Hydraulic System Priming

Windy Miller · Post by **Windy Miller** » Sat Nov 29, 2008 6:35 pm

Just put hydraflush in my BX and I'm having problems getting the pump to prime.

I've tried slacking off the 12mm bolt on the pressure regulator, removing the inlet pipe from the LHM tank and sticking a funnel in the end which I filled up with Hydraflush. When running the engine the Hydraflush dissappears from the funnel very slowly and even after 2 funnel fulls of Hydraflush the pump doesn't seem to work. Some of the old LHM back has made its way back to the tank so some fluid must be circulating but when I tighten up the bolt on the pressure regulator there is nothing - no PAS, brakes or suspension.

Any suggestions ?

Thanks

Ian

ken newbold · Post by **ken newbold** » Sat Nov 29, 2008 6:45 pm

Have a cup of tea or two, or even a fag.

It's probably got air in the system, next time you try it it'll probably be ok.

demag · Post by **demag** » Sat Nov 29, 2008 8:26 pm

As far as I know the funnel in the pipe thing is the way to go. Open the 12mm bolt half a turn for 30 secs then close. Keep funnel and hose topped up (with your third hand

) Cycle height lever slowly through all positions to help bleed the air. Repeat until something happens.

jeremy · Post by **jeremy** » Sun Nov 30, 2008 12:44 am

I did have similar problems with the original and weak pump on my DTR Turbo.

The pipe end is important - it must be free from splits and have an efficient clamp

There is no need to rush to close the regulator screw - you only open it o allow the fluid to recirculate - and hopefully purge that part of the statem from air.

I fill the pipe with LHM the - like everyone else fit it to the reservoir and tighten the clam and try and convice myself that the thing is pumping (hopefully LHM returned to the reservoir - ie disturbance or bubbles when I look through the filler) When I'm convinced I'll tighten the regulator screw and start looking for signs of life, like the suspension rising.

Raising the engine revs a bit won't hurt especially if you know there's some LHM in the pump. (I don't know how delicate they are if run dry)

AndersDK · Post by **AndersDK** » Sun Nov 30, 2008 11:31 am

The pump will run hot if it runs dry. Then things tends to accelerate and kill the pump.
But still we are talking accelerated idle revs for extendend length of time, i.e. several minutes.

The best method I've found in really bad cases :

Make sure the reservoir filters are clean.
Reservoir topped up.
Be sure the suction hose is in good nick and tight over the studs.
Open the pressure release (12mm) bolt 1 turn.
Set the suspension to normal height.
Let engine idle up to 1hour if necessary.

Do whatever small jobs you have while waiting for the pump to build up pressure.
Try close the pressure release screw every 5 minutes.
The wellknown clicking from the regulator will instantly tell you if pressure is building up.

This method has worked for me on several occasions on my parts cars, which had to be moved from time to time.

Jaba · Post by **Jaba** » Sun Nov 30, 2008 12:22 pm

I had this very issue a few weeks back after cleaning the lhm filters and renewing the lhm.
It just would not pump any fluid although the lhm disappeared down the supply tube into the pump every time I checked and topped up. Made no difference if the relief screw was open or closed.
I then had a flash of inspiration or faded memory and started moving the steering wheel to and fro. I was rewarded immediately with lots of froth in the tank and then the stop light went out and normality was resumed.

Don't really understand this. This pump is a good one, only done 80k miles and pumps up in the morning very quickly. I would have thought that the pump would easily force through and displace any air in the FDV, but obviously not in this case until I directed some flow through it by turning the steering.
AWTEW Shakespeare

AndersDK · Post by **AndersDK** » Sun Nov 30, 2008 4:35 pm

Yes - I forgot that -

The above description is for the standard manuel steering, no FDV.

On PAS BX'es the FDV is likely to cause problems and then the pressure builds up if you calmly and patiently hold the steering wheel against the left end stop.
If this is necessary to bring up pressure every morning, then the FDV needs an overhaul.

nige! · Post by **nige!** » Sun Nov 30, 2008 9:58 pm

i had a funnel attached to the pipe that goes to the pump, it was just a case of feeding LHM down the pipe with the engine runnnig. Took about 3/4 of a bottle till it was primed, then it was a case of quickly shoving the pipe back on.. like said above patience is the key here

Windy Miller · Post by **Windy Miller** » Mon Dec 01, 2008 8:54 pm

Thanks for the advice chaps !

The car is now sorted - after much fiddling around. I think it was turning the steering from lock to lock which finally primed it. The car drives better now with consistent power steering - the stop-start PAS was the reason for the Hydraflush in the first case.

Subsequent to the fluid change I've noticed that when I move the height lever from low to high, the stop light comes on for several seconds - is this normal or do I have a problem looming ?

nige! · Post by **nige!** » Mon Dec 01, 2008 9:03 pm

it dosen't happen on mine... am wondering if the hydraulic pressure is all it should be.. you have enough fluid in the tank right?

demag · Post by **demag** » Mon Dec 01, 2008 9:20 pm

Stop light usually indicates low lhm/hydraflush in tank. Put the height on "high" then fill the tank until the orange disk is between the two red marks on the looking glass on top of the tank. That should be the correct level.

jeremy · Post by **jeremy** » Mon Dec 01, 2008 9:35 pm

Its perfectly normal for the stop light to come on when moving the height control lever to a higher position.

The 'Stop' light has 2 feeds from the hydraulic system - the reservoir level indicator switch and the safety valve which is under the car at the back of the subframe. The safety valve is the first component after the regulator and also acts as a junction for the suspension and brakes. Its illustrated in Haynes but basically its function is to prioritise the supply of available high pressure LHM to the front brakes and to power the warning lamp - directly from its shuttle.

What is happening is that the thing settles and the pressure is at operating levels and the light is out. You move the lever which opens the height correctors and LHM flows from the accumulator to the suspension cylinders and starts to raise the car. The suspension will take quite a lot of LHM which discharges the accumulator to some extent. The pressure needed to compress the spheres and possibly raise the car is less that required for safe operation - so the safety valve does its job and turns the light on. As the system does its job the pressure rises and the light goes out.

Way2go · Post by **Way2go** » Tue Dec 02, 2008 3:16 am

jeremy wrote:The pressure needed to compress the spheres and possibly raise the car is less that required for safe operation - so the safety valve does its job and turns the light on. As the system does its job the pressure rises and the light goes out.

This statement cannot be right according to the laws of physics (Newton's 3rd law etc).

If anything, in compressing the spheres to raise the height increases the back pressure on the valve because you are causing the nitrogen to occupy an even smaller space in the spheres.

I would expect the problem is that the lhm level in the tank is low or marginal when the system is on high. The light should not come on again after the car is started and has started to rise.

mnde · Post by **mnde** » Tue Dec 02, 2008 10:51 am

I would say it is quite normal for the STOP light to come on for a few seconds when moving the lever from lowest position to high. Mine does it, and the LHM reservoir is, if anything, overfull.

It's the same as if you're starting the car after it has lain stationary for a week. There's no hydraulic pressure, then the STOP lamp extinguishes as the car is rising when full pressure has been reached.

Mark.

Aerodynamica · Post by **Aerodynamica** » Tue Dec 02, 2008 11:51 am

My stop light also comes on with the car running and having just moved the height control up - it is a common BX characteristic but it is not correct operation and I'm thinking the cause is the FDV since that device is present in the BX and not in Eg. CX, GSA etc that I've had that never displayed this characteristic. Also my first sheddy BX didn't do this either and it was non-PAS.

When I first got the BX the light would come on after moving the lever and it took an age to go out - replacing the accumulator helped but it'll still come on with raising the height with the engine idling.