Boxster overheating, need advice

[e_room_matt]

2000 Boxster S with 97K miles.

Very recently the temperature gauge warning light starting flashing (from start, regardless of engine temp).

Assumed I had a bad water pump or thermostat as those had never been changed on the car. Both have now been changed along with the coolant and oil, but the problem persists. Engine is indeed overheating after about five miles, so it's not a faulty gauge.

Only odd thing I noticed during the service was the coolant came out very inconsistently during draining over the course of an hour. Like a guy with a bad prostate, trickling for a few minutes, the going back to a stream. Leads me to believe I have either some blockage or air pockets in the coolant system.

Any other theories or advice?

[CarGuyNeil]

Air pockets could indeed indicate over heating if a pocket of air is trapped by the sensor. It could also be a bad head gasket. Usually you'd get a mix of coolant and oil which could show up in either. Did the coolant look like it had oil in it? Does the oil look like it has coolant in it? Does the coolant bottle smell of exhaust fumes? Otherwise look for the proper bleeding procedure for the cooling system and try that.

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[e_room_matt]

Coolant definitely had oil in it but I didn't think much of it because I drained it into my oil pan.

[e_room_matt]

If find it suspicious that the car knows immediately that something is wrong from the start before the engine even heats up. What triggers the temperature gauge light beyond temperature itself?

[JFP in PA]

Originally Posted by e_room_matt

If find it suspicious that the car knows immediately that something is wrong from the start before the engine even heats up. What triggers the temperature gauge light beyond temperature itself?

Four functions of the coolant warning light:

1. Engine coolant level too low
— light flashes slowly (0.5 Hz)
2. Engine compartment temperature too high
— light flashes slowly (0.5 Hz) (engine compartment blower might be faulty)
3. Engine coolant temperature too high
— light is lit; pointer on the right
4. Temperature sensor at water outlet faulty
— light flashes rapidly (1 Hz); pointer on the right

Note
The temperature warning in point three is indicated if the conditions "engine coolant temperature too high" and "engine coolant level too low" are present simultaneously
(1Hz = 1 flash per second. 0.5Hz = 2 seconds per flash)

[tonythetarga]

Originally Posted by e_room_matt

Coolant definitely had oil in it but I didn't think much of it because I drained it into my oil pan.

This is not good. If the car severely overheated, even once, then the head can crack. That is a main reason for coolant /oil intermix. It sounds like you overheated and now oil gas gotten into the cooling system. The options at this point are limited for your engine. You need a proper diagnosis. Don’t run the engine any further.

[CarGuyNeil]

Originally Posted by e_room_matt

Coolant definitely had oil in it but I didn't think much of it because I drained it into my oil pan.

They can do a hydrocarbon test for exhaust fumes in the coolant, which would signify a head gasket failure or cracked head. I think Auto Zone has a kit for rent to test that if you want to do it yourself.

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[ASD]

check your coolant tank for cracks, common issue.Underneath it too