Most stupid newb question ever?
 

Okay. There may be no such thing as a stupid question but there are stupid people who ask questions! So, here goes.

Could someone explain how the coolong system works on the 911sc? I see the fins on the cylinders. Is that the only cooling? What's with all the oil? I get that it's a dry sump with a tank and that oil is passed thru some sort of cooling device. (Trombone, Carrera fan oil cooler, etc.)

Then I see some hoods up and there's a radiator. I assume that's cooling oil? Is the fan drawing air in across that oil?

I guess there's no "coolant" but the fact the the oil is cooled allows for air to maintain tolerable temps?

I need a basic rundown of the relationship between all that oil and air cooling. I plan on buying an 80's 911 and don't want to be a complete doofis!

You've got air and oil as the two cooling media for old (pre-1999) 911s. No green liquid coolant.

Cooling fins on individual cylinder barrels: for air.

Oil and the front-mounted cooler: for oil.

You've pretty much got the basics right in your post.

"Then I see some hoods up and there's a radiator. I assume that's cooling oil? Is the fan drawing air in across that oil?"

Perhaps the 911's you have seen with the "hoods up" with the "radiator" were Turbos? Was it the rear lid that was up? In that case the "radiator" is an intercooler to cool the compressed air from the turbocharger before it goes into the cylinders.

Oh. Yes it was attached to the hood with flex hose on either side.

"Then I see some hoods up and there's a radiator. I assume that's cooling oil? Is the fan drawing air in across that oil?"


What you saw was the rear condensor for the air conditioner. Cars with no A/C will (of course) not have them.

Don't worry about stupid questions!

he's probably looking at the AC condensor.

Actually, those are great questions. I'll do my best to help.

1. The fins on the cylinders help dissipate heat. The large fan located in the "front" forces air to flow over the engine, also to aid in cooling.

2. The oil system is designed to allow the oil to flow through the lines to a cooler, most times located in the front fender(s) in a high pressure area. Like a radiator, it cools the oil as it flows through and back to the engine. A thermostat controls the oil flow to the cooler based on the need for cooling.

3. On 911s with a/c, the condensor is located inside the tail or deck lid. Again, this is for air flow. On intercooled turbocharged 911s(the 930) the air to air intercooler is the other radiator type device located on top of the engine.

I'm sure some details were omitted but I hope this helps a little. Do some research and you will be an informed buyer and get the best 911 for the money. Remember, get a PPI before making any deals. PPI=Pre-purchase Inspection.

There's no such thing as stupid questions!

(Just ignorant people making inane inquiries). ;)

Thanks for the info/clarification. I was so close last year to buying and then circumstances changed. Now I'm pretty close to back on track.

So, all that oil allows for a circulation loop that lubes and then gets cooled. The shear quantity provides time away from the heat created during lubrication. In other words, it doesn't really take 10 qts. of oil to lubricate the motor, it takes 10 qts of oil because you have to keep exchanging the heat out of it. (That's actually a question! :D)

Wouldn't "oil-cooled" be a more appropriate name or does the air provide the majority of the cooling and the cooled oil just helps out?

Right. Dont know why.... the first thing that came to mind was a Turbo :o

I havent owned a 911 with A/C in a long time ! Kinda forgot about that. Maybe we should mention here...dont expect it to put out as much cool A/C as a Crown Vic .

Let's not forget the primary oil cooler that bolted to the side of the engine case. The secondary oil cooler (radiator or trombone) is the one located in the front pass fender well.

A primary? That makes sense. I was wondering how these little fender coolers could provide adequate cooling. How does it work?

Once the oil reaches a certain temperature (I believe somewhere in the neighborhood of approximately 200 degrees fahrenheit), the heated oil activates the auxiliary oil thermostat which is mounted above the right rear tire. The auxiliary then allows the oil to pass through on its way towards the secondary oil cooler, which is mounted in front of the right front wheel.

Once the oil has worked its way into the front (secondary) cooler, the oil is basically radiated throughout and is aided by 1) air which passes through a slit in the front bumper, and 2) a fan, if you have a Carrera or a Carrera fan upgrade.

Here: This is good for hours and hours of cool reading. You can search whole threads or just for specific words in the thread titles. Good stuff!

http://forums.pelicanparts.com/uploa...1294887985.jpg

What about a primary?

primary oil cooler looks similar to a radiator, and is located on the lower portion of the engine on the right hand side near where the engine and tranny meet. Oil flows through this cooler at all times while the engine is running, then splits the cooling duties with the secondary cooler as oil temp reaches normal operating temps.

BKC:

You might consider buying a book on the technical aspects of the 911, possibly The Porsche 911 Story by Paul Frere. It's not a manual, rather a description of the technical history of the car. The Porsche 911 Buyer's Guide might also help you to find a good car.

Frank

Like the others said, you can do lots of reading. Ferre's book has lots of technical information. To help you a bit, below is a diagram of the oil system.

http://forums.pelicanparts.com/uploa...1268777877.jpg

Do not even think about buying a Porsche without PPI (pre-purchase inspection) by a highly competent mechanic. It will save you thousands of dollars and countless sleepless nights.