What colour is Pentosin

red=good
brown=not so good.
brown with bits floating in it = bad

I understand pentosin to be an american term for ATF fluid.

Pentosin is Pentosin Period, & must always be used.

Always make sure you have the engine running when pumping the pedal

Pedal pumping is done with the engine off or the level will never rise.

Pentosin is a really pale green for the Chf 11s series type. I'm not absolutely certain what color the 7.1 is.

its green emerald green

[quote="TerryY"]Pedal pumping is done with the engine off or the level will never rise.

OK now this is exactly the opposite of what i witnessed last week

Fabrice had a low level warning light, upon inspection after the pumping the fluid overflowed the canister & this was with the engine OFF, he was advised by Janne from Sweden to 1st start the engine the overflowing canister soon drained to allow top up proceedure.

This happened while on the Holland meeting last week

To recap

They started the Engine
pump the brake pedal
add fluid

Over to you Terry to Explain

Get it bled professionally by a garage- not something I messed with.
If its more than one centimeter from the top and you fill it often you probably have an O ring leak in the Master cylinder both my 91 850 and 84 840 i had replaced ,,,

This might help I'm now confused

http://bimmer.roadfly.com/bmw/forums/e31/6139740-1.html

You can also check the color by dipping a a bit white cloth or paper towel in it. The color shows right up.

Clarity and sediment is a good test in a glass jar.

Pentosin is a proprietary brand for a CHF-11s (or CHF-7.1) type of semi-synthetic fluid:

http://www.pentosin.de/shop.php?c=214,228

http://www.pentosin.de/shop.ph…5bed2c266ea0c69f536f726cb

According to the manufacturers, the older, mineral-based, CHF-7.1 cannot (some say it can) be mixed with the newer, part-synthetic-based CHF-11s. See below:

http://www.bimmerboard.com/forums/posts/202991/

http://www.bimmerboard.com/forums/posts/203366

I read somewhere that E31 built upto 09/91 used the older 7.1, but according to BMW, it's recommended to drain and refill with 11s, which has a wider temperature stability range (but see above link). However, the 7.1 apparently has extra lubrication additives, which may be required by older component versions and 11s contains smaller amounts of these.

Both versions are green in colour with the 11s being a paler shade. If your fluid is red, it may have been mistakenly replaced with regular ATF, which is used in some other BMW power-steering systems, particulary where the brake servos are vacuum-driven. Pentosin is used in central hysraulic systems which provide pressure for braking, power-steering and AHK.

If your fluid is red, drain and flush with the correct Pentosin. (Probably, if you're lucky, there will be no long-term damage with ATF, as it also has good hydraulic and lubricating qualities and temperature resistance, although there is some indication that seals can deteriorate with ATF.) If you syphon out the old oil, refill with Pentosin, drive a 100 miles and repeat the excercise, that should be OK.

If you cannot get hold of Pentosin, I think the manual list other types of fluids that can be used, some only in emergencies, but I believe it says not to use the LHM types of fluids.

The level in the main reservoir depends, among other things, on how much of this fluid is in the nitrogen "bomb" pressure reservoir. To empty the latter, one must pump the brake-pedal with the engine off , until the pedal becomes hard. The pressure reservoir will now be empty with its fluid returned to the main reservoir, where it now should be at its highest level. This point should be about 10-15mm below the top edge of the main reservoir. Adjust the level as necessary.

If you top up to this level with the engine running, the main reservoir will likely overflow, when the nitrogen-bomb gradually empties over time, like for example, if you leave the car parked for a few days.

The brake bomb is a hydraulic accumulator - a pulse dampening device.

It contains a bladder filled with nitrogen at High pressure. When the engine is running the pump is pushing the bladder back by providing a slightly higher hydraulic pressure than nitrogen pressure.

With the motor off a check valve keeps the system from leaking the accumulator pressure back through the pump. So the extra fluid remains in the bomb.

So if you check the level with the motor running or just after you turn it off the fluid in the canister will be low. Because the fluid is still in the pressurized brake bomb/accumulator.

With the motor off, pumping the brakes releases that pressure through the brake booster and it sends the fluid back to the canister at low pressure.

At some point during the pumping of the brake pedal the pressure is equalized through the entire system. Except of course for the pressure of the nitrogen in the bag inside the accumulator. But the bag pressure being higher than the now low hydraulic pressure, all of the fluid is gone from the bomb and is now in the canister.

This is where you can check the actual amount of fluid in the system.

If it is above the bottom of the debris screen in the canister but not overflowing is should be OK.

If it is overfull at this point you should take some out. But if you drive the car often you may never see any difficulty at all.

Just don't park it for too long or it will be sitting in a really nice puddle of Pentosin

Remember that high pressure nitrogen filled bag? It will eventually push the fluid back through any leaks in the check valve and operating side into the canister.
The fluid now has just under 3000 PSI (207 BAR) pushing it back and a thumb tight seal at the top of the canister won't be much of a match.

As a side note, you should be able to diagnose the health of your brake bomb by how many times you have to pump it before the fluid level stops rising or the pedal gets really hard to push.
I don't think that anyone has collected the data for a definite test but I would think that any number under 10 would start me thinking about it.

Is that wordy enough?

SUMMARY
Motor off and pedal pumped down until the fluid stops rising is the correct procedure--that is what is in the Owners Manual.

pentosin

Hi,
FYI, the Pentosin 7.2 and 11s both are green color.
Best regards
Thierry

Tis green