how much will going to 11 blade fan help my cooling

[willyw]

Hey guys, my 76 911 will get up to 280 degrees plus on a 75 degree day just pleasure cruising. I still have the original 5 blade fan, all other upgrades though. I have the idle surging problem as discussed in another post when my cars temp gets over 210 degrees also which drives me nuts. How much temp drop can I expect if I convert to 11 blade fan-----thanks

[ruf-porsche]

A Lot

[Adam]

280ºF is "too damn hot", Willy. Don't let it get upto that temp. Pull over and let it cool...

An 11-blade fan will make a big difference, but you really need an oil cooler on that car. In my car's "crusade" to find lower oil temps, an 11-blade fan, HeetSheets and a Carrera oil cooler (with electric fan) all found their way onto my car. It barely gets over 180º, even when being spanked. Check out the recent thread on thermal expansion, which nicely explains why extremes of heat and Mg cased 911s (your car) don't mix well. You really should plan a few cooling upgrades in the short term. The motor won't suffer those temps for sustained periods. You'll get lots of help here.

Start off by making sure that your engine-mounted oil cooler is free from any debris (leaves, mud etc). While you're under the car, check the cylinder head fins for gunk also. Shine a flashlight in through the fan and inspect the tops of the cylinder heads. Make sure there's no critter's nests (possible if you store the car over the winter) or crud in there. Clean the exterior of the oil tank in the right-hand rear guard and (if fitted) check to see if your external trombone cooler is getting hot when the motor is running at this temperature. If not, then you might need a new thermostat insert (found inside the rear passenger side guard, forward of the rear wheel).

What kind of oil are you running? I suggest (as recommended by Pelican members) a 20W50 oil, which should help. Good Luck! It's worth it in the long run.

[RoninLB]

you gotta have a front cooler to get serious

[willyw]

Thanks guys, I have cleaned my pitiful little oil cooler. What is a trombone oil cooler? Is this an after market add on? Does this fit on the large suction hose from the oil tank? If so then I don't have one. As far as oil, I am running Castrol GTX 10/40 but will go to 20/50 if it will help. What about synthetic oil?----Thank, again

[RoninLB]

the trombone is better than nothing.. but not much better.. a full set up is serious bucks.. IMO, Elephant Racing stuff is ahead of the curve on oil cooling...........Ron

[RSupdate]

O.M.G. !!!!!!!!

Please !!! Stop driving when your oil temp stays over 210 for any length of time. Pull over and let it cool....no other choice is available to you !!!

Adam's recommendations above are very sound. Run with them!!!


Cool your 911 down fast or be ready to buy a new engine very, very soon!!

Best of luck!!

[Rick Cabell]

The above advice is sound, except for the 11 blade fan part--it will do nothing to cool your engine. I've had two cars (a '76 911S and a '77 Carrera 3.0) that both had the 5-blade fans on them. I took careful temp measurements comparing the 5 and 11 blade fans, thinking that I would observe cooler temps with the 11 blade fan. However, the difference was within, literally, a couple of degrees (easily within the margin of error). The 5 blade fan has fewer blades, but the blades have more surface area and thus move more air, and they spin faster because the upper pulley is smaller.

Now, if you don't have an external oil cooler--there's your problem. Sinking a couple hundred dollars (at least) into changing the fan will do zero to cool your car. You also may have debris or a mouse's nest on top of your engine underneath the shroud preventing proper air flow across the cylinders, heads, and oil cooler.

[RoninLB]

Originally posted by Rick Cabell
. I took careful temp measurements comparing the 5 and 11 blade fans, thinking that I would observe cooler temps with the 11 blade fan. However, the difference was within, literally, a couple of degrees

the cfm of the 2 are almost equal in stock pullys

[kstylianos]

280 is way hot for just a casual drive. Feel the bottom of the internal oil cooler when your temps are hot. If should feel as hot as your guage reads. If it feels cooler (a pyrometer works well here) then you may have internal thermostat problems.

Also, may want to verify you have the correct sender/guage. Your temps may be fine, but mismatched/broken sender/guage could be giving you false readings. Again, a pyrometer reading from the metal housing of the temp sender or metal on the oil sump will tell you roughly what your temps are.

[willyw]

As always, you guts are very helpful. I keep hearing about an internal and a trombone oil coolers. Is the internal the one that is viewed from under the car on the right side just behind the drive axel? I have asked about the trombone but haven't gotten an awnser. Is it an after market add on that connects to the oil suction line such as the ones you see in the parts catalogs?

[willyw]

Forgot to mention that I have attatched a magnetic temp guage to the oil filter and verified the temp readings

[kstylianos]

Unfortunately, the internal thermostat is located on the top front part of the engine, above your internal oil cooler. Your CIS will be in the way to see.



Well, its good to see you have verified your temps. At least you indeed have high temps and not chasing your tail.

[RoninLB]

Originally posted by willyw
I have asked about the trombone but haven't gotten an awnser. Is it an after market add on that connects to the oil suction line such as the ones you see in the parts catalogs?

"the trombone is better than nothing.. but not much better.. a full set up is serious bucks.. IMO, Elephant Racing stuff is ahead of the curve on oil cooling...........Ron"

it's a factory setup.....Ron

[willyw]

How about the aftermarket oil coolers that connect to the outlet line of the oil tank? Pelican has one listed as a compact oil cooler, price $250, do these work and what kind of temp results can I expect to see?

[kstylianos]

Willyw,

I'd try to isolate the cause of your overheating problem first. Adding an external cooler is a great idea, but will only mask your current problem. These cars should not be running at 280 during a casual drive. An external cooler is $$$, where a little troubleshooting, cleaning and possibly a internal thermostat will cost $100 max. Normal operating temps should be between 180 and 210 when its all sorted out.

[willyw]

Thanks Charlie, I will take the fan shroud off and see if there are any obstructions or other obvious problems. I will also "feel" the internall oil cooler bottom the next time the car is hot. I assume the internal oil thermostats function is to by-pass this cooler when cold and open to the cooler at a given temp?

[willyw]

Okay, ome more comment on this thread. Some of you say an 11 blade won't help much, some say it will help a lot. Can I here some feed back from anyone running a 5 blade as to what normal temp is on their car.

[Targa Dude]

Hi Willy, I have to agree with everyones comments and recomendations
But, I also believe that your high temp situation is far more than not having a eleven blade fan. Your 2.7 should be running around 200-210 at normal driving conditions with a five blade fan and trombone cooler. Besides checking your internal thermastat, Temp sending uint, External Thermastat, cleaning the Engine oil cooler as sugested, I would like to recommend you verify your timing is properly set , Verify CO Mixture is properly adjusted and make sure your fan belt is not worn and slipping.

Jorge (Targa Dude)

[willyw]

Jorge, thanks for the input. I have checked the timing and it is correct. I will look into the other things asap. My car has no trombone cooler, just the internal one. Should it have the trombone? I thought this was an extra and not on all cars.----Thanks, Bill