Hey all,

I have a 97 blazer with the 4.3 Vortec. I know I have some kind of gasket leak because my radiator is always full of brown disgusting fluid. However, it usually doesn't overheat. On Thursday I heard some wierd clanking noises from around the heater core, but they went away after a few minutes. Later that night the car overheated and the air from the vent , when I turned on the heat, was cold. I took the car on Friday and got the radiator and heater core flushed. The casing around the heater core had cracked somehow. Anyway, the car was fine the next day. However, it's starting to overheat again. After I drove the car this morning and parked it, I noticed around 2-3 oz of coolant was leaking onto the ground. I drove it home and at first it was ok (temp kept fluctuating between 210 and 245 most of the way) and then towards home it began going to red. Anyway, when I opened the hood there was steam and I heard a hissing sound coming from somewhere under/in the engine with steam billowing out) (After doing research here I think it might be coming from the "weep hole") The belt had coolant on it too. I figure my next step is to change the thermostat, as the temp. might be fluctuating bec. of a stuck thermostat. There's a 24 hour mechanic near me and they only have the thermostat from the 4.3 Astro. I'd like to go get it changed tonight, so can anyone tell me if this would fit in my car?

BTW, if there's coolant leaking, shouldn't the level in the reservoir go down? It doesn't seem to be budging. I wonder if they didn't reinstall the reservoir tank in properly after they took it out to clean.

Thanks guys.

 

If you have a leak in the cooling system, the radiator will not pull coolant out of the overflow bottle.

As the cooling system heats up, pressure builds in the system. The radiator cap keeps the system pressure at 15-16psi. Anything over that pressure pushes into the reservoir. Once the truck is shutoff and begins to cool, the pressure drops. It will get to a point where there will be a slight vacuum in the system which will pull coolant back through the radiator cap and into the system. A leak will allow the system to pull in air from the outside rather than recovering coolant from the reservoir.

Bottom line is that you need to get the leak(s) fixed. Steam is not good. I would NOT recommend driving it again until you repair the problem or you very well could make things MUCH worse.

 

Swart..how do I know it's a leak and not steam coming from the weep hole? Or were you referring to the gasket leak?

I figure if it's a bad thermostat then I can prevent any further steam by changing the thermostat and making sure the engine never gets too hot again. No?

 

Steam = leak. If there were no leak, there would be no steam. If it is leaking from the water pump, then the seal in the water pump is bad.

 

Oh, my mistake. I thought steam could come out of the water pump weep hole.

 

I have an update for whoever is interested:

The car continued to overheat today, and i heard the bubbling noise from around the heater core. I just got back from the mechanic. As soon as he opened the hood and saw the steam, he knew I had a bad water pump. Apparently I was leaking coolant from the weep holes. Anyway, he replaced the pump and since I ordered a new t-stat, he replaced it too. Now the car is great. The temperature is perfect and the heater blows out almost scalding hot air. I don't know how long it'll last, but until next time I'll just enjoy the heat!