# Sprung a coolant leak yesterday - weird



## Poncho Dan (Jun 30, 2009)

Remember, I'm an '05...

I was driving to my moms place yesterday to help out with some landscaping, not getting on it too hard... I parked in her driveway, took my son out of his car seat and came back around to the front of the car and noticed a giant wet spot around the overflow tank area about 16" x 24". I searched everywhere and it appeared as though there was indeed a leak originating from the overflow tank. I didn't notice any cracks or holes, just coolant dripping. It had stopped, but there were telltale signs that's where it was coming from. I rolled the car back a few feet, started it up, and even revved it a few times, made the same checks again... no leaks. I shut the car off, and left it sit for an hour or so. I then pulled the overflow tank dipstick, and it showed coolant all the way to the highest mark, past full - strange, higher than usual. I then removed the radiator cap and noticed the radiator was only 2/3 full, so I added about 3/4 gallon of distilled water to fill it. Took it for a short drive to see what was up, came back, NO LEAKS. I went to my dad's house later on, and except for a drip mark about the size of a dime, NO LEAKS :confused. I came home last night, checked underneath it this morning, and no drip marks.

This is a real head scratcher... I still show full coolant on the dipstick, my temps are normal, so wtf? Is it possible the previous owner simply overfilled it, and it decided to just purge all of a sudden yesterday, or could there be something else wrong?

Thanks for your insight.


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## jpalamar (Jul 22, 2008)

T-stat is like 10 bucks and won't hurt to change just to be safe. Could be an air pocket. I thought our cars had a perge unit though. Atleast my 04 looked like it did. I know the LS2 is very different the mine when it comes to where cooling stuff is.


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## HP11 (Apr 11, 2009)

You might also check the radiator cap. I had to replace one on my other car because it wouldn't hold it's specified pressure and would occasionally allow coolant to escape through the overflow whenever to pressure was exceded. I had actually replaced the thermostat first and the problem still existed until I replaced the cap.


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## jpalamar (Jul 22, 2008)

HP11 said:


> You might also check the radiator cap. I had to replace one on my other car because it wouldn't hold it's specified pressure and would occasionally allow coolant to escape through the overflow whenever to pressure was exceded. I had actually replaced the thermostat first and the problem still existed until I replaced the cap.


Do the LS2's actually have radiator cap or a presurized overflow tank like the LS1?


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## HP11 (Apr 11, 2009)

05s and 06s do have an acutal 18psi radiator cap.


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## batmans (Aug 16, 2007)

at 70k I had GMPP warranty replace the radiator.

they said that these radiators are one of the cheap part of the GTO.

If that is the case, get a Griffen.

Year: 2004
Make: PONTIAC 
Model: GTO 
Edition: 
Part: 6-204CD-FXX 
Core Size: 26.50 x 17.62 x 2.22 

Griffin Radiators and Thermal Products


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## Poncho Dan (Jun 30, 2009)

Thats cool, a radiator cap is a cheap fix.

I didn't notice any spots today everywhere I took it, and I literally just got back from a, shall we say, "spirited" drive. I just checked now and there is a spot about 1-2" in diameter coming from the same spot.

This morning, before I went anywhere, I took the cap off the radiator, and noticed it was down a bit again, but the overflow dipstick showed no change. Is it normal for the radiator to not be 100% full when its cold?

Also, if I do replace the thermostat, what are the advantages/disadvantages to a 160* versus the stock 190*? I was under the assumption that an engine that ran cooler wasn't as efficient, but it seems as if enough of you guys are running the 160 ok. I remember getting crap mileage when my thermostat was stuck open on my Grand Am.


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## batmans (Aug 16, 2007)

my leak was so small that it took days to weeks for the temp needles to even move.

I never had any drip.

Then after a couple months of observing it I took it to the dealer and sure enough it was a bad leak...........


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## jpalamar (Jul 22, 2008)

If the leak is from the radiator, if the thermostat doesn't open. The resivour would still be full since it isn't circulating in the pressurize system right? I got a Silla as my radiator replacement. 1/2 price of the others and seems decent. Even if it fails 3X its cheaper then going back to GM for a crappy one of payuing 600 for some of the others out there.


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## HP11 (Apr 11, 2009)

Also, if the radiator cap is bad, the reservoir would stay full because the bad seal would prevent the coolant from drawing back to the radiator as the coolant cools down. In that scenario, once the coolant reaches the top of the reservoir, it has nowhere to go but out. That would also explain the low radiator level when you check it later.


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## Poncho Dan (Jun 30, 2009)

Just replaced the radiator cap, $4.19  We'll see if that fixes it.


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## Poncho Dan (Jun 30, 2009)

Just an update - no problems whatsoever since I replaced the radiator cap. Thanks!


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## HP11 (Apr 11, 2009)

Glad that worked for you. Seeing the word 'weird' in your topic title made me flashback to when I had the same problem. I recalled trying everything on my 1978 Datsun 280Z only to find out it was the cap.


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## 04gto1999lude (May 12, 2010)

I had the same problem too my comp. would tell me that my coolant was low and it seemed that my overflow tank was leaking but eventually my radiator busted over time. and the whole yime it would leak drops and some other times it wouldn't.. so i guess you might wanna start with your radiator and water pump


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## Gotagoat (Jan 6, 2006)

I had a similar situation a couple of years ago and it turned out the hose clamps were loose on the short hoses that are beneath the tank.


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## Poncho Dan (Jun 30, 2009)

04gto1999lude said:


> I had the same problem too my comp. would tell me that my coolant was low and it seemed that my overflow tank was leaking but eventually my radiator busted over time. and the whole yime it would leak drops and some other times it wouldn't.. so i guess you might wanna start with your radiator and water pump


Problem is long gone, however I will be investing in a pressure tester, since now my dad's truck is springin' leaks. Pressure testers are the tool to use to find leaks the easy way, so time to nut up. It's one of the few tools I _don't_ have yet.


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## batmans (Aug 16, 2007)

My leak was the radiator after 70k miles on it.


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## HP11 (Apr 11, 2009)

Poncho Dan said:


> Problem is long gone,........


Should be, the thread was, what, 8 months old when it was revived? 04gto1999lude, I realize you're fairly new here but you should try to respond to something more up to date unless you have something pertinent to add....just sayin...


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