I just had a motor installed and went carbureted. The car runs for maybe 3 minutes and the temp gauge already reads 250. I shut it down raise the hood but nothing appears to be hot. I get brave grab the radiator hose and it was maybe luke warm. Crazy. Any ideas

 

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The motor was just put in everything is brand new. the car is not actually getting hot just the gauge says it is

 

If you really think its your gauge and the engine is not getting hot, try one of these radiator caps. Its called a thermocap and ive seen them at advance auto. Cheaper than an autometer gauge, plus u can make sure your car isn't overheating while your working under the hood with the car running.

 

you can buy one of those but if your head gasket is pressure locking your cooling system then the radiator coolant will read cold while the engine is hot. try touching the valve cover.. is it warm or hot? is it smoking out of your exhaust? your guage could be off try replacing that first. Or take off your radiator cap and let it idle real slow. Is coolant puking out of the top? if so its a blown head gasket. is your oil black or milky? we need more info please

 

It sounds like a temp sender. Run the car with a thermometer in the radiator, or a thermocap, and see if the engine is actually getting hot. You can check the gauge by unplugging the temp sender(gauge should read max) then ground the wire(should read min). If the gauge is right, you need a temp sender.

 

It couldn't posibly just have an air lock in it. Had similar trouble with mine after rebuild and was just an air pocket stuck in the cooling system.

 

Had this problem on a frends car after he had someone rebuild it for him. I checked it out, the thermostat was in upside down. You can remove the thermostat to see if the problem goes away if there is any question of it functioning correctly, but I recommend not running without it indefinitely. When it is removed, the coolant may be passing through the rad too fast to be effectively cooled before re-entering the engine at certain speeds. This could even make an otherwise adequate cooling system appear insufficient under certain circumstances. A good flowing water pump could even suck the lower rad hose closed (if the hose is not coil supported) when revving quickly (not all engines can turn up that fast) and your rad is not capable of keeping up to the flow easily. This can happen with the stock rad and water pump in our cars, I've seen it happen, and the momentary spurts of soaring temperatures can really get annoying and hard to find, especially if it does not happen everytime. Not good for a hard run.

Besides, no temp control is not good for engne wear due to inconsistent or chronically low oil temps.

just food for thought