Oil Pump Pressure Relief Valve (aka Non-Return Valve)

Has anyone replaced one of these? Located in the oil pump, not the oil filter housing. Already replaced the oil filter housing relief valve. No improvement.

I'm chasing the daily, early morning M119 rattle. Goes away at the same pace the oil pressure gauge rises. Along with the rattle dying as the pressure rises, there is a squeal that rises in pitch and also ends at 3.0 bar. Every morning, every time.

No chain rattle. Rattle is from cam area. Squeal comes from the oil pan area.

So I'm getting ready to replace the oil pump pressure relief valve. Theory is the oil leaks past the relief valve overnight, and when re-pressurizing at startup somehow causes the squealing noise. Pressure's at spec while running. Just the engines runs dry overnight.

Valve piston, spring, and new plug (kit) costs $180 at the dealer and $120 at ecstuning.

Have searched every site, in every combination of terms, designations, ideas I can think of. Open to any suggestions. Thanks for your help.

If the relief valve was bad I think you would see very low oil pressure at idle.
If the relief valve is bad, is the bore it sits in also bad and will that bore be changed with the new parts?

Thanks Chas. Depends on how much of a gap exists where it seals, I imagine. If the spring has weakened with heat and age, it might not seal completely but just tight enough enough to hold pressure while driving. It does take about eight hours to hear the symptomatic noises again, so the leak must be minor. If the bore of the valve and piston in the pump is damaged, then the pump will have to be replaced. $400+ for that, so fingers are crossed. There have been suggestions that the cam oilers are the culprit but I would expect a failure there to guarantee low oil pressure and constant/regular ticking noise as the dry cam lob slaps against the lifter (bucket?). Anyway, I checked the one cam oiler that I could see through the oil filler hole and it appears to be metal (same color as rest of metal components) and not dark plastic as I've seen sold by the parts houses. So, probably not a problem with these.

How are the fall colors in Bucks these days? Used to live in Montgomery county. It is beautiful there.

Colors were just about at peak last week, then we got 6"-12" of wet snow on Sat. which took down a lot of trees branches and power lines. So this year wasn't as nice as it could be.

Let us know what the ultimate cause is my buddy has a 500e with the same problem as you he descibes rattling ever morning untill oil pressure builds, and he already replace checkvalve in oil filter with same result, still rattles lifter /lifter noise untill oil pressure builds

Right. I was daydreaming and forgot all about the snow. Hope everything turns out okay.

Nulu, I will update as I sort this thing out. I've seen that Porsches and VWs among other european cars have how-to's on replacing oil pump relief valves for some reason...some sort of fail point, maybe similar. Ours may not fail as often, but if there is any insight to be gained by reading about their efforts, that might help with mine and your buddy's morning clatter.

The original post does not mention the miles on the engine or anything about the tensioner or if any work has been done on the engine.

My M119 (400SE) does the same thing if it sits for about a week, not overnight. According to my technician there are different lengths of chain, and the chain is slightly too long. A chain rail broke at 142K miles and 8 valves were bent hitting the pistons. Both heads were rebuilt with new valves, lifters, chain, rails, tensioner etc, and the rattle on startup started immediately after all this work. The shop that did the job was somewhat clueless, and I didn't want them to do any more work on it.

I doubt that the squeal has anything to do with oil. It could well be something like an air pump bearing that coincidentally stops squealing when the oil pressure goes up.

Good point, Harry.

227k miles. No engine work other than new water pump, front crank seal, oil filter relief valve, trans cooler hoses, radiator, thermostat, new fuel filter, and plugs. I run it with Delo 15w-40 and a Hecht filter. No idea what the previous owner had done. Bought it for $500. so it was a gamble that has paid off in a reliable, once leaky, smooth running, noisy in the morning car. I love it.

I didn't mention what had been done because I wanted to hear what was suggested without prompting on my part.

So, does the chain tensioner work from oil pressure or not? I've heard conflicting reports. Maybe the original did, but the upgraded replacement doesn't...or not?

Thanks for your feedback.

This happened to me once too - brand new chain, new guides, new tensioner, new oil filter check valve, clean oil pump screen, and yet it still had cold start up clatter after the work. There's something else going on with these 119 motors.

Deanyel, sorry to hear of all your efforts without resolution but (selfishly I admit) it tells me I may not need to bother with these items. Frankly from all I've read I've never come across anything that solved the problem directly.

I'm beginning to wonder too what is really going on if all the usual suspects are not the problem after all. Maybe its all about aging oil pumps? Perhaps these pumps work well enough during idle and drive time according to our dash gauge readings but tolerances are no longer adequate for the deamnds of initial initial start ups?

Anyone tried a new oil pump with good results?

Anyone have any insight into oil pump at all?

Process of elimination is expensive.

So, I dropped the oil pan to see what was causing all the noise (needed a new pan gasket, too) and found my problem: fragments of timing chain guide crammed in the small space against the screen of the oil pump suction thing..and to prove its impact on oil flow, as I cleared the junk out a cup or more of oil stored in the oil passages above gushed out once the pocket was cleared of all the bits and pieces of chain guide. Now when I start the engine, there's hardly a second of clatter and the oil gauge shoots up to full pressure almost immediately.

Fingers crossed but this is all good.

I ignored the idea of plugged suction tube thing with bits. Not smart.

I didn't dismantle the oil relief valve since my 27mm socket wouldn't fit and I didn't have a wrench that size, so I gambled, again.