'74 Temperature Guage Problems

The in-line resistor was 10-ohm and was usually near the front of the engine, taped into the wiring loom. These gauges tend to be inaccurate in the extreme, due to an Italian gauge & a stock US sender for Mustangs. The sending unit was originally in the side of the swirl water tank (smaller tank), but this is a very bad place for detecting water temps. Far better is the stock Ford location for the 351-C, in the front of the block, horizontally positioned. THe sender can be swapped with the pipe plug in the block and the stock wiring is long enough to reach either location. By running both seats all the way fwd, removing the 2 shoulder harness bolts & a few sheet metal screws at the floor, the rear upholstered panel casn be removed. Underneath is a steel panel; remove it and the entire front of the engine (belts etc) is at your fingertips.

quote:

---

Originally posted by jack deryke:
The in-line resistor was 10-ohm and was usually near the front of the engine, taped into the wiring loom. These gauges tend to be inaccurate in the extreme, due to an Italian gauge & a stock US sender for Mustangs. The sending unit was originally in the side of the swirl water tank (smaller tank), but this is a very bad place for detecting water temps. Far better is the stock Ford location for the 351-C, in the front of the block, horizontally positioned. THe sender can be swapped with the pipe plug in the block and the stock wiring is long enough to reach either location. By running both seats all the way fwd, removing the 2 shoulder harness bolts & a few sheet metal screws at the floor, the rear upholstered panel casn be removed. Underneath is a steel panel; remove it and the entire front of the engine (belts etc) is at your fingertips.

---

Jack - thanks for your help! Given what I just described, do you think it's really running hot or could it in fact be an electrical problem. When the car gets really hot, it does produce the "bulub-blub" sound in the swirl tank.

The sound is likely either steam or air bubbles, neither of which are encouraging news. The problem with the sender in the tank is, if/when the water level drops below the sender, the gauge temp will suddenly drop to about 160, which is the air temp above the very hot water. Be very sure the tank is full to the top, that the small hose connecting the small swirl tank to the large overflow tank is not cracked, and that the pressure cap on the small tank is not leaking, then go drive it a while & recheck the water level after it cools off. If the water is now low, there's something not working right.

On another forum, we talked about "how do you really know if your car is overheating" and "how hot is too hot for a Pantera". The consensus was that if you have no boiling, then your car is probably ok. If you hear "blub blub", then you probably have a problem.

The first thing I'd do is replace the radiator cap. It's cheap, and if the cap is faulty, you don't have a pressurized system and you'll have boiling at 212 instead of higher. What you want to avoid is boiling, because it means little pockets of steam in the system, which means localized VERY hot spots in the heads. Increasing the pressure in the system may be able to eliminate the boiling.

If you have a good pressure cap and you still have boiling, then your problem lies elsewhere. But, to oversimply the (long) discussion we had, "boiling is bad".

------------------
Charlie McCall
1985 DeTomaso Pantera GT5-S #9375
"Raising Pantera Awareness across Europe"
http://briefcase.yahoo.com/gt5s_1985

quote:

---

Originally posted by Charlie McCall:
On another forum, we talked about "how do you really know if your car is overheating" and "how hot is too hot for a Pantera". The consensus was that if you have no boiling, then your car is probably ok. If you hear "blub blub", then you probably have a problem.

The first thing I'd do is replace the radiator cap. It's cheap, and if the cap is faulty, you don't have a pressurized system and you'll have boiling at 212 instead of higher. What you want to avoid is boiling, because it means little pockets of steam in the system, which means localized VERY hot spots in the heads. Increasing the pressure in the system may be able to eliminate the boiling.

If you have a good pressure cap and you still have boiling, then your problem lies elsewhere. But, to oversimply the (long) discussion we had, "boiling is bad".

---

I HAVE BEEN TALKING TO THE MUSTANG GUYS WHEN WE GO TO THE TRACK. THEY ARE PUTTING HIGHER
PRESSURE CAPS-FROM 19-25 LBS AND STATE THE CARS RUN COOLER. ONE RACERS STATED THAT FOR EVERY POUND OF PRESSURE YOU CAN CHANGE THE BOILING POINT BY 7 DEGREES. MY MECHANIC THINKS THAT THIS JUST PUTS MORE PRESSURE ON THE GASKETS, HOSES AND RADIATOR. WHAT IS THE PROPER SIZE CAP?? DOES IT GO ON THE RADIATOR AND PRESSURE TANK??? HOW MUCH CAN
YOU INCREASE THIS TO LOWER TEMP???
THEY ALL CLAIM IT HAS HELPED WITH OVERHEATING CARS. MY MUSTANG RUNS RIGHT AT 190 TO 200 ON THE TRACK WITHOUT INCREASING THE CAP SIZE. REMEMBER WE ARE RUNNING AT 6000 RPM UP AND DOWN FOR 20 MINUTE SESSIONS
WHICH IS DIFFERENT THAN NORMAL STREET DRIVING.

ANY THOUGHTS- BOB

Increasing the pressure on the system will not aid in cooling. It merely increases the boiling point of the coolant.

It should make no difference in temperature readings - they will be the same with a 5 pound cap or a 15 pound cap. It won't boil over as readily though. They may interpret this as "increased cooling", but the cooling capacity of the radiator remains unchanged.

------------------
Charlie McCall
1985 DeTomaso Pantera GT5-S #9375
"Raising Pantera Awareness across Europe"
http://briefcase.yahoo.com/gt5s_1985

Thanks for all the help!!

quote:

---

Originally posted by Charlie McCall:
Increasing the pressure on the system will not aid in cooling. It merely increases the boiling point of the coolant.

It should make no difference in temperature readings - they will be the same with a 5 pound cap or a 15 pound cap. It won't boil over as readily though. They may interpret this as "increased cooling", but the cooling capacity of the radiator remains unchanged.

---