cblinkdude182

I'm driving last night, start up my car, get about 300 feet down the street then my temperature gauge starts going up and my CHECK GAUGES light comes on. So seeing as the temperature was going red I pulled over and see some green radiator fluid on the ground. So... after some checking with a flashlight and looking for where the leak was, I'm thinking it's the the thermostat and the fluid was excess from the emergency reservoir? So I'm assuming getting a new thermo and I'll be good to go?

BUBBA

Could be the stat, but if you have little or no coolant you are going to heat up fast. Could be a bad radiator cap. If the cap is not allowing pressure to build up, the coolant will boil at a lower temperature and either boil over through the cap or fill up and over flow out of the reservoir. Try using regular water, so as not to waste coolant along with a new "good" cap. If that solves the problem you are good to go. If not, then have pressure check done to see if you have leaks and if the top hoses are full of coolant once the engine heats up, the thermostat is probably the culprit. Start easy and procede. Do not drive with an overheated engine or you will be looking for a short block very soon. JMHO

mzgp5x

A possibility...
The gm LT1 Gen 2 engine WP has an internal bypass coolant port. The Thermostat has an additional bypass plate which closes the WP bypass port when it gets to temperature (ie... 160*f stat full open @ 185*f). If the WP bypass port is open, coolant will re-circ thru the pump back to the engine, and, not much will be diverted to the rad for cooling. Gm uses a this WP stat design on the pump suction side (all gen 2 and 3 engines). If the stat does not go to full open, coolant will not flow thru the rad, and, allow the engine to run hot. They use this design for a fast heat-up cycle.

Also, if the head vapor port (ie... reverse cooling) is blocked or plugged, the LT1 will probably overheat due to coolant critical boiling and vapor entrapment in the head. Make sure this line (both heads) is not blocked.
(a good source of information... HP books #1425... Summit).
B.

95Blackhawk

Make sure and do a good flush while you are in there and use only RO or distilled water for final fill...with of course you choice of antifreeze.

cblinkdude182

Well I got a new stat and installed it and then after I started it up it got real hot again after a little driving. So... I unscrewed the bleeder screws and let up some of the air pressure in the line then poured some water in and left the radiator cap off and let it run a little. Then put everything back and ran it down the street, seems to be running a tad hotter than normal but still not in the red. Now I need to flush it and put some radiator fluid in and hopefully be good to go... We'll see.

cblinkdude182

Well this past weekend I changed my radiator fluid and it was a little harder than I thought. First it took a while for all of it to drain out of the system, then it didn't take as much as I thought. After a little driving it started to overheat and since then I have been putting a little in the radiator cap before I drive, but it's starting to get really full... It hasn't overheated recently but I'm still nervous, could it have anything to do with "breaking in" the new thermostat?

NukeFPE

No such thing as breaking in a new thermostat ~ it works or it does not. You are aware that LT1s take a special Thermostat and not the run-of-the-mill standard Chevrolet ones sold at the parts store? The cap could be the problem as Bubba stated, but, did your electric fans start before it overheated? If not, then the fans may be the problem.

Injuneer

Did you drain the entire coolant system, by using the radiator drain plug, and the two drain plugs in the block (one of the "plugs" is the knock sensor)? If you only drained the radiator, you only got about 1/2 of the coolant out of the system.

Did you correctly bleed the air out of the system after you changed your "radiator fluid" (aka "coolant")?

What is getting "really full"? The radiator is always supposed to be totally filled with coolant. That's the purpose of the pressure/vacuum cap, and the overflow system. When the coolant heats up and expands, the pressure (above 18psi) relieves through the cap, and the excess coolant goes into the reservoir. When the radiator cools down on shutoff, the coolant contracts, and the resulting vacuum pulls coolant out of the reservoir to keep the radiator completely full, and all the air out of the system. A faulty cap screws the system up. A cracked overflow hose between the radiator and the reservoir will also screw things up, since the radiator vacuum can't pull the coolant back from the reservoir.

cblinkdude182

Wow. I just got the coolant out of the radiator... embarrassing. Well thanks!