1977 911S w/ 3.2 Cooling Issues

[DanMan68]

Hello,

I have a 1977 911S with a 3.2 Carrera motor swap (by previous owner) from a 1985. I have been struggling with the car running hot (220~230f) depending on the temperature outside and the length of the drive that I am going on. The car was recently serviced for a variety of issues (due to the car sitting for a while) by a local shop specializing in air-cooled cars. They cleaned and pressure tested the engine mounted oil cooler and confirmed the engine mounted thermostat was operating properly. They drove the car and confirmed it was running between 180~210 when the gauge was reading around 230f (due to the temp sender mis-match), and gave the engine a clean bill of health at this time.

The issue is, when it's hot-ish out (80deg) and I am driving the car in moderate traffic is starts to overheat based on the gauge reading 250f or above, and IR-gun temps reading around 230f at the engine oil cooler, and 215f at the front Carrera cooler. The car has some kind of aftermarket oil cooler and rubber oil lines that run all the way to the Carrera cooler (w/o fan).

I have been considering getting an oil cooler fan and metal lines to help with this situation, but my question is, do these seem like normal temps considering the setup and driving scene? Or is there some other issue I should potentially address 1st before throwing ~$1000 at new oil lines that may not actually be the issue.

[75 911s]

It sounds like the thermostat fwd of the passenger rear tire is working as you are getting 200+ temp readings at the front cooler, so hot oil is moving up there. It's just not cooling it effectively. You might also check your timing. That can lead to hotter than normal temperatures.

If it were my car, I would replace those junk rubber lines with stock metal lines or even better, Elephant finned lines. Put in a Carrera cooler with 'widemouth' fittings and electric fan. You'll have no problems after that.

[911pcars]

I would address this and most non-life threatening issues incrementally.

While the final solution might be as advised by Duane, I’d start with an electric fan on the bumper-mounted cooler. Air flow is at a premium in this space. Use a manual switch and see how much of a difference with it ON and OFF. The factory did its best to ID a location to fit a cooler. Unfortunately, the fender was the best they could do. German 911s didn’t need a cooler due to their climate. If AZ were in Germany, they would have dealt with the issue at ground zero more efficiently.

Tell us more about the mysterious inline cooler between the engine and the external thermostat. Pics help. Approx dimensions of the aftermarket oil lines?

Sherwood

[DanMan68]

Originally Posted by 911pcars

I would address this and most non-life threatening issues incrementally.

While the final solution might be as advised by Duane, I’d start with an electric fan on the bumper-mounted cooler. Air flow is at a premium in this space. Use a manual switch and see how much of a difference with it ON and OFF. The factory did its best to ID a location to fit a cooler. Unfortunately, the fender was the best they could do. German 911s didn’t need a cooler due to their climate. If AZ were in Germany, they would have dealt with the issue at ground zero more efficiently.

Tell us more about the mysterious inline cooler between the engine and the external thermostat. Pics help. Approx dimensions of the aftermarket oil lines?

Sherwood

I'm in Michigan so not crazy hot weather usually. The 1st cooler I mentioned is the stock cooler mounted on the back the engine that all 911's have (excluding 964/993). I will take some pictures tonight of my setup. I agree that I would rather incrementally improve things rather than just throw money at it so your (and Duane's) advice is greatly appreciated, thank you!

[dfhtrhjn]

I had cooling issues in my 77 as well, but I swapped the bumper and put a large center mounted Setrab and it did the trick.

My '74 had the same issue and I noticed a huge drop in temp when I switched to carbs because I was burning so much more fuel with a richer mixture. (Oxygen burns much hotter than gas)

If I were you I'd stuff the biggest fender mounted cooler you can with a thermostatically controlled fan. Don't worry about the oil lines so much.

[grant lyon]

+1 "start with an electric fan on the bumper-mounted cooler"

I run 2 spal 5.2" fans (~313 CFM, ~$60 ea) on an external thermostat controller pushing thru a Terbatrol cooler, connected with rubber lines. (Expect Carrera cooler with radiator type construction is a better unit, not sure about Carrera tube type.) This is enough to keep temps to ~220 F on hot days 95 --100 F in stop and go traffic. I run two small fans only because of the peculiar space limitations of my configuration. You could try one fan, whatever fits, and worse case you could later use the fan on an upgraded cooler.

[Quicksilver]

Fan

[E Sully]

My stock '73 911T used to get very hot in 80-90 degree temps. Only had the engine mounted cooler. When I installed an '86 3.2, I added a stock brass pipe front loop SC system. It never got above 220 on hot days. I think the metal lines running exposed below the rockers aided the cooling quite a bit to the basic trombone SC loop.

[911pcars]

Correction. I meant installing a fan on a fender-mount cooler. Unless the front bulkhead is modified, there’s no space for a fan AND cooler behind the front bumper - not needed as air pressure is highest at the middle front. My front-mount cooler behind an RS bumper works fine despite So Cal summer temps and with hardly any exit air space behind the cooler. YMMV.

OTOH, air flow in the fender area is woefully inadequate. Introducing forced air makes a big difference. Those with 3.6+ engines may need either both or a larger surface area cooler.