jeff jackson

As Jim Bailey pointed out....the correct therrmostat o ring is very important to getting a proper seal at the rear of the housing assy....BUT...the sealing gasket at the rear of the housing is equally responsible for creating the flow through the radiator, and NOT just recirculating the coolant in the block. And I suspect lots of folks do the Tstat and flush and refill tricks, but totally neglect the poor old OEM seal at the rear of the housing. At least thats what I found was the overheating culprit on my 4 previous owner 86.5...Good luck.

ErnestSw

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Bill51sdr

Belushi! Animal House!! You remember, when Dean Wormer finally threw 'em out...

TAREK

Do you have an update on this? did you get the chance to replace the water pump and verify ?

deliriousga

Pop in the exhaust signals unburned gas to me. Rolling down the cat. then small explosion. Really scary if more starts rolling down.

Rich9928p

Is the fan clutch working? You need air pulled over the radiator for cooling.

Also, don't over look a clogged radiator, it isn't too difficult to pull the radiator and have a flow test done. Lets hope it isn't that. You've got one shot at removing the side tanks and having it rodded out, after that the radiator tabs may be too week to be rebent and hold the side tank lids on.

AJK

One more vote for a seized water pump. Remove one of the air ducts going to the air filter so you can look at the timing belt. If the pump is seized you will see tons of rubber bits (from the shredded belt) and the back side of the belt will be heavily scored.

kshipp

I'm having a similar concern, but mine is not completely overheating.
History: This has happened consistenly since my last TB retensioning. I also had the other belts replaced. This was approx. 1 month ago.

Observation: Going down the interstate it creeps up close to the last white mark (190 degrees?). If I sneak up to 75 or 80mph (accidentally of course ), the gauge will be on top of the last white mark. Fortunately, it hasn't gone past that last white mark. Coolant level is fine, no leaks. After returning to idle or slower speeds, it will cool to somewhere between 1/2 and 2/3.

I must admit, I know little about the cooling flap. Could someone give me some details on what to look for/verify the flap is working correctly?

Any other suggestions? Thermostat likely the culprit?
Forgive the mechanical ignorance, at least I'm trying.

shaaark89

kelly,
the '91 my doesn't have the cooling flaps. they were deleted after the '90 my as far as i can recall.

dr bob

Kelly, the fact that it warms up as you go faster points to either a partially plgged radiator of a WP with a slipping impellor. My vote goes to radiator problems since that part suffers most from neglect. As Rich suggests, you get one reliable shot at taking the end tanks off and cleaning the original core. Reminder also that this is a job that requires a big clamp, so it's not a DIY project. 928 International (www.928intl.com) sells the tank seals that your radiator shop will need to reassemble the tanks. They will also leak-test the finished unit with air, drown it in water to look for leaks (bubbles...) before you reinstall.

I use low-dosage coolant (30-40%) in distilled water, and a bottle or two of Redline Water Wetter to make the most of the cooling capacity. It never freezes here though, so take that low-dosage recommendation with a grain of salt.

And last but not least-- the target operating temp on the S4 is 190-195F. By my best guess eye, that's about the third mark on my S4. On the hottest days with the AC on, mine will go a needle-width or two above that for brief periods. Otherwise it sits at just below that third mark when warmed up.

Reality is that the gauge is not really 'calibrated', but is there more as a reference. It will run a little higher when it's hot out. a little higher still with the AC on. That's normal. If you start to see a big change from where it's been ruinning, that's the time to get more concerned. Watch the trend and decide what's up, and whether you really do have a problem.

Rich9928p

To amplify Dr. Bob's post. If it is not in the red, it isn't too hot! Everyone gets paranoid if the needle in at the 2/3 mark or higher. This may be a rational fear for a ford, chevy, or other auto, but Porsche decided to calibrate their gauges this way - I think more so in S4s ... though my '87 seems to register a bit higher than my GTS.

It is perfectly natural for the temperature to go up as you go faster, especially if you are climing a grade and it is warm out. The engine is putting out more power, therefore the radiator has to move more heat, and the temperature will rise. My recommendation is that if you see the needle rise, let up on the power and determine if it falls. If it does, go back onto the throttle as you wish but keep it a needle width (or two) below the red zone - how, by keeping the speed down to where the needle stays constant.

Duing my last trip across I40 past Needles there was a very long climb, problably over 2000 ft. It was a hot day, the A/C was up on max, and I regulated my speed according to temp (80 - 90 mph). After we reached the summit, the temp dropped down to normal (a little above the 2/3 line) and all was well.

That is how I drive, and my stable has survived. YMMV.

kshipp

Thanks Tom, Bob and Rich! You guys are great!

Tom - I didn't think I'd seen any flaps, but I didn't want to seem to ill-informed of my mechanical expertise.

Bob - excellent info. I'll keep a watch on the needle and radiator.
Rich - great info. I feel much better now. Ironically, the increase in driving temp just happened to correlate to the rising temperatures of early Summer.

For now, I'll accept it as the norm but keep a close eye on it during hot days at speed.