So lately, my wife's XC90 has been getting the "no oil pressure stop engine" warning.

The first time it happened, I checked the oil to see if it was low, and it definitely was. I topped it off, warning went off for a few weeks.

It came back a week ago, and again I added a couple of liters of oil.

There have been no drips or spots on our garage floor, nor is the exhaust emitting a blue haze of any kind. Yet I've now added 5 liters of oil over the last month or so.

Oil pressure warning came on again today, plus she noticed the needle in the oil pressure gauge isn't moving much. Engine seems to be running fine. It isn't louder than normal, still runs smooth, power/acceleration feels the same.

I've done some reading about the pressure sensor, which makes sense, except it doesn't explain why I've had to add oil.


For context, it's an '06 XC90 with the 2.5T. We've had it for 12 years now, and it has 340,000km on it. Maintenance is up date to date and always done at the dealer.


Thoughts?

 

there's a few things to check out here. If the oil pressure light comes on, it will usually be one of a few things 1) sensor issue 2) wiring/connector issue 3) oil pick up issue 4) worn oil pump/o-rings 5) very low oil level. When you say the oil was low - I'd be suprised if down a liter or two would cause the oil pressure light to come on - unless you were doing some hard cornering. If the light comes on randomly even when full, then I'd probably check to see if there's any debris in the oil (drain into a clean container through filter paper or a paint filter you can find at the hardware store) then check what's in the container. If you see something there then you'd want to drop the oil pan and see if the pick up is clogged. That's also a good time to service the pump. You can also inspect the wiring and connect/ test or replace the sensor.

If you believe the problem is related to oil level, then the discussion moves to where is the oil going? 1) Inspect under the car and remove the splash shield to get a good look. Also pop off the timing belt cover to inspect front cam seals and main seal. These leaks can happen when your PCV system is clogged 2) check the condition of the PCV system. Its possible the oil separator has failed and you are sucking some oil vapors/mist into the intake (which will also mess with the throttle body and MAF) 3) issue with pistons/rings. compression test/bore scope may give some clues here, also check the color of the plugs. 4) issues with the turbo seals. Cars will run fine with a weepy turbo until the cat gets gummed up :-( this may throw CELs for things like O2 sensors, cat efficiency etc. To see if your car is making any smoke, have somebody drive behind you, put the car into a lower gear then accellerate to say 4000 RPM and lift. The engine braking will suck oil past any weak/broken rings and produce a puff (or more) of blue smoke). Also check for any smoke on a cold start up (in case oil is leaking down via the valve seals etc.)

My bet is you either are leaking oil or have a piston ring issue...but you should schedule a service to have this looked into before you run low on oil again and do permanent damage to the engine.

 

It's not your oil pressure sending unit. If the oil pressure warning comes on when you are a few quarts low, in turns with the oil sloshed to one side - it's coming on due to low oil level.

If it's coming on at idle or while driving in a straight line - you may have a clogged oil pickup tube in the oil pan. Sludge or a charcoal like substance forms in the oil pan/pcv system. That partially blocks the oil pickup tube which will create low oil pressure. That low oil pressure will eventually damage the turbo - hence possibly the oil consumption.

I had a few customers with this scenario. Usually they come in with a bad turbo first. Replace the turbo (it's smoking too bad to drive to diagnose any more than a bad turbo) Once a new turbo is on - low oil pressure appears after driving. Then the oil pan is removed - and it's full of a charcoal like sludge material.

If the oil has been changed with regular oil (not synthetic) every 7500 miles/12000 km as Volvo suggests - the oil pan is full of sludge. You won't see a "blue haze" from the exhaust because the catalytic converter is very good at burning extra hydrocarbons. (if it's a slow leak from the turbo seals)

Clean pan, replace oil pickup tube with new style, Inspect and usually replace rod bearings, clean/replace pcv system, replace turbo. Several thousand dollars later and the problem is fixed.

Sorry for your troubles.

 

Thank you both!


As a little more info, it seems to only happen upon first start up. Warning comes on and then turns off after 5 or 10 seconds. It doesn't come back on if the engine has been running and is warm, and has never come on while driving. Engine cools down for a few hours though, and it will come back on upon start up, then shut off after a few seconds.

I checked the oil this evening after I got home from work, and levels are normal. Currently.

It's going in to the dealer on Monday, so will see what they say.

 

The dealer can use their VIDA tool to monitor the oil pressure in real time including start up and during a driving cycle. Just make sure you report that it happens during a cold start. BTW, who did the last oil change ? Is it possible the wrong oil weight or an overly restrictive after-market filter was used?

 

We do our servicing at the dealer. With the discounts they give for older models, they're actually a better price than the independent shops, with amazing customer service.

I suppose it's possible they used the wrong oil and/or filter, but I doubt it.

We have it booked in at the end of the month, when it's convenient to leave it with them for a day or two.

 

my gut says that with your mileage (340Km/210K miles) your oil pump may need to be serviced - mention the light to the dealer and see what they say. They should be able to monitor the oil pressure in real time from a cold start and through a driving cycle.

 

Unfortunately - the only oil pressure sending unit on a 06 B5452t engine is the simple switch that becomes an open circuit when oil pressure is above ~7psi, and no longer provides a ground for the light bulb. (yes, it's more complicated than that now with the CANBUS cars and warning messages in addition to a warning light.) But it's still just a on or off pressure switch.

The only way to monitor oil pressure is to connect a mechanical gauge. (which is not something I would do or recommend)

 

good point. I had this experience on a 2012 so I guess that's the benefit of owning a newer model. I'd be curious to see that the dealer recommends doing at the next servicing to investigate the oil light concern.