still having overheating problem

[madmann29]

Hey, i have an 87 supra turbo and i've have a problem with it overheating lately. I thought the problem was the fan blade b/c one of the blades snapped off, so i replaced that, the shroud, and the fan clutch, and it still seems to over heat after i drive it for a good 40 minutes. It seems that when it overheats i fill it with coolant and it will be ok for a while, but then it will start to overheat again, and then the coolant is around the engine bay. Also the needle for the gauge varies, it will be almost in red then go back down and sometimes just stays in red. I was going to try to replace the thermostat, but then i was thinking it could be a cracked cylinder head. Please help, this is my first car and i would really like it to be fixed.

[Jeeves]

If it's been staying in the red, I'd guarentee the head has warped, and if you don't have a BHG you are developing one.

Get a compression or a leakdown test done.

[mrnickleye]

Personal experience...When the temp gage fluctuates, it is because water is low in the block. The sending unit is a variable resistor, and needs water (coolant) to touch it to 'read' the temp, thus changing the resistance of the flow of electricty to ground. The gage interpretes this and gives the reading. It fluctuates because water is intermittantly contacting the sending unit.
A beginning 'BHG' will put pressure into the cooling system, thus causing coolant to overflow into the bottle. Coolant will be sucked back into the engine 'only' when it cools down over several hours. Driving short distances (a few miles) and then sitting for a few hours will fool you, because you may not have to ad water. But, a long drive, especailly in hot weather, will push most of the coolant out of the engine, thus getting the engine very hot. The gage may not show hot because it takes coolant to make it work accurately .
So...either buy the kit, (or go to a shop,) and test the coolant for a BHG.

[yotasrcool]

I made my own pressure tester out of a raditor cap some hose a T-fitting a bicycle pump and a valve stem. Worked great until i misplaced it. Just pump it up to 12-15 psi and look for leaks its that easy. LOL what you find is good when its not dripping is bad LOL BHG