Oil Light and Transmission question

[Imprezme]

Hey guys so i recently picked up a 91 325ix, the other day i was driving the car and the oil light started blinking on the dash. First time it ever happened, when i came to a stop light the light would flicker. When i stepped on the throttle it would go away. Any ideas what might cause this? oil pump failing? or maybe the oil that im running in the car? Light only seems to come on when the engine is fully warmed up.

Another question i have is when the car is in neutral i can hear a noise, but when im clutched in the sound goes away. i assume that's my input shaft?

Any ideas or information toward the right direction would be helpful. thanks!

[325ixa]

i have a dumb question, have you chekeck oil level, on dipstick?

second is probably clutch bearing.

[Nisse Järnet]

The sound from the trans is the input shaft bearing in the gearbox propably, not much to worry about.

Try to measure your oil pressure.

[101]

Agree on the transmission shaft input bearing being the likely cause of the noise.

What weight of oil are you running?

[The Dark Side of Will]

Yes, what weight? If running multiple viscosity oil and the 2nd number is significantly lower than what BMW specifies, then you could see low oil pressure at hot idle.
I don't have specs in front of me, but if BMW asks for 10W30 and you're running 5W20, that might happen.

[Northern]

10w40 winter/ 20w50 summer is typically what I run, since it occasionally dips below -10 in the winter and just shy of 40 in the summer.

[Imprezme]

The sound from the trans is the input shaft bearing in the gearbox propably, not much to worry about.

Try to measure your oil pressure.

Agree on the transmission shaft input bearing being the likely cause of the noise.

What weight of oil are you running?

Yes, what weight? If running multiple viscosity oil and the 2nd number is significantly lower than what BMW specifies, then you could see low oil pressure at hot idle.
I don't have specs in front of me, but if BMW asks for 10W30 and you're running 5W20, that might happen.

10w40 winter/ 20w50 summer is typically what I run, since it occasionally dips below -10 in the winter and just shy of 40 in the summer.

thanks for the info guys, i believe the pass owner was running 5w30. ill give the oil a change and see what happens before i measure the oil pressure.

so input shaft bearing, nothing to worry about?

[nando]

that chart is nearly irrelevant now - oils have improved a lot since it was made ~30 years ago, especially synthetics.

[Northern]

Still a better guideline than throwing 5w30 in.

I also don't think the majority of e30/m20 owners run synthetics.

[The Dark Side of Will]

that chart is nearly irrelevant now - oils have improved a lot since it was made ~30 years ago, especially synthetics.

A 10W30 is a 10W30 as far as viscosity goes... and the viscosity is what results in the oil pressure warning.

HOWEVER, low oil pressure hot *could* be a sign of worn bearings, but changing the oil is the first step.

My Pontiac 6000 AWDwith 3.1 pushrod V6 would light the oil pressure light at heat soaked idle also. I swapped in a high volume oil pump but kept the original pressure regulator spring and the problem went away.

[nando]

it is and it isn't. a 10w30 synthetic and a 10w30 conventional for example are not the same at all. the conventional will have thinners and additives in the base stock to make it flow at lower temperatures. the chain of molecules in the synthetic is different in that it already flows better at low temperatures without additives, but it expands to provide protection at higher temps.

I'm willing to bet if you tested any decent oil made today (conventional or not) it would outperform an oil made in 1985 by a pretty good margin. Synthetics are just better, and the conventional oils have a lot better additives packages than they did 30 years ago (which is what makes them work at all to begin with).

[Nisse Järnet]

I always used 5w40 synthetic when my M20 was stock (and still in the car hehe)
Never had a problem!

I would still try to check the oil pressure just to be sure, a ~25 year old oil pressure switch might not be very accurate either.

[nomansland92]

As for the transmission noise it's probably the layshsaft bearings, seams to be pretty common with high miles.

[Imprezme]

Gonna give it some new oil tomorrow, see how it works out. Been waiting for a brake light sensor to come in before i start working on the car. Car seems to also take forever to start up, takes like 5 seconds to crack and it will start, guess i gotta check for vacuum leaks

[The Dark Side of Will]

it is and it isn't. a 10w30 synthetic and a 10w30 conventional for example are not the same at all. the conventional will have thinners and additives in the base stock to make it flow at lower temperatures. the chain of molecules in the synthetic is different in that it already flows better at low temperatures without additives, but it expands to provide protection at higher temps.

I'm willing to bet if you tested any decent oil made today (conventional or not) it would outperform an oil made in 1985 by a pretty good margin. Synthetics are just better, and the conventional oils have a lot better additives packages than they did 30 years ago (which is what makes them work at all to begin with).

What I meant was...
The viscosity rating is based on a standardized test. The performance of two products with the same score on that standardized test is going to be the same.. on that test.

The viscosity test has nothing to do with film strength, ZDDP content, or even with viscosity at other than the two standard test temperatures.

So... yes, a 10W30 is a 10W30 is a 10W30 is a 10W30 from the perspective that they all score the same on the standard test. Yes, those products can ALSO have very different performance on other tests or operating conditions other than the test conditions.