72T runs hot, help

[IAN]

I have a 72T 2.4 w/MFI that runs hot. No front cooler.

When it is 80 degrees out I can see temps of 250 when driving at highway speeds. This problem really only occurs when I'm driving at highway speeds or during 'spirited driving.' When i'm driving around town or in traffic ironically it doesn't get very hot, around 210.

So really it gets hot under load.


I have tried:

1) confirmed ignition timing
2) had oil cooler removed and cleaned professionally
3) removed debris from top of engine. There was a mouse next on the left side of the engine that I removed with no improvement.
4) I have pulled out the thermostat and boiled in water and it did open at 180 degrees. I was ready to replace it but didn't once i tested the one in the car.
5) confirmed that metal cooling pieces are in place correctly
6) confirmed seals are decent around perimeter of engine.
7) replaced temp sending unit.
8) oil tank has been removed cleaned, tested, etc.
9) read all of the posts i can on the subject of hot running cars

What's left?

Is it possible that oil lines get clogged? I guess i could pull the hard line that runs from the bottom of the motor.

Could my thermostat function correctly in a pot of water during the test by not work in the car for some reason?

I'm not sure what else to do and it driving me nuts.

Any ideas?

Thanks.

[SP2]

Maybe you should feel the oil lines going to the front cooler when the engine is hot. The lines should get hot with oil flowing to the front cooler.

The cooler you had cleaned is the one near the engine block, right? That one can get a lot of dirt in the cooling fins.

[BK911]

If there was a mouse there, there could be some remains of a mouse nest. How did you remove the debris from the top of the engine? Maybe remove everything including the shroud and see what you have.

My 3.0 was running hot. Turned out to be from a blown head gasket. Combustion gases were leaking out the cylinder / head interface and being blown across the cylinders and engine oil cooler. She ran great, I did a leak down just to see what I had and found the leak.

[356RS]

You have no front cooler so the mouse or rodents nesting on top of your engine could be possible if your car is not driven for like during the winter months. Photos below show a worse case scenario.

[jpnovak]

Are you sure the gauge is accurate? Test with an IR thermometer when it gets hot. A 2.4T should run nice and cool. Is it running lean?

[dtw]

Is it stock?

Is the temp accurate (per Jamie above)?

If yes to above, and all else has been checked, it is time to check fuel delivery. If even one of your injectors is leaning out, you can have problems. Try something as unscientific as a plug cut, but if possible, get on an exhaust gas sniffer.

If mixture is good, time to check basic engine health w/compression and leakdown checks.

[Grady Clay]

All good suggestions here and you have done very through homework.

First, buy some instrumentation.

I paid $27 for my IR thermometer, HF on sale.

Many multimeters have a temperature function using a Type K thermocouple. You can find thermocouple wire at industrial salvage. With an oxy-acetylene torch you can make your own thermocouple junctions.

All total, this should be less than $100 and can be useful for a lifetime.


This will let you see what the actual temperatures are under a variety of conditions.

First will be to calibrate your gauge. Find a large electrical O-terminal. You want one that will fit under the temperature sending unit and fits a small wire, say 22 Ga. (1 mm). Get a terminal about the same thickness as the aluminum sealing washer. Leave the sealing washer out as soft copper terminals will seal just fine.

Once you make a thermocouple junction, simply crimp it in the terminal. Run the thermocouple wire into the cockpit. This will let you measure the actual temperature and the ‘Porsche’ temperature at the same place and under the same conditions. Simply make a measurement at every mark on your Porsche gauge. As a fancy alternative, print a little label to stick on the gauge glass.

Is the engine actually running too hot?

A good clue as to the proper cooling is to compare the thermocouple at the sender (the coolest oil in the engine) to the oil in the pipe coming out of the engine.

At the pipe, use another thermocouple on the pipe. Use a hose clamp and a little piece of a rattle-can cap between the clamp and the thermocouple (this prevents the clamp from cooling the thermocouple). Again run the thermocouple wire into the cockpit.

During engine warm-up, you will find the pipe temp & gauge temp will track each other, pipe hotter. As the thermostat opens (starting about 180F), the pipe temp and gauge temp will diverge. Above where the thermostat is full open (about 210F), the two temperatures will tend to converge )mostly by the gauge temp rising).

Lots of data points are necessary so get a passenger.
Repeat the process many times.



The IR thermometer is a great tool for measuring exhaust temperatures at the 3-into-1 junctions to spot L-R differences. With heat exchangers it is a bit more difficult to measure individual exhaust. Hard-wired thermocouples are better.

When measuring cylinder head temperatures with the IR thermometer, choose a location and position where all six measurements are taken the same – well, as much as possible. Thermocouples mounted in the heads are better.

Knowing the temperatures will help with the MFI.


Assuming everything is as it should be, how do you make it cooler?

Easiest is with the engine cooling fan ratio. Your ’72 911T fan turns 1.3:1 of the crankshaft speed. At 4500 rpm, the fan is turning about 5850 rpm.

There is a crankshaft pulley and fan (or just hub) that changes the ratio to 1.82:1 with standard used Porsche parts. At 4500 rpm, the fan now turns about 8190 rpm. That is a 40% increase in cooling. There is marginal increase in power to drive the fan faster; not noticeable. A good (undamaged) fan can turn above 15,000 rpm safely.

A second, easy fix for track use is the ‘Rubbermaid Solution’.
Water vapor cooled 911 - the Rubbermaid Solution


Every 911 benefits from having a front mounted oil cooler.
There is a great deal on Pelican about this.

Best,
Grady.

[IAN]

It is stock.

The remains of a mouse next was found 7 years ago on the left side of the engine. I dropped the engine removed the fan shroud, fuel injection and removed every single piece of it.

Engine has approximately 38k on it but it was rebuilt in 1983. I have the receipts from the rebuild.

MFI pump and injector spray patterns were tested recently by Jerry Fairchild industries and all is good.

MFI was tuned by Gordon Ledbetter in Portland in 2001. He is the MFI man, period. I have not messed with any MFI settings since then. Gordon thought my car tuned up very easily and ran great.

I have not done a leakdown test in a while. I have owned the car since 1998 and did a leakdown test then.

I do have an HR thermometer from HF and I have taken temps on the oil tank and they are close to what the gauge shows.

Any easy way to see if I have a blown head gasket?

Is there anything telling about the fact that it heats up and load VS. just driving in traffic or around town when it is hot outside?

I'm about to drop the engine from the car to do a little work. Everything is ready for the drop so i can't really start the car right now.

Again I appreciate the help. i would drive this car a lot more if I wasn't always worried about it heating up. Not that much fun when you are always looking at the gauge.

thanks.

Ian

[daepp]

Could his fan belt be loose?

[IAN]

Fan belt is fine and has been replaced several times

[gptom]

Any chance you have a 5 blade fan instead of the original 11 blade?
Tom

[IAN]

I have the 11 bladed fan.

Thanks.

Ian

[dtw]

I'd get it on a sniffer next.

[daepp]

To get mine to run at 210 or below I had to add a front oil cooler. That was for driving a 72T 2.4 MFI at 75mph in So Cal with compression ratio of 9.5:1.

[tobluforu]

My 72 runs on ave about 180, I have 2.7 rs p and c's, not sure if that does anything or not. The oil cooler is org. and in the stock location. The only thing I have done is place high heat reflective tape on the cooler where I could since it's kind of next to the HE. My car runs rich as well which helps some.
Good luck.

[TargaT]

My 73T was doing the same. There were two issues I believe which eventually fixed the problem. I believe my MFI electric pump was leaning out as it warmed up. It was the original and as it got warm it began to crap out and leaned out the mixture.
The other was my distributor. I checked the timing over and again but not once the car was overheating. When it was overheating the timing was off. The distributor was a little dirty and the weights were sticking.
It's hard to tell if the electric pump is margina.l All I know is that mine was orginal and it would eventually leave me stranded so I replaced it $$. I now typically run from 180-210.

Regards, Joe