Checklist for reducing heat in hot-running engine.

[pgsandiego]

I added a euro premuffler in place of the cat in an attempt to run a bit cooler (less exhaust restriction). It seems to run about 10 degrees cooler. Not huge, but every little bit counts.

Too bad about the synthetic oil. I thought Id read it helps cool a bit and was on my "to do" list. I guess now I'll wait until the next scheduled oil change...

Patrick

[RoninLB]

Originally posted by Chuck Moreland

Trombone won't respond well to inceased airflow. The Carrera cooler will.

ditto..
180deg oil temps are nice. Actually I usually run a bit less than 180 except on 90+deg/3.5k+ in 5th gear days.

Does anyone know what the max CHT's are Designed by PAG into our cars? I'm speculating around 350deg?

[RoninLB]

Originally posted by Jim Richards

Also, for cars older than 1977 (?), I think the air deflectors will need to be modified to the later design (remove some metal) to get better airflow.

Hi Jim..
I had to snip my deflectors. I'm not sure if it's directed at only CHT or + small oil temp drop. CHT control is very important imo.

[RoninLB]

Originally posted by Grady Clay

There has been some discussion of a fan pulley size of 80 mm as opposed to the published 84 mm fan pulley diameter. Who can shed some light on that? What years, models, part numbers? If there are standard Porsche parts available with an even smaller fan pulley the overall ratio might be 1.9:1.

I figure you have this already. I don't have the dia's

[fireant911]

pgsandiego,
I would not be too hasty about dismissing the ability of synthetics in reducing the oil temperature. Reducing friction will in turn reduce temperatures which is one of the advantages of synthetics. I would visit Mobil 1's web site and do some informative reading about the subject and make my own decision first. My car(s) responds extremely well to Mobil 1 - not everyone here agrees but it is certainly worth looking into. My daily driver gets 3-4 extra miles per gallon when synthetic is used (I have been keeping records since I purchased the car in 1995) and it is my belief that this can be attributed to the added lubricating properties offered by synthetics. The Porsche leaks no more with synthetic than with conventional oil.

[Bill Verburg]

For those that don't know, the tin mod was incorporated in all 911 and 930 engines built from March '77 on. Earlier engines should have this done.



I also recommend the '76 -'77 pulley w/ '84- fan. This will give the large ratio and the fan has additional cooling slots for the alternator.

Of course a nice big cooler never hurts. Best power will come from keeping temps in the 180&degF - 210&degF range, some like it hotter to boil off condensates, but they do boil off at lower temps, it just takes a bit longer.

[Grady Clay]

I agree with Bill V. There is great advantage to the thermostatically controlled oil systems. On 911s with the front cooler there are two independent thermostatically controlled coolers – one at the engine and the other in front. Both operate in the 180-210F range. The issue is the coolers are not of sufficient size and air flow to dissipate the necessary heat. Consequently the temperature rises into the 275F+ range in order to dissipate that heat.
As Bill points out, it is very important to get the engine to operating temperature to boil out the contaminants (mostly gasoline & water.)

Changing the fan arrangement dissipates the heat not via the oil system. It’s too bad Porsche didn’t develop a thermostatically controlled, variable ratio engine fan. The technology certainly exists.

Yes the ’84- fan with alternator cooling slots is desirable (necessary) for the larger capacity alternators. This brings up another issue when fitting the 245 mm fan to SCs originally fitted with the 226 mm fan (’78-’79) – you must also change the fan housing. All fan housings are not equal. Starting in the late ‘70s, the housings were machined progressively deeper to accommodate the larger alternators. You need to have the correct fan housing to match your alternator.

Best,
Grady

[barlowdo]

"I think mine are black, perhaps coated......are they supposed to be bare bronze/copper?"

I think you want to keep them black to act as a "Black body radiator"- to draw the heat away from the oil. And remember- correct me if I am wrong -but I believe oil does not transfer heat as efficiently as water.

-Don B

[kach22i]

Originally posted by 911pcars
The problem with the trombone cooler is insufficient surface area. If you braze fins onto the tubes or lengthen the coil, it will dissipate more heat, but it still won't be as efficient as a properly engineered oil cooler.

Sherwood

There is the right way, then there is the "let's try this and be different" way. I have paid that price too many times.

[kach22i]

Originally posted by fireant911
pgsandiego,
I would not be too hasty about dismissing the ability of synthetics in reducing the oil temperature.

I think synthetics in an old car is pure evil. However it does flow better, right out of the seals sometimes.

I believe the oil designed for high miliage cars will make the car run hotter, and synthetic will make it run cooler...........but that's just my theory.

I did try a tank full of regular gas once, I swear it ran 5-10 degrees F. cooler, but also had a bit less power.

Nothing like a cool day or a little rain to cool things down.

[JMPRO]

How about an electric driven fan. The motor could be hooked up to a transducer the is controlled by motor rpm like a tach.The controll could be adjustable to overdrive the fan or even a delay to slow the fan behind the rpm of the motor for additional cool down . You might even free up a couple of hp with the system.
Jerry

[Jdub]

Well here are results of my "research" yesterday. I drove to a bicycle race about 50minutes away. Going down, ambient temp is 86degrees. Car oil temp gauge comes up to 9o'clock exactly and moves slighty up from this only when I rev the car higher: shift down to fourth, or third, and get some speed. Funny thing: stop and go, the temp drops back down to horizontal. Revs seem to increase the temp. I had Grady's advice in mind and was trying to stay same road speed/higher revs. Seems to raise the temp on my car.

Going back later in the evening, has cooled off to upper 70's. Same temp all around, same results in rev testing.

Seems my car likes that temp. I think that the engineers at Porsche must have used my car, my area to create that gauge cause if you didn't know any better, you'd think the car was operating at perfect operating temp.

I am off to put a Carrera oil cooler in and switch to synthetic. I won't play this game.

Anyone have a clean Carrera cooler for sale?

John

[wente]

No one has mentioned this, but cleaning your engine mounted oil cooler should be on the checklist. I recently cleaned my 87' engine cooler and achieved about a 15 degree drop in oil temp. I didn't do an engine drop or
anything that involved, just pulled the fan/alternator. Scrubbed the cylinder fins with a brush, then attached a small tube to the end of a can of brake cleaner and stuck it down the air scoop to the engine oil cooler. Sprayed a bunch in there, waited, put the garden hose in the scoop and watched flakes of greasy crud come out of the cooler. I repeated that several times, and also used some simple green. worked like a charm! We have cottonwood trees here, so I was always suspicious that my cooler may have become clogged up with fuzz on top over the years....

Ellsworth

[Randy Webb]

Yes, it's a good idea to clean the outside of the engine-mounted cooler, all the cylinder fins, and any remote coolers.

[Grady Clay]

Ellsworth,

Welcome to Pelican. Great recommendation.

For those more adventuresome, it is also easy to remove the engine oil cooler with the engine in the car.

What was the condition of your cylinder fins? It is a reasonable assumption that your head fins are similar.

Best,
Grady

[Jdub]

How easy is it to remove that engine-mounted oil cooler? I'd guess that would be something to do during a valve job/oil change.

Am I looking at removing fine-thread oil hose that might be stuck in place? That is a bit of a nightmare!

John

[Grady Clay]

John,

Good point. The ’66-’71 911s have a thread fitting hose to carry oil from the sump to the intake of the pressure pump via the large aluminum tube that is below the cooler and part of the structure. That fitting may be very old, some were steel on aluminum and others were aluminum on aluminum. Great care should be exercised when attempting to detach these fittings. Undoing this fitting is necessary for engine removal so you should maintain it in good condition. Often the fitting is seized at the cooler and mechanics will disconnect the oil hose at the tank.

So long as you can get one end disconnected, the oil cooler removal is relatively easy. Everything else is just tin removal (usually three pieces.) You will want to have new case-to-cooler seals (3).

Best,
Grady

[wente]

Am I correct in the assumption that the engine mounted cooler on my 87' carrerra requires a partial engine drop to get to the top bolt? I chose to not remove it and go the route of just cleaning it... Isn't it true that it's easier to get the cooler off the older 70's cars?
I picked up a set of the o-ring seals and I plan to take cooler off the next time I go in deep for a valve adjust/oil change. Figure it has 130k on it, probably could use a good internal cleaning.
Grady, thanks for the welcome... been lurking here for years and living over at rennlist, just never got around to registering! My cylinder fins were actually very clean, just gave them a quick brush while I was in there. The oil cooler had some stuff in it, and had a good greasy coating on the underside from a P/O oil leak.
Ellsworth

[ga_mueller]

I pulled and cleaned the engine oil cooler on my Carrera a couple of months ago without partially or fully dropping my engine. Bentleys has a fine set of instructions. It took about 4 hours, and it was incredibly filthy. Now I can tell that I really DID fix all those oil leaks from the back of the motor!

[Grady Clay]

ga,

Can you post a step-by-step for wente and others. You can do it far better than I can.

Did you do anything other than cooler to address oil leaks at the flywheel end of the engine?

Best,
Grady