Lhm loss into thin air.

DavidRutherford · Post by **DavidRutherford** » Sat Nov 22, 2008 3:52 pm

The BX of amazing tattyness is losing LHM. Not a massive amount, but enough that it needs a top up every few months. Only thing I can't tell is where it's going.

There are no drips on the driveway, I've had it up in the air and checked all over the pipework, rear strut gaiters front strut gaiters, brake calipers, steering ram etc.etc. There's no LHM leaking from anywhere.

.. and yet still the level drops. It's most noticeable first in the steering, as (especially when cold) you can feel the air in the steering as it goes stiff and light and stiff and light again. Top up and all is fixed.

Where on earth is it going?

Post by **docchevron** » Sat Nov 22, 2008 5:37 pm

Nicked by pikies?

Duno mate, that is rather odd!
It's not venting into the rear subframe or something??

BX Bandit · Post by **BX Bandit** » Sat Nov 22, 2008 10:04 pm

My money is on the doseur valve...IMHO if in doubt, suspect the doseur......

Post by **docchevron** » Sat Nov 22, 2008 10:06 pm

Hadn;'t even considered that!
Where's a picture of a man pointing at a doseur when you need one?

OR, could it be that the LHM tank is getting fatter?

BX Bandit · Post by **BX Bandit** » Sat Nov 22, 2008 10:18 pm

Well, if the coefficient of expansion of steel is sufficient in warm weather to suggest the malfunctions that David is suggesting then that is a possibility Sir Docness.........

Jaba · Post by **Jaba** » Sun Nov 23, 2008 12:45 am

Just a thought as you can see no leaks anywhere but have dead steering when cold.
Are the lhm filters clean ? If not the flow might be a bit marginal when cold and topping up brings the level to a cleaner part of the filter masking the cause by removing the symptom.

DavidRutherford · Post by **DavidRutherford** » Sun Nov 23, 2008 1:03 am

Jaba wrote:Just a thought as you can see no leaks anywhere but have dead steering when cold.
Are the lhm filters clean ? If not the flow might be a bit marginal when cold and topping up brings the level to a cleaner part of the filter masking the cause by removing the symptom.

The level is definitely falling between top-ups. It probably needs 1/2 litre every couple of months at the moment. The level got low enough a while back that the low-fluid warn lamp came on in high. First time I've ever seen that happen.

DLM · Post by **DLM** » Mon Nov 24, 2008 6:40 pm

How's about...

Possibility #1

Nitrogen loss from spheres, on the basis that nitrogen escaping through a porous diaphragm is the only "lossless" possibility. Gas returns through system, vents through tank breathers, compressionless lhm has to make up the volume lost. Cause of the copiously-piddling-sphere-syndrome when swapping for a new one. However as the largest possible spheres are 500cc capacity this doesn't seem possible with a 1/2 litre difference over 2 months. And there's the small matter of loss of ride comfort that'd hopefully be noticeable.

Possiblility #2

Some serious "slow" leakback that's causing a return pipe subsystem to be full of lhm where previously it just held air. Again, just a bit iffy if it's a question of 1/2l per 2 months.

Possibility #3

How much leakback is there from the rear syspension cylinders? there's potential for leakback here and in the worst cases for the boots to start to fill, despite the return and air vents on the way. Short of octopus subsections these are the only thing anywhere near the return pipes that have any appreciable volume.

Possibility #4

One of those pesky leaks in the return pipery that tends to very gently spray/drip directly to the road or onto the underside of the car. Not very obvious unless you're under the relevant section, possibly with the engine running.

Possibility #5

Little green lhm gremlins greedily drinking from a t-piece tapped into the return pipe system.....?

pitman · Post by **pitman** » Mon Nov 24, 2008 11:27 pm

I just want to add that I had a very small leak in the front suspension return pipes that only showed up at MOT testing.

As the car parks on the driveway, I never saw a single drop but I had to top-up some LHM about every six month.

It started only leaking when the MOT guy applied those hydraulic jacks under the car to test steering and ball-joints.

So, possibility #4 from the former posting is quite possible.

Geoffrey Gould · Post by **Geoffrey Gould** » Thu Nov 27, 2008 8:20 am

Hello David into the rear subframe sounds good but how about a small leak from the steering pinion into the rack so that you have a very well lubed rack?
All the best.
Geoff.

mnde · Post by **mnde** » Thu Nov 27, 2008 1:30 pm

Geoffrey Gould wrote:a very well lubed rack?.

Err...

no I won't even go there...

Umm... Is it possible that LHM is dripping onto somewhere hot (e.g. exhaust manifold) and evaporating, hence no evidence?

Mark.

AndersDK · Post by **AndersDK** » Sun Nov 30, 2008 11:42 am

DavidRutherford wrote: There's no LHM leaking from anywhere.

Try the cardboard under car test over a weekend.

nige! · Post by **nige!** » Sat Dec 06, 2008 5:50 pm

mine was dodgy pipe or seal, it was spraying a very fine mist of LHM at the joint, i replaced pipe and seal.

Slagtrooper · Post by **Slagtrooper** » Sun Sep 07, 2014 1:10 am

I don't know if i'm doing "pseudo-science", but the PAS vent have its tube ok? Because mine hasn't yet and i thought about that:

Car stopped, little diameter: Opened, but not enough to drip.
Car running, little diameter: Opened, but with wind drag pulling the oil.

Something like that is possible?

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