A homage to coffee filters - and David Rutherford

cauchoiskev · Post by **cauchoiskev** » Fri Oct 10, 2008 12:22 pm

My BX has been boringly reliable lately. Luckily, the steering started to get a bit heavy, the tick time dropped, and it was on the stops after a few hours when parked. The brake and strut return hoses had noticable if not catastrophic flow. At last, a problem !

I first thought of changing the LHM, but then remembered it was only a bit more than a year old. So I decided to try David Rutherford's "filtering the LHM with a coffee filter" trick.

It turned out that he LHM was relatively clean, only a few fly-shits or similar in the filters and very moderate silt under the plastic disc, nothing like as bad as the photos I have seen in other threads. So I stuck it back in, thinking nothing would be changed.

Result : steering and tick time are back to normal, and the car is still up after more than 24 hours. There is no noticable flow in any of the return hoses.

How do you explain that then ?

Rob_e (UK) · Post by **Rob_e (UK)** » Fri Oct 10, 2008 7:41 pm

Perhaps your BX was feeling neglected so started to misbehave and now it's had some attecntion it is happy again.

That does seem quite strange behaviour, the only explaination I can think of is that the filter has removed something that doesn't show visibly; perhaps removed some moisture that had been absortbed by the LHM by soaking that up rather than the LHM. Although being mineral oil LHM shouldn't really absorb much moisture compared to DOT type brake fluids. Or perhaps if some of the LHM molecules breakdown to smaller ones and so thin the fluid over time, perhaps these are more easily soaked into the filter and so refreshing the LHM by raising its viscosity a bit again.

However it did it at least it solved the problem

Perhaps it should be an upgrade to have a coffee filter permanent fitted into the LHM tank.

Rob

cxprestigeauto · Post by **cxprestigeauto** » Tue Oct 14, 2008 5:40 pm

All in all an 'expresso' job that gave the car a quick 'perc'

Rob

cauchoiskev · Post by **cauchoiskev** » Fri Oct 24, 2008 12:26 pm

Rob_e (UK) wrote: Perhaps it should be an upgrade to have a coffee filter permanent fitted into the LHM tank.
Rob

Maybe that's not such a bad idea !

Although you would have to be careful about the filter clogging up if the LHM is very dirty. I'm going to give it a try.

DLM · Post by **DLM** » Fri Oct 24, 2008 1:20 pm

Interesting - Grolliffe seems to be heading in the direction of your pre-filtering state at the moment, so I'm reading this with some interest.

I'd be cautious about ascribing improvements to the filtering alone, unless you went through the whole gamut of citaerobics first before trying this approach. There's more than one factor at work here, methinks. Any cleaning of the tank-to-pump-supply filter, however cursory, could make a difference, as some of the symptoms sound a little bit like those which occur when there's low lhm.

However, if it works, I won't knock it - an approach that I find useful when indulging my fish-bothering tendencies. Mountains of theories and speculation are generated amongst anglers as to why such-and-such a method works, when the most important thing is that it DOES work in certain circumstances. All you can do in the way of reasoning is to observe and try to cut out the extraneous factors.

I've filtered lhm for re-use when dealing with return pipe probs, though normally because it's been picking up up gunge and dirt on the way to the drip point. Coffee filters seem a good idea, though there's always the risk of the bottom of the filter disintegrating unless you actually use a genuine coffee filtering funnel, as the bottom of the filters is prone to burst if unsupported unless you pour very gradually. How did I find this out? When making filter coffee using a standard funnel.... failure here is altogether more messy.

Erm...sorry about the non-BX diversions.

MULLEY · Post by **MULLEY** » Fri Oct 24, 2008 9:12 pm

Not knowing much about hydraulics, at first glance cauchoiskev, that filter looks like a great idea. How long have you had it fitted, & have you noticed if it works or causes any issues?

Anyone else tried this? & should this be considered potentially standard practice to keep the bx hydraulics in good fettle as well as being able to see the condition/colour of the lhm?

cauchoiskev · Post by **cauchoiskev** » Sat Oct 25, 2008 12:18 pm

MULLEY wrote:How long have you had it fitted, & have you noticed if it works or causes any issues?

It's only been on for a few days, Mulley. So far so good. My idea is to prolong the benefits of the coffee filter as far as possible. As Rob says, there seems to be something virtually invisible (moisture ? dust ?) which progressively enters the LHM and causes problems. The plastic filters in the tank and FDV do not seem to catch this perturbing element.

For the moment, I am not sure enough to recommend this technique to anyone, but I am willing to be the guinea-pig and see what happens. I will keep you posted.

tom · Post by **tom** » Sat Oct 25, 2008 1:14 pm

I can see little wrong with it in principle and I reckon that it would be a great idea when hydraflushing .

Debelix · Post by **Debelix** » Sat Oct 25, 2008 5:02 pm

Hi guys!

I very much like the idea of an additional filtering element added to the system! I think it would make much of a difference, because the default filters in the LHM tank are quite large in terms of things and "mud" that sooner or later clogs the hydraulic system. The additional paper filter will catch that sort of waste and who knows... we'll see

For now I also added additional filter (I use a filter designed for fuel lines in petrol models) and will keep you updated if there are any problems or anything else... I will also add some photos tomorrow

MULLEY · Post by **MULLEY** » Sat Oct 25, 2008 8:14 pm

My main concern was regarding flow rate/pressure that might change by having added the filter.

Not actually knowing what that particular pipe in question actually does, doesnt help with my thoughts. Is that the best place for the filter, or is one of the other pipes a better choice?

Debelix · Post by **Debelix** » Sat Oct 25, 2008 8:46 pm

Well, currently I've put the filter at the same pipe as cauchoiskev did, because it was the only one perfectly fitting without any major remodeling. As far as I know that pipe holds the operational return from the brake valve and nothing else. Surely it will be much more effective if the filter is on the main return pipe (number 5 in the picture below), but if we put it there it will definitely cause trouble because of the return flow's pressure. At the current position there are no problems with return pressure and LHM flow at all (which by the way surprises me).

Some guidance about the hoses at the LHM tank:

1 and 2 are return pipes for the operational leekage from the suspension struts; 3 is... hm, er, I forgot

... number 4 is for the brake valve operational return, and 5 is the united return from the LHM pump idle work, FDV, PR, front and rear height correctors and PAS return, if any. 6 is the feeding pipe of the LHM pump

I don't think it will be a good idea to put such a filter on pipe number 5, because the flow there is VERY strong and will most definitely cause troubles... Also, regarding the fact that all of the LHM is circulating in the system it's ok to assume that sooner or later it will go through the filter at pipe number 4.

...we just need some patience, young padauans

EDIT:

And here is how I've done it:

MULLEY · Post by **MULLEY** » Wed Nov 26, 2008 8:20 pm

Time to resurrect this thread.

cauchoiskev & Deblix, how have you gotten on with your modification?

MULLEY · Post by **MULLEY** » Thu Nov 27, 2008 11:30 pm

Debelix · Post by **Debelix** » Tue Dec 02, 2008 8:34 am

Sorry for the late answer, but I've had quite a lot of work lately

I'm planning to change the filter and see what is the condition of the old one; I will post pictures when I do that - maybe in a few days.

For now, I can't say that there is some kind of difference after adding the filter - the car is rising fine in the morning, maybe in about a 1-2 minutes after starting. By the way, last week here the temps were at about -12, but that wasn't a problem for a good old Bazil

Anyway, when I change the filter we'll see what is stored in the old one

MULLEY · Post by **MULLEY** » Tue Dec 02, 2008 12:57 pm

No worries Debelix

I was very intrigued to see how the 2 guinea pigs had gotten on with their filter systems in place. Deffinately will be good to get your views & piccies on this, who knows it might even warrant being added into the DIY section of the website if its deemed a success?