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Overheating GT3


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Hi,

i own a 996 gt3, and im having overheating problems. the problem first occured when i noticed that coolant was dripping from the reservoir. I had it checked and the mechanic discovered a hole in the reservoir and fixed it. After a few days, the car temp still increased even though the leak has been fixed, and the level of coolant sometimes goes doen min level, and then goes up again. Is my thermostat busted? Thanks!

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Hi,

i own a 996 gt3, and im having overheating problems. the problem first occured when i noticed that coolant was dripping from the reservoir. I had it checked and the mechanic discovered a hole in the reservoir and fixed it. After a few days, the car temp still increased even though the leak has been fixed, and the level of coolant sometimes goes doen min level, and then goes up again. Is my thermostat busted? Thanks!

Sounds like you may have a bad tank cap. It only cost around $20 or so to replace it. I change mine every two years because that's the average lifespan for those caps, then you start having cooling problems like you've described.

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I would suspect that the system needs to be bled. Depending on how the leak was fixed, there may be air in the system. The workshop manual process to fill and bleed the system is very involved, but you might try adding coolant when the engine is cold.

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  • 2 weeks later...

I just had problem with my cooling system on my GT3! I have spoken to many people and red alot on the internet so I almost feel like an expert:)

In my case it was a crack inte the coolant resorvair. I replaced it with help from Lorens thread in DIY. Thanks!

So my suggestion is to follow Lorens advice, bleed the system properly!

Good luck

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  • 5 months later...

I had a similar problem with the MK1 leaving nice big puddles of water underneath it when parked and having to top up the reservoir every so often. Turns out my problem was the water pump and after having changed it, there are now only a couple of drops of water on the garage floor, which shouldn't be in an indeal case but, it's a major improvement!

If you are referring to the MK1 overheating in traffic, I get that too and, turning off the air conditioning seems to work. Nowadays I just don't drive it in traffic unless it's absolutely necessary.

I guess these are the problems with owning a non-homologated for tropical weather sports car!

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May be worth getting the system pressure checked if non of the above (ie Lorens) bleeding sorts the problem. You may have holed a rad, as somebody has said, you'd be surprised at the cr4p that accumulates in there. If the front pu is full of debris, then it's also common for the rad to corrode and thus leak. Hope it isn't this, but on my last C2, I had both the cracked headertank prob and corroded rads...thankfully all changed under warranty from the dealer.

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  • 2 weeks later...

Don't forget that topping up coolant requires the engine to be held at a steady 5k rpm or so whilst filling... this will charge the system correctly and eliminate some of the possibly trapper air). At the same time, check the hoses at the back of the engine... the jubilee clips sometimes have a way of working themselves slightly loose thereby causing leaks (at high pressure often).

I understand the GT3 engine is filled with coolant at the factory by a process that rotates the engine whilst filling to ensure air leaks are fully removed... sadly not something we can do easily!

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polar, i presume you should be filling up with coolant when the engine is cool so, would it be advisable to rev it up to 5k and hold it there whilst water is being poured in?

If you fill up with coolant on a hot engine, you will be low on coolant when the engine cools. The tank is an expansion tank as the coolant expands considerably when warm. You also do not want the engine running. It is best to fill the engine with coolant with the engine off and the vent open. The colder the coolant, the better. The tank is at the highest point in the system and letting it sit for several minutes between fills with the vent open will allow the coolant to reach most parts of the system. Once the tank is full, be patient and it will slowly empty as the liquid fills the system. Once gravity has done it's job and the tank level is stable put the coolant cap on, start the car and run to operating temperature. Turn it off and let it cool for an hour or more. Remove the cap and fill the tank again, keeping the vent open. Close it up and take it for another run to full operating temperature. Let it sit overnight and refill the tank in the morning.

HINT: It is best, but not necessary, to fill the system with the front of the car pointing down a hill. This helps eliminate air being trapped in the system and minimizes the number of top offs you will have to do.

Edited by 1999Porsche911
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You also do not want the engine running. It is best to fill the engine with coolant with the engine off and the vent open.

I'll let Manthey, JZM, and the Rupert Lewin Racing team that they were wrong on filling the coolant with the engine running ;)

That's good. Even professionals can learn somethng new every once in awhile. :D

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You also do not want the engine running. It is best to fill the engine with coolant with the engine off and the vent open.

I'll let Manthey, JZM, and the Rupert Lewin Racing team that they were wrong on filling the coolant with the engine running ;)

That's good. Even professionals can learn somethng new every once in awhile. :D

Ah, so you say Porsche the vehicle manufacturer also wouldn't know either? Have you actually read the Porsche workshop manual? Nup, I don't think so because if you did then I believe you missed section 19-3 where it specifically states after filling at idle, seal the system, run till at operating temp, force fans on, unseal system, continue to top-up while running engine at 2500rpm, "Every 30 seconds, briefly rev the engine to 5000rpm. RPM Surges are IMPORTANT FOR PROPER BLEEDING.

I'm all for advice, but factual and correct, no incorrect and misleading.

Jeff

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  • 2 years later...

Open the bleed valve and drive the car for a few days that way -- checking daily to add coolant as needed.

This is the slow but easy way to bleed the system.

I followed the above suggestion to bleed the cooling system of air and added daily until level stabilized.

I also followed the advice of Scottsdale Porsche mechanics to just add distilled water for top off.

I have added approximately 1.2 Liters of only distilled water and the coolant level has stabilized.

My question is: have I diluted the protection properties of the anti-freeze beyond acceptable limits by just using 1.2L of distilled water?

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  • 8 years later...
On Saturday, November 17, 2007 at 12:20 AM, JMeager said:

Ah, sy Porsche the vehicle manufacturer also wouldn't know ethe ither? Have you actually read the Porsche workshop manual? Nup, I don't think so because if you did then I believe you missed section 19-3 where it specifically states after filling at idle, seal the system, run till at operating temp, force fans on, unseal system, continue to top-up while running engine at 2500rpm, "Every 30 seconds, briefly rev the engine to 5000rpm. RPM Surges are IMPORTANT FOR PROPER BLEEDING.

I'm all for advice, but factual and correct, no incorrect and misleading.

Jeff

Holy thread ressurection baTman!

 

-->It does begg the question how to 'unseal' the system and prevent  coolant spewing out of the expansion tank since the system will no longer be pressurised and hence the hot coolant will start boiling.

Edited by hardtailer
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8 minutes ago, hardtailer said:

Holy thread ressurection baTman!

 

-->It does begg the question how to 'unseal' the system and prevent  coolant spewing out of the expansion tank since the system will no longer be pressurised and hence the hot coolant will start boiling.

 

We would do it by using a vacuum filling system which completely eliminates all of the "burping" nonsense.

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