Old Volvo - oil light at startup idle...then goes

[ryan2022]

Hi guys, I picked up the old Volvo 940 non turbo and the oil light stays on at idle. If I give it a quick shot of gas it goes out and stays out.....until I shut the car off and start it again. Hot or cold....the light stays on at idle....and will eventually go out on its own, but usually only after I've hit the gas. ***I changed the oil and filter from a Fram and 5w30 high mileage, to a Mann and 10w30 Dino and it didn't do it for two days.....now after some driving it's doing it again. What are your thoughts? Oil pressure sender? Oil pump crud? Bearings? Either way, this car has so many issues I'm thinking about buying something newer. It's too bloody cold to work on it right now. Thoughts?

 

[Whipcitywrencher]

I'd start with the oil pressure sender...

 

[ryan2022]

Thanks. I have one on order and it's easy to get to. Fingers crossed! To me...it wouldn't make sense that it was the bearings, as it didn't do it for a while after the oil was changed and is intermittent. I figured if it's the engine, it should do it at idle regardless, and not go out and be fine one minutes and not the next.

 

[Johnny2Bad]

Oil pressure sender, Oil pump gear wear, or main bearing wear. An oil passage obstruction would increase oil pressure, so it's not that. All normal for a high mileage engine. Some people would drop the pan and replace the pump and bearings, but as long as your oil light is going out after initially lighting, you can probably just run the thing and it will last probably as long as it was going to last in the first place. Loose main bearing clearance makes for easier winter starts, as you are in southern Ontario that might matter to you.

 

[Sam_Julier]

Oil pressure sender. Sam

 

[Linctex]

I think the sender is working fine. They usually fail "hard" (either 100% or 0%, nothing in between)

Originally Posted By: Johnny2Bad

Oil pump wear, or main bearing wear.

It wouldn't be the first bad oil pump I have ever changed.

 

[ryan2022]

Thanks a ton guys. Fingers crossed. The motor has roughly 120k miles so not terribly high for these. I'm feeling more optimistic though!

 

[Rick in PA]

Oil pressure switches have hysteresis, i.e. they switch off at a slightly higher pressure than they switch on. My car switches off at ~7psi, and switches on at between 2 and 4 psi. I had a discussion about oil pressures recently with my brother, a long time mechanic. He said it's not unusual for oil pressure to drop very low at idle, and it's generally not a problem. In fact one car manufacturer was having a problem with the oil light coming on, the factory fix was to install a pressure switch with a lower setting. I'd say your car is operating in the dead band during idle. Once you get over the "switch off" pressure, the light stays out because it doesn't drop below the "switch on" pressure.

 

[Ethan1]

This is all just WAGs until you get a pressure gauge on it

 

[ecotourist]

Originally Posted By: ryan2022

The motor has roughly 120k miles so not terribly high for these.

120,000 miles is not high at all. I assume it's not making any funny noises? Unless the new oil pressure sending unit "fixes" the problem, I'd get a pressure gauge on it.

 

[OneEyeJack]

Try a mechanical gauge?

 

[Brad_C]

Similar symptoms to popping an o-ring out of the oil delivery tube that runs from the pump to the block. 120k is only just run in for a b230, so it's most likely to be the o-rings, a duff oil pump (very rare on a b230) or a duff oil pressure switch. A gauge will make quick work of the diagnostics. Because of the baffle in the sump, unfortunately you need to drop the sump to check the delivery tube as you can't get a bore scope up there.

 

[ryan2022]

thanks guys for all that responded. Just to follow up, it was the oil pressure switch. i finally got it installed tonight after 2 weeks of -20 and below!! now on to the e brake cable....brake pads.. tie rod... stereo.....locking system....ahh..I think thats it lol Happy New year! Ryan