M119 oil draining into sump.

PDmotors

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Apr 13, 2022
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W124 500E
Hi guys, new to the group and hoping someone has the answer to my question. At about 250.000 kilometres, I decided to have my M119 rebuilt by a specialist in Germany, who apparently the MB Museum use. I had a blown head gasket on one bank and a noisy rattle from the timing chain on startup. As the timing chains on these engines are prone to stretch, I figured a new chain, guides and tensioner would take care of the noise. But this is not the main issue, which is the longer I leave the engine stood static, the worse the rattle, and all the oil in the heads and filter bowl, empties into the sump. So for sure, once you crank the engine over, there is no oil in the filter bowl, chain tensioner or heads....So I have to bump the starter over on the key until I see oil pressure, at which point, l can allow the engine to catch and fire up with no timing chain rattle.
The rebuild sheet shows timing chain replaced, tensioner, timing chain guides, and of course the rebore etc, etc. The one item not changed, much to my surprise was the original oil pump which was not replaced. I have to assume they decided the oil pressure was okay, which it appears to be.
My take on the issue was to replace the check valve(non-return valve) in the filter housing, which I have done, thinking that this was the obvious fail point. The valve seat looked okay, but now I am wondering just how tight a seal it makes once you switch the engine off. Even if the oil pump was completely worn out, I cannot see it causing the oil to back flow into the sump. It does have a pressure relief valve, which I am thinking of changing anyway, although because of the kilometres, I would rather fit a new pump.
I am pretty sure because of the oils draining back into the sump, the timing chain rattle is a red herring. Once the engine is started and up to temp, you can start it all day long, and the engine sound and startup is normal, with an instant indication of oil pressure.
So my future plan is to change the oil pressure sender, timing chain tensioner, and possibly the actual pump and filter housing, but if anyone has experienced this issue before and knows what is actually failing, I would love to know. That way I don’t have to keep throwing parts at it.
Thanks guys.
 

E55BOF

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Have you asked the specialist in Germany what they think is the problem? They've rebuilt the engine, so I'm sure they will have no problem giving some free advice.
 

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