Best Strategy to Fix SLS on 300TD
 

Hi everyone,

I've been going through this forum to find answers for this issue. I recently bought a 1984 300TD. I did a little bit of a blunder and purchased the car site unseen, but only after having a lengthy conversation with the mechanic that was working on it fro the old owner. There are some things he did not mention to me, like the SLS not having any fluid in it, and this not working. That came at a surprise to me (maybe all the fluid leaked out when the owner drive it 600km to me after the sale). Problem is now: I don't have any indication as to what is wrong. How did the fluid leak out? (struts, pump into engine, lines?) I don't know. So here the questions:

I want to avoid wasting hydraulic fluid. What's the best way at doing that? Is there a "cheaper" way to figure out where the leaks might be before just losing all fluid? Maybe buy cheaper fluid just for testing? Can the SLS pump leak into the engine, if I don't find any leaks on lines, struts, accumulators or valve? What is most likely to be broken? I haven't seen any obvious issues yet, but I have also not looked too much yet either. Car is currently winterized

(btw, that's one of the reason I purchased it: it hasn't seen winters in 14 plus years, maybe ever. Very solid underneath. Euro import with Euro headlights and euro tach. Unfortunately quite a few thing the mechanic didn't mention, which I'm now stuck with.)

I'd appreciate if someone has some goods tips on best strategy on how to tackle this.

Cheers, Hans

fluid is cheap and you won't find any leaks until you pressurize the system. rarely do they just drip with the engine off.

Yep

Some will say don't do it, but you can use transmission fluid to test.

Pressurize with air at the pump??? Remember to block the car up because it will lower, but the SLS valve up/down lever should be moved whilst testing for leaks.

Thanks for the tips.

I didn't know that it rarely drips with the engine off, but I suppose it makes sense as no pressure on the system.

It sounds like using ATF is too risky and might be tricky to get out of the system afterward.

I just found 2l febi ZH-M for $40CAD online (I think I need 4l total). I'll give that a try. Hopefully I can find the leak without wasting it.

Can I empty out the system by catching the liquid on the return line at the tank? Or do I risk running into issues by running the pump dry? (I could stop before the tank is empty)

Could be as simple as the cloth braided hose on the reservoir.

definitely don't let the pump go dry.

i would not use atf because then you need more hyd fluid to flush the system. also, atf has additives for engaging the clutches in a trans. which is why mb switched from atf to ps fluid in the 70s. MBDOC told me that 25 yrs ago.

Well, it’s too late for the pump not running dry. That was under previous ownership. I’ll see what the damage is soon. Will charge with proper fluid to inspect, and then rebuild what I can. Trying to source parts to rebuild the pump using the original repair manuals I received with the car. Thanks for all your help.

From memory, you can rebuild the pump without a lot of headaches. There are or used to be a lot of videos on YouTube and threads on this and other forums.

if the pump's gone dry, rebuilding it won't help. basically, it's seals and orings for leaks, not worn parts from lack of fluid.

i wouldn't open it until you prove it won't build pressure. then look for a used 1 if need be.

?????????

Thanks @Porkface I'll give it a try. I suppose can't break more than it already has been, in case it's broken.