overheating

[GLIDER]

My 82 fi spider started overheating and i haven't been able to identify the cause. I've removed the thermostat and tested it in boiling water...works fine. I drilled the hole on the interior of the thermostat as outlined in the IAP bulletin and have discunnected the fan and tested it directly to the battery, runs fine. I replaced the thermo switch a couple of years back and probably haven't driven the car 750 miles since then. Does anyone have any thoughts before I buy another thermo switch ? I did change the fuse just for kicks also. thanks

[So Cal Mark]

is the fan not coming on? Is it overheating only at idle?

[GLIDER]

thanks for the questions. the fan is not coming on at all. I've started it a few times over the last couple of weeks and let it idle....it gets into the red without the fan kicking in to cool.

[So Cal Mark]

when it gets up to temp, is the bottom of the rad hot? If not, the t-stat is probably not opening. If it is hot, then use a jumper wire to bridge the contacts at the fan switch. That will test the integrity of the fan circuit. If the fan comes on, you have a problem with the switch. If not, you've lost power or ground in that circuit

[GLIDER]

hey, sorry for the delay in responding. I've been out of town and just had the opportunity to do the jumper. That did the trick ,the fan runs and I've ordered a new sensor. Should have it this week end and will let you know if that cures the problem.

thanks,

[zachmac]

There is a chance your snesor and fan wiring are fine. IF you have an air bubble in the system the pump can't circulate water through the radiator. The water in the block (where the heat is produced and where your temperature gauge sensor is located) gets plenty hot, enough to do damage. meanwhile not enough flow gets to the radiator to get that water's temperature up to that sensors trip point. Have you dane anything recently to drain or partially drain the coolant? Could be you just need a proper vent and fill.

[zachmac]

Re-reading your post, you say you removed the thermostat so you could indeed have the dreaded bubble. Ral simple to check. Pull you r car into the driveway, lossen the hose from the coolant T to the thermosatat on both ends. Pull it off the T and rotate it skyward on the thermostat. This creates a conveinent hich point fill. Start the car and let it warm up and begin filling the "sky" tube from the hose (distilled water if you are anal like me) and keep doing it until you have lots of coolant spilling out of the T. I then put my finger on the T hole and keep filling until the standpipe overflows. Quickly rotate the hose and retighten the clamps and hopefully the system will be primed to where the radiator gets as hot as the block and the fan kicks on. Then use the hose to rinse off all the spliied coolant and let it run until the fan cycles a few times. It should kick on when the gauge is just past the 0 on 190 and shut off when it gets back near the 1.

BTW, I also usually leave the radiator cap off until I see the coolant heated up enough to expand it to the top and then put the cap on while I finish the rest of above.

[GLIDER]

Hey thanks to all, Mark was right on target with the fan sending unit. Replaced it and it works like a champ and running cool. Thanks again, the Va. weather is getting great for driving.