressure because of the weak spot in the system, pressing the pedal causes the doseur to take pressure from the suspension which in turn lights up the "STOP" sign.

Now thats a good possibility either didnt tighten them enough or they worked loose.

Always afraid of over tightening them but maybe thats the problem air being sucked in,

cauchoiskev · Post by **cauchoiskev** » Sat Jan 24, 2009 4:16 pm

To be honest, Kiwi, if they are not leaking I would leave them well alone. You will only damage the pipe or joint or strip a thread.

The LHM is under massive pressure, if there is none leaking out how can air get in ?

kiwi · Post by **kiwi** » Sat Jan 24, 2009 7:22 pm

Good point thats what I get for replying late at night

Since I found the problem with the filter in the reserviour being not connected. I have a extremely strong feeling the problem is crud related meaning a good flush first them strip if that dont work. Its lucky its the primary BX or else it would be parts by now.

Geoffrey Gould · Post by **Geoffrey Gould** » Sat Jan 24, 2009 8:34 pm

Hi I would be a bit wary about petrol as unleaded will melt certain types of rubber pipes/seals etc. If there is any doubt then get some LHM proof pipe seals or '0' rings and pop them into a jar of what ever you are thinking of using and let them soak for a week or two and see what happens. I would hesitate and be careful, it would be a right royal pita if all the seals would have to be replaced.
Cheers.
Geoff.

kiwi · Post by **kiwi** » Sun Jan 25, 2009 9:24 am

I have not forgotten Geoff the problems associated with rubber O rings and piping from the balls up NZ made when they phased out leaded fuel back in 1996. The fuel over here has higher aromatic properties than elsewhere in the world because of where its shipped from.

Really like the idea of flushing the system with petrol even less than kerosene.

Cleaning filters and certain parts yes but pumping petrol in the system, well it will certainly find the rotten rubber faster