Hello, I have what I think may be a leaking return line for the SLS fluid on the 1985 Mercedes 300td wagon.

The fluid I am using for the SLS is red and is similar in color to transmission fluid and so I have been trying to search and diagnose a transmission cooler hard-line leak in that area. I have been checking my trans. fluid levels for the past few days and it is the same so I have eliminated the leak coming from the transmission lines.

There is no visible leak anywhere near the tank under hood or the pump. The high pressure hose and hard-lines appear dry on the pass. side of the car. The tank is on the drivers side on the 85'. Funny thing is that the level in the SLS tank looks to be the same. Power steering looks good. The car has new hydraulic ram shocks in the back and a rebuilt valve. All good back there.

Always has a small puddle under the car in the morning about 8' diameter directly below the frame cross-member under the engine, where I put the floor jack to jack up the front. It is wet and has red drips coming from it. It soaks into the stone bricks, so I shouldn't say a puddle, but it leaves its mark in the same spot. The suspension works great but the car sinks a bit overnight and I feel it lifting a bit after start up.

I believe the return line is the culprit?

Please tell me they didn't route the return line under the engine between this frame cross-member!!! Why would this be leaking? I can't see in between there very good if at all to tell where this line goes after it comes out of the tank and snakes down to the cross-member abyss. There seems to be very little room between that cross-member and the upper oil pan.

Is it possible the engine is resting on this return line and is causing this leak? Why would they route it in such an inconvenient spot?
Am I having motor mount issues if this is occurring? How much clearance is supposed to be in there?

Thanks.

Yes indeed, Mercedes has run the line between the cross-member and the engine (upper oil pan).

I imagine with the limited clearance in there, that the line has rubbed a small leak in it over the years from engine vibration. They could have easily run that line along the back of the cross-member. Anyone know what that section of this line looks like as it passes under the engine along the cross-member? Wondering if there is a chance that there is a coupling under there that just needs tightening or if it is straight line...guessing the latter.

I pretty much need to remove the engine or lift it, to properly remove the rubber buffers that hold the line to the TOP of the cross-member to properly install a new line???
Since there is no way I am going to all that trouble....I guess I need to figure out a suitable way to bypass that section that runs under the engine.
The plus side to this if there is any is that I can easily get to the line fairly close to where it snakes down under on each side of the engine...to cut into the line...to splice in the bypass section to get from the passenger side back to the tank.

My question now is.....where to run the new bypass section of line....and what to use in place of the steel line that will be bypassed?

Can I use rubber hose since it is just a return line?
I am thinking I may just route it along the rad support somehow?
That will require some extra travel length to this circuit.
Will it be a long enough bypass to affect the operation of the system? I would think that I would be adding about 4 feet to route it differently?

Anyone else come across this problem?
Thanks.

I think I may just zip tie the bypass hose to the high pressure hose along the front of the head area over the SLS pump and sneak it through the fuel filter tower area to the tank fitting.

Any opinions on using rubber hose...type/size? That steel line looks pretty small.

No expert here but did you say the fluid is red? ATF is red, and the SLS system shouldn't have ATF in it.

Now my limited memory of SLS lines has them over the RHS of the engine (that would be passenger side to you guys) well out of the way of the cross member. However the ATF lines are in that area somewhere.

Are you able to post pics? They would help a lot.

__________________
1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

You might try to get the car on a lift with the engine running to really pinpoint where the leak is coming from. It would be best to use a high pressure washer to clean the under side of the car first. Being that the fluid leak is red I would also tend to believe that it is ATF related. The hydraulic fluid used in the SLS system is clear.

Why are you using red fluid in the SLS system? febi or mb are the accepted fluids for that very expensive system... Rams are $800 a set, the spheres are similarly priced, and the pump and valves designed for the correct fluid are not cheap either... Why put in the wrong fluid?

That said... I think the only lines under the engine are transmission cooler lines... And they are known to rub at the mount points when the rubber protectors disappear...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

The 85 300TD has the SLS reservoir on the driver's side. The lines from the rear of the car run along the passenger's side and then near the turbo cross to the driver's side of the car, under the engine and along the crossmember. The 87 TD also has this setup.

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Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

If you do need to change the hoses, search for posts on that. They have "field repairable" fittings you can undo w/ box wrenches. Might be just on the high-pressure hose. I don't have SLS, but similar on the power steering hoses.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

The fluid I am using is correct as per having the same specs for the"proper" clear or whatever color the ridiculously priced MB/Febi stuff is....no worries. It is used in aircraft landing gear and probably gets dyed red for some sort of aviation reason. Don't know. Don't worry about what fluid I use....It gets cold up here and I have used it before for years with no problems with any of my components. I used new rams as well as rebuilt the valve with a kit, on this because the old were worn out and leaking....not because of the fluid I used, but because they were old and the previous owner did not take care of them. It was working great until this leak came up...used it for the past 6 months no problem until now. It gets cold up here in the winter and this is the fluid I choose. I think others are using it as well. I agree that it is a downfall using the red dyed fluid because it looks the same as ATF fluid, but it is the way it is.

I have traced all transmision lines and it is NOT coming from them. It is definately the line under the engine that is leaking. I am familiar with the high pressure line fix as I have done it before, using this sites help. It is not the high pressure hose leaking. I can see down to the little junction box where the two lines part in different directions, when it turns to steel line.

Is there anyone that has bypassed the section under the engine, on the 85' w123 or w124 wagons.... if they (w124) have these under the engine set-ups as well?

I think it was just the 85's that got the drivers side tank?

The section of the steel line under the engine is unaccesable as we would have to lift the engine to get it out.
I would like to cut the steel line on either side of the engine and re-route a new section back over to the tank to seal the circuit up again, as it is dribbling from the leak point under the engine. I want to avoid running my new rams dry as well.... as they are expensive.

Anyone see a problem with my idea to bypass this to fix the leak?
Recommendation on a size of line or type of line to use. I am most likely going to use something flexible like hose...and just hose clamp it on there since it is just a return line.
Thanks, for the responses... I appreciate the effort to help, anyways.

I would recommend that you try to find out what sort of pressure (PSI) is flowing through the line in question. If it is relatively low pressure then a flexible line rated for the appropriate pressure is feasible with the appropriate clamps. You might want to check with a hydraulic hose shop in your area for their recommendation.