Walk me through the cooling system? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Hey y'all: I was going to drive my car to the office today, after finishing reinstalling the motor last night. I let it idle for a bit while I was getting ready to go. When I got int he car, the temp gauge read 180d, on the nose. about 1/2 mile down the road, the red light on the temp gauge came on and started slow-flashing at me. I turned it around and took it home and parked it. I did notice that the cooling fans weren't on. Now I'm here at the office scratching my head. Wondering what I've jacked-up, but can't test or look at anything. Maybe someone will indulge me with a walk around? It's possible that I hadn't completely burped the coolant system. IF THAT's THE CASE: what initializes the cooling fans? Where is that sensor located? Could low coolant levels keep those fans from engaging, even when the temp gauge is climbing and the red-light is on? Is the red-light a separate sensor from the gauge? Somebody walk me through these components, please? :dance:

Hey Maytag Sounds like you didnt burp it completely. Keep the valve open and drive it keeping some coolant available for refill. Just happened to me. The best way however is to use a vacuum fill setup where you pull vacuum on the coolant tank and then let the coolant get sucked in. Coolant temp sensor is on the driver side oil pump manifold in the front of the engine. The coolant tank has a level sensor that sets off the red light on the temp gauge.

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aaaahhhhh..... very good. Is that single temp sensor responsible for the Gauge as well as the fans coming-on? And also the engine compartment purge fan?

AZ986s is probably right. Try re draining the fluid into a very clean container so you can reuse it and use a vacuum system to check for leaks and refill. I bought a vacuum system from Amazon for $60 it makes refilling with out air pockets so much easier. I still left the bleeder open for a few days but only had to top off a cup or so of coolant. Cheers

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The engine compartment temp is measured by a different sensor located at the green arrow in the photo (courtesy of our forum sponsor)...

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).

My guess is that you need to burp the system. The Pelican site has good directions for doing that. I followed the directions and was successful in not having any further issues.

Thanks everyone. I should've followed-up the other day. it was indeed in need of a better "burp", haha. I see the various sensors & such now, but it seems everything started working correctly once I got the system burped. (I think I just hadn't gotten it hot enough for the engine purge fan to kick-on... I only THOUGHT I had, because I didn;t realize the red light was about coolant level, not temp, haha) In the last 2 days I've put-on around 250 miles on the motor, and everything seems to be shaking-out correctly. I think I may make the PCA D.E. event this month at UMC, at least for one day, and see how everything feels. There's a NASA day I'd love to get to as well. And then I'ma roll 'er back into the shop for some coilovers and some other cosmetic fun over the winter. :dance: thanks everyone for your responses and help !!

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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!

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+ 1 Wonder if this applies to the 9A engine type as well. PS Great news Maytag! .

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?

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.

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Thanks for searching before posting !