I've recently been getting low oil pressure lights at idle toward the end of my trip. In my past experiences, this is usually due to being low on oil. The oil is running fairly low (bottom of dipstick) so I added a quart before driving about 50 miles. No problems until the end of my trip when it started happening again.

Before I added a quart, I tried to look around and see if I could find any source of a leak. I didn't see anything dripping down onto the ground. VCG is brand new - no trace of oil around there. Replaced the head about 5k ago, so it's crossed my mind that something went awry with that? I looked into the coolant reservoir and everything looked kosher in there - leads me to think the oil cooler isn't a problem. I didn't see any drips around the oil filter housing, granted didn't have the best angle.

My thought is it's most likely the crank seal - but I couldn't verify since there's no line of sight without taking the wheel liner out. I haven't checked oil level again quite yet as I just got home about 15 minutes ago - I'll run out and check it in about an hour and see just how much I've lost.

Has anybody else ever dealt with this? Would crank seal leak that much without leaving a trace? Any other possible leaks that wouldn't leave a trace?

 

Could you be burning it? How many miles on the rings?

 

Always a possibility, but would rings fail all of a sudden like that? Didn't have any consumption issues once I did the head. I guess I should pick up a compression tester this week.

 

If indeed low oil level causes the low pressure warning light to come on, you have a major problem. Just seconds of low oil pressure when the engine is taxed will do immense damage. Thankfully in my judgement your's is most likely due to a semi-defective oil pressure switch. The next and more dire possibility is the drain back valve is crooked or failed. Others had destroyed their engine because of it.

You allude to you have oil consumption problem but gave nothing quantitative.

 

Walk me through this... Why do you say major problem?

By drain valve you are referring to the ccv system, or whatever the mini equivalent is?

What quant data do you need? I'm about to go check the oil level right now - will update with results. Unfortunately I haven't been tracking it - I'm a bad owner I know - so I don't have any historical data to work from...

edit: Apparently oil doesn't even read on dipstick right now. Put in the last 1/2 quart I had. Will pick up more oil tomorrow and start tracking.

 

My limited experience and with other brands of cars is a leaking crank seal leaves a trace even if just a drop or two make it past the seal. For a quart to leak out in 50 miles the underside of the car from the seal on back would be oiled.

No smoke from the exhaust under acceleration from idle, not smoke under hard accelleration after a prolonged closed throttle coast down?

Chances are the oil then is not getting past the rings or past the valve stem seals and guides.

A plug check should confirm this as likely just one cylinder would be bad not all of them and the one that is bad is burning all the oil.

If a cylinder is not bad then my guess is the oil is being passed through an air/oil separator possibly aided/abetted by a malfunctioning PCV, if the engine is so equipped.

A check of the intake manifold for signs of oil wetness can help confirm this diagnosis.

If the engine is turbo-charged another leak can be past the turbo oil seals. A compressor wheel with oil on it and an oil wet intake from the turbo to the engine is a good sign bad things are happening in this area.

 

As far as exhaust goes - I'm not a good judge of that. Couldn't diagnose the head gasket from the exhaust... Especially difficult in colder weather. I'll definitely pull plugs tonight, though. Didn't even think about them getting fouled.

PCV is another culprit. I'll run it with the oil cap off and see if there's positive pressure, as well.

Any other bits of advice guys? Will update all answers tonight.

 

Wouldn't advise you to run with the oil cap off.

Running with the oil cap off is likely to cause the engine to run lean. The engine controller will adapt but still...

And unfiltered air can get pulled into the open oil fiilter cap. I had the oil filler cap off my 2018 JCW the other day to add oil and there's a nice shiny cam lobe directly under the cap. No way I'd run with the oil cap off.

If you supspect the PCV just replace it. These are (well, used to be) pretty inexpensive and the SOP was just toss the old suspected bad one a replace it with a new one.

A "trick" I used to check for exhaust smoke is to drive with low sun at my back to look for visible exhaust under various engine operating conditions. Water vapor will dissipate in no time while any oil smoke will linger. Never spotted any oil smoke from any of my cars. An overactive imagination was all I had going on.

An engine sick enough to smoke is rare. I see one occasionally. Well not the same one but if one drives in traffic a lot like I do one sees a lot of vehicles and once in a while he'll spot a car with oil smoke coming from the exhaust outlet. For instance, taking off from a stop light will leave a visible cloud of oll smoke behind. It may not be a billowing cloud but if one bothered to check the rear view mirror he'd almost certainly see it.

 

My head was cracked in 3 spots before I replaced it and I didn't notice any heavy smoke - not like my celica had in HS.

Don't idle with oil cap off? I thought SOP was to do the "latex glove test" for positive pressure?

 

I wasn't sure what PNW was referring to with the drain back valve until I read Sarom's thread. I don't think I have my socket for the oil filter cap at my apartment... I'll have to see what I can do to open that up and have a look in there.

 

You should also school yourself on the purpose of the oil pressure switch, which function is not to indicate you are a bit low on oil, but rather immanent catastrophic engine failure. The oil pump pick up at at the bottom of the wet sump and if the switch is not defective, the pump is sucking air, and/or you have excessive loss of oil pressure.

For your engine's sake, let's hope it is a defective oil pressure switch. As to the drain back valve that is another story...

 

I'm aware that low oil pressure is a bad thing and potentially catastrophic. If it's only at idle, though, my experience has shown that it's typically just very low oil - likely below pickup so pump is sucking air - verified that I have very low oil as well. I will pull the pressure switch to see if there's anything funky going on there, though.

Just been my experience, something has to go very wrong for true oil pressure loss issues. I believe that this is due to sucking air at idle which stems from low oil rather than a pump issue or some other catastrophic internal failure. However, I'm typically wrong more than I'm right so... I'll be troubleshooting every possible item.

 

Hopefully I picked the right pictures.... The plugs all looked fine.









I realized how few tools I actually have at my apartment, though... Gonna be hard to get the PCV off without a wrench over 5/8" and no monkey wrench. Off to home depot I go for oil and a wrench! Too dark and wet to see anything behind the motor by the filter housing. Will update on pcv later tonight though.

 

Plugs look good.

We just went though the low oil pressure light drama about 2 months ago on my kid's car.

Checked all the things mentioned and we did not have oil consumption issues since I make my kid check the R53's oil religiously.

My son mentioned the light kept turning on in the afternoon on his way home. Once it started turning on more frequently, I checked everything again.

Ended up replacing the oil pressure switch since it had been leaking for a while. Once replaced, no more idiot light and less oil mess to deal with.

If you're headed to Home Depot and you're thinking hey, I think I might replace that , grab a deep 27mm socket while you are there.

 

Sorry for delay - Finally got around to pulling the PCV and it seems to be functioning correctly. It rattles when shaken lightly so the flap is moving and the one-way valve functions with blowing through both sides (meaning I can blow one way and not the other).

I guess next is to pull the switch that everyone keeps talking about. It looks like I can reach it from the top if I remove that heat shield? Sound right? If that checks out alright (I'm assuming it will but hey, I hope it's only a $20 part!) I need to pick up a 36mm socket and pull off the filter cap.

As far as drain valve - I've never heard of this being a problem before so I'm in unknown territory. Would this cause oil pressure issues immediately? I don't see how this could be faulty as I haven't recently done any work there. I did an oil change about 5k miles ago and didn't notice anything wrong - only got oil pressure issues in the last few miles.

Assuming that checks out alright - where would I look next?

 

Yep, you can reach it from the top. Bend the flexy heatshield up and unbolt and slide the fixed heat shield out of the way.

If you are removing the cap from the oil filter housing. Just make sure you tighten it back up before you restart the motor. I don't think it was necessary though if you're curious to see the drain back valve, now would be the time.

5K miles on the oil, good time to change that too!

Also, after I purchased the oil pressure switch on Amazon, I found the same switch on rockauto for a whopping $9 (plus shipping). Go figure.

Good luck with the repair.

 

I am probably just really daft - but the punctuation is throwing me for a loop right now. Can you clarify this for me?

Also, thanks for link to oil pressure switch and confirmation on reaching it from the top

At $13 and I'm pulling the switch anyway, I'll just swap a new one in. Just ordered. Will be here Tuesday. Not too bad. Since I don't have a 36mm socket, or drain pan, I may just go get my oil done at the shop down the street and have them look at the drain valve while they're in there.

 

If you were planning to take the oil filter cap off to check the drain back valve while you're in there replacing your oil pressure switch, just remember to tighten up the oil filter cap before you start up the car or else you'll get oil squirting everywhere.

When we did the switch replacement, we did take the cap off to inspect the drain back valve and also gain a bit more space to work the socket wrench on the oil pressure switch. Almost forgot to tighten the cap before my kid started up the car!

Post #21 in this thread: Oil pressure relief valve

 

New to MINI, but not cars and engines. Sounds like the switch but since you are going to pull out the tools and if access permits tee in a oil pressure gauge and mount it in the engine compartment so you can verify what is going on.

Run you finger up the tail pipe after it cools to check for oil. Park the car on clean cardboard to look for leaks.

I have a 76 TR6 which I drive to car shows all the time (normally a few hundred miles)with 70K on the original motor. English roadsters are known for their oil leaks, and she has a few, built in rust prevention system, and I very seldom add oil between oil changes. Change oil once a year whether driven or not.

Good luck and post what you find out.

 

Maybe I can plumb in a mechanical gauge this summer. Not doing it in Feb, even if the weather is warm. It's wet and disgusting in Chicago still with no place to really work on it other than the street.

 

Pulled the switch because it's 50 degree and sunny at the end of February for some reason. It was definitely leaking. Huge thanks to PNW for the early diagnosis. My new switch gets here Monday so I'll reinstall then and keep an eye on both level and pressure.

It's surprisingly difficult to get a good picture of oil, but you can see below that there's oil all over the outside, couldn't get a picture that showed it on the inside - you'll just have to believe me

 

Glad you found the culprit. I know about Chicago winters, spent a few months at Great Lakes at A School in the middle of the winter back in my Navy days.

Jim

 

I hope this is all it is. It was definitely oily down there even when I just unplugged the connector. I had no idea it was so readily reachable. I guess I'll need to figure out how to mount some gauges this summer... I am not too keen on extra gauges floating around but... hey... way better than an idiot light!

Thanks, everyone. Truly appreciate your input/suggestions/help.

 

Does anyone know where the oil pressure switch connector routes from? It's probably 90% because it's dark outside, but it seems to have "fallen" away and I can't see it. The easy solution would be to put it on a jack and go from under, but that's not doable at the moment. So I'll just need to feel around for it and find it. Any advice on where to start looking?

 

If you remove the exhaust top heat shield, which you should to replace the switch you can see it there. See my post here with big photos.

I am pretty sure it share the same branch with power steering pump and fan so likely it got pulled down into the underworld like Don Giovanni abyss if you are not careful.

note that I have a t-adapter so protrudes out farther