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Old 05-28-2014, 04:05 PM   #1
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Slow blinking coolant light diagnosis

It's getting hit here in AZ and on my way home today I had a slow flashing coolant light. I just cleaned the radiators and the car was running at a reasonable temp, around the middle. After quick research it is likely engine compartment overheat or low coolant. It has not cooled down enough to check the level and I suspect it's the engine compartment temperature that is causing the light. For the first time ever, after the car was off and the key was out the engine compartment fan kicked on and I could feel air coming out of the passenger side vent. The air was of low volume and not very hot. I have a dura metric.

Looking for additional insight into how this system works, troubleshooting and possible repairs. To date I have done all my own repairs. More specifically is there a temp sensor that could be bad? Since the fan is working, are there more than one or is blockage a possible cause. Any insight from those that have gone down this path much appreciated. With the durametric I'm assuming I should be able the manually turn on the fan. Are there other test? Thanks

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Old 05-29-2014, 02:28 AM   #2
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Originally Posted by runjmc2 View Post
It's getting hit here in AZ and on my way home today I had a slow flashing coolant light. I just cleaned the radiators and the car was running at a reasonable temp, around the middle. After quick research it is likely engine compartment overheat or low coolant. It has not cooled down enough to check the level and I suspect it's the engine compartment temperature that is causing the light. For the first time ever, after the car was off and the key was out the engine compartment fan kicked on and I could feel air coming out of the passenger side vent. The air was of low volume and not very hot. I have a dura metric.

Looking for additional insight into how this system works, troubleshooting and possible repairs. To date I have done all my own repairs. More specifically is there a temp sensor that could be bad? Since the fan is working, are there more than one or is blockage a possible cause. Any insight from those that have gone down this path much appreciated. With the durametric I'm assuming I should be able the manually turn on the fan. Are there other test? Thanks
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)
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Old 05-30-2014, 04:47 AM   #3
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The engine compartment fan does work and the vents on both sides of the car are not blocked in any way that I can see from the outside.

I plan the check the entire system this weekend. Does anyone know where the engine compartment temperature sensor is located and if there are other components between the sensor and the engine compartment fan? Thanks!
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Old 05-30-2014, 08:49 AM   #4
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Probably just a little low on coolant. Happened to me last year, the sensor is very sensitive.
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Old 05-30-2014, 01:30 PM   #5
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I wish it were something simple but the symptoms are more consistent with an issue with the engine compartment cooling system.

The coolant level is near max, the light started to blink well into a drive on a hot day and after turning the car off I heard the engine compartment fan run for the first time.

I suspect either the sensor is telling the system the engine compartment it is too hot (185 degrees?) when it is not (such as the sensor move to an area that is more hot) or the engine compartment system is not operating efficiently.

Since the fan does come on an inoperative fan is ruled out…

Again, any insight into the components of the engine compartment cooling system, and how they interact, appreciated…thanks!
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Old 05-30-2014, 07:42 PM   #6
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Your coolant's probably low.
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Old 06-03-2014, 02:47 PM   #7
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Just had the chance to hook up the Durametric and I think I understand the nature of the issue but will need more time to figure out the cause and correction.

Some details. The engine compartment temperature can be monitored real time. I started the car and let it idle. The temperature (all engine compartment) slowly rose to 75C until the engine compartment fan kicked on. It went down to 74.3, but then continued to slowly rise while the fan continued to run. At around 77.5C the coolant light started to blink. My conclusions are the temperature sensor and fan are working but there is not enough cooling capacity to keep the compartment cool enough. This assumes that the coolant light should come on around 77.5C. Next step is to open it up and look for air restrictions and fan condition. Any other ideas/insight appreciated.

It is not the coolant level….
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Old 06-04-2014, 04:04 PM   #8
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Fixed. Engine compartment temperature sensor had come loose from the grommet that hold it in position leaving it hand on the manifold (e.g. hot!). Will post pics if I can figure out how to...
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Old 06-04-2014, 06:07 PM   #9
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Did you bleed the air out of the system? On mine (an'03) I had the identical problem until I bled the air. When I bled the system the level dropped, I added more coolant, shut the valve, screwed on the filler lid and all has been well for over a year.
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Old 06-04-2014, 06:17 PM   #10
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The solution/problem had nothing to do with the coolant/level. There is a temperature sensor that triggers the fan (around 75C) and then the blinking light (77.5C). The sensor slipped off it's position and was resting on the hot manifold.
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Old 07-11-2014, 04:41 PM   #11
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Originally Posted by runjmc2 View Post
The solution/problem had nothing to do with the coolant/level. There is a temperature sensor that triggers the fan (around 75C) and then the blinking light (77.5C). The sensor slipped off it's position and was resting on the hot manifold.
Where is this sensor located?
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Old 07-11-2014, 06:32 PM   #12
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Runj...you really need to check the coolant level. ;-)

Ditto Jager's question....I'd like to know where that sensor is. Congrats on a nice find.
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Old 08-13-2014, 06:43 AM   #13
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I've got the same problem now. Yesterday, while driving home in cool temps (70s) I hit a bump on the road. Right afterwards the red light started blinking slowly.

The engine temp is running at its normal position. I drove home and check the coolant when the engine was cool, and it was full.

This morning I started the car and within 1-2 minutes the red light started blinking slowly. The temp needle was still cold. As I drove to work the needle came up to normal, and the light kept blinking.

This summer I did hear the engine compartment blower running once, so I know it worked then. I don't think it is running now.

Maybe my engine compartment temp sensor has "slipped" like the poster above. Can anyone post a picture of this sensor?
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Old 08-13-2014, 12:12 PM   #14
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I tried to post the pics and keep getting an error. On my '97 there is a grommet that is located between the front two cylinder intakes that holds it in place. This is maybe 12 inches directly in front of (e.g. toward the driver) of the AOS as seen from the top. I had just replaced my AOS a few month ago…. Putting the sensor back in place fixed the issue.
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Old 08-13-2014, 12:39 PM   #15
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My situation adds a new twist to this discussion. When I start my car while it's cold I immediately get the coolant light flashing. After I drive it a while (maybe 10 min). Turn the engine off, and then start it up again the light stops flashing and DOES not flash again until it sits and gets completely cool again. Any thoughts on this weird situation ??
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Old 08-13-2014, 01:27 PM   #16
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Coolant tank level just barely too low, and once heated, is not considered 'low' anymore by the level sensor.
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Old 08-13-2014, 01:27 PM   #17
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Originally Posted by gmboxster View Post
My situation adds a new twist to this discussion. When I start my car while it's cold I immediately get the coolant light flashing. After I drive it a while (maybe 10 min). Turn the engine off, and then start it up again the light stops flashing and DOES not flash again until it sits and gets completely cool again. Any thoughts on this weird situation ??
This was exactly the experience I had. I assume that the coolant expands enough when it heats up so that the low level light goes out, because as soon as I added some coolant, the problem went away and never came back.
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Old 08-13-2014, 03:11 PM   #18
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Thanks guys. Damn are these cars sensitive , or what ? Just like a woman.
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Old 08-13-2014, 06:00 PM   #19
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Well to be fair the coolant expansion thing will happen on any car. Now, the reason your coolant is low....might or might not be a 986 weak spot
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Old 08-13-2014, 06:11 PM   #20
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Well, it turned out that my coolant was vey slightly below "MIN" when the engine was cold. My local Indy topped it up to MAX (for free!) and the light is out.

I don't think there is a leak. I'm ashamed to say I never really carefully checked the coolant level and it may have always been this way. No drips or puddles on the garage floor. In my defense, it IS pretty hard to see.

The mechanic told me that it takes like 4.5 gallons, and the difference between MIN and MAX is less than a quart, maybe even a pint. No wonder the sensor is so touchy.

From now on I promise to carefully watch the coolant level!

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