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Flashing coolant light - already searched

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I just got my car back from the auto trans specialist after they repaired/re-built the transmission for the second time.

Now I have a flashing coolant light. The conditions under which the light comes on is as follows:

1. The light flashes only when the engine is warm - takes around 7 minutes from cold start before the coolant light start to flash.

2. Turning the engine off, and restarting the engine will result in the flash going away at first, but it would start to flash again after about 3 minutes of driving.

3. When the engine is warm, turning the engine off, and then turn the key into the ignition position WITHOUT starting the engine, will also result in the light start flashing some 3 minutes later.

4. When the engine is cold, turning the key to the ignition position without starting the engine will NOT result in the light flashing 3 minutes later.

5. Coolant temperature is normal at the half way mark all the time.

6. Engine compartment fan on the driver's side (RHD, Australian car) is working and sucking in air normally when the coolant is at normal operating temperature.

I have already topped up coolant to the Max level and tried to bleed the system by releasing the bleeder bow and the deactivating tiptronic pneumatic coolant shut-off valve by pulling out B1 fuse.

In the context of a recent tiptronic overhaul, which required the disconnection of coolant hoses and re-filling of coolant, what do people think is the likely cause for this flashing coolant warning light? TP? Loren? Anyone?

Edited by Jinster
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I had that last year. Cant remeber exactly what the cause was,either a very small leak in the expansion or water bottle, he also mentioned the level sender. The repair was to put a new expansion bottle. Parts were about £120. Took about 1-2 hours labour.

Edited by Wacked
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Sometimes it takes a couple of weeks of driving with the bleed valve open to clear trapped air in the system. It is fine to drive the car with the bleed valve open - Cupcars do it all the time. The only other choice is to use the Porsche recommended vacuum filling technique to refill the system.

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I do not know if you did this but here are the bleed instructions:

1. Remove the engine oil and coolant caps

2. Remove the plastic cover that is under the caps

3. Lift the bow on the bleeder valve

4. Fit the protective cover (this is a plastic sheet that has a hole in it that fits around the coolant fill area and covers the trunk in case the coolant splashes out when the engine is turned on. You probably do not need this but the time I did it I used a large piece of cardboard with a hole cut in it)

5. Top off the coolant to the MAX mark

6. Strart engine and warm up to operating temp at APPROX 2500 rpm. Briefly rev engine to APPROX 4200 rpm once each minute until operating temp is reached. This will take approximately 10 minutes.

7. Switch off engine and let cool

8. Top off coolant to MAX mark

9. Lower bow on bleeder valve, replace plastic cover, engine oil and coolant caps.

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Thanks for the replies. Loren, is it safe to drive the car with air bubbles in the coolant system?

I was thinking about draining and refilling the coolant myself. I don't have a vacuum tool. But the porsche factory manual I have didn't seem to state that it requires a vacuum tool. I must have missed it. The manual just says to refill and then bleed like ar38070 says.

The other problem was that the factory manual says the tiptronic pneumatic coolant shut-off valve needs to be open for the bleed procedure. This is achieved by pulling out the B1 fuse. B1 fuse also controls the instrument cluster. So I have no instrument display when the fuse is out.

Also, how does the warning system pick up trapped air anyway?

What I thought strange about all this is that when the engine is warm, but not running, with only the key in the ignition, the light still comes on a few minutes later. When the engine is not running, the coolant is not circulating, so how does the system pick up a coolant anomoly?

Edited by Jinster
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A flashing coolant light can mean more than air bubbles. So the light comes on without the engine running could mean several things.

Here is the long explanation from the service manual on the flashing coolant light.

"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."

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I have read those from your earlier posts Loren.

It would seem that my problem is - dare I tempt fate - solved.

I left the coolant reservoir cap off, with the bleeder open, and B1 fuse out last night overnight. Went for a drive today. Didn't get anymore warning lights.... let's hope this lasts.

Where did you extract the info about the cooling light from, Loren? I have the Boxster factory manual on CD and a search with the term "coolant" through the entire manual did not reveal the excerpts you quoted. Is it from a 996 manual?

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Yes, my information is from the 996 manual (Group 1: Engine, Part 2 (as of Repair Group 15 - Engine - Cooling). Chances are that your Boxster manual does not have all the update supplements. This was added in a later supplement in the 996 manual so I suspect it was added to the Boxster manual too.

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Removal of the tiptronic transmission requires the disconnection of several coolant hoses. The shop may have not used a vacuum assisted coolant refilling tool and there might just be air in the system. Sometimes these cars are hard to bleed, period, even if a vacuum filling tool was used.

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I got my car back from the shop last night and my dad drove it home. When i came to their house to pick it up I saw a big stream of coolant on the ground and condensation around the cap and on the trunk lid cover. Anyway, he said the car did not overheat so I have no idea what it is. The car was in the shop to replace the oil separator and j hose connected to it. I was told there is some vacuum in the oil separator but I don't think it has to do with the coolant. What do you think?

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It is possible that the coolant cap wasn't screwed on tight enough and the coolant overflowed. It will then drip onto the ground from the drain hole next to the coolant reservoir. This explains all your symptoms.

An update on my problem:

The coolant light slow flash unfortunately came back. It keeps coming on every time the car gets warmed up about 1 minute after the engine fan comes on. I have been driving with the coolant bleeder lifted for 1 week now. Coolant level is fine. Car doesn't overheat.

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I have been getting the same flashing temp light on my Boxster. I had them check it yesterday when the car was at the dealer for the 45k mile service. The diagnosed it to be a crack in the overflow reservoir. Quote to replace was about $300 for the part(s) and $400 for the labor. I'm having it taken care of next week by a reputable local import shop for about $100 less.

I had noticed some water under the car from time to time but, I'm talking maybe an ounce or two, tops. Nothing significant. I assumed it to be condensation off the air conditioner. I have no idea where that is in the car and I don't break down engines for giggles on the weekend. I simply don't have the time or the knowledge base. So I'm leaving this one to the pros.

Jinster - You may want to look into the condition of your overflow reservoir. You may have the same issue. Best of luck to you.



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