Big Johnny

I have a 72 mustang that I just installed a new radiator and thermostat in. I ran it a couple of times with no problems and now all of a sudden it is overheating. I changed the thermostat (180 degrees) again. It is doing the same thing. When I idle it the temp comes down, but jumps back up when I start driving. Could it be the pump, or something else?

67mustang302

What's the temp when driving? Temp usually goes up driving cuz it's producing more power/heat.

Unless it's getting over 230* it's not overheating.

Big Johnny

The temp gage is pegging out past it's normal operating level. It does not have a numerical temp gage on it. It just has C/Normal/H. It has never run to the max like this before. The engine is a 351C with manual tranny. I have no power accessories on it. The antifreeze is clean as well.

67mustang302

Factory gauges suck. You need to verify the gauge and sender are working correctly first. Could just be a bad sender or gauge.

Big Johnny

I would agree on the gauge accuracy, but she is really cooking, and ready to blow out the cap. I will try and get a temp reading. Is there any other thoughts if we are at true high temp that would cause the overheating such as the pump or a restriction somewhere that I can check? It just seems odd to be able to run it for 20 miles fine, and then all of a sudden it is pegging out every time. I know my old radiator ran to the high end of the normal to Hot range but never pegged out. I brought it in to be cleaned and they said I needed a new core because it was plugged too badly and it started to leak all over when they were cleaning it. When I put the new one in I also reduced the thermostat from a 195 to a 180. By the way thanks for your input. Much appreciated.

deepbeech

I have no idea what to make of this.

jimkaray

Since the problem wasn't this bad before the new parts it should be something simple. You confident its not the guage so that's out. How about the fan belt? Are you sure its not slipping? Are to sure the thermostat is oriented properly and not in backwards/upside down? If so I would put the 195* back in and see if that helps. Seems counter intuitve but the 180 may simply be over circulatiing the coolant and not allowing it enough time in the rad to cool the fluid. One other thought, did you move the distributor when replacing the thermostat? If you advanced the timing it could be causing it to run hot.

Diputado

Running too low an initial timing will cause overheating, as well. I'd also check for potential head gasket leaks. That suggestion about checking to see if the thermostat is backwards is good advice. Could be just a simple fix like that, and it's real easy to put a thermostat in backwards if you're not paying attention.

Gun Jam

Ive found my temp gauge to be very accurate...its not precise but it is accurate. If it starts to read hot I know the engine is hot...the cap blows a few seconds after the gauge pegs. I have questioned the temp gauge before I backed it up with a non contact IR temp gun and found that it was my interpenetration (reading cold) and not the gauge directly.

Obvious first. Is the water level above the top of the rad core...it should be about 1" below the rad cap. Check it again air pockets will take up space.

If thats good then check the T stat orientation. the cone should face towards the rad hose and the round temp probe into the block. You can remove the rad hose from the t stat housing to verify this.

-Gun

Big Johnny

The thermostat is in correct. I will check the timing, and it may be off a bit. I was wondering about the possibility of a air lock. Maybe I will drain some fluid and run it with the cap off for a while. I guess I will hold of on the pump. The belt is new and tight so I shouldn't have any slippage. I am heading out on a 4th vacation so I will tackle this when I return. Thanks a bunch and have a great weekend. I will report back on my results.