Power steering - PeachParts Mercedes-Benz Forum

junker68 · #1 03-07-2004, 12:07 AM

Hi,

1983 300D Turbo, 125,000.

Went through some searches on power steering fluid and filter change in preperation of a fluid/filter change.

Bought a new filter and removed and replaced the old one. After two or three partial fluid removals and replacing with ATF, I began to notice a groan when turning left and right.

A couple of questions: The fluid I removed was brown. Assuming this was the original fluid, was it ATF?

I never had a "graon" before the fluid switch. Should it subside with time as the new fluid gets "settled"?

Do you think air got in the system? And am I correct that to bleed the system just keep turning the steering wheel back and forth, self bleeding.

Thanks in advance!

Being a little new here I was happy to post my first assist a couple of weeks ago. What a site to learn and share ideas!!

whunter · #2 03-07-2004, 12:41 AM

You picked a dangerous question.

#3 03-07-2004, 09:17 AM

junker,

Do a search on Power Steering. In 1983, your owners manual specified ATF. Since that time ATF has gone through ENORMOUS formula change. Use Power Steering Fluid from the auto parts store, or if you insist on using ATF, find some Type A if you can.

The modern Mercon stuff is harmful to the seals in your older power steering unit. I lost a pump a few years ago before learning this.

I'm sorry to rain on your parade, because it sounds like you did a great job flushing and changing the fluid.

If you do a search you will find some threads where I describe the flush method as found on the ASE test. You can do it in fifteen minutes and since you have already flushed with ATF, just blow it out and then flush about one quart of PS fluid through, then fill it up with ps fluid. Your system will then be ready for 100,000 or more trouble free miles before another change.

Remember, your owners manual was printed in 1983 when they had no way of knowing what ATF was going to be in the future.

Best of luck,

P.E.Haiges · #4 03-07-2004, 10:39 AM

Junker68,

Thats what happens when you fix something that isn't broken.

Usually a groan in PS system means you have air in the system.

P E H

junker68 · #5 03-07-2004, 11:44 AM

Well, the car sat overnight and the "groan" is gone.

Thanks for all of your replies!!

#6 03-07-2004, 11:16 PM

Next time, simply turn the wheel lock to lock a few times to bleed the system. This is what you should do after flushing/changing the fluid also.

Good luck,

junker68 · #7 03-08-2004, 08:53 AM

Thanks again, that was one of my questions.

JHZR2 · #8 05-18-2004, 12:06 AM

Out of curiosity, is there a check valve in the power steering system?

My pump is fine, Ive replaced the steering box, but whenever its warm to hot out, I get a groan when either I start the car, or steer the wheel a lot after going relatively straight for some time.

It seems to be getting worse now. Unfortunately, I just put in ATF, thinking that with the new steering box in, Id like to clean the system out with a detergent-laden ATF. My plan wasnt to keep it in too long, but with the results just given, with a ruined pump, Ill swap it out right away. I did start to have a feeling that I was develloping a leak.

Thanks,

JMH

KPMB82 · #9 05-18-2004, 12:21 AM

I flushed and filled my P/S about 2 months ago using ATF and now it leaks like a sieve. Looks like the seals in the back of the pump are gone. That's what I get for trying to fix things

P.E.Haiges · #10 05-18-2004, 12:38 AM

KPMB82.

It wasn't broke so you fixed it until it is broke.

So now its time to fix it again.

Maybe you should have used power steering fluid.

P E H

KPMB82 · #11 05-18-2004, 12:47 AM

The P/S was working ok even with the brown mud in it. so yes I fixed it till it's broke. In my spare time I'm just now adjusting my transmission, put it back in yesturday after rebuiling it. Next time P/S fluid.

P.E.Haiges · #12 05-18-2004, 01:06 AM

KPMB82,

You rebuilt your transmission yourself, I'm impressed. I would never attempt to rebuild an auto transmission.

Even the transmission shops around here don't want to rebuild MB auto transmissions.

P E H

lrg · #13 05-18-2004, 01:08 AM

PEH,
By your logic we also shouldn't change our engine or transmission oil until something breaks. A power steering fluid and filter change is a regular (albeit infrequently required) service procedure and done with the right fluid is a good idea to do BEFORE something breaks. Oil is cheap, pumps are expensive.

LRG

P.E.Haiges · #14 05-18-2004, 01:20 AM

Irg,

I never said we shouldn't change engine or transmission oil, just not more frequently than necessary.

But power steering fluid, I don't know if changing is necessary. Its pretty much a sealed system. Mine has been in my '80 300SD for as long as I've had it, 14 years and everything works fine.

P E H

langpfeife · #15 05-18-2004, 05:42 AM

Run whatever was in there before, if it's ATF, and it's not leaking, you can continue to use
it. (I recommend Castrol.) If it's MB/Elf oil, or the fluid has been in there for 25 years, I would
run the thicker oil. Likewise a newer vehicle. Dexron ATF is quite a bit more "slippery" than Type A
(the main difference between them) or MB oil, so in a pump with worn seals and years of neglect, it's
conceivable that ATF could cause it to leak. There is no additive in Dexron however that will "attack" or
otherwise harm good seals. (Radial-type and other seals in Vickers/ZF pumps are usually constructed
of the same materials (and made by the same manufacturers) as those in MB transmissions, and obviously
Dexron is OK to use there.)

ATF is a hydraulic oil, ZF and Vickers recommend them for their pumps so it won't cause
leaks in new/rebuilt pumps, or those which have been serviced on a regular basis. Several years
and cars here with "0" leaks, original pumps on all of them.

Another thing to consider, is that seals "do" harden and deteriorate with age...especially V8 boxes since they're right under the exhaust manifold.