Oil pressure?

mouss · #1 (**permalink**) 30-11-17, 08:54 PM

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 · #2 (**permalink**) 30-11-17, 10:22 PM

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 · #3 (**permalink**) 01-12-17, 09:19 AM

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 · #4 (**permalink**) 02-12-17, 11:26 AM

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 · #5 (**permalink**) 06-12-17, 12:02 AM

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 · #6 (**permalink**) 06-12-17, 11:58 AM

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 · #7 (**permalink**) 06-12-17, 07:51 PM

Of course Geoff, with great pleasure!

image1(2).JPG

Geoff Dowdle · #8 (**permalink**) 07-12-17, 11:17 AM

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 · #9 (**permalink**) 07-12-17, 10:51 PM

I'll ask my friend.

mouss · #10 (**permalink**) 10-12-17, 11:49 AM

Hi Geoff,

Yes, his car has been partially restored a couple of years ago and it looks in good condition and is working very well.
Here is its commission plate.
image2(1).JPG (249.8 KB)

The number stamped on the LHS of the cylinder head is 2254.
Are you sure it is a Bristol head?

Regards
Michel

Geoff Dowdle · #11 (**permalink**) 10-12-17, 10:30 PM

Michel ,
Thanks for the confirmation of the chassis number.

The head "2254" is a 85C/2254 originally fitted to a Bristol 401.
I don't have a record of which car it was fitted to .
The head casting and water pump is different to original BMW 328 and it is definitely a Bristol head

Geoff