Increasing oil pressure

Working on a Volvo V70 wagon. When its hot the oil light flickers and a message comes up saying to immediately turn off the engine. Hooked up an actual gauge and engine has 40lbs cold at idle and 15lbs when it gets hot. I let it run for awhile and it never drops below 15lbs. Car runs great, has no strange noises and it doesn't smoke.

I pulled the pan and there are no blockages in oil pick up tube. While I was in there I replaced the O ring at the top of the tube per a TSB for that vehicle. Tried a new sender and I still get the light after the car warms up so apparently 15lbs is below the threshold for the light.

So the question for the hive is how do I raise the oil pressure 5 pounds or so to prevent the light from returning. Thicker oil, thinner oil, lucas what works what doesn't?

The car runs so well I would hate to replace / rebuild the engine if it can be avoided.

New relief spring/pump. Or go up on the bigger viscosity number a step.

Ranger50 wrote: New relief spring/pump. Or go up on the bigger viscosity number a step.

I was going to say this at first, but wouldn't a bad spring affect cold pressure too?

Could be a worn pump I guess.

What about the light? Could there be extra resistance/short in the signal wire that effectively means the light comes on too soon?

I agree that some Lucas stabilizer is probably the easy fix.

Worn spring would affect cold pressure too. But probably not as much. And 40 psi at cold idle sounds low to me. Most engines I've seen make at least pump relief psi, if not more, at cold idle when first started.

rslifkin wrote: Worn spring would affect cold pressure too. But probably not as much. And 40 psi at cold idle sounds low to me. Most engines I've seen make at least pump relief psi, if not more, at cold idle when first started.

I agree with the above. My race car which has a gage reads near 80 psi when cold but drops quickly as the oil starts to warm up. If you can drop the oil pan do that and check the rod bearings for wear. That is where most wear occurs as opposed to the main bearings. I had a Chevy BB that had the same issues. I replaced the rod bearings that showed some wear and added a Hi Volume oil pump, not high pressure, and the gage would jump up to 75 psi on start up and kept the pressure at 40 psi at everything but idle. And this on a 120K mile motor that was worked hard it's whole life.

15 psi at what rpm ? at idle that would be normal.

Face it guys, low oil pressure is the result of wear of the crankshaft bearings first, a worn pump or broken relief valve spring possibly.

Cheap fix would be run rotella or something equally heavy

I'd just run heavier oil and call it a day. Be glad the oil pressure sender has that high a threshold; on BMWs the idiot light only trips when pressure drops to ~7psi.

The oil pressure switch is going bad. It shouldn't be turning on at 15psi. IIRC the spec is 6psi.

That said, my S40, which has the same family engine (maybe even same oil pump) has a note in the owner's manual that says the oil light may come on at idle after extended heavy operation, and to just hold the idle speed up a little until the engine cools off some. So as far as Volvo is concerned, this is acceptable and within engine design tolerances, so you probably have nothing wrong anyway. Replace the switch and don't worry about finding problems that aren't there.

I only ever noted this behavior when I entered a rallycross at a hilly site on damp soil so runs were basically a 60+ second dyno pull. The PO noted the oil light coming on in city traffic, which makes me wonder about his driving habits.

I never had a gage on my 850 with the I5... but not all cars run the same pressure. My Fiat 124s always ran notoriously low pressure, even from the factory.. like 40psi stone cold and less than 10 at idle when hot. This was normal for them.. and the reason they deleted the oil pressure gage in 1979.

I would think that newer cars might run lower pressures due to efficiency.. it takes power to pump that much oil

Run 5w40 in it.

I just did an oil pressure test before and after an oil change on a 183000 mile dodge 3.8 engine.

It made 28psi at hot idle on old oil. I put new 20w50 in it and it had 38psi at hot idle. So 10psi bump from an oil change. Also yes, a near-200k mile dodge 3.3/3.8 makes close to 40psi of hot idle oil pressure. They're amazing.

But i also think that 15psi at idle is completely fine. You can try to fix it but you could be opening a can of worms as far as effort vs return. I recently put rod and main bearings in one of my old dodge 4cyls and at hot idle after running a while it had 12psi (which im ok with). So if opening up your engine and swapping all that and not getting a great result would just piss you off, then don't do anything (except maybe an oil change with thicker oil or a new sender) and learn to love the 15psi you got.

mad_machine wrote: My Fiat 124s always ran notoriously low pressure, even from the factory.. like 40psi stone cold and less than 10 at idle when hot. This was normal for them.. and the reason they deleted the oil pressure gage in 1979.

My oldest brother made a good living for a few years doing head gaskets on Fiat in winter and spring people would park them outside on a cold New England night and fire them up and head to work the oil pump relief hole was to small to flow enough oil when it was thick and cold the result was 80-120 psi going to the head and POP goes the gasket.

Vigo - Some engines are just known for high idle oil pressure. Jeep 4.0s making 35-40 psi at hot idle on 5w-40 with high mileage isn't abnormal. On the other hand, my small block Mopar has idled around 15 psi hot on 5w-40 for as long as I've had a gauge on it. And if you work it hard and get it good and hot, 10-12 isn't uncommon to see.

lucas is the easy bandaid and for some reason people love the stuff. my turbo sundance would turn the idiot light on at hot idle with 10w30 in it, added lucas and no more issues.

Don't worry about idle rpm pressure. See what it is a road speed rpm. anything over 30 is good.

I'd just like this on the record, Lucas is pretty awful stuff, just a thick mineral oil without much of anything else in it. Go crank that display at the parts store as fast as you can, the Lucas side will foam up. If you insist on using an oil thickener rather than buying thicker oil, STP at least has some (but not much) zinc in it and won't thin out the oil additive package as much. The Lucas trans/power steering additive is pretty good to keep something limping along though.