Just got my new to me '93 Polo/Tan conv.
Very clean car, 59K, Auto,
Had the coolant changed as I had no idea how old it was
(looked fine) and drove it to work (8miles) without issue.
Sitting in the parking lot for 5 minutes idling I notice the
coolant temp gauge at the 3rd notch and rising. Shut car
down and return to shop after work who changed coolant. Shop re
flushed/changed coolant, bled system at top of engine and
all seemed OK after several minutes of idling but overheat
returns. I know that:
The coolant is moving in the tank.
Should be no air in system.
Fan does operate when defroster turned on as it should.
Car returns to normal temp after driving short distance
at 30-45mph.

It was suggested that a new thermostat is needed.
If so why does it cool down driving it? Cooling down
means thermostat OK by me.
I'm stumped. My only thought is that the fan is not
operating when it should. It does go on when
defroster turned on.

When I drove the car from Wisconsin Saturday no such
issue but it never sat around idling, it was going 70 for
400 miles.

The new fluid is green as it should be for this year.

Thanks for your opinions.
Craig

When you say overheats, just how hot does it get? They actually tend to run pretty warm and 230-240 doesn't seem to be out of the ordinary when sitting still. These cars are bottom breathers (intake under front bumper), and air flow is not the greatest when sitting still. Another thing that you might want to check is the build-up of junk between the AC condenser and radiator, because they also tend to act like a vacuum cleaner and suck up all sorts of road debris.

There is a tech tip on how to remove the radiator and clean the junk out. Here's one that I wrote and posted on "another forum". http://www.crossedflags.com/nuke/html ... =&order=0&thold=0

I would bet there is air in there somewhere.

The t-stat will make it run super hot... or not... realize that the t-stat does not regulate temperature, it only says how hot the coolant has to be before the engine is at full temp. I agree, if the temps drop as you move, the stat is more than likely ok.

I would be sure that the intake area is clean. That is a real killer. Debris gets stuck between the radiator and the AC condenser.

I also suggest adding a bottle of Red Line Water Wetter. It works! It chemically reduces the surface temperature of the metals so the coolant can better transfer heat. I use it, and it works!

A properly functioning cooling system should not exceed 200F during regular use... and if you are cruising along, 195F is normal.

A question, did you press the gauges button to see what the digital temp was reading? There are 2 temp sensors on the engine, one on the front of the waterpump (digital, ECM feed) and the other is on the right head (between plugs #'s 6 & 8), this one feeds the analogue gauge.

From where I am sitting, if the analogue gauge was reading hot, and the digital was not, then I would bet money on it being an air bubble.

If the digital was reading hot, it would light up the IP with a "check gauges" warning.

Oh, with these cars, the AC will fire up the fans, not just the defrost. If you have C68 (electronic climate control) the AC is on all the time, regardless of heat/cool. It provides humidity control, too.

A lot of people freak out at a temp reading around 200* but when the temp is taken at the cyl head this is fine. remember if not in this range you will not make good power. if you are not pinging you are not overheating. This is not always an audible ping, knock many times is inaudible and can be seen by timing being taken out by the esc system idle/load vehicle while on a machine or timing light and wait. Too low of a press cap can give you steam pockets as well. Aux fan may be working but not main fan. ALOHA