My 305 TBI is overheating when driving for more than half an hour or so. The driving is mostly town driving, ie stop/start driving

The engine service soon light isn't displayed indicating there aren't any known problems.

Has the thermostat died or something else ? I originally thought that the engine coolant was leaking or something, but last night when car overheated it seemed to have plenty of coolant.

Thanks
Geoff

 

Sounds like the fan is not kicking on. Check your connection to the fan switch (it's on the passenger side head, between the #6 and #8 spark plugs). If the connection is tight, unplug the wire and (while the ignition key is in the ON positon), touch a bear part of the wire to ground (anywhere on a non-painted area/bracket on the engine). If the fan turns on, it's the switch. Before you take the switch out, drain you're cooling system first! Otherwise you'll have a nice mess to clean up!


If the above doesn't work, check the fan itself, disconnect the plug near the fan and supply it with 12 volts. If it turns, then the fan is ok and most likely your fan switch or a bad wire run.

 

I'd say look at your fan when the temperture gets up to normal, if thwey come on then either you're fan motor is dying, or it's not a fan problem. You can also turn on your a/c and if the fans come on but not at normal temp it's your fan switch. An easy fix ios to buy a new thermostat if you suspect it's sticking. Otherwise you may need a new water pump if you suspect it's not circulating coolant properly.

 

Ouch. Sounds like a lot of info, but, verify fan operation first. Simply let the engine idle up to operating temp, and see if either fan comes on. (this assumes a/c, and dual fans) If both fans work, check to see if the air dam under the "chin" of the car is intact. (this only affects cooling over 40 mph) If all looks well at this point, take a look between the radiator, and a/c condensor for debris blocking air flow. (this is a major contributor to overheating) If that looks ok, chances are the thermostat is toast. (not a fun thought on a tpi car.....)

If the fans DO NOT come on, turn on the a/c (assuming that it still works) after the compressor runs for a few, BOTH fans should come on. If not, then you have multiple problems.

The primary fan (drivers side) is completely ecm controlled. It will ground a circuit to energize the primary fan relay (located at the passenger side of the radiator (firebird....)) when coolant reaches a specific temp. It will also turn on the primary fan if it senses the secondary fan comes on. (secondary fan is controlled by the temp switch in the pass. head, and a pressure switch on the a/c line) Temp has to be pretty high for the secondary to come on.

If neither fan works, it is time to whip out the service manual, and start going thru charts.........

Good Luck.

 

What everybody is saying sounds right. But if the fan and thermastat don't fix it check your lower radiator hose. Mine was sucking shut at about 2000 rpms. Like I said, probably fan or themastat, but keep the hose in mind. Would have saved me a lot of headaches, time, and money.

 

I would check everuthing else before this. This should be last ditch, check your radiator or have someone check it for flow. Myabe your radiator is clogged? It happened to me on another car that I had a while back. Car just overheated all the time and i changed the thermostat and all that other stuff and turned out to be that my radiator was clogged up. Good luck man