Oil pressure?

[mouss]

Hello,

A French friend of mine has just bought a BMW 238 the oil pressure of which seems very low.
Would you please let me know what should be the correct pressure wit a hot engine, at, say, 2000rpm?

Also, we would be interested in technical info regarding this engine: can this be found through the club or anywhere else?

Thank you

[Geoff Dowdle]

Mouss,
I assume your friend has a BMW 328 (not a 238 as stated)

The BMW manual that I have states that
a. at idle 1.5 atmospheres (which I understand is about 22psi)
b. 60kph 3.0 atmospheres (which is about 44psi)
Both with oil (SAE50) to running temperature

Oil Pressure of 6 cylinder Bristol engines ,which are based on the BMW engine, should be
60psi at 3000rpm with oil at or above 70 degC

I have had no direct experience with BMW engines ,but if it were mine I would like to see the pressure as per the Bristol spec . This might need a later Bristol oil pump adapted & fitted.

What pressure is the engine achieving at 3000 rpm with the oil hot ?
What grade oil is he using ?

There are quite a few Pre WW2 BMW specialists in UK , Germany and Switzerland who could give your friend advice
or
the various BMW Clubs

Geoff

[mouss]

Hi Geoff, thank you very much for your kind answer.

Of course, I meant BMW328...
At the moment, oil pressure is about 1.5bar @ 3000rpm when hot, which seems a bit concerning.
The oil grade is 20w50.

There is no pressure warning light on the car and we haven't checked the electric manometer yet: that's what we'll do first with a mechanical one.

Do you know if the relief valve is adjustable on those engine?

Also, the car is equipped with an oil radiator and a non original oil filter on the pressure circuit, we also wonder if this couldn't be a problem...

[Geoff Dowdle]

Mouss,
The pressure relief valves are adjustable but I doubt that is the cause .
My guess is it could be wear/excessive clearance on the crankshaft bearings/journals and /or Camshaft bushes .
I doubt the problem would be with the oil filter and oil cooler.
I would initially try a thicker oil to see if it helps .
Penrite have a HPR50 which is a SAE 40/70 and designed for older engines,with larger clearances than modern engines.
At the worst it will need a new eccentric rotor oil pump and/or complete engine rebuild.

Definitely check the pressure on another gauge , as many older gauges are not accurate.

You or the owner should get advice from a Pre WW2 BMW Specialist , there are surely some in France .

Regards
Geoff

[mouss]

Problem solved!

We checked the pressure wit another manometer and got the same indication.
I removed the relief valve for checking and discovered it vas open because of a piece of dirt blocking the ball.
Fortunately, my friend didn't drive the car like this!

I cleaned it and readjusted the spring: now, 1.5 bar at idle and 3.5 to 4 bars @ 2500rpm when hot, that's far better!

Thank you very much Geoff for your help

[Geoff Dowdle]

Mouss,
I'm glad you sorted the problem .
Could you please post a few photos of the car on the Forum as I'm sure many of us would like to see it .

Regards
Geoff

[mouss]

Of course Geoff, with great pleasure!

image1(2).JPG

[Geoff Dowdle]

Mouss,
Thanks for the photos of the 328 it seems to be in nice condition.
Do you know its chassis & engine number?
One photo shows it has a Bristol head and water pump fitted to probably a BMW block .
On the distributor side of the head there will be two raised bosses close the the lower face of the head .
Could you please advise the numbers stamped on those bosses, this will confirm its origin .

Tks
Geoff

[mouss]

I'll ask my friend.