Normal Engine Temperature?

[merbesfield]

What would be considered a normal engine temperature for my 73S. I realize conditions will make normal vary, but it would help to have some understanding of the range and various temps for various conditions. I have only driven the car for a couple of weeks so I do not have a good feel for it. So far the hottest I have seen it get was around 225, but I have a feeling that once it gets really hot here it will go higher. It does not have a front cooler and the A/C compressor is not connected right now. Thanks for the help.

[kentf14]

Good question! I'm not sure how accurate my sensor or gauge are, but my '73S usually operates at a hair above 180. I've got a carrera front cooler with the thermostatically controlled electric fan in the wheel well and no AC.
So, obviously not exactly the same set up as your car but at least a data point to start with.

Cheers

[edmayo]

Mark, that was the only disadvantage of the 73S, no front cooler as standard (available as option that year), I think it was a combination of cost cutting, corrosion problems with the previous year's coolers, and the Germans didn't think we drove fast enough to need one. As Kent just noted, with a front cooler much over 190 is unusual. Even at time trial events I don't see over 200. I've only really ever seen it get to 220 on a few occasions, once sitting in Dallas traffic on a 100 degree day, got back to 200 soon as we moved again. The other was running 90 through the Mojave with 100 or so ambient. Now my 71T will get to 250 when running hard on a hot Texas day, even up to 220 when just putting around town. Now I find it difficult to believe that you've gotten to high 90's in New Jersey recently!!! So your 225 seems high for the ambients you're seeing. I would suggest at some point you may want to remove your engine oil thermostat and see if it is opening all the way.

[MountainRoads]

What would be considered a normal engine temperature for my 73S. I realize conditions will make normal vary, but it would help to have some understanding of the range and various temps for various conditions. I have only driven the car for a couple of weeks so I do not have a good feel for it. So far the hottest I have seen it get was around 225, but I have a feeling that once it gets really hot here it will go higher. It does not have a front cooler and the A/C compressor is not connected right now. Thanks for the help.

I posed a similar question several months ago about my 'stock 71E. I asked, because this car alwasy managed a rock-steady 180-185 during a previous tenure with no external cooler, and under any conditions. Now (two decades later and without any mechanical modifications) she settles in at 210. The advise I received was that 210 was normal and nothing to be concerned about. In fact, one respected mechanic suggested 210 was better because less water would collect in the oil. My amateur assessment is cooler is generally better. The mystery for me was what had caused the change, since the engine was still stock.

- MR

[RSTarga]

My 73S in San Antonio summer (say 95 and up) never gets above 210 on the hiway. Around town with A/C and stopped in traffic she might hit 250 and I get very nervous, but as soon as I get rolling it drops right down into the 210 range. In cooler temps (say under 90) Im pretty much stuck at 180.I am running the 28 tube front cooler with no fan. I wonder if anyone here has done any comparisons between the 28 tube and the carrera style radiator type.
IMHO the very first thing you should do is add a front carrera type cooler with a fan. If you want to extend the life of your engine.All S cars ROW had a cooler in 73.

[edmayo]

I posed a similar question several months ago about my 'stock 71E. I asked, because this car alwasy managed a rock-steady 180-185 during a previous tenure with no external cooler, and under any conditions. Now (two decades later and without any mechanical modifications) she settles in at 210. The advise I received was that 210 was normal and nothing to be concerned about. In fact, one respected mechanic suggested 210 was better because less water would collect in the oil. My amateur assessment is cooler is generally better. The mystery for me was what had caused the change, since the engine was still stock.

- MR

What might account for your change in running temperature is that the engine now has more miles on it. As an engine wears it will tend to run slightly hotter just because clearances have changed and it's working a little harder. Your mechanic is right in that oil should be hot enough to burn out moisture and such, 210 is ideal, much hotter is not. My T has 180,000 miles on it, so I'm not surprised at its temps, I'm sure with a comprehensive engine rebuild it would run cooler.

[edmayo]

Mark, one other thought comes to mind, the 73 has a removable duct over the engine oil cooler, you could remove it and make there isn't any "driftwood" that has accumulated on top of your cooler.

[MountainRoads]

MR

Any change in oil pressure readings when the temp change occurred


raj

Thanks for the info guys

Good question raj, but no, not really. 60 - 80+ psi when warm and depending on revs, etc.

[MountainRoads]

What might account for your change in running temperature is that the engine now has more miles on it. As an engine wears it will tend to run slightly hotter just because clearances have changed and it's working a little harder. Your mechanic is right in that oil should be hot enough to burn out moisture and such, 210 is ideal, much hotter is not. My T has 180,000 miles on it, so I'm not surprised at its temps, I'm sure with a comprehensive engine rebuild it would run cooler.

Also a good thought, Ed. Coincidentally, I went back and reorganized my records on the car last weekend. This car had 106K miles when I sold it in 1991. I bought it back late 2010 with 118K, which works out to about 12K miles in 20 years. Not exactly high mileage or a lot of difference. I noticed the jump in oil temp the first (or maybe the second ) time I drove it after re-purchase. It's been consistent at 210 fully warmed, ever since.

My next step is along the lines of your "driftwood" thinking. I did notice a bit more oil/dirt on the engine fan last time I looked. Nothing major. Just hadn't had a good bath for a while. I started thinking that maybe some of that is on the oil cooler and cylinder fins also, and running a couple of cans of Gunk through the fan, oil cooler, and other exposed parts, followed by a good hosing, might make a difference. The other question is if the temp sender and/or gauge might not be completely accurate.

Bottom line is 210 doesn't appear to be anything to be overly concerned about. I just don't *like* it after being used to 180-185 in my other flat-sixes, and am curious what might have changed.

- MR

[Grady Clay]

Mark,

I’ll encourage you to get a good front cooler setup.

The original (optional on your car) ’73-only front cooler was the ‘trombone’-type.
Since there was not a (more fragile) full-fin cooler, Porsche chose to not install a safety pressure relief valve.
The device that attaches to the ’73 oil tank is a thermostat only.

If you retrofit an original ’73-only system, you can only use a trombone.
Without a safety pressure relief valve, cold weather over-pressure can damage a full-fin cooler.

The good news is the system for models 1974-1989 fits your car and includes a thermostat / pressure relief assembly.
Elephant Racing makes excellent aftermarket replicas.

I agree with a switch operated electric fan on the front cooler.


Keep in mind that the engine oil temperature varies a LOT depending on where you measure it.
The hottest oil is actually in the scavenge pipe coming out of the crankcase under the #3 cylinder.
The oil at the temperature sender is after all the oil cooling.
I like to keep that oil at 180-190F ideal and 210F peak.


Another cooling update is to turn the engine cooling fan faster.
There are pulleys and fans available where the ratio of fan-to-crankshaft can be increased from 1.3:1 (yours) to 1.82:1.
The higher ratios use a bit more power (not noticeable) but keeps important parts of the engine (cylinders & heads) cooler. Keeping the oil cooler hardly effects the temperature of these parts.

Keeping the heads and cylinders cooler increases horsepower and reduces detonation tendency.
As Ed notes, everything transfers the heat to the air better if it is clean.

An additional benefit of the faster fan is it allows the A/C (if you get it working) to function better.

If you want dramatic increase in engine cooling for track or desert, read this:
http://forums.pelicanparts.com/porsc...-solution.html

Best,
Grady