I've got a 04 Mini Cooper S, 165k miles. Once the engine is warmed up, at idle, the oil pressure light will come on sometimes. I know that the oil pressure switch only comes on when the oil pressure drops below 3 PSI. Oil level is slightly high. Oil is fresh-oil colored. The engine sounds normal, no strange valvetrain sounds with the hood open @ idle. I recently changed the oil, and the problem seems like it away for a few days, but then it came back. Oil light only come on near idle, and only when the engine is warm.
I tried replacing the Oil pressure sensor, but I'm still getting the light. No sign of filter collapse. My car doesn't have the cage on the oil filter housing. I got the correct filter cartridge with the plastic cage inside the oil filter. No Oil leaks. Yes, I removed the old oil filter cover gasket and replaced it when I replaced the oil filter.
I know that the two springs at the bottom of the oil filter housing are critical. The large spring is present and stiff. The bypass spring/valve is present as well, and I can depress it with light force. Looks just like the pictures of how it's supposed to look.
So... What's the next most likely part on the list? I'm going to have to replace the oil pan because the shop I took it to a while ago to get an oil change over-tightened the drain bolt (I swear the used an impact wrench!) and I'm unable to get it off. I used a through-the dipstick siphon to do my last oil change. So I'll get a view of the bottom of my engine soon.
Recent repairs include replacing the harmonic balancer (it was wearing out), oil filter + oil change, Oil filter housing gasket (it was leaking, because it was dried out), oil heat exchanger gaskets (since I had the oil filter housing off, and those gaskets were dried out as well), front seal, crankshaft sensor o-ring, lower engine mount, rear-upper engine mount, AC compressor, belt, air filter.
And yes, I know to use the car as little as possible because I'm tearing up my engine by driving without proper oil pressure, etc, etc.

 

Where are you in the line of owners? Have you thought about doing an oil sludge cleaning?

And, there are some failures to the oil pumps.

 

I'm the second owner.

How/where do I clean the sludge out of?

Yeah, i'm afraid it's the oil pump as well. What checklist of things should I do with my timing chain cover off?

 

They sell bottles of motor flush at autoparts store. Basically you put it in, run the motor for 5 minutes, shut off, drain and change oil/filter. I think if you read about motor flushes they have transmission fluid in them that serves as the agent to dilute the sludge and get it to drain down.

If you took your valve cover off and you have anything other than a nice coffee type stain, you could have a sludge build up.

 

With the higher mileage I'd check the pump itself as the two seals on it could just be leaking off pressure. Also a good time to do a timing chain as we find them stretched all the time over 150k. Or if the chain has slapped the pump it can crack it leaking pressure too.

 

Not to say that this isn't the case here, but failure of the R53 oil pump is almost never heard of...
Out of curiosity, what viscosity oil are you using?

When you get that oil pan off you'll get a good look at whether there's sludge on the internals.

As to timing cover related maintenance, here's a list:

Part # 11141485162 / Timing Cover Profile Gasket
Part # 11111485171 / Crankshaft Seal
Part # 11411485173 / Timing Case Cover (internal) Seal - Upper
Part # 11411485172 / Timing Case Cover (internal) Seal - Lower

 

I'm using mobile 1 synth 5w-30. I haven't seen any sludge when I replaced the oil filter housing gasket, but I wouldn't rule it out either. I'll take off my oil cap and try to get a good view under my timing cover and see what it looks like.

My oil filter housing and heat exchanger gaskets had both dried out, along with my crankshaft seal, which is why they got replaced. Could my problem just be the internal seals inside the timing cover? I don't have a good understanding of how the oil pump works. I'll probably understand it better once I see it pulled out.

Good call on the timing chain, I'll have the the job half done already, so I'll do that at the same time. Yes, I had timing chain slap for a while, and recently replaced the tensioner. I was planning on checking the timing chain guides, but I might as well replace the timing chain while I'm at it.

 

As a follow up to this... WMW was correct. It was the seals between the oil pump on the timing chain cover and the block. They were so flat at first I didn't realize they were gaskets. I then poked them a bit and realized they were. Replaced and the oil leak stopped.

I didn't replace the timing chain, I didn't have the right tools for it.

As a second note, the Bentley manual is incorrect on the torque between the oil pump and the timing chain cover. The specced value is way too high, and it lists the wrong thread size. It's probably for a different bolt.

 

Having a vendor that also has a complete shop is icing on the cake.

Thanks for letting us know what was causing the issue.