No oil pressure after oil and filter change

[Burnerman]

I've done this so many times I've lost count - must be high hundreds.
Cars, vans, motorbikes, trucks - the lot.
Always the same procedure - engine hot, remove drain plug, then filter and allow to drain completely.
In the meantime, fill up the filter with fresh oil, getting it as full as possible. Prepare the sump seal as appropriate.
Sump plug back in, filter back on, fill up to dipstick mark and start engine.
Check oil light goes out and look for leaks around the filter.
WOT NO OIL PRESSURE Switch off sharpish and think you're dreaming. No you're not dreaming and still no pressure when you try again.
If this happens to you.....slacken off the oil filter, but not quite completely.
Start but dont rev engine. Slacken the oil filter, get a faceful of oil, then quickly spin it up...oil pressure restored
Get down on your knees and give thanks. Its best to check the underwear soon....
This has happened to me twice. Once on a 406 Hdi, once on a Honda Pan European.
Its obviously an air lock in the oil pump or galleries.
If it happens to you, I hope this helps!
John

 

[Peter.N.]

Never had it happen to me John but I know you have done considerably more oil changes than me, so I will bear it in mind. The most memorable jobs were on Perkins 4/108 engines, they required an oil change every 2,000 miles, if you left it much longer when you took the sump plug out - nothing happened, I used to chuck a pint of diesel in before I changed it.

Peter

 

[ColJack]

I was told it helps if you warm the oil you're putting in before you do.. stand the can/s in a bucket of hot water fora bit..
and let it stand for half an hour after filling before starting.. let's any air bubbles rise..

 

[TicklyT]

Some oil pumps seem to have poorer self-priming capabilities than others. If the oil pickup pipe from the sump has drained, the pump has to shift a pipe full of air (a fluid it's not designed to pump) before it primes, a process eased by removing any restrictions on it's outlet (unscrewing the filter).

If the oil pickup doesn't drain, the pump will start working as soon as the engine starts.

Some oil pickups had a foot valve to stop them draining (if the valve worked), others rely on surface tension and atmospheric pressure to support the column of oil inside when the sump is drained. it works most of the time, but sometimes something 'breaks the vacuum' like the last few drops of water that run from a tap or shower head a couple of minutes after you turn it off.

IIRC one manufacturer used to recommend packing an oil pump with petroleum jelly to temporarily render it capable of pumping out the air if the oil had been drained from it.

 

[Belle427]

The rover v8 is one that can be a nightmare and is the one ive had to take off the pump and pack it with petroleum jelly (ooh er missus!)

 

[Infidel]

Might be being a bit thick here but doing an oil change on any of my motors I just pull all the plug leads off and crank it over on the battery, is that wrong?

 

[Burnerman]

I'm not too sure what you mean here, but if you do this to establish oil pressure after an oil change but before a start up then thats fine - although not really necessary.
However, on some cars coil packs, you must earth each plug out before you do this - failure can destroy the coil pack and rarely the ECU.
John

 

[Infidel]

Yep see what you mean, just to used to whipping the distributer cap off not that any of these new fangled bloody machines have one.

 

[Peter.N.]

Don't they have distributers and carburetters now? I've been running diesels for 30 years..