Lhm/hydraflush And Added Ingredients

I've just re read the fascinating thread from a while back about flushing the hydraulics and the debate about Hydronet and other fancy stuff. What I was wondering was whether anyone who added petrol or paraffin to the hydraulics noticed any bad/good effects over the long term? That is, if they haven't ignited...

I'm finally getting round to changing the fluid in my new/old J reg 2.1 as the suspension is absolute rubbish, in spite new spheres being fitted less than a year ago.

Jamieb

maybe theres a reason for not reporting back after adding explosive mixtures into a high pressure system....

on an educated guess stance i cant see much harm coming from a few weeks of parafin abuse, or even maybe engine flush, although it would require more debate and stuuffs first..


on a flushing front, just had a front room radiator pipe come off, and the water in the house's heating sytems was black and oily and stunk, so that had to be flushed, took them most of day and needed lots of anti-acid stuff in it..

I will report what I find in the LHM tank tomorrow. I'm quite curious. If the spheres really are new-ish and the suspension is as bad as it is, I sort of hope it's full of gunk so I know I'm doing something...

If you must add something, I would recommend diesel rather than petrol or paraffin. Diesel as well as being a good cleaner and lubricant also has anti-rust quality. Paraffin, whilst a good cleaner is nasty rusty stuff, and I would regard it as a fairly bad thing to contaminate your hydraulics with...

H Jamieb,i've advocated the use of paraffin (kerosine) for some time after i experimented a few years ago.Since then i've run continuously with a 2 to 3% mix - approx 100 to 150ml.My car has anti-sink,so has the 6+2 pump and no fdv.It can sit for 10 days or so at a time and remains within a centimeter or two of normal ride height for that time.The initial detergent effect of the paraffin produced further cleaning after the hydraflush had been flushed out.The hydraflush did around 3k.Thereafter the mix produced clean, good clarity lhm.The most noticeable effect was the overall improved system response,particularly smoother steering and more precise braking control.This more so in the winter,and here in the Highlands we regularly experience days on end below freezing,and savage minus temperatures.Clearly viscosity is the main factor here.The car also spent 2 years or so in the S France with me,where summer temps were in the mid to high 30's,so it has been fully tested in all climates.There was some question with regard to the hygoscopic characteristics of paraffin,but as i change the fluid mix annually and the fluid is as near fresh as you could expect, it hasn't been a concern.The concentration level of paraffin is really quite insignificant with regard to effecting the properties of the lhm.I've just read jonathan's post and raise issue with his determination of rust.I've spent 31 years in aviation and never seen a gas turbine engine fuel pump,or any fuel system component with rust.
robertm

This post has been edited by robertmnorton on April 30, 2010 11:24 pm

Interesting stuff Robert.

My thoughts on rust were based principally on use of paraffin as a cleaner on finding that if you cleaned, say, a bare engine block with paraffin rust would almost immediately then form on the machined surfaces, whereas with diesel an equally efficient clean would be achieved but without the attendant risk of rusting. On reflection this is likely due to the paraffin (as a solvent) simply evaporating without leaving a protective film, unlike diesel, and not paraffin being a substance that encourages rust.

Incidentally, how does the aviation industry deal with flushing hydraulic systems, or is it the case that the change intervals for hydraulic fluid and/or filtering systems makes such an undertaking unnecessary?

Jonathan.

Hi all,with regard to airborne hydraulic systems in the first instance the fluid is an esther based synthetic compound with extreme fire resistance and will rot normal rubber based seals almost on contact.As such teflon and spcial compound seals are used.Due the quantity of fluid in the system an external rig is used to flush.In maintenance the system service fluid is used,in manufacture a high detergent level fluid is normally used prior to first flight.Fluid samples undergo spectral analysis at regular intervals and only when the acidity or level/type of particles indicate excessive wear of a component will a drain and flush be done,exceptionally at a major o/haul input or after an o/heat condition.Esther based fluids can jellify or even solidify under extreme heat.As you would expect being just another hydraulic system there are is little difference in it's operation to that of a citroen.With the usage of fly by wire flight systems and rapid response actuators system operating pressures are now 5000psi.
robertm

Thanks for sharing your experience Robert. At the moment I've noticed one immediate effect of the hydraflush - car rises and sinks without groaning - and will try parafin, if I can find it for sale anywhere! A note on temperature - after the old LHM got really warm, ride did improve marginally, a result of increased viscosity I suppose.

A bonus (I suppose) was discovering an outer gaiter had split when I took the front wheel off - must have happened been very recently - so that's next weekend taken care of.

Hi Jamieb,
Parafin you can buy a B & Q where i bought mine i left mine in for 5 thousand miles a mixture off parafin and hydocarnaige and it freed off my sticking front suspension then replaced the lhm for new it come out a quite brownish colour.

Regards,
Norman

This post has been edited by Norman on May 02, 2010 09:15 am

B&Q it is. Thanks.

One other thing I've noticed is that the car stays up a lot longer. Just out of interest, why should new fluid help the system retain pressure?

Hi Jamieb,principally just removal of contaminants on the seal edges allowing better sealing of valves and pistons with clean fluid at the interface.
robertm

Always wondered about that. Thanks!

Hi Robert, I'm not sure that high pressure helps with response times. Isn't it more a case of reducing component size?

In my day it was good old OM15 (which I believe is compatible with XMs)

Derek

This post has been edited by DerekW on May 03, 2010 03:45 pm

Hi Derek,yes smaller components are used,in most cases now individual power control units with built in processor and valve modules,but still fed from centralised hyd systems.The jump to 5200psi is to allow instantaneous reversal of the flight controls with reduced lag.It's a curious thing to watch ailerons flipping between full up to full down up to 50 times a minute during testing.The reason is to offset wing loads,reduce drag and allow better control in windshear conditions.The theories now outside grasp.
robertm

Sorry Robert, that was a case of operating mouth - or typing finger - before fully engaging brain. Of course the smaller component operates quicker because it needs less fluid volume. If we had an "embarrassment" emoticon I'd use it!

Derek