Nissan Micra K12 - Strange oil pressure issue | Technical matters | Back Room Forum

Sun 6 Mar 2016 22:14

Nissan Micra K12 - Strange oil pressure issue - Cogitosus

Hi folks, hoping someone can help here, because I'm stumped.

I was asked to look over a 54,000 mile 2003 998cc Nissan Micra K12 at a small dealer's for a cousin of mine. Drives well, feels and sounds like a 54,000 mile car. There were a few small issues which the dealer sorted, but my suspicions were raised as, once he had the deposit, he seemed extremely keen to get it off his hands, to the point of delivering it 25 miles to my house.

The next morning an issue became apparent: when started from cold it takes 12 seconds at idle before the oil pressure light goes out. During this time the engine is very quiet with no top end noise. In contrast, when the engine is hot, the light goes out instantly.

Upon collecting the car from me, the cousin dropped it to his local mechanic who offered the same diagnosis I did: a partially blocked or faulty oil pressure switch, but it seems, not so. The mechanic dropped the sump and cleaned the (already clean) strainer, then he flushed out the gallery, changed the oil and filter and finally replaced the oil pressure switch - all to no avail. He put a gauge on to it and said the pressure was fine, but I suspect the engine was probably hot at that stage. I'm a little vague on this as he's on the other side of the country and I'm getting this second-hand.

He also noticed that the sump and timing cover were sealed with gasket goo. I should have spotted this; clearly I'm getting old.

The car seems fine in every other way and is perfect when hot. There is no evidence of wear or noise. I can't figure out how a car can apprently have lower oil pressure when cold, than when hot. This is really bugging me and I'd be grateful for any suggestions.

Thanks.

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Sun 6 Mar 2016 22:45

Nissan Micra K12 - Strange oil pressure issue - bathtub tom

I had this many years ago.

The non-return valve in the oil filter. It had a 'standing' oil filter, that is the filter was fitted with the open end facing down. A filter was supplied without the built in non return valve, allowing the filter to drain when the engine was switched off. It took a while for the oil pump to re-fill it at start up.

I'd suspect something similar in your case.

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Mon 7 Mar 2016 03:47

Nissan Micra K12 - Strange oil pressure issue - RT

I had this many years ago.

The non-return valve in the oil filter. It had a 'standing' oil filter, that is the filter was fitted with the open end facing down. A filter was supplied without the built in non return valve, allowing the filter to drain when the engine was switched off. It took a while for the oil pump to re-fill it at start up.

I'd suspect something similar in your case.

Some 3rd party oil filters fit the mounting physically but omit the non-return valve as some engines have that mounted within the engine.

I found many years ago that simply buying the right filter from a franchised dealer, even at list price, was barely more expensive than the cheapest 3rd party filter and guaranteed the correct specification.

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Mon 7 Mar 2016 09:52

Nissan Micra K12 - Strange oil pressure issue - Peter.N.

That would sound about right. The oil pressure OK good when hot is a good sign as it usually drops considerably when the oil thins out.

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Mon 7 Mar 2016 10:24

Nissan Micra K12 - Strange oil pressure issue - gordonbennet

Sounds on the money to me too, can't be that bad engine wise or it would be rattling like a skeleton in a biscuit tin till oil got round.

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Mon 7 Mar 2016 10:35

Nissan Micra K12 - Strange oil pressure issue - Cogitosus

Thanks folks, that all makes perfect sense, but if you look colsely, you'll see that the mechanic changed the filter. It is of course possible that the replacement was the same make and model as the original, but I can't help getting a 'grasping-at-straws' feeling.

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Mon 7 Mar 2016 11:08

Nissan Micra K12 - Strange oil pressure issue - gordonbennet

Can you get hold of an oil pressure gauge kit and see for yourself whats happening there.

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Mon 7 Mar 2016 13:54

Nissan Micra K12 - Strange oil pressure issue - Cyd

Many engine designs have the oil non return valve in the filter and the pump is self priming. This ensures full drain down when the filter is removed for oil change.

Many 'cheap' aftermarket filters leave out this valve for cost saving. Make sure that the filter that you had fitted has the non return valve. If there is any doubt, I'd suggest getting one from a Nissan garage. If that doesn't solve the problem at least you will have eliminated it as a causal factor.

Another possibility:

On my Saab, the filter is not the canister type but just the paper element fitted into an integral housing on the block. The cap has the non return valve in it. If yours is like that, try another cap in case the valve has failed.

I'm not familiar with th eK12 engine, but it does rather sound as if the oil is being allowed to drain back into the sump and the pump is then having to reprime itself each cold start. It might only be partial failure hence okay when still warm. I feel that's where I'd be looking first anyway.

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Mon 7 Mar 2016 14:02

Nissan Micra K12 - Strange oil pressure issue - Cyd

timing cover were sealed with gasket goo.

Is the oil pump behind the timing cover? Is the non return valve part of the pump mechanism? Broken spring? lump of instant gasket getting in the way?

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Mon 7 Mar 2016 17:41

Nissan Micra K12 - Strange oil pressure issue - Cogitosus

Assuming the mechanic is telling the truth, then the oil pickup pipework is clear and, if he measured the pressure correctly, then the pump is OK and it has to be a drain-back issue.

I popped out today and bought a genuine Nissan filter which I put in the post to my cousin, living out in the wilds. I shall report back if it resolves the issue.

Thanks for the advice folks.

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