Intermittent No Oil Pressure light......Cause, Effect, Result

Volvo XC 70, 2.4t, 2001, 95Km, Eng B5244T3

A bit of back ground, I have recently replaced the turbo charger, due to the end result of oil sludge/ Black Death as some so eloquently call it, but that is another story....

Dropped out the sump pan and cleaned up, removed all internal oil pipes, and plugs and cleaned replaced all sump O rings.

Installed new /rebuilt turbo and cleaned out all oil lines supply and drain lines.
Boxed back up and refilled with oil.

Test ran the engine for 15min and removed and changed the oil filter a little dirty but not bad.

Things were going well....., after a tank full 425km of gentle driving; I changed the oil and oil filter.

Shortly after this 10km, things started to go less well, the No Oil pressure light came on. Stopped the engine and checked oil level in case the oil filter seal had popped oil leaks etc. Oil level was fine. Restarted car and light does not come back on and drove home.

Checked engine compartment, oil filter, oil level for anything strange, zip. Started engine and brought up to working temperature, everything fine, no strange noises.

Drove around the block and down to the shops and back about 8km and then the oil light came back on again when I was waiting for my gate to open. Parked and put back on the car ramps.

Had a think! Had a read of the Volvo boards!! Had another think!!!

The most popular theories for this intermittent No oil pressure would appear to be:

a/ O rings on the sump pan leaking.

b/ the oil pressure switch is faulty.

c/ the oil pump is faulty.

d/. Change out the engine. No good reasoning but changed out everything else, see above.

I did not like the look of any of these, because:

aa/ the O rings were new, having just replaced them when cleaning out the sump, and why would the pressure be OK at start and then drop off. No if the seals had gone or were misplaced the pressure would be low all the time.

bb/ I did take the oil pressure switch out and cleaned it and gave it a prod and the switch felt good. It seems to work on start up and for sometime thereafter before giving a low pressure reading. They are designed to last the life of the vehicle and usually do, so a fairly reliable component generally.

cc/ Unlikely that oil pump should go bad so quickly, on a relatively low mileage car, when its job is to pump lubricant oil. The pressure seemed OK at start and when the car was warmed up.

dd/ Worn engine? Low mileage engine, no engine noise of bearings rattling around, or top end noise. Was running fine before turbocharger went.
So what next?

The oil circuit is relatively simple. A sump for the oil storage, an oil pick up, a pump, a filter , an oil pressure switch and then to the oil way and pipes which feed the bearings, and journals etc.

It is always best to start at the beginning, (or do the easy stuff first) so I of course dropped the oil filter to check the condition of the filter. It was a little dirty with the black carbon flakes still being flushed out of the engine. But not enough to cause that low oil pressure.

I then dropped the sump; the sump was relatively clean with a few flakes of black carbon at the bottom.
Looking up at the bottom end of the engine, the oil pick up pipe tube screen looked clean.

BUT! Taking my pinkey (This is the smallest finger on the hand opposite the thumb) and running it around the inside of the oil pick up there was a good deal of carbon flakes.

I removed the oil pick up pipe from the engine and when turned upside down all these back carbon flake dropped off the trough of the oil pickup head and covered the mesh screen.

The mesh screen was also dished up into the oil pipe. It was flat when I removed it from the last sump clean out during the turbo-repair, the mesh material had also started to tear at one section.

I have elected to remove the mesh screen to prevent the mesh being sucked into the oil pump at some blockage of the mesh screen. This seems the lesser of a number of evils.

The mesh on the pickup tube is to prevent lumps of metal going through the oil pump. These lumps being larger than 1mm the size of the oil pick up suction mesh. Some of these carbon flakes seem to be ideally sized to block off the mesh and thus prevent oil flow. About ½ a teaspoon full was inside the oil pick up trough, which was enough to cover the mesh screen. There was about another ½ teaspoon full in the sump once I cleaned it out and less than ½ a teaspoonful in the oil I drained out. I can expect more as the engine gradually cleans its self of the consequences of the sludge.

Since the mesh screen was dished inside the oil pipe once the mesh is blocked you will have no/little oil pressure. Hence on the stopping of the engine, the back flow of oil will flush the contents of the mesh screen off and give you normal oil pressure on start up. Until the screen blocks up again.

I toyed with the idea of drilled holes in the dished oil pick up trough to allow the carbon flakes to drop back into the sump, but rejected the idea.
i.The mesh was dished and had started to fail.

ii. Does the pickup trough have some self cleaning design for the mesh screen, as the oil is sucked through it?

iii. The flakes will continue to circulate around in the sump until the next oil change.


So the solution Synopsis the removal of the pickup suction screen:

The debris that is causing my problem is carbon flakes from the sludge issue I had.
These are products of combustion, carbon and oil baked onto the hot surfaces of the engine.
These will slowly come away from internal surfaces of the engine with clean fresh oil and the mechanical abrasion of the oil splashing around inside the engine.

They are relatively soft, and can be broken down by rubbing between the fingers.

So these going through the oil pump should not be an issue. The oil filter will then catch and remove these partials.

Regular inspection of the oil filter, and change as required will help to clean up and remove the carbon flakes from the engine.

The other options are:

Complete dismantle of the engine and the thorough clean of all parts.
a new engine

remove the sump each time the oil pick up screen blocks up and clean out the pickup trough.

All rather expensive and time consuming for an older car.

I am indebted to Alanjackson2011 and Luvinvolvos from Volvo forums who have been there!

Hope this post is of some use to others in the same situation with low and intermittent oil pressure problems that have had sludge affected engines.

Bydand

 

Mineral oil is refined natural crude (with additives). Synthetic oil is man made, and contains less carbon. It also has other additives to help clean the engine (as does mineral), but it can stand higher temperatures for longer without breaking down. That is the primary reason that it is much better to use in turbo'd vehicles.

 

Thank you,,,so it is a local term thing. My off the shelf stuff is "mineral oil". Mineral being mined from the earth.

I do use as you say mineral oil. Planing on changing to synthetic mostly for the detergent qualities. I have already dealt with a slug problem that took out a cam seal so I am not in a hurry to work on the turbo.

Thanks again for the reply

 

I am not sure if there are any rules, but the important thing is that the idea of what you can call "synthetic" oil in the USA has changed. Years ago, synthetic oils were not "really good" mineral oil. The idea was they were poly alpha olefins. That has changed. Now, a lot of the synthetic oil is mineral oil based and has some advertising applied.

I don't like to make long posts, so I would say if you are curious about oil performance spend lots of time at bobistheoilguy.com; if you read any marketing material at all on oils you'll see right away that it's all baloney. The oils themselves aren't baloney. Oil companies have been improving them for over 100 years and they do an enormous amount of testing. They seem to keep all the interesting information a secret.

P.S. I should add here that oils marketed as synthetic would indeed be the best for resisting oxidation and coking, and that's what you want for a turbo.

 

You do not need to use synthetic oil because the car is a turbo. I have been working on Volvo's for a long time and the rare times I've seen a turbo fail it was due to not changing the oil. 40k on an oil change, synthetic or not, is not good.

 

I used some fuel conditioner/ injector cleaner at double the recommended amount and started having noisy tappets and intermittent oil light. (possible coincidence) The oil light came on if I was doing hard accelerate and brake or swerving.

I used a can of seafoam in the oil as directed. when the oil was sufficiently black (400km) I changed the oil and added gasket conditioner as directed. Changed oil again after 200km, added another dosage of conditioner and problem solved. I'll change the oil again to remove the conditioner.

My goal was to break up any sludge, remove carbon flakes and condition the O rings in the sump. Seemed to work