kevinlieb

Personally before doing the rad flush I'd check the operation of the fans and flaps and perhaps pressure test. If you do the flush and still find there is an issue you might have to drain and refill again, wasting a lot of coolant (unless you are set up to drain cleanly and reuse it, I was not).

flyrade

And why do you recommend the stock 83 C thermostat vs. the 75 C? It seems to work well here in FL and the temp gauge is right in the middle, or slightly cooler.

Bilal928S4

Check this thread to see what a cool running engine looks like from the inside.
https://rennlist.com/forums/928-foru...zed-motor.html

Tom. M

That GT was running the stock 83 C thermostat...so unlikely the cause of the carbon buildup. More likely oil ingestion and not running it hard enough

Hilton

The counterpoint is, why do you think that Porsche's choice to use an 83 degree thermostat was wrong?

jon928se

Good that you found what I believe to be one of the most common causes of overheating in S4+ 928s. Quite often this cause is not apparent with the car stationary as the plastic guides move back to their proper position with no airflow.

flyrade

I would not say Porsche's use of an 83 deg. thermostat was wrong, but I think there could be better choices depending on the local operating temp. When I was stationed in Germany it was always cold, and I'm sure an 83 would work fine. However, I live in FL, and as you know, we have been having a heat wave down here - even for the winter. Also, I'm looking ahead to the summer when it could be even hotter. I think my philosophy is to keep the engine as cool as possible - but within normal operating limits. So far, the 75 deg seems to be doing it.

sendarius

I am not sure that you understand how a thermostat works, or why it is in there.

At "normal" to "hot" environmental and operating temperatures, both a 75° and an 83° thermostat will be wide open. At these temperatures, the thermostat is doing nothing to regulate engine temperature.

Where the thermostat "does its thing" is when the environmental temperature is low enough that the engine doesn't NEED the cooling system, or the engine is not at operating temperature.

In other words when the engine operating temperature is BELOW where it should be, the thermostat bypasses the cooling system to speed engine warm-up.

In a cold environment, it is possible that the engine will either
a) NEVER warm up to operating temperature, or
b) not stay at optimal temperature,
if the cooling system is being used.

In this regime, the thermostat will be determining the MINIMUM operating temperature of the engine, by opening and closing coolant passages, and thus activating and bypassing the cooling system.

A lower temperature thermostat has NO effect on maximum temperature.
It ONLY aids in engine warm-up and affects the MINIMUM steady-state engine temperature in cold environments.

Chalkboss

Call me simple-minded, but on a basically stock vehicle I choose to accept the wisdom of the manufacturer's engineers. I used to own old VW busses and was amazed at how many people threw out random cooling tin because they they thought it was not needed. Then folks wondered why they had cooling issues. Same principle: Trust the experts.

FredR

I live in a very hot climate, I have the run the 75C theromostat for several years and have decided to dump it- why?

1. The S4 onwards fan programme is designed for an 83C thermostat. In cool weather the motor struggles to reach 80C on the gauge and with the fans running if the a/c is on it struggles to warm up. In summer in makes no difference when things heat up a bit more.
2. The temp gauge shows white lines and red lines. Unless you cross into the red zone what is the big deal? I always feel that my motor is not optimal until the needle hits the last white line.
3. Everyone knows you do not work the motor until the engine "warms up" so what is the definition of warmed up? - presumably when the thermostat is fully open and the cooling system is cooling. Thus we are looking to control the engine temperature within a narrow band acceptable band- not too hot and not too cool- I think Porsche got this one right just that a stock cooling system is challenged in a hot climate when you work the motor hard, have the a/c running and things such as cooling system cleanliness are less than perfect.

Regards

Fred

69gaugeman

I agree with this. In fact if they had a higher one, I would be inclined to use it. Many people simply do not take the time to understand what a thermostat is for. Engines running cold WILL build up carbon.

I agree that my engine was ingesting a lot of oil to create that much carbon, but if it was running cool (thermostat sticking open, etc) it wouldn't burn off the carbon.

Almost all engines I have ever worked on had a 88 or 90 degree thermostat in them. All my Audi's and VW's run at 90 degrees

This is all true...

Tony