Low oil pressure, is this a common problem?

Don't mean to scare you but I used to have an '86 535i and was told by several knowledgeable BMW enthusiasts that the engine was virtually indestructible. Well, when I bought it (with about 200K miles) it had a bad leak from the cat which I had rewelded... then I found that I had a tapping noise from the engine... well next time I had a free weekend I took it to my parents' house (about 150 miles away) and reset the valve clearances... noise still there... that's when I started to get worried. On the way back the oil light started flickering when I stopped for tollbooths etc. D'OH! Next time I started the car it immediately spun a rod bearing. Not good. I'd maybe put 2K miles on the car and I had to spend as much as I paid for the car to have a junkyard motor put in it.

IOW, get it checked out soon...

nate

You pull a trailer with a BMW? Wow, that would make a great story/picture for Car and Driver.

I don't pretend to know diddly about BMWs so I don't even know if this applies to the engine in yours, but I happened to read this a while back:

Ulf wrote:

No, the x35 uses a straight six engine based on the old 3.0 - the V8 would be a x40. Personally I thought the 3.5 was a hell of an engine... I think mine was just abused.

nate

Steve wrote:

I'd be making sure the engine was full of oil. If the oil pump is in the front, and the oil level is low, then the oil pressure will be low too.

Don't take this as an insult, but are you sure it's the oil pressure (red) and not the oil level lamp (yellow)? In my '91 525i it turns on (well, the CC pings) after hard driving if there's just under half or about a third of oil between the marks. If the sensor is at the front it might the reason.

On a former 735i, if the oil level was low (but above the lower mark) and the car was worked hard (e.g. up a big hill) then the oil level warning would sometimes if one suddenly eased off (leaving a lot of oil in the head & galleries). Never did it before starting except the time the garage didn't tighten up the filter properly and some ran out.

I know the difference. It was the red low oil pressure light that was on, and after a few seconds the check control panel started flashing warning messages as well.

Ulf

LOL. My 535 is actually very capable of pulling a trailer. Despite the fact that the trailer was probably ~50% overloaded I still didn't have any problems.

Ulf

How many miles on the car. Chances are the bearing clearances and the oil pump are not going to be as tight as they once were. The combination of larger clearances and oil thinned from the heat of pulling a trailer could trigger the oil pressure lamp.

Did the light go out as you reved the engine on a hill?

You should have a BMW dealer put a real pressure guage on the engine and check it out.

snip

You shouldn't have any trouble pulling it (except if it is very steep), but stopping in a straight line, that's a different matter and nothing to do with the towing car*.

• You canna change the laws of physics - McCoy.

If the oil level was correct, the likely cause is a faulty oil pressure switch. Cheap and easy to replace. My E34 had two replaced in the time I owned it.

Quite often, the limitations on towing isn't getting going, but getting slowed down again. I gotta wonder if a yard of sand or gravel is more than a BMW should be working with. It's one thing to drag a SeaDoo or two to the river, and quite another to to deliver a ton or more of building materials.

Agreed, but it's not like I'm in the construction business... :-) Speaking of braking, I did have the ABS kick in once when I was braking for a red light. The brakes on the trailer weren't really that great, but I guess that can't really be expected on a rental. Then again, the sand might have weighed a little more then I first thought too. I just did some calculations and the volume of the bed is about 1.6 m^3, the question is if the sand would cover the whole area up to the top of the sides or not. Assuming it would, and with a density of 1.5 tons/m^3, that's like 3 tons including the trailer. I regret not using the scale they had where I bought the stuff, it could have been a nice surprise... :-)

Ulf

No, only when I got the car level and restarted the engine. I'll do an oil change tomorrow. According to the lights on the dash it's about time, and I've also used two bottles of injection cleaner in the last couple of tanks.

I'll see what happens after the oil change.

Ulf

... except no oil pressure... :-p

If the sump shows full on the level and the problem only appears when on an incline then you need to have it checked out soon. It may be nothing, but the dealer should be able to replicate the low pressure indication with a real pressure meter. The dealer will also be able to go through a complete diagnosis are rule out reasons for the low pressure light to come on.

In the construction business or not, I can't help but think you are overloading your car and putting yourself at serious risk. I gotta think the chassis isn't very happy to have all of that tongue weight hanging off of it either.