Piston cooling valve V70 2.4T 2001 (No oil pressure)

[draser]

Did they say what the pressure reading was?

[alanjackson2011]

They just said the pressure drops to nothing.

I have replaced all the O-rings in the sump and it made no difference at all, they were brittle.

There was a lot of sludge and the square drain from the top end was completely blocked.

The sump is now spotless and I filled with fully synthetic 5W30.

It is still as bad as ever - seems much worse if I drive it two miles. It will tick over for nearly an hour before the warning is displayed..

Could it be anything to do with the turbo? There are no noises from it, but if I accelerate hard that seems to make the warning appear.

Engine sound nice and quiet

Any suggestions would be greatly appreciated – I am now desperate !!

[alanjackson2011]

One more point, it seems many people have the light on only at tick-over and it goes out when reved.

Mine stays on until I turn the engine off and wont disapear when I rev the engine.

[jimmy57]

If it not going out when revved that is usually major problem. The only simple problem would be the oil relief valve hung open since that could dump enough oil volume to keep it from making pressure when revved.

I have seen bad oil pressure switches. Has the oil pressure on your engine been measured with a gauged fitted where oil pressure switch is removed from?

Does the engine have any noises like there is no pressure?
You should have the grate down in oil filler opening that stops you from seeing oil moving but after it is run is there evidence of oil splashed up on the grate?
You could stick a screwdrive down in slots of that grate and pry one open enough to see oil with a flashlight while engine is running.
I don't know how long you've been running it with light coming on and staying on but no oil flow would make engine do seriosu damage quickly if there truly less than the .5 Bar that puts light off.

[alanjackson2011]

Thanks for the reply.

Can you tell me where the oil relief valve is? I shall check that as you advise. And see what is visible theough the filler.

I have also seen reference to a "piston oil valve" causing oil pressure problems.

My Volvo dealer canfirmed that the pressure drops tyo zero after a few miles, but the engine sounds realy sweet. I always turn it off as soon as the message is displayed.

The sump was badly "slugged up" and the square drain that returns oil to the sump was totally blocked; I cleaned the part in the sump and the one going upwards as best I could.

Is it possible the oil is not returning fast enough to the sump and is below the pickup?

[J5T]

The oil relief valve is in the oil pump. I have seen where the relief piston has been made out of plastic and destroyed by the retaining ring to cause zero oil pressure. Replacing the oil pump relief valve fixes this problem. However, I have not heard of Volvo using anything other than metal pistons for the relief valves since the late 90s in the white blocks. The oil pump is behind the crank pulley and would have to be taken apart to check the relief valve. If the valve is stuck open or busted, there would not be any oil pressure at any time. I have had this happen on an 850 and 960 white block Volvos.

[alanjackson2011]

Many thanks for your reply.

The engine sounds fine, no clatter or rattles, but I always turn off as soon as the message appears.

I do not want to run the engine with no oil p[ressure to look into the filler cap.

It will idle for an hour with no problems, but as soon as I drive it and accerate hard I get the message.

The oil pressure was checked by the Volvo dealer, and the code reader sometimes gives a valve timing error, which I have been told is caused by low oil pressure to the valve timing control unit.

Is there a diagram of the oil circulation path do you know?

[jimmy57]

oil pump discharges into an area of pump with relief valve. Relief valve dumps any excess back into the inlet side of pump.
Oil flow exits pump and goes into filter housing. Filter housing has an air dump valve that oil flow closes, it is a small plug with a hole drill through and a trapped teardrop shaped metal piece that seals opening when air escapes and oil pushes it closed. This is too small to lose your oil volume enough to have light on when revved.
Oil passes thru filter and then goes through the tube to oil cooler, passes thru cooler and comes back to front of block to go up from sump into intermediate section (bedplate) where it has a trough the length of the block. The mains are fed by holes drilled from bearing openings into this trough. The oil pressure switch is screwed into this trough.
Oil goes up in to block to go to top to go through head gasket to cylinder head.
In that passage is a hole drilled from back of block to feed the piston jets and turbo. The hole has a cross-drilled bolt and has the turbo oil line. The passage has the oil cooler relief valve screwed through it into a length of block drilled passage into which each piston spray jet in mounts for their oil supply. The relief valve only opens when oil pressure reaches 1.5 Bar and closes a bit below 1.5 Bar as oil pressure falls.
The cylinder head has troughs in the edges with intersecting holes to cam journals and to tappet bores. The CVVT solenoids have hole drilled to intersect the troughs.

[alanjackson2011]

Thank you very much for your knowledgeable reply.

I can now think about where I could possibly be loosing oil pressure.

It is not my O-rings, so it doesn’t leave much.

A previous owner had a rear seal replaced and the joint between the intermediate section and block was sealed with black silicon when it was re-assembled.

The Volvo dealer pointed this out, but didn’t seem to know if it could cause low oil pressure.

I guess to do anything about that is a head off job.

It looks like the car is scrap unless someone has any other suggestions. Any help would be very much appreciated.

[alanjackson2011]

I have had another suggestion from another forum that the oil cooler may be becoming blocked when the oil is pumping and "backwashing" when the enine is turned off and the sludge being released from the fins in the cooler until it is pumped back into the cooler blocking it again next time the engine is started.

There was a lot of sludge in the sump AND a garage had tried a "seal repair addative" to try and repair a leaking rear crank seal. The seal was eventualy replaced, but I guess the sealing crud could have got somewhere nasty.

This does seem to be possible because if I only turn the engine off for a few minutes the pressure returns - but only for one or two minutes. An easy thing to check, so I am about to take it off