Oil pressure warning light coming on and off, 1996 850

eleaf · Post by **eleaf** » 02 May 2018, 14:47

Hey guys,

Just yesterday I drove about 3 miles and then the low oil pressure light came on. Turned car off and checked oil level - OK, in the middle. Started car a few hours later and on the next start the light was off at first, got another couple of miles and the light went back on, and then turned off about 15 seconds later. Then it came back on (maybe 30 seconds in-between) right before I shut her off at home. This is a 1996 Volvo 850 GLT manual, 240k miles. Wondering if you guys have any suggestions what would you do? It's about a 100 mile trip to the closest reliable indie volvo mechanic.

I'm thinking one of the following:
Oil pressure switch needs replacing
O-rings in oil pan
Sludge getting caught in pickup screen.

Oil was changed about 2500 miles/4 months ago with 10w-30 full synthetic with Mann filter.
PCV system was serviced ~3 years ago alongside rear main seal.

Would idling 10-15 minutes with seafoam in the crankcase followed by an oil change be a good idea?
I'm considering ordering a 'cheap' mechanical oil pressure checker from amazon to see if it is just the switch or actually intermittent low oil pressure - not sure how I'd check it if it only comes on after driving for a bit.
I looked at the howto for removing the oil pan for cleaning/o ring replacement but I'm not sure I'm comfortable having to jack up the engine part way, not very flat ground here...

Appreciate your guidance...

Post by **abscate** » 03 May 2018, 07:09

I'm considering ordering a 'cheap' mechanical oil pressure checker from amazon to see if it is just the switch or actually intermittent low oil pressure - not sure how I'd check it if it only comes on after driving for a bit.

Thats the best you can do without getting it to an indie. Get a decent one because engine replacement is going to be a good thing to avoid.

Tape an iPhone into the engine compartment and shoot a movie of your oil pressure readings on a short trip.

eleaf · Post by **eleaf** » 03 May 2018, 19:56

ordered the oil pressure guage, should be here next week and i'll try it out

Post by **erikv11** » 03 May 2018, 22:42

Maybe you already did but, definitely check the connector on the oil pressure sensor, and the wires that lead to it.

Probably no junkyard parts sources around you to grab and try another pressure sender? Although I guess I've never heard of one going bad. Have definitely seen them come unplugged for no reason.

sventastic · Post by **sventastic** » 04 May 2018, 00:05

At 240k the oil pans could quite possibly be on their way out. Replacing them isn't terribly difficult if you have some wrenching experience, and there is no need to jack up the engine part way. If you use a ratchet strap to move the power steering lines out of the way that part is a breeze. It's mostly just annoying to be on your back under the car wiggling around to get anything done.

eleaf · Post by **eleaf** » 09 May 2018, 12:52

Okay, couple interesting things. I attempted to get the oil pressure sensor off to put the pressure gauge tester on but I had a really hard time getting the socket wrench down there. Any tips for that? I'm thinking it needs a u-joint + extension bar...? The bolt seems to be 24mm with almost zero clearance to rotate anything using a deep socket.

I could barely begin to rotate the wrench when I managed to make some sparks fly between the sensor and towards the left, and decided to hold off on that for a moment. I fiddled with the pressure sensor wire and made sure it was on tight. The only weird thing I noticed is a wiring harness that passes over the top of the pressure sensor switch - it looks like the plastic covering had flaked off and the wires were touching the top of the sensor switch. I thought maybe one of the wires was grounding out (though it seemed like there is plastic insulation around each individual wire) so I wrapped some electrical tape around the wire strand collection where it touches the top of the oil sensor. The oil light was still coming on at times and staying off at times.

The next thing I did was check the oil cap and it looked like the o-ring (replaced 2 yrs ago) was slightly raised on one side, so I pushed the o-ring all the way down into the cap on that half that was slightly raised and wiped off the oil on the o ring. Looks like oil was getting up to the top of the crankcase ok. I would think whenever the oil cap is screwed down the o-ring would seat into the cap on its own? Anyways, started it up and let it idle until it was warmed up and the light didn't come on... Haven't test driven far yet. Could it really be something as simple as the o ring on oil cap not seating properly?... Any tips to access and unscrew the pressure switch easier to be sure? Access from below the car didn't seem easier as I couldn't even fit my hand up to the engine block from that direction.

sventastic · Post by **sventastic** » 13 May 2018, 09:23

Everything is conjecture until you find out what actual oil pressures you're achieving. Could a loose oil filler cap cause low oil pressure? Possibly, but that seal should seat reasonably well unless it was completely messed up. I would replace it though, they're $1. I wish I could help about access to the pressure switch but that's not something I've dealt with. However, I think that still needs to be your next step so you can evaluate oil pressures. If you posted some photos, I'm sure some suggestions could be made on how to access it

Post by **abscate** » 13 May 2018, 12:09

The oil cap will not influence gallery oil pressure, no.

sventastic · Post by **sventastic** » 14 May 2018, 21:22

abscate wrote: ↑13 May 2018, 12:09 The oil cap will not influence gallery oil pressure, no.

True, I wasn't thinking about that quite right.

eleaf · Post by **eleaf** » 23 May 2018, 21:01

Update:
Took for a test drive, no oil pressure light first 6 miles or so, then it came on for the last half mile stretch and shut off again right before I returned to the driveway. Did notice a tiny line of oil dripping out of oil cap side.

Did a PCV system test by placing a nitrile glove over the oil filler cap opening and the glove filled with air.. Not suctioning the glove into the crankcase but instead inflated it out. Looked like plenty of oil sputtering around in crankcase. Also could see a little air/steam was coming out of the oil filler dipstick when removed with hot engine.

The pcv system was replaced about 30k miles or 3 years ago alongside rear main seal.
Possible it got clogged up again - most likely culprit? Replace flame trap?
I imagine a clogged pcv system could be the culprit for intermittent low oil pressure? Wouldn't it cause higher pressure instead?

Thanks for all the suggestions!