Self Leveling System Mystery
 

Hi All,

This SLS system mystery has me baffled. I am gaining oil in the SLS system while losing oil from my crankcase. The oil gained in the SLS is the exact amount that I am losing from the crankcase. How is this possible? I thought there was no connection between these systems.

No, I am not losing excess oil by burning it or dropping it on the highway. The oil
in the SLS system highly resembles engine oil, and not hydraulic fluid.

Any ideas? Its a 82 300TD Wagon.

Brian

Speaking of mysteries, what year is it?

Has to be coming through the pump on the head somehow. (providing it is of the correct year for said pump) I had no luck getting gaskets for the pump on my last wagon.

The Year
 

Sorry, its a 82 300TD

Brian

Gasket
 

So, the gasket would be a something other than rubber? Perhaps I can make one with one of those DIY gasket kits?

I should probably start tearing into it to see what I can find.

Brian

It's got to be coming through the pump somehow. There's no mistaking black crankcase oil for the correct SLS mineral oil. Old mineral oil may darken but nothing like oil that's been in the crankcase for more than a few miles. Once you find your problem be sure to throughly flush the SLS system through the bleeder in the rear leveling valve. I've never heard of one of the SLS pumps going bad unless it was run dry so you must be an (unlucky) outlyer. The good news is that if you need one, a used pump is probably a fair alternative.

Yes, this seems really strange. I still cant see how the engine oil would be pushing into the SLS pump, especially at the top end where it is located. I suspect that high crankcase pressure from blowby is partially to blame.

Is there a way to tell if the pump is destroyed? Excess play in the pump shaft maybe? I disconnected the filter to see if I could oil to squirt out of that pipe (while the car was running). I saw very little coming from that pipe, and it was more of a steady drip-drip-drip. A very slight increase in oil flow was observed with increased throttle.

Brian

I have a 82 300TD and have replaced the SLS pump gasket. It is available from the dealer.

If your getting a lot of blow by it could be pressurizing the hydraulic pump. that is the only place the engine oil meets the SLS system. The gasket is not the problem. It would be the pump.
I just don't see how the oil would enter the pump. But I guess it is possible. I did not look at the pump, trying to figure that out. The pump rear just has a drive shaft setup.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1UJ057HUE1UJ05JUKC&year=1982&make=MB&model=300-TDT-001&category=L&part=Suspension+Pump

Consider flushing the SLS system and installing a new filter and see what happens to the fluid. It may be that the 2 oil levels are coincidental. Drain the SLS system at the rear and renew the filter. Add new Mercedes hydraulic fluid and see what happens. If it still happen then consider finding a used pump. It's $940 for a new pump. That's expensive.

sls
 

I just sent you a message to your mailbox. Mike

Your flow on the SLS system sounds about right. It won't come gushing out, even at high RPM. By the way, be careful when you bleed at the rear leveling switch as the rear can lower and if you don't allow enough room you'll have a big problem. Be sure to use ramps at the rear and block the front wheels too as you'll be under the car with the engine running (it's necessary to run the engine so you'll have pressure to bleed the system).

I believe the SLS is a self-bleeding system. There is a bleed screw/fitting at the valve, but comes more into play for a complete fluid transfusion. The task of bleeding small pockets of air is automatic.

JimmyL

You are quite correct, it is a self bleeding system but I was referring to using the bleed nipple to flush the system. Perhaps "bleed" was a poor use of words on my part.

LRG

Bleeding that rear valve whilst the engine is going to be interesting indeed. I will definitly support the rear on jackstands and chock the hell out of everything. I have a 5 speed, so I can just put it in neutral.

The pump causing high pressure in the engine? I would be inclined to believe that given the current strangeness. This warrants an investigation...

I will post my observations tonight after I do a teardown of the pump.

I forgot to add that I drove the suspect car for about 100mi today, and the same missing crankcase oil occured. It definitly found its way into the SLS reservoir. Weird.

I ran this question by my master Mercedes mechanic friend, and he had never heard of such a thing. I suppose after 24 years of abuse, you are bound to see some unexpected issues.

Teardown Completed
 

My findings were that there is a rubber skirtish looking seal which has deteriorated. It is the seal that seals the pump shaft where the pump mates with the head. There doesnt seem to be any scoring on the cam surface, and the radial pumping action works when I spin the pump shaft. The pistons are nice and flat where the cam makes contact. I can probably service the pump in its condition.

If anyone is interested, here are the Mercedes SLS pump gasket part numbers for an 82 300TD:

SLS gaskets

(1) 004 997 01 47 seal ring
(1) 010 997 43 45 seal ring
(1) 114 236 00 80 gasket