kmascotto

My 89GT will show an Oil Pressure Warning Light when the engine is at normal operation temperature and the Bar indicator drops below 3 bar. The indicator never goes below 2 Bar at any time.

I have replaced the pressure switch and both springs.

The only other thing ive done differently this season is, I started using Shell Rotella T3 15-40 oil. In the past I've used Mobil 1 15-50 Mobil, without issue.

Has anyone else encountered this issue?
Thanks

JWise

Yes. 40 weight is too thin for most warm climates. I experienced the same issue after filling with Mobil 1 Delvac 40. I immediately drained and refilled with 15w-50. No more issues.

Cosmo Kramer

What kind of sending unit did you put on? If it's an aftermarket one and not the VDO unit they have a high failure rate.

One of the two, either the light or the gauge isn't reading correctly. I would put a mechanical gauge on it and verify pressure first.

kmascotto

Thanks guys, the sending unit I replaced it with was from Porsche, so that's not the problem. I suspect its the oil too, but I've been told its not likely the issue.

Time to replace the oil and see if that fixes the issue.

FredR

I would be surprised if the oil viscosity was the root cause of your problem. I live in a very hot climate and the local agents did some work for me and when running the car I was alarmed that the idle oil pressure when hot dropped to 1.5 barg. When I checked they told me they had put Mobil 1 0W40 in the motor. They said it was recommended by Porsche but I told them to drop it and we filled with Shell 20W50 mineral oil as per original Porsche specs. Even with this witch **** in the motor the low pressure alarm never went off- as i know it alarms at 1 barg.

So, given your indication shows the normally expected characteristic idle pressure of 2 barg suggests to me that the alarm contact is making when it should not. A mechanical gauge test should confirm this is the case but...? A slightly more viscous oil might just be enough to stop the rogue alarm tripping but it would not fix the fundamental problem or so my logic processes [?] suggest.

Canada is not what i would call a warm climate but on the one occasion I visited I drove through the Frasier Canyon the needle hit 40C believe it or not when driving to Vancouver airport - in early July! A few days later it snowed in Calgary!

Rgds

Fred

Imo000

Just because it's from Porsche, doesn't mean it can be faulty. Put a mechanical gauge on it or else it's just a guessing game.

kmascotto

Thanks Fred, we here in the Canada seem to be treated to many different climates from very cold to very hot & humid. That said, it’s the car that regulates the temperature of the engine. And it seems to be doing that well. I did noticed that when this oil (Rotella) gets warm it has the viscosity of water. I have read that 15w50 will increase the oil pressure…and as I mentioned already, that I’ve used it before without issue. I do regret not making a mental note of the oil pressure at idle with a warm motor when the 15w 50 was in there.
You make a good point about the electrical contact, which I will have another look when I have an opportunity

terry gt

Just had that low oil warning with my GT . One cooling fan quit at a autocross and the water temp was starting to get into the red ( I parked it and finished my last 4 runs with my friends new Ferrari 488 ) the engine block was reading 244 deg . These GTs have a poor oil cooling set up . So I am just looking for a solution , aside from a new fan . Or a new Ferrari .

kmascotto

Unfortunately I don't have a mechanical gauge to play with. But the old unit that I removed reacted exactly the same way.

Imo000

Then the chances are a lot less that the sending unit is the problem.

kmascotto

Its very annoying

FredR

Kent

Have you checked the condition of the wires in the engine harness?

Disconnect the 14 pin plug next to the hot post, pull the cover off and take a look at the condition of the cores. Cannot remember which core is the alarm signal.

Not sure if degraded signal can cause the alarm to initiate falsely. I have a feeling it is open circuit to alarm and closed circuit is system healthy but not at all sure that is 100%correct.

JET951

Hi Terry GT , you mentioned that during a autocross event ( and one rad fan out ) you had oil warning come on , was it the oil pressure warning ? & if so what is the oil viscosity did you're 928GT have in it at the time ?

Many Thanks
Bruce

kmascotto

Thanks Fred, I'll give that a shot.

Mrmerlin

NOTE running the engine hot will in most cases damage the oils viscosity, thus thinning it.
I had a few cases with Castrol GTX oil causing the light to come on,
fresh Valvoline and a new filter oil pressure was restored