M52B28 Turbo Engine Build Low oil pressure

[Leegee]

Hi Guys

So i have been building up my 328 turbo project over the last couple of years in spare time, i finished building the engine put it all in and started it up, all ran bang on but as soon as the oil started to get any temp pressure dropped right off and to be honest is a little low at cold too. i have been over so many things to work out what the issue is here is the list of what iv done to the motor,

M50 cast block
original M52 head
Cometic 0.140" HG
Arp big end bolt
Arp Head studs
S50 M3 oil filter housing and mocal cooler
re ringed and new bearings i put 360 degree oil groove mains in though 180 came out but that would not account for much if any drop in pressure.

Pump should be fine came straight off my engine before i stripped it and was fine then.

Any suggestions would be massively appreciated as im out of ideas and have had the head off again to check if the return valve was in place (it was in there wasted another £150 on a gasket )

[someguy2800]

What pressures are you getting? About 15 psi when warm is normal at idle. 360 degree bearings will cause a drop in oil pressure. They are useless.

[Leegee]

At warm idle maybe 5psi if im lucky closer to 0 to be honest

[TheJuggernaut]

Can you detail how you are measuring the pressure? I would start with verifying your measurements before anything else - get a known good mechanical gauge. Most electrical senders get very non-linear towards the extremes and might read 0 below like 20psi.

[Leegee]

I have had mechanical and the electric gauge on the both read the same and the idiot light comes on once it warms up.

[IR M5]

Did you forget the oil squirters by any chance?

[Leegee]

I could have sworn they were in there, but if they weren't surely the pressure would be next to 0 even cold.

[TheJuggernaut]

My amazing expert engine builder left my oil squirters out, I still had 10psi on hot idle.

- - - Updated - - -

I have had mechanical and the electric gauge on the both read the same and the idiot light comes on once it warms up.

Where are you picking up the pressure? Any pics?

[Leegee]

My gauge sender is on an in line adapter on the an10 fitting for the oil cooler, and i put the mechanical one on the vanos take off on the filter housing.

[TheJuggernaut]

What did you do to the block? How far did you strip it/clean it etc? Did you pull the main gallery plugs for cleaning?

[Leegee]

It came pretty clean but i sent it over to the machine shop to be honed and faced and he re cleaned it, bit didn't pull the main gallery plugs.

[TheJuggernaut]

Do you know that for a fact, IE you remember the plugs being there visually during reassembly? Or you just didn't ask him to pull them? That's kinda all that's left in my mind.

[Leegee]

As far as i can remember, where exacly are they as it was a while ago i actually build the motor up.

[TheJuggernaut]

#13

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[e46cruiser]

Yes! Make sure the oil galley plugs are there! If you’re engine was cleaned by the machine shop there is a good possibility that they took them out to properly clean the engine. This literally just happened to me on my S52, super low oil pressure. Another thing as well, if the rear oil galley plug is out you will be dumping oil into your bell housing and it will saturate your clutch, if the front one is out you will not know unless you take the timing cover off.

[milKt]

Good info.

[Nutzy]

I freaked out when I first saw the hot oil pressures in my new M50 build, but they were normal. According to the factory M50 tech manual, 10 - 15psi pressure when hot is normal, but uuuh, yeah 0-5psi....not so much.

[Leegee]

As far as i am aware the plugs are in and i have the head off at the moment and it doea not apear to be leaking around there.

[TheJuggernaut]

The only thing left that I can think of is the filter housing. I didn't think of it sooner as I don't use the stock housing anymore. Someone else may have a clearer description but maybe you're losing pressure through the housing? I remember there being an O-ring in the housing bolt, not sure what it seals but maybe you have a leak inside the filter housing, bypassing some flow?

[Nutzy]

The only thing left that I can think of is the filter housing. I didn't think of it sooner as I don't use the stock housing anymore. Someone else may have a clearer description but maybe you're losing pressure through the housing? I remember there being an O-ring in the housing bolt, not sure what it seals but maybe you have a leak inside the filter housing, bypassing some flow?

That is a possibility, or, the relief valve is in the housing isn't it? What if this was put in incorrectly, or not at all.

[someguy2800]

The pressure relief valve is built into the pump. There must be an internal leak someplace or the pump is trashed inside. On the filter housing the bottom hole is coming from the pump, the top is going to the main oil gallery, and the middle one is bleed hole going to the crankcase. I don't remember what its function is. If there was a cross leak between the middle port and one of the other ports that certainly would be a larger internal leak but I doubt it would be large enough for the pressure to drop to zero.