Thread: Hydraulic oil as a replacment for clutch brake fluid.

Originally Posted by richard4u2

was told to use water as an emergency then flush asap

Ditto.

AFAIK brake fluid and therefore clutch system seals and cups are made from Ethylene Propylene Rubber or EPDM/EPM and are NOT compatible with any mineral based fluids at all.

Originally Posted by Brid

[snip]

I used to supply silicone brake fluid (DOT5), and the manufacturer claims are that it never needs replacing, as it does not absorb water (as DOT 3 & 4 do). In my view it is far superior & of course doesn't affect paint work. Dear? Bloody oath!

I'll pass thanks

There's a reason why silicon based brake fluids are never used in motorsport, the small (or very large for a driver) issue of compressibility.

DOT 5 fluids compress dreadfully (compared to conventional fluids) and so make braking very inconsistent.
I'm sure there are applications that they are worthwhile, but IMO normal car/truck brake systems aren't one of them.

No race brake fluid manufacturer uses a silicon based fluid, they are all ether glycols (most) or silicon ester (the best and only a few and not to be confused with silicon DOT5 fluids) and are totally compatible with each other, unlike silicon brake fluids which as you say, must be used alone.

The brake fluid by which all others are judged in terms of dry and wet boiling point and compressibility, Castrol SRF, used to retail for around $98/litre back in the day. God only knows what it retails for now.

I have been using silicon fluid for over 25 years and will not use anything else. Only problem I have had is some rubber seals swell up. There is only one way to tell which rubber is good and that is to soak the rubbers in a small jar over night and see if they swell. This was the advice I received from a manager of PBR in the 70's when he supplied me with a set of front disc brakes for my S2A. They are still working, even if I leave it parked for 18months. No corrosion either with the silicon fluid. We have 9 cars in the family, all with silicon fluid and that includes a 95 D1. Its not cheap, but in the long run I think it is a better way to go, if you are keeping the car for a long time. On the bottle it says not suitable for ABS, the bloke I bought it off said none wants to pay $50,000 to get it tested and okayed.

Originally Posted by blackbuttdisco

[snip]
On the bottle it says not suitable for ABS, the bloke I bought it off said none wants to pay $50,000 to get it tested and okayed.

No, it's the compressibility issue, it wouldn't pass.

Glycol ether fluids aren't a problem if regularly (two yearly) flushed either.
That's their only downside, they are hygroscopic and so need to be flushed so it's a waste, but most people are changing there engine oil every six months or so too.

Originally Posted by JDNSW

Conventional seals (and probably hoses) will be chemically attacked by hydraulic oils and will fail quite rapidly.

A good example of the problem is given by Citroens. Up until 1967 the very elaborate hydraulic system on Citroen cars used a special fluid (LHS2) that was effectively the same as heavy duty brake fluid. It was then replaced on new vehicles by a mineral based fluid, (LHM) that is very similar to an automatic transmission fluid. As a result, every rubber component in the system is different - look the same, but different, causing serious problems if the wrong part or the wrong fluid is used. (They tried to minimise this by a change in fluid colour from red to green, with matching changes for parts packaging, and painted bits changes from black to green.)

John

We have a similar thing with the 'SprintShift' in Mercedes Benz cars and trucks. The fluid used is Pentosin, a mineral based fluid but not compatible with anything else. Reservoirs are different colours with a warning attached.
People still don't read.... Mmmmm hoooooooooge repair bill if you can't read.

Originally Posted by LOVEMYRANGIE

We have a similar thing with the 'SprintShift' in Mercedes Benz cars and trucks. The fluid used is Pentosin, a mineral based fluid but not compatible with anything else. Reservoirs are different colours with a warning attached.
People still don't read.... Mmmmm hoooooooooge repair bill if you can't read.

The wet disc brakes inside machinery axles are the same. Use DOT fluid and it eats it's way out of the brake system, into the front axle oil where it eats all the disc packs and every other axle seal.

I hate to think how much that mistake cost them. At least on a telehandler the front axle is easy to get to.

Originally Posted by LOVEMYRANGIE

We have a similar thing with the 'SprintShift' in Mercedes Benz cars and trucks. The fluid used is Pentosin, a mineral based fluid but not compatible with anything else. Reservoirs are different colours with a warning attached.
People still don't read.... Mmmmm hoooooooooge repair bill if you can't read.

Which Pentosin ? CHF11-S ?

Pentosin is a German oil company like and competitor to Fuchs, the CHF11-S is used in quite a few Euro vehicles for PS, suspension, etc.
Not sure what so 'special' about it, but Fuchs apparently have a cross with it, Fuchs TITAN ZH 4300 B which has the same MB and VW approvals.

Originally Posted by rick130

Which Pentosin ? CHF11-S ?

Pentosin is a German oil company like and competitor to Fuchs, the CHF11-S is used in quite a few Euro vehicles for PS, suspension, etc.
Not sure what so 'special' about it, but Fuchs apparently have a cross with it, Fuchs TITAN ZH 4300 B which has the same MB and VW approvals.

No one seems to know!! It comes in a MB bottle and is marked "Multigrade Oil". Theres no spec on the bottles!
Part number off the top of my head is A001 989 24 03.

VW approvals are exactly the same because the Krafters are actually made by Mercedes Benz! They come off the same base production lines.

Its only used for the hydraulic shift control and clutch actuation, not gearbox lubrication.

Cheers

Andrew