'99 GT puking up coolant at idle

[mystic96]

Lately my car has been purging itself of all it's coolant anytime I let is sit at idle for more than a few minutes, or if I'm sitting in traffic. Every couple of days I'll have to put about 2 gallons of water in it, until it pukes it all up again.

I planned on fixing this today hopefully, so just wondering where to start. I already put a new cap on the overflow tank. That seemed to help for about a week, but not anymore.

I was going to replace the thermostat first, but it seems like it might be the water pump too.

I can hear the fan coming on so I think i'm good there.

[BEARY]

May need a new radiator cap, that would be my next step...

[green1995gt]

May need a new radiator cap, that would be my next step...

It looks like he already did that. Those have the sealed system so the resevoir is the radiator cap.

[green1995gt]

I would do the thermostat and waterpump. It sounds like the coolant is not flowing as good as it should so when you sit still it heats up in the engine and overflows. either the thermostat isnt opening far enough or the water pump isnt spinning how its supposed to.

[mystic96]

Put a new thermostat on, topped off coolant, and drove around about ten mins then let it sit idle for about ten mins. Noticed a little trickle of water when I checked after ten mins but not gushing out like before.

Then turned the car off and after a few seconds the little trickle became a pretty steady stream. Left it alone then came back a half hour later and took the cap off and the overflow tank was empty.

So it seems the overheating problem has slowed down but not gone. I'm not real sure how well the deal is between the overflow tank and the cap. What are the odds of a new cap going bad already?

[DON SVO]

Put a new thermostat on, topped off coolant, and drove around about ten mins then let it sit idle for about ten mins. Noticed a little trickle of water when I checked after ten mins but not gushing out like before.

Then turned the car off and after a few seconds the little trickle became a pretty steady stream. Left it alone then came back a half hour later and took the cap off and the overflow tank was empty.

So it seems the overheating problem has slowed down but not gone. I'm not real sure how well the deal is between the overflow tank and the cap. What are the odds of a new cap going bad already?

Where's it leaking from?

[mystic96]

Where's it leaking from?

From around the cap on the overflow tank. Replaced the cap about two weeks ago.

[Z06killinsbf]

Is the tank cracked?

[psdtech]

Is the high speed fan coming on?

[crapstang]

remove all of your coolant and replace it with water ONLY, nothing else, then wait until it freezes. High performance mode

[mystic96]

Is the tank cracked?

No, no cracks that I could tell from looking at it today. Just leaks once it's been sitting idle for a few minutes. It'll just start running out from underneath the coolant cap then running out all over the place until I turn the car off or it runs out of coolant or both.

Is the high speed fan coming on?

Not sure. The fan will come on at some point, but it's not on all time.

[JC316]

Overflowing at idle usually means bad fan, bad cap, or head gasket pressurizing the system. What are the temps looking like? If it's not overheating when it's puking, then my money is on the HG.

[mystic96]

Overflowing at idle usually means bad fan, bad cap, or head gasket pressurizing the system. What are the temps looking like? If it's not overheating when it's puking, then my money is on the HG.

Only has the factory gauges on it, and the needle hardly ever moves from dead center. In fact, the only time I have seen it go into the red is 2 weeks ago it had puked all the coolant out, I didn't realize it, and drove from Southlake into Trophy Club and stopped there to put more coolant in it. That's when I replaced the coolant tank cap.

since then, it's continued to puke out coolant pretty regularly, but the temp gauge never moves

As for a head gasket...no oil/coolant mixing anywhere, and I've always heard that's a tell tale sign of a blown head gasket

[JC316]

Only has the factory gauges on it, and the needle hardly ever moves from dead center. In fact, the only time I have seen it go into the red is 2 weeks ago it had puked all the coolant out, I didn't realize it, and drove from Southlake into Trophy Club and stopped there to put more coolant in it. That's when I replaced the coolant tank cap.

since then, it's continued to puke out coolant pretty regularly, but the temp gauge never moves

As for a head gasket...no oil/coolant mixing anywhere, and I've always heard that's a tell tale sign of a blown head gasket

Do a compression test or a hydrocarbon test kit. Head gaskets don't always get water into the oil, in fact unless it's a serious blow that is left unchecked, they rarely get water in the oil.

Just did the head gasket on my sisters 96 Saturn and it was leaking outside of the car, the gasket was completely eaten away around the water jackets, but it still didn't get water in the cylinder or the oil.

Blew the HG on my 96 GT and there was no water in the oil, same with my 98 Cadillac and a half dozen others that I have worked on.

[DON SVO]

Only has the factory gauges on it, and the needle hardly ever moves from dead center. In fact, the only time I have seen it go into the red is 2 weeks ago it had puked all the coolant out, I didn't realize it, and drove from Southlake into Trophy Club and stopped there to put more coolant in it. That's when I replaced the coolant tank cap.

since then, it's continued to puke out coolant pretty regularly, but the temp gauge never moves

As for a head gasket...no oil/coolant mixing anywhere, and I've always heard that's a tell tale sign of a blown head gasket

A headgasket that blows between cylinders and out the side typically only takes out water jackets. If it's a seeping HG issue, it might be the reason that it slowly builds pressure into the coolant system... it's only noticeable when the T-stat opens fully while warming up (idling, etc).