S54 Rebuilt but low pressure @ idle

[gscavalli]

Hello guys.


I built an E36 with a S54B32 Engine and MSS54. My client bought the engine in the US and shipped it to Brazil. When the engine got here I started inspecting it and found out the rod bearings were worn. We decided to do a full rebuild. New BMW OEM STD Rod Bearings, Glyco STD Main Bearings, new piston rings, full set of gaskets and so on. We measuread crankshaft journals, oil clearances and double checked it with plastigage. Oil clearances on rod and main bearings are between 0.038 mm an 0.040 mm (0.0015 in). Also did a Vanos rebuild using a Beysan Systems Kit and the engine was ready to be installed on the E36. As usual here at the shop we always check engine oil pressure with a mechanical gauge, specially with rebuilt engines. Let's talk about the problem now... Engine works perfect, but Oil Pressure has been a nightmare... With engine at operating temperature oil pressure readings are below 0.4 bar (6 psi) and BMW states the minimum oil pressure for this engine is 0.7 bar (10 psi) at idle. I'm measuring oil pressure with the gauge attached on the oil filter housing, next to the OEM oil pressure sensor location. Oil pressure light on cluster never blinked during the tests and I didn't road tested the car, just let it hit operating temperature inside the shop... I was concerned about the oil cleareances so I removed the engine and inspected every single clearance again. Same results, everything within specs... So we decided to buy a new oil pump and got the engine back on the car once again. I noticed a little improvement but oil pressure is still below 0.7 bar. Right now it's reading 0.4 - 0.5 bar at idle with oil temperature of 90 degrees Celsius... This is driving me crazy... Car has been in the shop for months and I don't know what to do anymore. Oil pressure behaves normal when revving the engine, oil pressure goes above 4.5 bar. I know there's a 1 bar constant pressure valve and if I'm correct its function is to keep oil squirters closed when oil pressure is below 1 bar. If this constant pressure valve fails it would let oil flow to oil squirters dropping engine oil pressure ad idle . What do you guys think?
Is there any other thing I could be missing? Is there any VANOS related problem that could led to low oil pressure?



Thanks guys!


Cheers from Brazil
Guilherme Cavalli

[180SXTCY]

There's a thread over on NAM3FORUMS where a guy is having similar issues to what you describe, although he used extra clearance bearings the first time around, then replaced it with standard clearance bearings the 2nd time around and I believe he is onto the 3rd round of trying to find the issue....

Heres the thread you might find something useful inside:

https://nam3forum.com/forums/forum/m...ng-replacement

One thing that springs to mind is the o-ring on the oil pickup tube, was this replaced ?

[gscavalli]

There's a thread over on NAM3FORUMS where a guy is having similar issues to what you describe, although he used extra clearance bearings the first time around, then replaced it with standard clearance bearings the 2nd time around and I believe he is onto the 3rd round of trying to find the issue....

Heres the thread you might find something useful inside:

https://nam3forum.com/forums/forum/m...ng-replacement

One thing that springs to mind is the o-ring on the oil pickup tube, was this replaced ?

Thanks for sharing!! I just read the full thread and looks like the exact same problem...
Yes, oil pickup tube o-ring is new!

A litte update: Yesterday I got another CPV and welded it in order to block oil flow to oil squirters. Oil pressure at idle is exactly the same, so I assume the valve was working good if we consider it should be closed below 1 bar. I'll road test it today monitoring oil pressure to see what happens

Cheers bro!

[gscavalli]

The worst part is that I've never seen this engine working before rebuilding it. It may have a crack somewhere, who knows...

So far:

Rod bearings clearances OK
Main bearings clearances OK
Crankshaft axial play OK
Oil Pump is new (SHOULD BE OK)
Constant pressure Valve OK (TESTED)

Next I'll be changing Oil Filter Housing...