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

[Vivek]

I honestly cannot remember if there is a check valve in the filter housing where the oil comes in from the pump. If there is no valve, then you should be able to pull the filter element and pour some oil in to get things primed. Try it, and if pressure does not start building within 5 seconds shut it off. Maybe someone else can chime in about whether or not there is a check valve after the pump (I don't believe so).

Okay so remove oil filter cap, remove oil filter, pour oil in there (how much, and any specific spot it should go?), replace filter and cap, start it up?

[bmwman91]

Cool, must have been thinking of the little spring-loaded filter bypass between the dirty and clean sides.

[bmwm42]

There isn't the only valve is the oil relief one

[bmwman91]

So if I pour some oil in my oil filter housing and start it, it may work? Or will I have to pull the filter housing?

I honestly cannot remember if there is a check valve in the filter housing where the oil comes in from the pump. If there is no valve, then you should be able to pull the filter element and pour some oil in to get things primed. Try it, and if pressure does not start building within 5 seconds shut it off. Maybe someone else can chime in about whether or not there is a check valve after the pump (I don't believe so).

[jntar]

Pack oil pickup with Vaseline.

[Vivek]

So if I pour some oil in my oil filter housing and start it, it may work? Or will I have to pull the filter housing?

[kwill22]

Basically yea that's it. Just need the grease or oil thick enough to do the job.

[bmwman91]

I don't think that there is really any easy way to shoot grease up into the pump. You would probably have better luck pouring some 15W-50 into the oil filter housing and letting it flow backward to the pump gears to get them lubed up. I don't recall if there is a check valve in there, so you might need to remove the filter housing to be able to pour oil into the pump outlet. I assume that the idea is that a dry pump will just be circulating air between the small tolerance gaps in the rotors, and adding some grease/oil will fill in the small gaps and allow it to build suction?

[kwill22]

There's a specific type of grease that's used for for pumps. It usually dissolves into the oil. It isn't a problem with hydro pumps usually but on a car I'd change the oil after just for peace of mind. But as far as just greasing the pump with a gun. I don't see any issues with that just make sure the proper lube/grease is used. You can do more research on grease or fluids to use and how "safe" it is. If it doesn't prime with grease usually the pump is most likely bad.

[wazzu70]

I know the pumps can fail, its just a long shot due to the robustness. At this point though, the options of being much else are being reduced and the pump is one of the only things left.

The RB Nissan motors have a similar pump, and they have issues so its not unheard of.

I have never packed any with grease though. I usually install dry and have no issues getting it to pick up oil and work fine.

[bmwm42]

Depending on the routing of the oil system to the sensor/oil filter block. Is that the first stop along the path? I cant remember.

If the main galley is before that and its missing a squirter the oil system will not build pressure because there is no restriction. The oil just dumps out the open hole. 0 pressure does not mean 0 flow, it means there is not the right amount of flow restriction.

Maybe remove the oil filter housing block and see if any oil exits the pump when you rotate the crank.

The oil pump is a gerotor driven by the crank snout. Not a lot to fail there.

Ive had many people that say ....I mean the oil pump is nothing but a sprocket rotating inside the timing case but they do wear. ...and the pump does need to primed just ask gerta he had a similar situation....I don't claim to be a expert but I do have a fair amount of knowledge regarding the m42.

[roguetoaster]

Could he just stick a grease gun in the oil pickup (to pack the pump) and perhaps prime/create resistance at the pump? Along with some hand rotation of the engine I would think that would solve it if the pump simply needs to be primed/filled.

On the down side, if that does not work it will create quite a clog that would have to be cleared.

[kwill22]

When it primes it only takes a few seconds. If it's taken a minutes then it probably isn't going to happen. But the pump needs to be lubed in order to prime. It needs restriction as said above to work. Sounds funny but that's how hydro pumps work.

A slightly different design but same concept


The only way those gears move any fluid is if you pack them with some kind of grease usually to create resistance and vacuum

[bmwman91]

Depending on the routing of the oil system to the sensor/oil filter block. Is that the first stop along the path? I cant remember.

If the main galley is before that and its missing a squirter the oil system will not build pressure because there is no restriction. The oil just dumps out the open hole. 0 pressure does not mean 0 flow, it means there is not the right amount of flow restriction.

Maybe remove the oil filter housing block and see if any oil exits the pump when you rotate the crank.

The oil pump is a gerotor driven by the crank snout. Not a lot to fail there.

The sender is before the outlet to the galley. Looks like it has toe pump based on what Vivek is saying about cranking it with the sender removed and nothing coming out.

Vivek, if you remove the oil filter cover is there any oil in there?

I've never had an issue with the pump not priming. When I had my new engine start for the first time, it was noisy for 3-5 seconds and then built the necessary pressure. After oil changes, it is noisy for 1-3 seconds usually. Being a positive displacement gear pump, I cannot imagine it having any real difficulty sucking oil up the sump if it is properly submerged. But then again, my range of experience is fairly narrow so maybe it really is a big issue.

[Vivek]

Well I pulled the pressure sender and cranked the engine (before replacing the valve) and not a drop of oil came out. I couldn't find the right fitting to hook up an analog gauge. I'd guess a dud/incorrectly installed tensioner if it is indeed getting pressure. I installed it uncompressed. The timing should be correct unless it jumped a tooth, in which case I think it'd bend the valves/not run at all.

About priming the pump, the engines been run for about a minute, minute and a half, would that be adequate to prime it?

Would a broken oil squirter fall down into the pan? There wasn't anything in it when I pulled it.