Walk me through the cooling system?

[JFP in PA]

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)
So it might be the temperature sensor is faulty (if the light is rapid flashing).

[maytag]

Originally Posted by JFP in PA

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)
So it might be the temperature sensor is faulty (if the light is rapid flashing).

As always: very helpful. If I were still chasing a squirrel around that engine bay, this would've made all the difference in diagnosing. I'll stash this in my "reference library". Thanks JFP!

[Gilles]

Originally Posted by maytag

As always: very helpful. I'll stash this in my "reference library". Thanks JFP!

+ 1

Wonder if this applies to the 9A engine type as well.

PS Great news Maytag!
.

[besturgeon]

Thanks for the info...my 2004 986 has had cooling issues. I recently noticed that the coolant tank would be full when cold, and then after it is up to temp (190 deg F), the tank level would drop and the red flashing light on the temp reading would come on. This, i think, indicates that there is a "air void" that gets compressed (and replaced with coolant) when the temp goes up...and hence the the tank level drop. I have and will continue to burp the system until this decrease in coolant tank level is no longer observed...does this make sense?

PS. where did the red flashing light info come from...Bentley Service Manual?

[besturgeon]

i now believe that i have removed the air from my coolant system...warned up the car and rev'ed it to 5000 rpm a few times...then i needed to fill the reservoir with another 1/2 gal of coolant. Seems to be fine now. Thanks for this thread.

[BYprodriver]

Originally Posted by besturgeon

i now believe that i have removed the air from my coolant system...warned up the car and rev'ed it to 5000 rpm a few times...then i needed to fill the reservoir with another 1/2 gal of coolant. Seems to be fine now. Thanks for this thread.

Thanks for searching before posting !