I have a 95 Lt1 auto, with low temp stat and hypertech programming. It seems that about a year ago after a coolant flush someone put the orange dexcool in my coolant system. About six to eight months later a coolant hose busted. I brought it to another shop that put the same coolant in after replacing the hose. They said that they could not get the temperature to cool down and wanted to replace the whole system with over $1000 in repairs. Yeah Ok! I was able to make it home and flush the coolant out completely for several hours and replace it with the correct green fluid. I used the pressure valve to release all the air from the system. Everything was ok for a copuple of weeks. Then I got the low coolant light. I looked at it and realized the coolant tank was low. So I put in another gallon or so. About a month later the same thing happened and it started to overheat. Again I added coolant and everything was ok? I can not figure out where the coolant is goin to, there are no visible leeks anywhere in the system. It has been ok for over a month now but I have a feeling it will do this again soon. When I first added coolant I put the recomended amount that it holds and then some while the engine was running. I used the resivoir by the firewall to fill it. I first made sure it was exiting from the pebcock valve then cut it off and used the air bleed valve. Plus I filled it since then with two or three additional gallons in the following weeks. Where could the coolant be going to? When I flushed it the system was pretty funky. But like I said I flushed it for several hours with the engine running until it was pure water flowing out then pure coolant that I wad adding (not in addition to the recommended amount to fill it). Any ideas? I'm hoping it doesn't happen again but I doubt it.

 

I think the "orange" that was installed after a flush a year ago, was probably the same as the factory fill for a '95. Whether it was changed by you, or an owner prior to you, with a very thorough flush, the green and the orange shouldn't have been mixed, as you seem to know. I don't think the change in coolants has anything to do with the current problem. The coolant has to be going somewhere, and three unconventional outlets come to mind.
The first is a leaking heater core. If it is leaking, you should smell it. You can feel the passenger side carpet as a double check. Usually fogged windows and the oder, precede the moisture.
Second, is a bad manifold gasket. Check your oil for contamination.
The third is a bad head gasket. The coolant would be exiting via the tail pipe. That gives you some starting points.

RACE ON!!!

 

I would get the system pressure checked. Could be something simple.
Radiator cap??

 

You can rent a Coolant Pressure Tester at Autozone for free. With this tool you can pressurise the coolant system when cold and look for leaks. Keep an eye on the hose connections - not unusual for them to leak under pressure.

If you still don't see any leaks then you should probably look further into the gaskets and heater core as CFI_EFI mentioned. Start with the easy stuff.

 

Thanks for the advice. From what I have been told and read 96 was the first year for the extended coolant (aka orange stuff, aka dexcool, etc..) I completely flushed out the orange gunk first, making sure the two did not mix. I havn't really noticed any smell but the windows do tend to fog up occasionally but with a convertible that is sometimes typically. I also notice wet carpet a few times but it was on the driver side. I believe this was do to a weatherstripping leak where the convertible top storage door meets the body. I will double check this if I notice it again. I did forget to mention one other thing. I swapped out the pressure cap on the firewall resivoir for one that was 1 number higher pressure. I think that was all the auto store had at the time an old one had broke. I also broke the air bleed valve by the throttle body by tightening it too much. I know that it is not leaking there though I've checked many times. Anyone know where to buy a new one of these? Think I'll rent one of those testers and check for leaks. At least now I know what gaskets to check also. Thanks!

 

4th would be the radiator itself. Mine had a bunch of pinholes in the tanks that were not visible. They didn't leave any trace except every once in a while I'd see a few drops on the frame.

 

My 1995 came with Dex as the factory fill.; I converted it to green, once my Impala is off of warranty the Dex is coming out of it too. Good luck with the pressure tester!


Mike