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My 88 Spider’s temp increases steadily after being at idle for more than a couple of minutes. If at idle 10-15 minutes (school pick up line yesterday) the temp warning light comes on and the gauge darn near maxes out. Oil pressure drops as well as it heats up at idle. Cools down And oil pressure increases once I get driving again. Should add that it was 100 degrees here in Oklahoma yesterday. Any thoughts on this?
Thanks so much!
Derek
 

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shouldn't heat up so much that the overheat light comes on, imo...even if it is 100F outside.
when it cools down again, check the coolant level....any missing?
Any recent work done to coolant system...and maybe forgot to bleed the air out?
your fan ok? not bust.....if recent engine work, was it put on backwards (its possible iirc)?
fan shroud still in place?

fan belt ok, not slipping?
waterpump ok, not noisy or leaking?
perhaps a stuck closed thermostat?
radiator needs a cleaning?

Get one of those cheap infrared thermometers (10 bucks worth) and check temperatures all around the radiator...any cool spot and it has a block

does it cool right down to normal once driving?
 

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Usually overheating comes down to 3 things. A bad thermostat, waterpump or radiator. Like Dom said a infired camera is a big help but an easy place to start would be the thermostat. Pull it out and put it in a pot of water. When the water temp hits 180 it should open. Also with these alfas taking 7 quarts of oil and the huge bottom pan often times if your driving around the oil can turn into coolant so I would reccomend an oil change.
 

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Make sure the cooling system is actually full of coolant. The way the recovery system is supposed to work is that as the engine warms up any excess coolant is pushed out to the reservoir. When it later cools down coolant is sucked back into the radiator. A defective radiator cap or faulty hose between the radiator neck & the reservoir can allow coolant to go to the reservoir but prevent its return. After a few heat/cool cycles the reservoir is full but the radiator is low.
 

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When was the last time you changed the coolant? If the pump isn't making noise or leaking, and the belt isn't slipping, at a minimum I would do a cooling system flush. Replace the thermostat and radiator cap, and fill with new coolant.
 

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Discussion Starter #7
Thanks for all the info. Not much of a mechanic but I’ll look at the couple things I can and at least I’m armed with ideas if I have to take it to the mechanic
 

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Repeated overheating is not something that aluminum heads enjoy. Take these "hi temp warning light comes on" and "temperature gauge goes to max" indications seriously before continuing to drive the car (especially in 100° heat).
I suggest pulling the radiator and taking it to a good, old fashioned radiator repair shop (not many of them left as EPA, OSHA and L&I have shut most of them down) and have them power flush and pressure test it. After thirty plus years the core is undoubtedly clogged and the shop can re-core it for you as good as new.
As a preventative measure it will save you thousands in head and engine rebuild costs in the long run.
 

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I would definitely check as noted above the fan is in the correct position and not on backwards and check for a slipping belt as well
 

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I am definitely thinking the electric cooling fan no working since it goes back to normal after driving.
The next time it gets hot, turn it off and listen to see if the electric fan is running. If not, could be the fan, connections, fan relay, fuse at junction box on left inner fender or the sensor that turns it on.
Let us know what you find.
 
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Interesting comment. My 84 S3 is always at the edge of overheating (i.e slighlyt off centre of the gauge) and I expect the fan to run once I remove the key but it never does which worries me a bit. Should the fan run even key off?

I am definitely thinking the electric cooling fan no working since it goes back to normal after driving.
The next time it gets hot, turn it off and listen to see if the electric fan is running. If not, could be the fan, connections, fan relay, fuse at junction box on left inner fender or the sensor that turns it on.
Let us know what you find.
 

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The S3 electric fan will run key-off, but it only runs based on engine bay temperature, not coolant temperature. Anyway, you should not need it to keep your car from overheating under normal circumstances. If the car's lighting the warning light you've got other problems that aren't the electric fan.

Slightly off center on the gauge is fine. On the monopod cars they'll usually run a tick to a tick and a half right of center. Thermostat on an S3/S4 isn't even fully open until ~203F (93C).
 

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Thanks. I never had the warning light on. I think I am around 190-200 on the gauge so borderline and this occurs only in very hot days. So, for off center gauges, should the fan run key off or not necessarily?

The S3 electric fan will run key-off, but it only runs based on engine bay temperature, not coolant temperature. Anyway, you should not need it to keep your car from overheating under normal circumstances. If the car's lighting the warning light you've got other problems that aren't the electric fan.

Slightly off center on the gauge is fine. On the monopod cars they'll usually run a tick to a tick and a half right of center. Thermostat on an S3/S4 isn't even fully open until ~203F (93C).
 

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Correct, it will run with the key off. One of mine(1985) started running 5 minutes after a drive while I was working on another next to it. I opened the hood and in a few minutes it went off.
All of mine tend to run around the middle of the gauge or slightly above. Not unusual. 3/4 I would think unusual most days.
 
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And frequently found loose and hanging in the air. I like the description "oddball thing"
1646420
 
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Just a thought ... You may have a head gasket issue - pray you don't. Here's a step by step set of instructions.

1. With the motor cool, check the oil fill cap. If the underside looks like a chocolate milkshake, you have water in the oil - very bad.
2. Take the overflow tank cover off and check the coolant. If it's green, you're good (the more neon looking the better). If it's brown, it's bad. Go to step 3. If you see nothing, you have a leak or a really bad head gasket. Don't run the motor until you fill up the system and bleed out the bubbles (I think your car will bleed itself automatically).
3. Turn the motor on with the overflow cap off. Watch for air bubbles - bad sign if you see them = head gasket.

Here's what may be happening. Hot exhaust gasses are being pumped into the cooling system via the leaky head gasket. At speed, the cooling system may have enough thermal capability to cool the motor, but at idle, the pump is turning slow and the coolant will have hot spots. Even with the electric fan trying to push air through the radiator, it may not be enough to overcome the heat coming through the head gasket.

I hope I'm wrong.
 

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The S3 electric fan will run key-off, but it only runs based on engine bay temperature, not coolant temperature. Anyway, you should not need it to keep your car from overheating under normal circumstances. If the car's lighting the warning light you've got other problems that aren't the electric fan.
Make sure the cooling system is actually full of coolant. The way the recovery system is supposed to work is that as the engine warms up any excess coolant is pushed out to the reservoir. When it later cools down coolant is sucked back into the radiator. A defective radiator cap or faulty hose between the radiator neck & the reservoir can allow coolant to go to the reservoir but prevent its return. After a few heat/cool cycles the reservoir is full but the radiator is low.
Overheating or running at extreme temperature will cause havoc with an engine. Tom makes a great point. The car should be able to cool properly without the assist of the electric fan. Eric point is also a good one. A bad cap will not allow the engine to cool properly.
Old coolant losses its ability to cool properly by having a lower boiling point over time. A faulty thermostat may not be opening completely and restricts the volume of coolant that circulates. Most noticeable when the car is at idle and the water pump is turning slowly.
I still think that the best place to start would be with a system flush, a new radiator cap, a new thermostat, and fresh coolant.
 

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My only suggestion would be if the mechanic (if your troubleshooting leads you to taking it into one) suggests removing/cleaning the radiator, I would go with a three-row core versus the two-row. For me (in SoCal), on hotter days the temp gauge needle moves a little off-center, but I haven't had a overheating concern since going to the three-row core.
 

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Definitely check if the fan shroud is still installed. Some owners remove them because the fan sometimes hits it when the motor mounts begin to wear out.
 
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