oil light on when idle

[m3f_NSX7]

98 M3 with 168,000 kms (105,000 miles)



recently bought the car - did not have maintenance history with it - recently replace the oil and used 5W/40 synthetic liquimoly oil



oil light comes on when idle after long drives (engine hot) and the light goes away when I tough the gas.



The car came with aftermarket gauges. When cold, the oil pressure reads 10psi - as the car gets hot, it goes down almost a half point which could mean 5 psi or less - and when accelerating, it is @ 55 psi whether hot or cold



I had done some reading into this - and there are too many theories out there



Has anyone had this issue and it went away by simply replacing the oil pressure switch? or is it too simple to be true?

[m3f_mfanatic325]

My car does the same thing. I'm new to E36 M3s, but from the research I've done, this is a common issue. Has to do with some oil accumulator at the bottom of the oil pan. Some people swap it out and still sometimes have the issue =/

[m3f_Pierre i am]

Most likely oil pick up tube

[m3f_Olemiss540]

Most likely oil pick up tube

Or stuck oil squirter in the cylinder walls....



Common problem, worth dropping the pan to investigate and then driving it till it dies due to the low cost of replacement motors....

[m3f_vmbray]

I don't know if the oil light was on at idle since I bought the sedan broken, but one squirter was not just stuck but the spring was actually broken and the ball just banging around, and three of them were very slack in spring pressure so probably opening too early.

[m3f_MaynardZed]

My race shop guy that knows these BMW motors very well says its fine as long as it goes away when you touch the gas. We've dropped the pan a couple of times on my track car to put baffles in, weld oil pump nut, etc. and there is nothing wrong down there. My car does it after a heavy track session.

[m3f_pbonsalb]

The owners manual says the light may come on when hot at idle and this is ok as long as it does not stay on. Certainly pick up tube is a known failure point should you wish to investigate. Id lean towards taking a look, particularly if this has not happened before. The motors are all 17-21 years old now.

[m3f_Evtron]

This is a tricky problem that's difficult to diagnose, as there are a ton of parts within the system that can cause this. Oil pump, pick up tube, rod bearings, pressure sender just to name a few. This is the first I've heard of squirters being the cause, and will definitely check these out when I drop the pan (thanks Olemiss540!). I recently read that a bfc member resolved this issue by replacing the oil filter housing, apparently there's a pressure relief valve in there that can cause the issue (thread here).


You should definitely replace the pressure sender first and foremost. It's cheap and easy to do.


If that doesn't work, then it's time to crack open the oil pan and take a look. Do your research and know what to look for when you're down there. I'll be doing this in the near future and will be sure to document my quest in my journal.

[m3f_marvinstockman]

Did you have the problem before the oil change?

[m3f_NSX7]

Did you have the problem before the oil change?

Yes I did - when I bought the car in February, I didn't drive it due to Winter/snow - previous owner told me the oil was new. Then I started driving the car in April with no problems.



This month when the weather got hot, and after a spirited drive, that's when I saw the oil light, with no oil loss, and decided to do the oil change using the 5w-40



My gut feel tells me that the previous owner sold the car during winter because he knew this problem would come up during hot weather, but I could be wrong.

[m3f_NSX7]

My mechanic who is also a friend worked for Nissan for 7-8 years - so he is not familiar with BMW's unique issues - ie vanos, subframes, etc...



We will change the oil pressure switch first as he found out yesterday that it is an aftermarket switch connected to the aftermarket gauges