M52B30 stroker low oil pressure

[lionkingns]

Made a 3.0 m52 stroker for my e39,with M54B30 internal parts + M50 intake manifold , all parts where checked , measured and polished in a machine shop, and every possible bearing and seal is brand new, and the best quality I could buy. Also the original M52B25 block was too worn out, so I took a different one that was also checked and measured to spec.

The engine started, works great, has lots of power. The issue that came up after the build is that the oil pressure red warning light comes on at idle after the engine gets to temperature. While the engine and oil is cold its ok, once the temp needle gets around the middle it starts to flicker on idle, and later it stays on solid. I did use a analog pressure gauge and while hot the pressure is around 0.3-0.4 bar on hot idle, while bmw says it should be above 0.5 on idle, when you rev it at around 1000-1100 rpm the red light goes out, and the gauge showed about 2.7-2.9 bar on 3000 rpm (didnt want to spin a fresh built engine over that)

I bought new internal oil pump parts (the rotor and stator, and the pressure relive valve), sadly no luck, still the same.

The oil in it is shell ultra 5w40 synthetic

I did test the VANOS by pluging up the oil pump that feeds it since I found at a few forums that they do tend to leak, but also no luck, the red warning still came on after a few minutes.

Also I have changed and tried 3 different oil filters, no luck either

Any more ideas what to check and how before I pull out the engine and take it apart again ? Which I would love to skip if possible

Also how smart would it be to just put some thicker grade 50 or even 60 oil and run it ?

[pbonsalb]

I would try a different oil pressure gauge to verify. You could also try a tune that raises the idle speed to 850 rpm. Or you could fit a pump that increases oil pressure. VAC and others sell modified S54 pumps.

Is it possible an oil squirter is wide open? I am not exactly sure how they work but assume they have a check valve since they are not needed at idle.

There is also some sort of plastic anti return valve inserted in the head but I doubt you forgot that. In 15 years of being in the forums, that does not seem to be a common problem

[328 Power 04]

I have seen hot engine pressure light flickering around on the forums. Not uncommon.

I wonder how the check valve is doing in your engine's head, or if it's there?

I have an S52US that flickers on hot idle, but the oil temp is at 115-120 deg F when it does that. So the solution for me is an oil cooler first.

[bmwdirtracer]

Personally, I'd have bought a new oil pump, rather than parts, if going that route. I'm not saying your choice was wrong, that's just me.

When the crank was installed, were bearing clearances checked with plastigage?

Is the o-ring on the oil filter housing center shaft? The check valve in the head is a possible issue, as Abel pointed out. Just a single o-ring being MIA could be the issue....I'm rebuilding an S62 right now, so this is just my own paranoia.

[dworthy]

+1 or 2 in this case

Get an actual gauge on the motor, and at times the switch can get weak over time thus giving you a false reading.

[lionkingns]

So on the M52 the check valve is in the oil filter housing , so I got a second hand one just to check that route. The pressure is low since I had 2 (one brand new) pressure senders + a mechanical gauge, and all of them point out the engine has low pressure under a 1000 rpm

[bmwdirtracer]

https://www.fcpeuro.com/Parts/?keywords=11121735180

I don't know if it'll cause your issue, but it's important for oil control. I'd also check for parts #5 in this diagram; while they control oil drainback from the filter, if they're MIA it might cause oil pressure issues.
https://www.realoem.com/bmw/enUS/sho...diagId=11_7537

Mainly though, I'd really suspect that oil pump; while I was changing it, I'd unbolt a connecting rod, dry the bearing and journal, put a piece of green plastigage in there, torque with the old bolts to spec, check the results, then replace bolts if it all checks out.

I know that an oil pump is expensive, and it's a PITA, but 4 or 5 psi isn't adequate pressure.

By the way, this can be done without removing the engine from the car; you need to hang the engine and drop the subframe as far as it will go hanging from the struts (about 5 or 6 inches)

[dworthy]

+1

Just replace a oil pan gasket on a N-46 motor this past weekend, with an engine support from the top, no issues pulling the pan with the subframe dropped. Of course it would have helped if I had pulled the dipstick tube out before pulling the pan, but I was being lazy.

Just be sure to watch the power steering lines, and use something to support the subframe.

[bmwdirtracer]

And I've got an s62 undergoing conrod bearings and timing chain/rails....book says remove engine for either job, but books don't fix cars. Engine remains in the car, where it belongs.

[lionkingns]

So as I sadi I habe alredy rebuilt the oil pump, complete brand new OEM parts the pressure relive valve and the pump shaft and rotors all brand new, basically just left the old oil pump housing from the old pump, every part that does the job is new. So oil pump is not the issue. Checked the check valve, which is on the oil filter housing in the M52 not the head itself, put a second hand filter housing just to be sure, not the issue.

But I think I might be on to something, since my old engine block was too worn out, I took another one that was in perfect condition and while at it I used the cylinder oil squirters from it, not my old engine so I have no idea if they where good or not, and I have found online a few people that had the same issue with them since they have a small spring and ball valve which should cut them of on idle and let oil once the pressure rises, and if one of them gets stuck open it lets oil out while idling and thus loosing pressure, which exactly fits my symptoms. The engine has done 2000km from the rebuild, and no strange rattle on something so I guess the bearings are definitely good

Will update you after the oil squirters are changed if it fixed my issue