Two hydraulic resevoirs?

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Two hydraulic resevoirs?

Can anyone explain the purpose of having two seperate hydraulic resevoirs on the 8 Series. Obviously one is for the brake master cylinder but what is the other large one that uses a seperate and special type of fluid for? My owners manual doesn't explain its function.

Power steering!

Yeap, It uses Pentosin!

Do not use any other fluid than Pentosin or you will have big issues. The pentosin feeds both my power steering and the Brake "Bomb" Accumulator for my ABS in my 850i

And also make sure you use the correct Pentosin. I learned the hard way when I had a BMW mechanic (yes, BMW mechanic) here in L.A. pour in some ATF fluid into my 750 E32. He destroyed my rear self-leveling hydro system. Was it on purpose? Why yes it was!!! The dumbass thought he could hustle me for more $$$. Long ugly story, but suffice it to say, use Pentosin and use the correct Pentosin!

I had the same question, but after reading the manual I found it was for power steering etc....
I thought it said use power steering fluid, and have never heard the term
Pentosin.
can you explain the difference.

thanX

Pentosin is a large temperature range (Multi-viscosity like) Hydraulic system fluid.

Pentosin 7 is a mineral based oil and Pentosin 11 is a full synthetic.

ATF is basically a high detergent 20w oil with the lubricating property additives modified to make it Dexron or Mercon.

The additives and detergent levels in ATF make it very "Poisonous" to a Pentosin based system. Seal leakage is the result of mixing them.

Pentosin is a pale green out of the can but will turn a rusty red over time. It is NEVER bright red.

The E32 7 Series with self leveling was the most sensitive to ATF and the rear suspension would die leaving a puddle of fluid quite quickly. Repair costs at a dealer could easily exceed the value of the car even a few years ago.

The cap of the Pentosin resevoir has the correct fluid marked on it.

On the 8 series the entire brake boost and power steering systems are at risk.

The E32 7 Series with self leveling was the most sensitive to ATF and the rear suspension would die leaving a puddle of fluid quite quickly. Repair costs at a dealer could easily exceed the value of the car even a few years ago.

Yes TerryY, this is very very true about E32 iL cars. Sadly, my E32 is no longer thanks to that shady mechanic. The funny thing is, this mechanic is one of the most reputed and most famous BMW mechanics here in Los Angeles:mad:mad The things people do to make a fast buck...

Anyhow, please be careful with your hydraulic system. Use the correct Pentosin and never ever use ATF fluid.

Cheers

"Pentosin 7 is a mineral based oil and Pentosin 11 is a full synthetic."
So which Pentosin is proper for an E31 840 0r 850?

both types were used..........7.1 on early cars and 11.1 on later cars..........it will tell you which type you have on your canister lid.......

There are only 2 types:

CHF 7.1
CHF 11S

The reservoir cap will be marked with the approproate kind of Pentosin to use. It will depend on which year your car was manufactured; I think that there are some older E31's that use 7.1

Pump brakes with car off at least 30x until the pedal gets real hard. You should remove the old stuff with a turkey baster first. Then fill a little bit with fresh Pentosin, then remove again with the baster and refill to the bottom of the mesh filter. Don't fill the reservoir anymore than to the bottom of the mesh filter!

If you get your oil changed at Jiffylube or any other quick oil change place, 9 times outta 10, they will automatically pour in ATF! Do NOT let them touch this reservoir at all!

Actully it should be filled to 20mm from the top of the canister. Never mix the two (7.7 and 11) As for where u can get it ...I do not usually like to deal with BMW Dealers but they usually have it on hand @ $20.00 /liter. I also found that in very cold weather starts the rubber hose clamps tend to loosen and the Pentosin will leak out thus the top up is needed. This spring I plan to replace these crimp on clamps with a srew type clamp to solve the cold weather leaks.

I always fill to the bottom of the mesh filter, otherwise it leaks via the top of the reservoir.

And don't forget to depressurise it before you check it or fill it:)

Pentosin puddles are expen$ive puddles:)

"And don't forget to depressurise it before you check it or fill it"

A simple question from a BMW novice: How do you depressurize the powersteering resevoir?

I always fill to the bottom of the mesh filter, otherwise it leaks via the top of the reservoir.
My manual indicates filling it to 20mm from top.... is the manual "out to lunch "??

Pump the brake pedal with the motor off to depressurise the hydraulic system.

Count the pumps until the pedal gets really hard. It should be about 20 times.

If it is only about 10 or less then the accumulator needs replacement to make the car stop right. That is another thing to ask about if yours is in that range.

Anyway you pump it until the fluid in the Pentosin reservoir stops rising. It should be just visible coming thru the bottom of the screen. That is about 20mm.

I'm sure the manual is not out to lunch, but...

Like TerryY states, I've noticed on my E31 that if I fill it to the bottom of the mesh filter, I don't get Pentosin outside the reservoir. This is, of course, after pumping 'til the pedal is very hard. The bottom of the mesh filter is how I measure it.

I've also noted this with my ol' Pentosin suckin' E32 750iL.

Cheers

Finally, if I am interpreting these associated threads correctly, the power steering and the brake system use the same Pentosin fluid and circulation system. Now I can understand why the advised pumping the brakes relieves the pressure from the powersteering resevoir. I was puzzled because every other car (non BMW) I have worked on, the two systems were completely seperate and did not share a resevoir and I couldn't understand what pumping the brakes had to do with power steering.

I had a reputable mechanic recommend ATF... then upon further examination and reading the cover on the reservoir changed his story telling me to use Pentosin. He said it was available at local autoparts stores but I have not been able to find it. As Terry stated the type is on the cap. Glad I didn't use ATF.

I had ATF in mine and I've done the turkey baster thing twice now and the fluid is now looking green (ish). I also hate that little circlip that holds all the bits down on the rod, little pain in the a*** always flies off and you have to take everything to pieces again. Not sure if I should get the baster out again as the oil still isn't the same color as it comes out of the bottle. :rolleyes

what is the purpose of the filter located just below the radiator? i have ordered the filter element and plan to replace soon. i am replacing the filter in the cannister as well. it would seem that after replacing these two filters and my numerous turkey baster flushes, my system should be pretty clean

The little inline filter is for the traction control. The T in ASC +T- rumor is that it may be cleanable and reusable but replacement with new is always OK.

Oh cr@p!!! I just read this thread and remember the mecahnic I took my 840 to used ATF!!! How can I fix this before it's too late? I haven't noticed anythinhg bad, but this was like 6 months ago...

Get a Turkey baster, get the correct Pentosin from your local BMW parts dept, and remove the ATF immediately. Fill the reservoir with a little Pentosin, then drain it again with the turkey baster. Then fill up the reservoir to the bottom of the mesh filter.

Koizumi,
I don't have a problem and haven't opened up my cannister to see what is inside, but I need a little clarification. What does removing Troy72's ATF fluid from the reservoir, replacing it with Pentosin and then removing what you have just poured in accomplish? How does this sanitize all the fluid that exists in the power steering and brake system, which in reading all the previous threads imply is supplied from the cannister? Am I missing a procedural step here?

draining the cannister with the turkey baster will only remove some of the fluid, i'd guess about half but that is a guess. Once you start the engine the remaining ATF will mix with the new pentosin. I drained all of the ATF fluid in the cannister, then completely refilled with nice green pentosin, ran the engine for a minute of two and the fluid in the cannister had turned red again - suggesting there was still a lot of ATF in the system after emptying the cannister. I then repeated the process and the resulting fluid is a dark green, there's definitely some of the ATF mixed in with the pentosin and I really ought repeat the process again.

Turkey baster is one way. I have actually drained the fluid out of the PENTOSIN canister via the low pressure hose on the bottom (into a canister - not on the ground!).Change out the filter in front of the radiator (some are washable, some are paper elements).As far as "purging" the system, connect a small piece of hose to the bleed screw and let it rest in the open PENTOSIN container. Fill the container and then start the car, open the bleed screw slowly and wait until there ar eno more air bubbles. Turn off the car, pump the brakes until hard and check the level. Adjust accordingly - 15-20mm from the top edge (about 3/4"). Start the car ageain and turn the steering wheel from lock to lock 2 or three times and check the PENTOSIN level one more time and adjust. You should be good to go!

Very nice procedures layed out for you... The idea here is to remove all of the ATF fluid. Just draining the reservoir once will not do it - hence the need to fill, drain, refill a few times.

Do it as soon as you can because that ATF is coursing through your system and eating it from the inside out. I witnessed my gorgeous showroom condition E32 750iL die because of this! It can be prevented!

Cheers

Thanks all for the info, will let you know how it works out. But when it rains, it pours. My vehicle is starting to overheat, now. Had to stop on the side of the road and wait for awhile tonight for it to cool down. Luckily I had some antifreeze with me and added some when the engine was cooler, but then it overheated to the point of almost hitting red, then went back to 12 o'clock like 3 times within 6 miles. Is this related to the ATF???

Also, my heater doesn't work now, no matter engine temp. Just blows cold air...

Heater Control Valves are not working (stuck?) for the "No Heat" condition. As for the overheating, the cooling system needs to be bled, you have an air bubble in there and it will potentially cause some serious damage if you keep leeting that thing overheat. Aluminum Engines do NOT like too much heat!! (Cylinders out of round and heat gasket failure). Bleeding the system takes several attempts to get all the air out (7 times on mine after the radiator replacement).

Good luck.

You think 3 flushes would do it? About 3 liters of pentosin?

I think i'm screwed. I as I was coming back from the dealer with the pentosin, I had smoke coming from under the hood (temp was good). I couldn't pinpoint where it was coming from, car still drove fine with no strange sounds, just smoke, little whining on turns. Is it too late for me? I'm draining the ATF now and am crossing everything I can cross hoping i'm not royaly screwed, it has been about 5-6 months...

I'd be surpirsed if the ATF caused your smoke problem? If left long enough the ATF will eat the seals in the power brake/steering and trash the pump, etc but I don't think it's causing your problems. I think three turkey baster sessions should be enough, but I suspect GR8White's full drain procedure would be better but quite a lot more work.

The whining sound while you turn the steering wheel sounds like your power steering.

Like NickF said, the ATF eats away at the entire hyrdraulic system.

I'm still around. Funny thing... I turkey basted the hell out of maybelline last night( need to do it again, fluid still has a reddish hue but could only get 4ltrs pentosin from dealer, ran out!?!) then drove her home and I had heat. For the first time in a while I had heat and the creaking in the front end stopped. I think she is trying to lull me in to a false sense of complacency. What are some things I should be looking to replace SOON?

I am a little confused. In reading the replies associated with this thread, one gets the impression that Pentosin fluid is to be used in both the power steering and the power brake system, yet there are references made, in other threads, to fill the small brake resevoir with brake fluid?? Is the power steering line system seperate from the brake system? If that is so, why is Pentosin referenced in the brake booster accumulator?

Yes, both the steering & 1 part of the brakes use Pentosin. Only fill the Pentosin fluid in the Pentosin reservoir. The 2nd part of the brake system uses brake fluid. The Brake reservoir should only be filled with brake fluid. Essentially, the E31 braking works with 2 kinds of assists.
Thanks for the clarification. Being without a system diagram and relating to my older car experience, I was having difficulty visualizing this unique hydraulic system.

Yo Whale... off subject ... A3? Was on deck in 76, USS Ranger, aft elevator when I first saw one land. Thing is huge ... and bounced, have to admit I jumped at the sight.

Yo Whale... off subject ... A3? Was on deck in 76, USS Ranger, aft elevator when I first saw one land. Thing is huge ... and bounced, have to admit I jumped at the sight.
Full formal aircraft designation was "A3D" which was morbidily referred to as "all three dead" because there were 3 in the crew (pilot, bombadier, tailgunner) and the plane didn't have ejection seats, which other attack aircraft did, for quick exit.

Full formal aircraft designation was "A3D" which was morbidily referred to as "all three dead" because there were 3 in the crew (pilot, bombadier, tailgunner) and the plane didn't have ejection seats, which other attack aircraft did, for quick exit.

F4 Squadron VF-21... 1973 - 1976. NAS Miramar/USS Ranger, Plane Captain