Low oil pressure problem

[Michael9218]

Today while at Barber Motorsports running in a test and tune format, I started to have problems with oil pressure. All seemed to be fine until the last run of the day when I noticed my low pressure light (20 psi) come on in turns where I normally don't see this on this track. I then saw that my pressure was lower than normal. The pressure wasn't gone, but was slow to build to the normal 60 psi and quick to drop when off throttle. I eased back into the paddock. I didn't lose all pressure at any point (didn't drop below 20psi at idle) and heard no noises as I nursed the car back to the paddock.

I initially thought that I was low on oil, or possibly had blockage on the oil "Y" manifold that I use to tap for my oil pressure sender and oil pressure gauge (hoping that I didn't really have an oil pressure problem, but just a sender issue). I checked my oil level and it was full. I even added more oil. I removed the "Y" manifold and all was well. I restarted the car and the low oil pressure was still there. I could also hear more noise than normal from the valve train. So clearly, I'm not getting proper oil pressure. When I say low, it still has 20 psi at idle, but is slow to build pressure as the rpm's increase. Needless to say, I'm done for the weekend.

The car has an S50 with the stock oil filter housing. I replaced the pump a couple years ago with the VAC enhanced pump and baffled the pan. Until now, I've always had solid oil pressure.

Has anyone run into this before?

[CP Louie]

Oil pressure will also be a function of the viscosity (age and amount sheared) of the oil. I have seen 35 PSI with new oil (S52, M1 15w-50) and then have it drop to 20 PSI after some track pounding. How old is the oil? For a track car I would never exceed 1000 miles on the oil.

You could pull the filter and look for "bits". You could change the oil. (Save some and get it analyzed). Noises are an issue, they do not "heal". Good luck these types of issues can be very distressing and expensive.

Chris

[Michael9218]

Chris, thanks for the reply. The oil is fairly fresh Redline 20-50. A couple track weekends on the oil. But to be clear, I've always had strong oil pressure since installing the VAC pump regardless of the oil viscosity or age. I suppose it could be the pump or blockage somewhere in the system.

[jbrannon7]

I don't know about BMW oil pumps, but on V8 engines I am familiar with the oil pump has a presure bleed off valve that allows higher than safe oil pressure to bleed off. Sometimes it would stick partially open causing low oil pressure.

Joe

[NeilM]

I don't know about BMW oil pumps, but on V8 engines I am familiar with the oil pump has a presure bleed off valve that allows higher than safe oil pressure to bleed off. Sometimes it would stick partially open causing low oil pressure.

The BMW oil pump is like that too. There's a spring loaded relief valve in the pump body. You can see this relief valve assembly as parts 6-10 here: http://www.realoem.com/bmw/showparts...76&hg=11&fg=30

I've not seen myself, but have read accounts by other people, of scored pistons that cause the relief valve to stick in its bore. Replacement parts aren't expensive, although of course the labour to get to them is non-trivial. If this problem is suspected you'd want to inspect the bore in the pump body very carefully to make sure that it isn't damaged too. Considering the possible consequences of a wrong decision it might be worth replacing the pump instead.

I'd also get hold of an inexpensive mechanical oil pressure gauge (Harbor Freight has one) to use for shop testing.

Lastly, there's of course the possibility that there's a shot bearing someplace that's bleeding off oil pressure. Let's hope not.

Neil
96 M3 - similar issue under investigation

[thejlevie]

I'm not familiar with the VAC pump, but does it have a safety wired OPN?

[NeilM]

I'm not familiar with the VAC pump, but does it have a safety wired OPN?

Different shaft configuration with a bolt instead of the nut.

Neil

[Michael9218]

That pressure relief valve certainly sounds plausible. I'll talk to VAC on Monday and see what they say.

Interestingly enough, this morning when I put the car on the trailer, the cold oil pressure was a solid 60 psi at idle when I started the engine and all sounded normal. Same when I unloaded the car when I got home.

Regardless, it looks like I'm going to be dropping the pan....what a PITA!

[MasterKwan]

Do you have an oil temp gauge? I wonder if you simply overheated the oil?

[Michael9218]

I have a temp sensor reading from the sump drain plug. Temps were normal (@240). I've had temps as high as 255 - 260 in the summer and pressure was always good.

[MilanM3]

Do you have an oil cooler on the car. how many miles on the engine. I always do the cheapest/ easiest thing first. change the oil and filter and see if that makes a difference.

[NeilM]

Regardless, it looks like I'm going to be dropping the pan....what a PITA!

Here's one way to make it slightly less of a PITA.

First, support the engine from above. Unbolt the engine mount lower studs.

I bought two 12" long M12x1.5 threaded rods from McMaster-Carr. Cut screwdriver slots in one end of each rod. Remove two of the original front subframe bolts, one each side, and screw in the rods with corresponding M12 nuts (wheel stud nuts work fine). Remove the other pair of original subframe bolts.Unbolt the lollipops (front control arm bushing carriers) from the chassis. Detach the steering column U-joint, unbolt the PS pump, remove and push down and through the PS reservoir from its clamp.

Now you can lower the entire front subframe with rack, PS pump and hoses, tie rods, control arms, struts and everything else still bolted up, simply by unthreading the M12 nuts along the M12 threaded rods. You can fine tune the height by turning the nuts. It will drop more than enough to unbolt and remove the oil pan, plus there's no jack or stands to get in your way underneath.

But yeah, it's still a pain.

Neil

[not2quick]

Here's one way to make it slightly less of a PITA.

I bought two 12" long M12x1.5 threaded rods from McMaster-Carr. Cut screwdriver slots in one end of each rod. Remove two of the original front subframe bolts, one each side, and screw in the rods with corresponding M12 nuts (wheel stud nuts work fine). Remove the other pair of original subframe bolts. Unbolt the lollipops (front control arm bushing carriers) from the chassis. Detach the steering column U-joint, unbolt the PS pump, remove and push down and through the PS reservoir from its clamp.

Now you can lower the entire front subframe with rack, PS pump and hoses, tie rods, control arms, struts and everything else still bolted up, simply by unthreading the M12 nuts along the M12 threaded rods. You can fine tune the height by turning the nuts. It will drop more than enough to unbolt and remove the oil pan, plus there's no jack or stands to get in your way underneath.

But yeah, it's still a pain.

Neil

Didnt you need a cradle to hold up the engine from the top?

[Michael9218]

LOL.... The hanging subframe is the least of the problem, but I like your creativity.

So I believe I found the pressure problem. I was sure it was likely the pump bolts that may have come loose due to vibration that was discussed a couple years ago, or the relief valve in the oil pump getting stuck...but the winner is the oil pickup tube has a big ole fatigue crack where it mates to the bell like bulb. I'm not entirely sure why it wouldn't have created an oil pressure issue when cold. Maybe the sump being full from sitting put the cracked part in oil and when running on track, it was out of the oil, scavanging air. Anyway, pics for your review...

[clopez95m3]

but the winner is the oil pickup tube has a big ole fatigue crack where it mates to the bell like bulb.

I believe that's the 2nd time I've seen that here on Bf although on a different spot IIRC. I believe the parts are brazed to handle vibrations better but they still manage to crack.

Carlos.

[Nivola]

My pick-up tube cracked in the exact same spot; I was having oil pressure issues when having high-G stops, or heavy breaking from straights into tight corners. Otherwise, my oil pressure would appear normal.

[savage217]

Scary site. At least you found it sooner rather then later.

[CP Louie]

Here's one way to make it slightly less of a PITA.

I bought two 12" long M12x1.5 threaded rods from McMaster-Carr. Cut screwdriver slots in one end of each rod. Remove two of the original front subframe bolts, one each side, and screw in the rods with corresponding M12 nuts (wheel stud nuts work fine). Remove the other pair of original subframe bolts. Unbolt the lollipops (front control arm bushing carriers) from the chassis. Detach the steering column U-joint, unbolt the PS pump, remove and push down and through the PS reservoir from its clamp.

Now you can lower the entire front subframe with rack, PS pump and hoses, tie rods, control arms, struts and everything else still bolted up, simply by unthreading the M12 nuts along the M12 threaded rods. You can fine tune the height by turning the nuts. It will drop more than enough to unbolt and remove the oil pan, plus there's no jack or stands to get in your way underneath.

But yeah, it's still a pain.

Neil

That is a brilliant idea!!!!! I use a motorcycle jack and if you are doing this for a period of time it can be dangerous. Thanks!! Chris

[magnetic1]

I was about to suggest the pickup tube... mine did the same :/

[scottbm3]

I was about to suggest the pickup tube... mine did the same :/

Mine did the same thing on my S52. heard you had some good GTS racing this weekend. Nice job.

[NeilM]

Didnt you need a cradle to hold up the engine from the top?

Whoops, forgot that part!

Yes, I have one of those steel beam engine supports that sits on legs either side of the engine compartment. Under $100 and one of the best investments I ever made.

For the benefit of those who don't want an engine in their laps, I'll add that point to my original post.

Neil

[magnetic1]

Mine did the same thing on my S52. heard you had some good GTS racing this weekend. Nice job.

Yea man... you need to come down and play in my home track Korey did pretty well and picked up LOTS of time over the weekend.

Here is my pickup:

[Mad Dog 20/20]

I am in the midst of swapping-out the pump/pan on my S52 and discovered that my pick-up tube had failed in the same exact way.

I had been experiencing low pressure at hot idle and in high G situations, especially if my oil level was less than a quart over-filled.

I suspect that when the oil is cold/thick, its viscous enough to "seal" the cracked tube and it functions semi-normally. But when the oil is hot/thin, enough of it leaks from the crack and/or some air is ingested causing a drop in pressure.

[94is]

Lucky catch. I was going to chime in and say that with my euro pump, when the relief valve would stick, I would have nearly no pressure at idle (obviously not the symptoms you were describing).

[Mad Dog 20/20]

Lucky catch. I was going to chime in and say that with my euro pump, when the relief valve would stick, I would have nearly no pressure at idle (obviously not the symptoms you were describing).

Yeah, I was kinda shocked. Did not expect to see that. I had been in there about 5 yrs ago to take care of the pump nut (punched the threads) and did not notice anything wrong w/ the tube, but its the kind of thing one could miss if they are not looking for it.

When I went in last night, I also noticed that my pump nut was actually loose, but could not be spun off because of the deformed threads. Although the thread punch alone seems to have worked, I intend to loctite, safety wire and thread punch the replacement parts.