Low oil pressure light cmes on when hot at low RPM

[GhostFlame]

2002 BMW X5 164K.

I had the oil changed the other day when I had my alternator replaced. Everything was fine for about 5 days then yesterday as I came to a stop the low oil pressure light came on along with a scary warning to shut the engine off!

As I put the car in park the light went off. What I have found is that at rpm higher than idle (700rpm) the light goes off. every time I come to a stop as the rpm drops below 1000 the light starts to flicker.
Today being Sunday I cna't take it anywhere. Is it a bad sensor or what else? BTW the oil level is right up to the max mark on dip stick.

I'm only half way to my goal of 300,000 miles with this engine... If you say its the engine failing then , I'll need another drink!

 

[94astro]

First, did you check the oil level? Next thing I would do is to have an actual pressure gauge hooked up temporarily to see the true pressure & go from there.

 

[Gabe]

I think a bad sending unit would be giving erratic signals, so the oil light would be coming on at random times.

Somebody else on here was having that problem with a 20 wt. in a Dakota. Moving up a grade in oil should 'fix' the problem. Try a thick 40 wt. or 50 wt. M1 and Castrol both make a nice 5w-50.

 

[Astro14]

Classic symptom of hot oil that's a bit too thin for the clearances in the engine.

You "had the oil changed". What did they put in it? Is it low (leading to excess oil temps)?

 

[crazyoildude]

check the oil sender with a real oil pressure gauge or try another oil sender if its low oil pressure it could be the bearings or pump and on a bmw it will get costly.

 

[Errtt]

1st.. have that drink.
You checked the level and it was full.
What oil & grade did they put in?
If okay... get another drink.
Think about the sending unit.. or another drink.

 

[Eddie]

#1. Oil level check. #2 Pressure sender.

 

[JAG]

Maybe sludge/chunks clogging oil pickup screen?

 

[wiswind]

Your signature says that you run Mobil 1 0W-40 in your BMW.
Is that what the shop put in?.....usually, you would have to specifically ask for it.
If this is not the oil that was put in.....I would change the oil to the stuff that you have been running.
It seems odd that it came up right with this oil change......which is why I mention this.

As advised, a diagnostic would be for the oil pressure sending unit to be removed, and a oil pressure gauge connected at that point....and the true oil pressure verified.
A shop can do this for you..(vs you buying a gauge with hose with the correct connector).

 

[901Memphis]

Shop probably put the wrong product in.

 

[SwampSurvivor]

Obviously completely different animals, but on Jeeps, a lot of times shops will knock the oil pressure sensor off when changing the oil filter.

 

[Donald]

Another thing is the filter. I had an Amsoil oil filter in my Camry that caused some oil light problems that were very odd. Verified by mechanical test gauge. Popped in new filter (no oil change) and problem gone.

 

[dparm]

Unless they put something ridiculous in there like 5w20, I doubt it's the wrong oil. M1 0w40 is going to shear over its service light and the car obviously can deal with that.

 

[uart]

Originally Posted By: 901Memphis
Shop probably put the wrong product in.

Yep, given that this started almost straight after the oil change I think you're correct. Probably 5W20 from their bulk tank.

Absolutely classic symptoms of an oil that's too thin at operating temperatures. The situation is usually worst when you come to a stop (idle) immediately after doing some sustained high speed driving. If it is the wrong oil then the situation will likely get worse the longer you leave it in there.

 

[SS1970chrysler]

My sister's car used to do that on 5w-30, so I started subbing one quart of 10w-40 in each oil change and problem never returned. In her case, it was the oil pump being worn. (92 Plymouth Acclaim)

 

[crazyoildude]

5w20 should not make the oil light come on in that engine

 

[bubbatime]

Originally Posted By: 901Memphis
Shop probably put the wrong product in.


My thoughts also. Probably bulk 5w20 or 5w30. I had a car that used to do this at low idle on a hot day. It was never a problem.

 

[demarpaint]

Originally Posted By: Astro14
Classic symptom of hot oil that's a bit too thin for the clearances in the engine.

You "had the oil changed". What did they put in it? Is it low (leading to excess oil temps)?


That's what it sounds like.

OP- You already know the level is correct. First thing I'd do is find out for certain what oil the shop put in the car. If they used the proper oil, I'd verify pressure with a good mechanical oil pressure gauge. Once you have that info report back. W/O that info all we can do is guess.

 

[Shannow]

Out there idea, but I have seen some stupid stuff on relief ports in hydraulic systems, particularly those that aren't supposed to be open in normal operation.

Think oil pump relief, think small bit of junk jamming it partly open...oil can bypass the engine, reducing the pressure of the oil to the galleries/bearings.

Said hydraulic systems (and steam systems) that I've dealt with, getting a consistent, clear lift of the valve can clear it of junk, and make it seat properly.

If it were mine, I'd grab a quart of Lucas and dribble it in with the engine idling...should make the light go out.

Then a week or so of off/on/driving. Off, the bypass piston should be seated. on, it should still be seated, and with the think oil, it will open fully regularly.

Give it some few hundreds of starts (a month or so).

Drain the overly thick oil out of it.

Like I said, if it were mine...

Sometimes hydraulic ports need to be lifted and flushed clean.

 

[tnt31]

I had the same issue on a 2000 Durango. I tired a new oil filter just to make sure not the filter and it did not help. The oil pressure sending unit was relatively cheap and easy to get to so I just replaced it and that fixed the problem. If that had not worked I would have taken it to a shop to get the oil pressure measured with a real gauge.