Overheating with thermostat

[Georgiapaver]

Ok, when I bought my 92 Z34 I noticed it would run cool while driving. So I took the thermostat housing off to find RTV sealant and no thermostat. So I put in a OEM thermostat and now the car will heat up to about 200 degrees, thermostat opens, cools down a little, idle's just fine. Put it in drive and drive down the street and you actually have to pull over and pop the hood to let the motor cool before it blows a head gasket. What could be causing this? I get hot air out the a/c before I drive off, but once I get going the air goes cold. Could this be the water pump not circulating water? I'm gonna take the thermostat back out tommorow and put some thermotex or RTV back on it and see if it still does it. Also do I need to put any kind of coolant in it or will just water make it over heat? Any suggestions?

[gpse3400]

If you aren't losing any water, I'd say you have a clog somewhere... The radiator would do this.

[patgizz]

are the fans coming on?

[crustycar]

simple test

let run till almost hot them spray radiator with garden hose and watch guage.
If it falls suddenly then radiator is passing coolant ok, if not then your looking at a core full of crud more than likely.

If you get a good response in the guage going down from the radiator being sprayed then its a matter of not enough air over the coils -- leaves, bugs, dirt FAN ? ? .

You wont believe all the crap that can get by the ac coil and get traped on the front of the radiator.

[Juglenaut]

Last time I checked 200 degrees is safe, I bet you have a vac leak in the line that goes to that circular ball thing. The line goes by the battery and I think it goes to the under side of the fender to the front under the bumber. What is the highest you saw the gauge?

Any word on the fans??

[Georgiapaver]

Fans come on when it gets to about 200 - 210 range. It will actually get so hot that the light comes on an goes almost to the red. Thats where I stop it and pop the hood and let it cool. Flushed the radiator... dunno, im gonna try it again with the thermostat back in as soon as it warms back up

[Juglenaut]

Have you actually had a temp scope on the engine??

Mabey you have a bad CTS.

If the water jacket had clogs over half of the total water jacket would have to be clogged and there would be noticable hot spots on the engine.

Well it would all depend on out deep a person would want to go, however you could take the upper and lower intakes off and run a long coarse pipe cleaner down the coolant passages.

It is possible the water pump is bad and still spin on the pulley, also the supply passages from the water pump could be narrow from deposit.

[Georgiapaver]

Found the problem when I took the manifolds and heads off... Its called STOP LEAK!!! This shit is everywhere. So Im starting to clean it, hopefully its not too bad else where, gonna replace all the hoses and water pump, new radiator (since I found the small hole were it looks like someone patched it) but if anyone has any good ideas on how to get all the stop leak out easly, please let me know before I go weekend warrior!!!