Oil Pressure on Start Up

Rek

Rek

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Just recently the oil pressure light has taken longer and longer to go out on start up, even when warm. Now its up to about 20 seconds and I don't want to ruin the engine.

There was a good thread on this forum whoch I can no longer find but it didn't answer my question. My car has a 1989 M30B34 with the top loader and later (supposedly resolved) drain valve in the oil filter mechanism. It would appear that this valve has failed and is leaking oil down into the sump. I cannot replace the valve and cannot find a replacement, with the oil cooler connectors, which my car has fitted.

I want to replace the filter housing with a rear loading one whilst I either mend the valve or locate a replacement housing.

Does anyone know what housings are appropriate? I will cap off the oil cooler pipes whilst a replacement is on my car if needs be so. Any help or advice gratefully received.
 
Also, does anyone know where the oil pressure switch is on the M30 B34? The official wiring diagram has it on the head just on right towards the rear whereas the RealOEM site has it plugged into the oil filter housing - part 10 as per the attached. As it's cheap, I thought I might try changing the switch as its a cheap first step.
 

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We won’t use the b35 housing- known problem area for that engine.
If you revert to earlier version- install the bolt in the hidden hole
 
I had a thread on oil pressure and the light coming on when warm and idling, which makes sense because the oil is "thinner" then. Mine was a false alarm, the oil pressure switch was the problem. I confirmed it by idling for an hour while using an oil pressure gauge.

I have no idea of the role of the oil filter valve. I thought the bad failure mode is when it stays closed because oil does not flow. If it fails open I guess the pump will keep picking up oil from the sump and life is good. But I may be wrong. I think DQ wrote about the role and danger of a faulty valve.
 
The faulty valve causes the oil to drain from the oil filter housing back to the sump. When starting, the pump has to fill the housing before the oil goes to the engine and the pressure sensor. It's quite nerve racking running with no pressure waiting for the light to go out.

I have found a non oil cooler housing for a reasonable price and will fit that plug the cooler hoses and fettle the original housing to see whether the valve is fixable.

My engine is a B35 rather than B34 I am told. I presumed the 3443cc meant it was a B34.
 
Close to three years ago I also started a thread about the oil pressure light staying on during the cold engine start up:

Oil pressure light stays on for some seconds

I found an advice in this forum saying: "Both yellow-orange Oil Pressure & red E Charging System lights should illuminate when key is in position 1 & start. Both should go out within 2 seconds of engine running. " Well, the oil pressure light in my car stays on for more than mentioned 2 seconds...
e9coupe.com e9coupe.com

Not sure if this is the one you had in mind, nor if it helps at all. Maybe not, as the light in my E9/M90 stays on some 5 seconds, not even close to 20 seconds but still it feels like decade while waiting.

SamiA
 
The drain back valve in the housing is plastic and after a while it doesn’t seat properly and that causes the oil to leave the canister. There was a design change for 1991 where they went to a more durable design.

If you put an M30B34 housing on, you need to install this DIN 908 plug (m10x1) in the hole or you will have no oil pressure.
IMG_5202.jpeg
 
wkohler said:
The drain back valve in the housing is plastic and after a while it doesn’t seat properly and that causes the oil to leave the canister. There was a design change for 1991 where they went to a more durable design.

If you put an M30B34 housing on, you need to install this DIN 908 plug (m10x1) in the hole or you will have no oil pressure.
Click to expand...
I think I have the newer design but the valve might be stuck open. It might be some debris but I'm glad its there rather than in the engine.
I have a replacement housing now but it was for a non oil cooler car. However, there are two allen key plugs which might be where the oil cooler lines go. It's a used part so it might be tricky to get them out but worth a go.
 
wkohler said:
The drain back valve in the housing is plastic and after a while it doesn’t seat properly and that causes the oil to leave the canister. There was a design change for 1991 where they went to a more durable design.

If you put an M30B34 housing on, you need to install this DIN 908 plug (m10x1) in the hole or you will have no oil pressure.
View attachment 163261
Click to expand...
Which hole? The one under the housing? Mine was missing anyway.
 
So I obtained a non leaking housing without oil cooler fittings and just fitted it. I put some oil in it and tried the engine. Still very slow filling the housing and getting pressure. I am changing the oil to 5W 40 as the difference in time it takes to push the more viscous oil around is staggering. Take a look at the attached.

 
Rek said:
Which hole? The one under the housing? Mine was missing anyway.
Click to expand...
I provided a beautiful photo of the plug. It’s not missing, it’s just not installed on the B35 and it has to be installed if you switch to a B34 canister or there will be no oil pressure. If you continue to use B35 canisters then you don’t need it.

Also never put a 5w40 in an M30. Tolerances in these engines are such that is way too thin and you will have lower oil pressure.
 
wkohler said:
I provided a beautiful photo of the plug. It’s not missing, it’s just not installed on the B35 and it has to be installed if you switch to a B34 canister or there will be no oil pressure. If you continue to use B35 canisters then you don’t need it.

Also never put a 5w40 in an M30. Tolerances in these engines are such that is way too thin and you will have lower oil pressure.
Click to expand...
Thanks for the advice. I wondered about the plug but I am using the B35 cannister. I take your point on the oil and can change that but it was taking so long for the pressure light to go out that I feared damaging the engine. I fear there is something amis in the oil sump.
 
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