SLS Reservoir Overflow - PeachParts Mercedes-Benz Forum

KenB · #1 04-05-2011, 12:37 AM

Hey all, I have had a really puzzling thing happen TWICE now, several months and miles apart.

On my 1980 300TD wagon, the SLS works well and I haven't had any problems with its operation. However, on two occasions now, several months apart, I have gone down to drive the car and found a large (several cups) puddle of SLS fluid on the ground under the reservoir and upon inspection, the level in the reservoir is well above the max line and it is clear that excess has seeped out through the cap and dipstick hole.

In both cases, I have moved the car a few feet away, left it for a few days more, not seen any further leakage, and then kept driving as if nothing had happened. I check the fluid level often and it gradually goes down to around normal. Performance is fine. The rear doesn't sag.

*There is NO oil in my SLS fluid or vice-versa. Oil is normal, SLS fluid is crystal clear. As black as the oil is, I would know if it was getting into the SLS fluid.*

How can this be explained then?

Thanks in advance,
KenB

vstech · #2 04-05-2011, 01:07 AM

... odd for sure.
it's a closed system, any chance it was really low one day with a real large load in the back, and you topped it off?

layback40 · #3 04-05-2011, 03:57 AM

Or each time one of your cells in the back have failed. If the suspension is still ok this will not be the case though.

vstech · #4 04-05-2011, 07:29 AM

By cell you mean accumulators? That'd make bouncy but functional, level up? Nah.

layback40 · #5 04-05-2011, 09:30 AM

Quote:

Originally Posted by vstech

By cell you mean accumulators? That'd make bouncy but functional, level up? Nah.

It was the only thing that could release a volume into the system. Air is about the only thing that could cause the system to overflow. If there is air in there, when the pressure comes off, it expands & the fluid overflows.

vstech · #6 04-05-2011, 09:35 AM

ahh, I see what you mean. first time it overflowed, one of the accumulators failed, and the nitrogen pressureized the system, causing an overflow.
second time, the other one ruptured...
got it.
now if it happens AGAIN...

kerry · #7 04-05-2011, 10:11 AM

Quote:

Originally Posted by layback40

It was the only thing that could release a volume into the system. Air is about the only thing that could cause the system to overflow. If there is air in there, when the pressure comes off, it expands & the fluid overflows.

That makes sense. Is it reasonable to think that the rubber membrane in the accumulator would fail when the car is sitting still? I've assumed that they would tend to fail when the suspension was active.

sd300td · #8 04-05-2011, 12:55 PM

I had similiar symptoms a year or so ago. You don't mention whether or not you found any hydro oil on the outside of the resevoir or on inner fender/metal work of the car.

I ask because I once mistook a leaky SLS with a waterpump going bad. Seems hard to to do, I know. Both fluids are the same-ish color and it was hard to figure out what it was (or even if it came from my car) when not a fresh spill.

KenB · #9 04-05-2011, 06:09 PM

interesting comments, all.

yes, it's on the outside of the reservoir and the metal underneath it before it leaks down onto the ground. it is pretty obvious what the fluid is and the path it took to get to the ground.

so, tell me more about the two accumulators having failed? these are the black plastic ball-shaped things, right? is this a real possibility that they have both tanked yet i still have decent ride height and non-bouncy ride?

I pretty much never load down my cargo area with a lot of heavy stuff. Not on principle, just not my lifestyle.

KenB

balge · #10 04-05-2011, 06:59 PM

The ride with failed cells is like massively over-damped, gentle bumps you won't notice it but crash over a speed bump or pothole and it will come down with a crunch.
Pretty sure the cells are steel.
Don't think the levelling will be affected if just the cells are gone?
I believe you can check the cells by poking something blunt into the cell and feeling for the resistance of the rubber diaphragm - not tried it with a good one myself....

sd300td · #11 04-05-2011, 10:08 PM

Another thought, could the return line be a little leaky? The issue may only manifest under certain circumstances.

zeke · #12 04-05-2011, 10:52 PM

I am very interested in this thread...I had consistent weeping oveflow at the reservoir, but had similar but smaller puddle more than twice, but less than a half dozen times.

I replaced the filter and the linkage to the leveling valve. Ride height is perfect and ride is good, but it does seem to crunch over bigger bumps, but not smaller ones, and it seems to lose its level fast...like overnight.

vstech · #13 04-06-2011, 12:02 AM

ah ha!
overnight sagging could send fluid back to the reservoir and overflow... no leaks at the back of the car? sagging is usually either leaking rams, or internal leaking of the valve.

compu_85 · #14 04-06-2011, 12:23 AM

If the rubber membranes in the spheres are leaking, couldn't the gas being forced back through the system displace some fluid?

-J

JimmyL · #15 04-06-2011, 01:17 AM

Usually when the accumulator membrane ruptures the fluid fills the void on the "gas side". Seems like the level would drop, not raise. I guess the escaping nitrogen could force the fluid out, but then you would think that the level would really drop. When they fail the accumulators can hold a bunch of fluid......