Overheating...kind of...

I have a 94 firebird with the 3.4, and it just started doing some weird things...If I drive in the city, I'll overheat, QUICKLY. And I'll lose my coolant, somewhere. I don't see any puddles under it if it sits. If I drive on the highway, it runs hotter than normal, but doesn't overheat. In the vity, before overheating, I have heat. On the highway, when running hot, no heat.

At first, I thought head gasket, but it holds pressure through cooling system. Then I thought water pump, which only has 30k on it. Then I thought thermostat, which only has 500 miles on it.


Also, It's going to be parked for the winter, and I want a few ideas on engine upgrades under $750 that an amateur with a few dozen wrenches and sockets can do.

the thermostat could be stuck. also what degree stat did you have put in 500 miles ago? wasnt a 160 was it?

That doesn't explain the loss of coolant really though...unless its overheating and spewing it all out of the overflow tank. I would definitely doublecheck that thermostat. Also, it doesn;t really overheat on the highway cause the speed blows wind over the engine and radiator keeping it from overheating. I found this out when my '94 T/A did that...I crippled it home using the interstate and stopping every 10 miles to let it cool for a few hours....plus I sped all over once I got in town to keep wind blowing over it.
Also, the waterpump may still be a problem. I had about the same mileage on mine and since it was a cheap replacement, it was bad in that short time...I had to buy a high quality one for the extra money to save on doing that pain in the ass job on that LT1 motor of replacing the aluminum waterpump. Check the thermostat first though...its easy and cheap.

the water pump could be leaking out of the weap holes while your driving it. you need to have it checked, the engine getting hot can warp your heads, also after a while it will damage your tranny

the pump went in my 94 TA and it was dripping out the weep holes, replaced with with a meziere electric. Not a fun install because i had to do some fabrication to get it in there. but the car runs a little cooler and picked up a few ponies too.

But getting back to the 6 banger--if you don't see anti freeze dried onto the engine or anywhere like that. I would say it has to be comming from the pump, the bottom of the radiator, or the bottom hoses. Also--make sure your radiator bleed valve is shut. Was the system bled properly when the new thermostat was put in?

Well, as for the temp of the thermostat, it was done at a garage, I had to backflush it cuz it was gettin cold out and I had no heat, so I paid the $105 to have it backflushed, and they replaced the thermostat, and I can only hope that it was the 180. And it worked fine for 2 weeks, heat out of the heater, and no overheating.

Tonight, I limped it home, 35 miles, it overheated 2x during the 4 mile trip to the highway, and my brother (in the chase car) ssaid he saw my pass side tires wet, and the overflow was full, to the top, and it was wet all around there, so I know it was spewing some out there. So I pulled over both times to let it cool, and refill.

When I hit the highway, it ran fine, if a bit hot, but no heat. When I got off the highway, 28 miles later, it overheated at the first red light, so I pulled over and let it cool...then things got strange. I refilled the system, and started the last few miles of city driving. I started off having heat, then about 4 minutes into the drive, I lost heat and it ran hot again. I hit the first red light and, oddly enough, the temp dropped, and I had heat again. I took off from the light, lost heat and the temp went up, hit the next light and the same thing happened.

I have the weekend, so I will start with the thermostat, and see if that's bad, then check the water pump.

For the techs out there, Quizzle me this...if the thermostat is upside down, what will happen?

You can't put the thermostat in upside down I don't think, but if you do it wont work at all. The heat keeps quitting on you because when it overheats and spews out coolant, air bubbles start circulating through the system and the heater core doesn't have hot coolant running through it to heat the passanger compartment. In town while stopping and going, you may just be sloshing coolant from the engine back into the radiator and it starts sort of ciculating back through the system giving you temporary heat again...til you start off the line again...then it sloshes back. It sounds like its just overheating and then bubbling out. I'd look to make sure the thermostat is proper and installed right and that the cooling fans are working.

check your hoses, check the thrmostat, check the rad, water pump. replace all if need be. i replaced the waterpump, hoses thermostat and rad all at the sa,e time in m,y truck. and it hass never ran better.

I had this same problem on my 96 chevy truck it was the water pump. When they start to were out they leak out coolant out of the weep hole. Some times and you can barly tell were its coming from. fill it up tape a rag or somthing to the water pump where the weep hole is drive it and if its wet when you check it get a new water pump.

it could need a radiator cap.

did you get it runing? if so what was it?

I got the old thermostat out, it was a 195, gonna refill and run it on saturday. I'll let you know then