Dana Drury

Hi Guys,

Some of you might recall I was having heating issues on my 1977 3.0l Carrera.

I have since replaced both thermostats, new oil lines to the front trombone style cooler because the uptake line was crushed slightly.

The car is in perfect tune (new plugs, cap, rotor, dwell and timing set and the mixtures set perfectly). The car purrs fine. Vavles are adjusted. There is no pinging/knocking going on.

My gauge is still going up to and sitting at 120 C (248 F) and hovering there.

We are seeing ambient temperatures of about mid to late teens (C) or 60 degrees farenheit. (though last test drive I did the car was in 50 degree F ambient)

The temperature rises to around close to 110, sits there for a while then eventually rises to 120 C after about 25/30 minutes.

The front trombone cooler eventually gets very hot to the touch after 30 minutes or so of driving. So the oil is circulating and the thermostats are doing their jobs .

Hard driving doesn't seem to cause excessive heat, i.e. it sits at around 120 C and the might just rise over the mark if I give the car a bit of stick.

I am running Mobil 1 (5W50).

I have a numbered gauge in degrees C.

The one thing I have noticed is that the oil pressure gauge in the car doesn't seem to always equal 1 to 1000 RPM's.

I now need to test what may be the cause which I would like some advice on, if I can't sort this out I will eventually go to my P-Mech and have him look at it - but I would like to get to the bottom of it considering I have learnt so much on the car already.

I can test the temperature sensor I believe by putting it in distilled boiling water, do I simply just put the bottom (the sensor part) in the water, have the power on and check the gauge to see what I get?

Also, I do understand that the actual temperature sensor that sits on the chain tensioner cover needs to match to be paired to the gauge. I do know that my car originally had a 2.7 litre engine that died, they then put the 3.0l Carrera in, is there a chance that my gauge is not compatible with my sensor?

I know if I get a Oil Temp tool on it then I will know for sure, but I am trying to track one down and I am not entirely sure where I should measure from?

Can a temperature gauge be recalibrated?

I was worried before, but i'm not now simply because the engine seems fine, the car is in an excellent state of tune and the trombone cooler is getting hot.

Anyway thanks if anyone can give me some advice as to how I test that sensor, I couldn't find anything in terms of specifics (I am a bit iffy about boiling a pan and then putting it in...

H. D. Smith

I think you are on it with the guage, make sure it is the correct guage and not broken.
If the mixture is lean, then you would run hot.
I was running hot with everything correct, so I upgraded to a Mocal cooler and all is well. 190-200 in city traffic and 190-210 on the highway. Best of all is 220 on the track where I was running over 250 with the trombone. All this with the ambient temps in the 90's.
Just a sugestion.

Tom F

What are you running for an oil pickup strainer, the screen that goes inside the plate on the bottom of the crankcase?

Dana Drury

Good question, I have no idea what screen I am running. Would that generate more heat? I haven't removed the sump screen. Could it need cleaning?

The reason I am baffled is because before I did all this work, the PPI Mechanic said that it was running too hot and oil was not getting to the front trombone (thus the external thermostat was replaced).

I know the cooling system didn't work before, and now it does so I am not, like I said, overly worried.

How do you work out what the correct temperature sensor is? Does someone have some parts numbers for one that corresponds to a number celcius gauge?

How can the gauge be recalibrated? I have the OHM resistance numbers for a 1973 Porsche, are the gauges the same?