M42 running VERY loud (video), low oil pressure light is on

[Vivek]

So basically all I do is drop the pan and the valve is right there? No need to remove the timing case cover or anything? The engine was running fine in my friends car. I'd known the car and engine the entire time he had it, and I also knew the PO. It had just started to make a timing chain rattle sometimes upon startup, so he pulled it for his s50 swap. Engine was excellent, cam gears and lobes were prefect at least before this issue happened. I can't think of any way the oil pump could be an issue since I never touched it, but who knows.

So what I'll need is:
Upper and lower oil pan gaskets
Updated versions of parts 5-8 on that realoem diagram

That's it?

[bmwman91]

Hang in there man. I know exactly how you are feeling at the moment. I was there about a year ago after my second broken valve spring on a brand new M42. You'll get it running and this will all be behind you soon enough.

If you unbolt the upper pan and slide it out of the way, the relief valve is on the driver's side in the timing case. It is reasonably easy to swap out. Check the diagram for parts & location.
http://www.realoem.com/bmw/showparts...04&hg=11&fg=30

Pull the valve cover and check the condition of the cam lobes while you are at it.

I can't think of anything else that it might be other than a missing or seized relief valve. The whole "priming" the pump thing never made sense to me since everyone routinely changes their oil and never has to deal with it after draining the system. Maybe someone here can shed a little more light on that before you start turning wrenches, but my bet is on the relief valve. Or, is there any possible way that the oil pump gears were not installed in the timing case? What is the story with the engine before you bought & installed it? Now that I think of it, seeing ZERO oil come out of the pressure sender hole might indicate that there are no pump gears in there. I can't think of any way that the filter housing would be so plugged up that nothing got past the filter or internal bypass check valve. Try removing the filter housing cap and filter and turning the engine over to see if there is any action. Even with the relief valve busted you should get a little something in there.

[Vivek]

Okay. Oil pressure is 0 under cranking. I pulled the oil pressure sensor, left the hole open, and cranked it. Not a drop came out. Does anyone have a DIY for the oil pressure relief valve?

If anyone is local I'd seriously pay you to do this for me at this point.

[Todd Black 88]

Don't start it if you cannot get adequate oil pressure by turning it over for a few seconds with the fuel pump fuse pulled.

Have you confirmed if your getting oil to the head? Is your oil pressure sender connected?

[Vivek]

Yup. Sucks. I think that you should be able to unbolt the upper pan and slide it enough out of the way to deal with the valve without totally removing it, but it's a pain either way.

You can pull the oil filter housing to see if the check valve is at least in there at all, or if it is in a weird position.

Where would it be? Does anyone know of a DIY link to this procedure?

So here's my plan:
Fill more oil (currently halfway between the lines on the dipstick)
Crank with fuel pump fuse pulled
Start it up and rev it a bit if anyone thinks that may help and not damage anything
Most importantly, I need to measure the oil pressure during all this and I really don't know how

If all that fails, I'll go ahead and replace the check valve. Would it read 0psi under cranking with a bad check valve?

[bmwman91]

No easier way.

Yup. Sucks. I think that you should be able to unbolt the upper pan and slide it enough out of the way to deal with the valve without totally removing it, but it's a pain either way.

You can pull the oil filter housing to see if the check valve is at least in there at all, or if it is in a weird position.

[wazzu70]

No easier way.

[Vivek]

If the oil pressure light is in, then it seems unlikely to be the tensioner. Letting things sit for a while is surprisingly hard on an engine. As has been recommended, you really need to check your oil pressure. Low pressure will make the thing super noisy like an old diesel. And kill the engine. Not the best.

My bet is on the pressure check valve in the timing case being stuck or having a busted spring.

Okay thanks. So it looks like the noise is definitely the timing chain, and that my oil pressure has something to do with it. Ill see if I can find a way to test the pressure. Cranking it with the starter should read more than probably 5psi, right? I'm gonna be out for a few days but ill look into replacing my check valve when I get back.

Edit: and I was just reading that I have to pull the upper oil pan to replace the check valve. dammit please someone tell me there's an easier way.

[bmwman91]

If the oil pressure light is in, then it seems unlikely to be the tensioner. Letting things sit for a while is surprisingly hard on an engine. As has been recommended, you really need to check your oil pressure. Low pressure will make the thing super noisy like an old diesel. And kill the engine. Not the best.

My bet is on the pressure check valve in the timing case being stuck or having a busted spring.

[roguetoaster]

Can I do this without risking damaging anything? How long should I be able to do that without burning up the starter? I'm thinking I should find a way to accurately meter the oil pressure first, unless maybe it just needs to be turned over for a while for it to build up, but I don't think that's normal.

Yep, keep your cranks under 30 seconds each, with 15 seconds being an ideal maximum. Clearly you need to let the starter cool at some point, use your best judgement and you will be okay.

The only easy place to check oil pressure with a gauge would be at the oil pressure sensor.

You could also pull your tensioner back out and just see if there is anything odd about it, broken spring, etc.

[Vivek]

I would pull the fuel pump relay, put the battery on a charger, and turn the car over with the starter untill you build oil pressure. Never start a dry motor without first confirming adequate oil pressure.

Can I do this without risking damaging anything? How long should I be able to do that without burning up the starter? I'm thinking I should find a way to accurately meter the oil pressure first, unless maybe it just needs to be turned over for a while for it to build up, but I don't think that's normal.

[bmwm42]

You should see oil flinging with the cap off my guess is either your oil pressure relief valve is stuck...or your tensioner is shit

[Todd Black 88]

I would pull the fuel pump relay, put the battery on a charger, and turn the car over with the starter untill you build oil pressure. Never start a dry motor without first confirming adequate oil pressure.

[Todd Black 88]

Not sure on the m42, but you can see oil flinging around on my s14 with the cap off.

[kwill22]

Take the valve cover off and see if everything is covered in oil like it should be