2nd Power Steering pump to fail in 2 months - PeachParts Mercedes-Benz Forum

240d-WVO · #1 06-02-2010, 05:14 PM

We're dealing with a 1982 240d:

This April I took out the engine and replaced the clutch. Before (and shortly after this point) the PS pump wasn't leaking. I replaced the alternator and PS belts when I pulled the engine, and I removed the AC compressor, condenser and belt. The PS belt was tightened so that it sat snugly in the pulley groove, yet there was enough slack that you could press it in the middle (between the crank and the PS pulley) and it would give about a half inch.

I noticed it started to leak when I saw oil creep out the front and on top of the hood (driver's side), during the second half of a 6hr round trip. The pump seemed to be leaking from the front seal and this caused oil to be sprayed on the underside of the hood, which crept out the front to the top of the hood. After this trip, I did another 8hr round trip during which time the pump leaked full container of PS fluid (8oz?). I wasn't sure if I could repair the seal, so I got another PS pump at a junk yard.

I put in the salvaged PS pump 2 weeks ago. On that first weekend, I did a 16hr round trip. I haven't driven the much since I got back last week, but yesterday I noticed a significant oil leak on the pavement where the car was idling. It looks to be coming from the front seal on the pump, the same problem as with the first pump.

I'm getting another PS pump from the junkyard (covered by the 30 day warranty), but is this just a fluke coincidence to have both pumps fail the same way or have I done something wrong?

Just to check the order of the belt pulleys on the crank... From the radiator, moving towards the engine it goes: PS Pump--AC--Alternator right?

My other suspicion is that I tensioned the belt too much on both the original and replacement PS pumps.

Last suspicion: I put brake fluid in the PS pump back in April when I put the PS pump back on the engine, thinking that it would work the same as PS fluid (brake hydraulic fluid is the same as clutch hydraulic fluid but I think I mistook it as compatible with the PS pump). The answer might be that brake fluid is not the same as PS fluid and that caused the seal to fail in the original pump, and residual brake fluid in the PS lines caused the replacement pump to fail because I didn't bleed them when I put on the "new" pump.

Thanks in advance for the insight!

bustedbenz · #2 06-02-2010, 05:31 PM

Brake fluid is definitely incorrect for use as power steering fluid. I use labeled bottles marked "Power steering fluid" (just because sometimes I like the obvious) but Dexron/mercon III automatic transmission fluid has also been used for generations as power steering. There are both opinions on the forum; some say that ATF causes power steering leaks, others say it works fine.

In any case, the brake fluid could well have been part of the problem.

Alastair · #3 06-02-2010, 06:00 PM

IF you did by mistake fill the system with Brake-Fluid, this will definately rot out the seals...

Really hope you didnt, or the steering-box will be the next thing to start leaking!

Brake-fluid isnt actually an Oil, Its an Ester which is different. (BioDiesel is one type of Ester, Brake Fluid another type--They both Hate/eat certain types of Rubber!)

charmalu · #4 06-02-2010, 07:30 PM

Bad boy, now go sit in the corner and think about what you did

.

Oh, and Welcome to the forum.

Yeah brake fluid isn`t cool for the steering pump. In this case, it`s break fluid, since you broke 2 pumps.

I think www.dieselgiant.com shows flushing out the steering system.
remove the return hose and place in a gallon jug. start engine and slowly pour in new ATF or Pwr steering fluid, and turn wheel back and forth. It will come gushing out pretty fast, so keep the reservor filled as it is pumping it out. and watch the recieving jug as it fills.

Have the assistant of your choice to turn the wheel and to kill the engine. might be better to raise the wheels off the ground, make it easier on the tires and system.

Charlie

240d-WVO · #5 06-02-2010, 08:05 PM

It didn't take long for the brake fluid to eat away the seal on the PS pump. Are the hoses likely to go next? Brake fluid has been in the system for 2 months and several thousand miles.

apsaulters · #6 06-03-2010, 03:44 AM

As another member advised above, keep an eye on the power steering gearbox. The brake fluid has probably had an adverse effect on the seals inside the gearbox, and I expect it will leak soon. You might decide to rebuild the gearbox using the seal rebuild kit available here (http://catalog.peachparts.com/ShopByVehicle.epc?q=1982-Mercedes--Benz---40d-Steering&yearid=1982@@1982&makeid=63@@MERCEDES+BENZ@@X&modelid=6142:MBC|1489:ED|10000129@@240D&catid=241580@@Steering&subcatid=241585@@Steering+Gear+Seal+Kit&mode=PA) and David Petryk's excellent tutorial (http://www.davidpetryk.net/Mercedes/Steering.htm), which is a pretty inexpensive solution. But it might be easier just to pick up a replacement gearbox from the junkyard if you need one.

layback40 · #7 06-03-2010, 07:00 AM

As Alistair explained, Brake fluid is not suited to other applications. It is a blend of petrochemicals, mainly glycol-ethers, similar to esters. That is why it does such a job on paintwork. Probably you will need to replace all components in your power steering that are rubber/polymer/plastic. A bit of a PITA but there isnt much else you can do.

vstech · #8 06-03-2010, 08:34 AM

I don't think a flush will solve this one. IF nothing else is leaking, you could try it, but how long do you have on that 30 day window?
I'd do like suggested, pull every part of the PS system off another car and don't put brake fluid in it this time...
pump, hoses, and gearbox.
sorry.

soothappens · #9 06-03-2010, 08:51 AM

I work on hydraulics daily. Your power steering system is a small hydraulic system . When brake fluid is introduced into the system as others have said it destroys everything made of rubber. This includes the inner lining of the hoses. The seals will melt and turn into a sticky goo similar to silicone.

When this occurs on large systems the costs go into the stratosphere. Not having the option of a junk yard. As others have suggested get a used pump and gearbox along with the hoses. Consider it a learning experience and get the satisfaction of knowing you can answer anyone's question on this forum about the power steering system.

240d-WVO · #10 06-03-2010, 11:56 AM

It's now obvious that what I don't know can and will hurt me. The system was doing so well before I started making an ass of myself (assuming brake and PS hydraulic systems are the same).

Here's my method of dealing with this issue, considering that I want to make an 8hr round trip this weekend, leaving Friday afternoon:

With the "bad" pump still attached, flush the system.
Drive to the salvage yard and pick up my "new replacement" pump, drive home (30min round trip).
Flush the system again, with the "bad" pump still attached.
Install "new replacement" pump with new PS filter.
Top off with PS FLUID, drive around and top again if needed.

As for the hoses and steering box seals, I'll replace them when I see they are leaking (?) I'm hoping that two flushes will get most of that sludge out and hopefully rinse out all the brake fluid.

The other option is to scrap my trip this weekend and wait for PS hoses from the salvage yard, rebuild the steering gearbox with new seals--taking me back to square one.

vstech · #11 06-03-2010, 02:24 PM

the problem you are facing is this...
the hoses will disintegrate from the inside.
bits of hose will fill your steering box, and cause issues with the pump.
it's only a few more bolts to pull the gearbox, just grab it while you are there. the return hose is held on with a phillips screw, and the supply hose is simple 13mm flare wrench( which you should already know since you've changed the pump before...)
if you wanna cheap out, at LEAST pull the pressure hose, and the return hose off the gearbox and change them after you have flushed twice with the old pump.

240d-WVO · #12 06-04-2010, 12:31 AM

Today I did an initial flush with 2 quarts of PS fluid, but it went so fast my assistant didn't have time to turn the wheels back and forth. But, the stuff that came out was pretty nasty. I went and picked up the replacement pump, then drove back and did a second flush with the leaky PS pump still on. I went through 4 quarts on the second flush. I had poured all 4 quarts into a gallon pitcher. It was pretty messy pouring it into the reservoir while my assistant turned the steering wheel back and forth. We got about 3 turns per side. I think it was good that we did this on the leaky pump because there were some instances where the reservoir went dry for a few seconds with the engine running. I could hear some grinding when this happened, but I don't think it damaged anything.

I installed the replacement PS pump with a new filter. I started up the car, let it idle for a while, then I drove about 10min during which time I made a lot of lock-to-lock turns. I checked the PS reservoir and it was still clear. It was better to see straight through the liquid than to see the opaque red-brown stuff that was in there prior to the first flush. I'll check it periodically as I put miles on the car this weekend.

Perhaps I'll take out the steering gearbox next week and rebuild it with a new seal kit (~$35). A high pressure hose is about $35 as well. I'll have to play it by ear and see what I feel like doing.

Will re-sealing the steering gearbox get rid of steering wheel play? I will use David Petryk's guide for this.

I've learned so much about the steering system from this little SNAFU!

layback40 · #13 06-04-2010, 04:20 AM

Take plenty of PS fluid with you on your trip. You may spring a leak!! I would be taking a spare high pressure line as well.

vstech · #14 06-04-2010, 08:39 AM

how much more would the junkyard pump be with the pressure line on it?
simple way to bleed pump system is to turn the pump pulley by hand with the belt off...
running the engine as you noticed will bleed the pump dry rapidly.