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Discussion Starter · #1 ·
Having a problem where the coolant seems to boil out of the cap. It doesn't happen all the time but it's happened at least three times recently where a large amount of coolant leaks out from what looks like the back side of the cap. Also, the cap makes hissing noises for hours after the car has been turned off, not sure if that's normal.

I've tried replacing caps and the same thing happens. Any ideas on where to look next?

Thanks
 

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You probably need to change your thermostat and coolant.
 

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Discussion Starter · #3 ·
I had the thermostat replaced and coolant changed last year so I hope the thermostat hasn't gone bad already.
 

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Pressure test it.
There could be a hairline fracture in the plastic of the overflow reservoir.
Thermostat's are dirt cheap so you would be lucky if that's the problem.
 

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Discussion Starter · #6 ·
Ok, thanks I will look into a pressure test and hopefully there is just a crack somewhere in the reservoir.
 

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Ok, thanks I will look into a pressure test and hopefully there is just a crack somewhere in the reservoir.
Any mechanic can pressure test it for you.
Follow up with us and let us know how it goes!
Good luck thumbsup3.gif
 

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Discussion Starter · #8 ·
The dealer did a pressure rest and said it was fine. They said they can't think of anything else and seem unwilling to investigate further. Any ideas on how to proceed?
 

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they are lazy, your car clearly has a problem. head gasket I would hope, cracked head/block I wouldn't hope for. thermostat stuck closed would cause boiling into overflow tank. leaky head gasket will cause pressure into cooling system and cause boiling over issue but coolant wont be boiling hot. I would lean towards head gasket as you've stated that it bleeds off well after car has turned off.
 

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Hi all, this is my first post here, I'll do the intro page soon but wanted to share my experience with having the same issue. Bought my '07 GT in March and had 4 times over the course of 2 months where the coolant would leak from the reservoir just as you described, vanmustang, but always after I stopped the car. The first 3 times anyway... The last time it happened I was actually driving on the highway and the car went into limp mode. I pulled off, let it cool and drove to the nearest parts store. One of the guys there said the same thing about the res being cracked. I wasn't particularly convinced so I suggested the cap might be the issue. They pulled a new cap from the shelf and were kind enough to let me try it before I bought it. When I put it on, I noticed it wouldn't click into position unless I pushed down with a fair amount of force as I was turning. So I put the old one back on and the same thing, no click unless I did it just right. Haven't had a problem since. So basically I just a ridiculous amount of verbiage to say this: are you sure your cap is on right? I know it's like one of the most basic things, but I'd rather know I've checked all the easiest things first. Has anyone else had this same experience?
 

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Discussion Starter · #11 ·
Thanks for the info Iamgnome, I think this might be the solution. I bought a third cap the other day and made sure to put it on so it clicked properly and so far the coolant level has stayed much lower than with the previous two caps so hopefully that was the problem.
 

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Hi all, this is my first post here, I'll do the intro page soon but wanted to share my experience with having the same issue. Bought my '07 GT in March and had 4 times over the course of 2 months where the coolant would leak from the reservoir just as you described, vanmustang, but always after I stopped the car. The first 3 times anyway... The last time it happened I was actually driving on the highway and the car went into limp mode. I pulled off, let it cool and drove to the nearest parts store. One of the guys there said the same thing about the res being cracked. I wasn't particularly convinced so I suggested the cap might be the issue. They pulled a new cap from the shelf and were kind enough to let me try it before I bought it. When I put it on, I noticed it wouldn't click into position unless I pushed down with a fair amount of force as I was turning. So I put the old one back on and the same thing, no click unless I did it just right. Haven't had a problem since. So basically I just a ridiculous amount of verbiage to say this: are you sure your cap is on right? I know it's like one of the most basic things, but I'd rather know I've checked all the easiest things first. Has anyone else had this same experience?
Great first post Iamgnome and welcome to AFM! I'm always glad to see some helpful knowledge and personal experiences with problems being shared to benefit others!

vanmustang, hopefully that was your problem all along. Much cheaper fix than a headgasket! (free ninty-free is always a welcome sight when it comes to car repairs!):bigthumbsup
 

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Thanks for the welcome KA06GT! This forum has been a great help to me over the last few months, I'm glad to contribute and maybe help someone else out. Vanmustang I hope this fix is as easy (and cost effective) for you as it was for me. Keep us posted!
 
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