LS6427

iTrader: (2)

A water pump can leak, then not leak for a few weeks...then leak again. I've had that happen. Its easy to check....just get it hot and put the front end up and wait 15 minutes...then get under there and see if coolant drips out of the weep hole.

I think if the gasket has been breached...it will do it all the time and only get worse with time.

I know you replaced the rad cap...it could be a dud....happens all the time with brand new caps.
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underpressureWs6

iTrader: (17)

ill try to check the water pump gasket thanks!

LS6427

iTrader: (2)

Not just the gaskets....the weep hole underneath the shaft in the center. Gaskets rarely leak......weep holes always leak.

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underpressureWs6

iTrader: (17)

gotcha! will do

dericksonZ28

I have a 2000 Z28 5.3 and I am dealing with the same thing. I took it to the shop and they tested everything and said it was the cap. Replaced it and it was fine for a little while and then once again when I would shut the engine down the coolant would come gushin out of the reservoir tank. I let it Idle the other day in the driveway and it got super hot and when I tried to back it into my garage it started to make some god awful noise, then when I shut it down it was boiling so bad it was making a crackling noise for at least 5 minutes.

underpressureWs6

iTrader: (17)

Does yours do it ALL the time or only when its hot outside? mine hasnt been doing it since september because its gotten cold out here in NY i guess we will see if it does it again when it starts getting warmer out over here...

Tzone21

iTrader: (2)

My 2000 Camaro SS is doing the exact same thing. The coolant reservoir tank is boiling over and alot of steam is coming out of the radiator cap. I have a brand new radiator, brand new thermostat (tested it and it opens just fine). I bleed the system but could probably be bleed again. The gauge in the car is reading in the 180 range at idle when it starts to boil over so the fans wouldn't even turn on yet. I bought a brand new radiator cap but it was junk, i need an OEM GM cap. I also just checked and my overflow hose is on the bottom nipple so im going to switch them and see if it changes anything. My lower radiator hose seems to be flexing in a way that doesn't promote maximum coolant flow (the bottom is almost twisting so its pinched a bit but Ive never had issues with it before)