Power steering hoses/flush on the 87 300D - PeachParts Mercedes-Benz Forum

BodhiBenz1987 · #1 01-28-2012, 10:44 PM

I've got very weepy low-pressure power-steering lines, so I bought a section of OE hose to replace them. That part is pretty cut and dry, but I'm assuming I have to bleed the system afterward since the hoses will have air in them, and figured I might as well flush it while I'm at it. I'm a little confused by the hose layout. The tutorials I've found say to just put the low-pressure hose in a bucket, but the low pressure hose seems to have two parts ... it turns out of the pump and goes to the front to the left of the radiator, then goes back to the steering box. When I flush it, do I only need to stick the end of the return hose where it connects to the pump in a bucket, or do I need to worry about the other section of hose seperately? I'm pretty sure the high-pressure line is fine so I won't mess with that.

Also, out of curiosity, would power steering fluid getting on the engine mount cause it to deteriorate faster? I know a lot of fuel spilled on it can, but wasn't sure about other fluids.

sixto · #2 01-28-2012, 11:54 PM

PS fluid goes the other way - out of the box, through the cooler, to the reservoir. You can catch it out of the box or before the reservoir.

Good question about the mount. It might degrade a rubber mount but I don't know about a sealed fluid filled mount. Check the gap when you go under the car. I can't think of any preventive measures after PS fluid rains on it other than a brake parts cleaner rinse.

Sixto
87 300D

BodhiBenz1987 · #3 01-29-2012, 01:06 AM

Thanks! Would it then be better to catch it before the reservoir so any old fluid or gunk sitting farther through the return hose gets pushed out? Now I just need to find an assistant ... hopefully my dad can stop by.
I'll check the mount clearance tomorrow ... I have actually been noticing a growing vibration at idle (door rattles plus this really low humming), which made me wonder more. Either way I definitely need to clean up the PS fluid mess ... it's started to get all over the frame and crossmember and drip on the ground. Oddly I'm not rapidly losing fluid from the reservoir.

sixto · #4 01-29-2012, 01:43 AM

You're replacing the return hose so there's little to be trapped in the cooling loop. It'll drip out while the hose is out anyway.

Sixto
87 300D

BodhiBenz1987 · #5 02-08-2012, 01:05 AM

I replaced the hoses Friday, but haven't been able to get anyone to come over and help me do a flush. My dad is going to try tomorrow, but, if he can't ... If I'm only bleeding it and not doing a full flush, can I just fill up the reservoir, start it, shut it off, re-fill, start, shut off, re-fill, etc.? If I'm reading it right that's the FSM instructions for filling it. I'm kind of afraid to do it that way because I know it sucks down the fluid really fast. It's kind of hard to guess how much total fluid was lost while changing the hoses.

sixto · #6 02-08-2012, 01:42 AM

You want to crank the wheels from side to side while flushing and bleeding. Having the wheels off the ground minimizes the risk of damaging something if there's a big pocket of air. If you don't have help, bleed as much as you can with the engine off, belt off and spining the PS pulley CW by hand. Eventually the fluid level in the reservoir will stabilize. It should be safe to start the engine at that point and top off as necessary.

Sixto
87 300D

BodhiBenz1987 · #7 02-08-2012, 04:42 PM

I was hoping after six or so years of working on cars, I'd run out of stupid questions, but they just keep coming ... how do you stop fluid from just pouring out of the return fitting as you fill the reservoir? I stuck the hose in a bucket, and had my dad start the car as I poured in fluid. The fluid got sucked in, but not as fast as I thought, and after a couple seconds it just steadily poured out the open fitting. Apparently he was not turning the wheel because he thought I would give him a seperate command to start doing that, but by the time I realized the miscommunication we didn't have time to try again. Will the turning of the wheel cause it to be sucked down fast enough that it doesn't drip out the fitting? Was thinking of putting a seperate hose and bucket on the fitting just to avoid extra mess (or loop a hose back into the reservoir? It's brand new fluid pouring out I assume). To clarify, I did put the return hose in a bucket and old fluid came out there, as expected ... but it's also coming out the fitting the hose came off of.

sixto · #8 02-09-2012, 12:26 AM

If you can't control pouring so the fluid in the reservoir doesn't reach the level of the return hole, temporarily cap the return line, or loop it into the reservoir like you said. I don't recall that turning the steering wheel makes it suck fluid much faster but it's been a while.

Sixto
87 300D

BodhiBenz1987 · #9 02-09-2012, 12:41 AM

Quote:

Originally Posted by sixto

If you can't control pouring so the fluid in the reservoir doesn't reach the level of the return hole, temporarily cap the return line, or loop it into the reservoir like you said. I don't recall that turning the steering wheel makes it suck fluid much faster but it's been a while.

Sixto
87 300D

I can probably pour a little slower ... I guess I read so many threads saying it sucked down rapidly that I just over-poured. I will cap the fitting anyway, and try again. At least the P/S fluid all over the garage floor goes well with the dirty oil spill I created the other night while trying to consolidate old oil for disposal.

sixto · #10 02-09-2012, 12:43 AM

PS fluid will lift that dirty oil nicely

Are you flushing with the filter in place? Maybe that's why it's going down slowly.

Sixto
87 300D

BodhiBenz1987 · #11 02-09-2012, 12:52 AM

Quote:

Originally Posted by sixto

PS fluid will lift that dirty oil nicely

Are you flushing with the filter in place? Maybe that's why it's going down slowly.

Sixto
87 300D

Ah, did not think of that ... I left the filter since I had changed it recently. I'll pop it out for the next try. Thanks, that might never have occurred to me!

Jeremy5848 · #12 02-09-2012, 11:55 AM

I found that an idling engine sucked the fluid out of the reservoir faster than I could pour it in. As an alternative, I made a crude belt from a hose and used a drill motor to turn the PS pulley.

That brought the fluid flow down to where I could keep up with it. I plugged the return hole in the reservoir and put the hose in a catch bottle. With the front wheels off of the ground, the steering wheel is much easier to turn. Yes, remove the filter.

An alternate method is to suck the fluid out of the reservoir and pour in fresh fluid. If you do that once a day for a week (and drive the car every day) you'll remove much of the old fluid. Better than nothing.

Jeremy

BodhiBenz1987 · #13 02-09-2012, 01:43 PM

Cool, maybe I'll give that a try ... looks less frantic plus I wouldn't have to wait for an assistant again. What did you use as the small pulley on the drill? A wire spool of some sort?

BodhiBenz1987 · #14 02-10-2012, 05:15 PM

Tried it again using the engine running method ... I think I made things worse. I stuck a hose on the reservoir fitting so that was not a problem anymore. My mom started the engine and turned the wheel as I poured in fluid quickly ... and suddenly froth starting coming out the hose (and all over, since the funnel I set up didn't work. I cleaned up and rearranged the funnel and bottle, then tried turn the whel with the engine off ... plain fluid came out, not froth. We tried again with engine running but not turning the wheel ... nice clean fluid shot out for a short while, then suddenly, froth. Maybe I'm not pouring in fast enough, but it doesn't look like the level ever reached the bottom of the reservoir. I hope I didn't damage anything. I guess my next step is to try Jeremy's method to be sure it's not sucking in air. I know there was some air in the lines, but it should have come out right away.
For whatever it's worth the filter is still in ... the nut turns but doesn't come off, so that's a whole nother problem I'm not sure how to solve. But I don't think the filter is causing a problem since fluid runs through fine at first.
At this point I'm afraid of what I'll screw up when I try to take the belt off, which is my first time doing it on the 603 ...

. It looks easy, but so did this flush job ...

Jeremy5848 · #15 02-11-2012, 11:38 AM

Quote:

Originally Posted by BodhiBenz1987

Cool, maybe I'll give that a try ... looks less frantic plus I wouldn't have to wait for an assistant again. What did you use as the small pulley on the drill? A wire spool of some sort?

I used a pair of adapter plates from an ancient drill kit that my late father bought in the 1950s. The adapter was used to hold various buffers, etc., to be spun with the drill motor. By themselves the adapter plates make a fair pulley. You could use almost any small pulley from the hardware store as long as you can put a bolt through the center hole and chuck that in your drill.

I also considered using a clamp on the drain hose so the fluid wouldn't come out so fast but I was afraid of bursting a nother hose somewhere so I never tried it. I also thought of teeing the drain line with a valve, thus creating a controllable "leak." That would allow bleeding off some of the fluid as you poured more into the reservoir while the engine idled. The new and old fluid would mix but you would gradually replace the old fluid with the new.

Jeremy