high to low pressure leak

BX Tech talk
User avatar
johnj
New Member
Posts: 17
Joined: Tue Jan 24, 2006 7:32 pm
Location: Glasgow. Scotland

high to low pressure leak

Post by johnj » Sat May 13, 2006 10:24 pm

I am hoping somebody can shed light on a problem I cant seam to solve. On wednesday i parked the car as normal with no problems, when i came out to it in the morning the contents of the LHM was deposited on the drive with the reservior cap blown off. and the back of the car sank down. The car never sinks that quick, usualy takes 3 days before sinking. Thought it was just a glitch so filled the tank and drove to work with no problems, parked in the car park and thought it was ok, came out to check at lunch to find the same again, reservior cap off and contents on the floor. Posted this on 16v forum and was advised it may be a bleed between pressure and return system but after 6 hrs today still no further forward. I can't seam to track down where this bleed takes place, so any previous experiance of this would be much apprechiated. Car is a 1993 16v so link to understand full story, thanks in anticipation http://www.bx16v.com/forum/viewtopic.php?t=2846
BX 16V 1992 53k Red.
Work in progress.
BX19D Estate 134k
what a load carrier

User avatar
ken newbold
Over 2k
Posts: 4408
Joined: Sun Aug 14, 2005 10:53 pm
x 5

Post by ken newbold » Sat May 13, 2006 10:31 pm

I think you'll need to stay with the car after you turn the engine off and watch and listen for the sound of fluid returning to the tank.

Once this happens you could start pulling the return pipes off one at a time to see which one is flowing.
Once you know which pipe it is, then you'll have an idea where the problem lies.

Just one daft thought though, you're not over filling the tank are you? :oops:

User avatar
johnj
New Member
Posts: 17
Joined: Tue Jan 24, 2006 7:32 pm
Location: Glasgow. Scotland

Post by johnj » Sat May 13, 2006 10:37 pm

i have tracked it down to the rear suspension return but what do i replace first?
BX 16V 1992 53k Red.
Work in progress.
BX19D Estate 134k
what a load carrier

User avatar
johnj
New Member
Posts: 17
Joined: Tue Jan 24, 2006 7:32 pm
Location: Glasgow. Scotland

Post by johnj » Sat May 13, 2006 10:40 pm

ps i stayed with the car for 6 painfull hours on my back 2day removing pipes and spheres looking for unusual back pressure but no unusual noises other than a sort of whistling in the tank when the fluid returns.
BX 16V 1992 53k Red.
Work in progress.
BX19D Estate 134k
what a load carrier

User avatar
ken newbold
Over 2k
Posts: 4408
Joined: Sun Aug 14, 2005 10:53 pm
x 5

Post by ken newbold » Sat May 13, 2006 10:48 pm

then it must be from the rear height corrector or the rear cylinders.

My guess would be the height corrector. You'll need the car on ramps to be certain before you start replacing parts.

One of the two metal pipes that come out of the top of the HC is the return, this should be the bottom one thats clipped to the chassis as they run along it's side. When it reaches the front subframe it connects to a rubber pipe and then up to the tank.
If this is the one that's passing fluid, then it is the rear HC at fault.

AlanS
BXpert
BXpert
Posts: 841
Joined: Mon May 16, 2005 9:53 pm
Location: Queensland, Australia

Post by AlanS » Sat May 13, 2006 10:59 pm

Apart from asking the bleedin' obvious; when it does this, have you tried starting the car to see if it pumps up and acts normal? By that I'm wondering if perhaps it's just a case of a sphere blowing (possibly an accumulator) that is loading up with LHM and returning the lot to the resevoir when the car is stopped and simply overflowing the tank; in other words, is it simply been overfilled following the last event?
I can't understand why any HP could get into the return side when the car is parked up, after all, that's when the HP is decreasing, due to the pump not operating.
Failing that, could it possibly be a feedback (if that's possible) from the Pressure regulator, after all, it is supposed to regulate pressure and I did hear in the early days of BXs that it was not unheard of these creating some very strange symptoms and even self destructing.



Alan S
By the time you're old enough to know it all, you can't remember why you were learning.

AlanS
BXpert
BXpert
Posts: 841
Joined: Mon May 16, 2005 9:53 pm
Location: Queensland, Australia

Post by AlanS » Sat May 13, 2006 11:03 pm

ken newbold wrote:then it must be from the rear height corrector or the rear cylinders.

My guess would be the height corrector. You'll need the car on ramps to be certain before you start replacing parts.

One of the two metal pipes that come out of the top of the HC is the return, this should be the bottom one thats clipped to the chassis as they run along it's side. When it reaches the front subframe it connects to a rubber pipe and then up to the tank.
If this is the one that's passing fluid, then it is the rear HC at fault.
That's something I intended mentioning; the height correctors as regards high pressure becoming low. I posted somewhere a few weeks ago (FCF possibly) about the inside workings of them and the series of stainless reed valve things they have inside with cappiliary holes in them where the LHM passed through and in the process this lowers the pressure and returns it to the tank, but this didn't explain the volume or why it does it when stopped rather than when going as the volume involved would be the same as during normal operation.


Alan S
By the time you're old enough to know it all, you can't remember why you were learning.

User avatar
johnj
New Member
Posts: 17
Joined: Tue Jan 24, 2006 7:32 pm
Location: Glasgow. Scotland

Post by johnj » Sat May 13, 2006 11:17 pm

when the car is running it is pumping the fluid round but when stopped the fluid is stagnent. this may justify the surge. just like when you turn your tap on with the plug out, the minute you plug it then you get a build up. Another day undwer the car 2morrow then, keep you posted.
BX 16V 1992 53k Red.
Work in progress.
BX19D Estate 134k
what a load carrier

AlanS
BXpert
BXpert
Posts: 841
Joined: Mon May 16, 2005 9:53 pm
Location: Queensland, Australia

Post by AlanS » Sun May 14, 2006 2:06 am

By the same token, if you have a system that holds say 5 litres and you have it full, it's not going to come out, but if you have a totally flat sphere and top it up with the engine/pump operating, it will stay at the level until the car is stopped whereupon the car settles and sends the extra fluid normally stuck in the sphere back to the tank and overflows it.
Difference between an LHM tank overflowing and a sink with a plug in or out is that the LHM tank is a set amount whereas the tap is adding to whatever might already be there.
It might be said that if you were to set the height adjustment lever to its lowest setting would force it to happen which eventually it possibly should, but when spheres blow, they often do so in such a way that the membrane acts like a non return valve which is why it's often a case of getting a green shower when a blown sphere is removed, but I have also seen it happen that it will retain fluid in there for a time but gradually release it and this is my suspicion on this one.
Try setting it on the lowest setting and then waiting to see what happens, but the wheels and weight of the car must remain on the ground or on a ramp if need be, as if you raise the car and remove the weight off the wheels, it could be that lack of load may cause the problem to not happen as it wouldn't be forcing the fluid back to the tank. I take it the system has been bled properly and you're not getting weird tricks from air in the system?


Alan S
By the time you're old enough to know it all, you can't remember why you were learning.

User avatar
johnj
New Member
Posts: 17
Joined: Tue Jan 24, 2006 7:32 pm
Location: Glasgow. Scotland

Post by johnj » Sun May 14, 2006 10:29 pm

no all spheres check out ok, begining to suspect rear suspension unit. car has not been over filled, dumped first contents when i have not touched the fluid level since January when i changed the filters. when i lower the car to the bottom the fluid returns seaminly fine with no over surge, but back is still very lazy returning back to ride height.
BX 16V 1992 53k Red.
Work in progress.
BX19D Estate 134k
what a load carrier

AlanS
BXpert
BXpert
Posts: 841
Joined: Mon May 16, 2005 9:53 pm
Location: Queensland, Australia

Post by AlanS » Sun May 14, 2006 11:16 pm

Have you thoroughly bled the rear brakes in case it is air getting trapped in there?

The reason I was suggesting the overfilling/blown sphere was that I had a similar experience a few years back.
I was in the CX and attended a business meeting. Came out (all dressed up like a sore toe) only to find a large pool of LHM running from under the car. Dressed as I was, I could do nothing, so called one of the boys who had a crawl around and decided it was just overfilled or something weird had happened. Started car, all went well. A day or so later, the LHM level warning light came on, so I topped it up still concerned at where it was going as by this stage, no fluid leaks showing anywhere. Drove it for a couple of days without problems. Parked in garage for a couple of days and sure enough, LHM everywhere when I shifted it. Took it to a guy with sphere regassing gear and found a couple of spheres were full of LHM. Replaced the ones that were full and had no more problems.
Difference of course is that Ausiie spec CXs have about 7 sphewres on them and a couple are unnecessary, as a result they can be blown without showing any ill effects.
So on the presumption that the fluid is definitely coming from the overflow of the tank and you're 100% certain it isn't overfilled, it can only be a pressure stuck inside the system and to me the only thing has to be air which will build up pressure and the rear brakes (which are possibly not working anyway due to being seized) are dead ends and a good chance of being where the air is trapped and buildng pressure.
I bleed mine usually by setting suspension to the highest, putting a sissor jack under the end of the arm and imposing weight on the suspension and then getting someone to stand on the brake pedal and letting the fluid run into a bottle until it runs clear with no bubbles at all.I find the passenger side is the one most likely to have air in it, but do both anyway.
I usually remove the pistons before I start, wash the calipers in petrol and lube the pistons with silicone grease so they are moving smoothly, that way I know I have done it right.
Hope that helps give you a few more clues.


Alan S
By the time you're old enough to know it all, you can't remember why you were learning.