thermostat

[cuda hunter]

78 400 with 727. 
No shroud around fan.
22" radiator.
195 thermostat.

When I drive the car it is almost always at 207 degrees.  When it sits still running it creeps up to 220,225.

If I change my thermostat to a 180 thermostat will that help the problem of just being too hot at 210? 

[Chryco Psycho]

it can't hurt to use a 180*
if it heats up sitting there is not enough air flow , this where a shroud & 6-7 blade clutch fan is nessisary

[headejm]

Doubtful that a thermostat change will help. The 195 thermostat should be wide open at your 207 degree temperature. A 22" radiator should be able to cool your engine assuming there are no restrictions in the core or fins. Is your radiator good? Adding a proper shroud would be my first recommendation. Fan/clutch would be next. 

This assumes your water pump is flowing the correct amount and there are no restrictions in your cooling  system.

[cuda hunter]

There should be no blockages.  Low mileage engine.  installed recently with only a few hundred miles on it. 
The radiator is good I'm assuming.   It doesn't leak.
I just replaced the water pump as there seemed to be a small leak that would hit the fan's just a little bit.
Pic of fan and lack of shroud. 

[MoparLeo]

Pressure test the cap. If it doesn't hold 16 lb. psi it will allow the car to heat up. Put a fan shroud on it. Ditch the flex fan blade NOW. Those blades will come off ! The flexing causes fatigue in the blades and at high rpm they come off with bad results. Hole in radiator, wiring, hood damage ( another reason for a shroud)  The factory used a shroud to direct as much air through the radiator as possible and a fan clutch to save the engine from wasting power over 40 mph. At those speeds the car is moving through the air faster than the radiator fan can suck air. Distilled water and new coolant. the cooling system must work properly before you can start to diagnose anything else.

[cuda hunter]

New radiator fluid but not distilled water.
New water pump
180 thermostat

I put a stant 270 pressure tester on the radiator, pumped it up to 16 pounds and lost pressure in about 5 minutes.

I'll replace the fan and I'm looking for a shroud. 

[MoparLeo]

Put a viscous clutch on it with the new steel fan The pressure test failed. It should not lose any pressure at all. Need to find the leak in your cooling system. If you can't find any visual leaks you may have a leak in a head gasket. A hydrocarbon test can find that.The cap needs to be tested to 16 psi.    Just an FYI, the number ONE cause of automotive break downs is cooling system failure. Whether it is hot or freezing outside.

[72 Challenger]

I had the same problem in my 74 Challenger and it was all resolved by a shroud. When the car is sitting, at lights or traffic, with no shroud, there is nothing directing the air through the rad. Your fan is spinning in free air. That lack of air movement is preventing the radiator from exchanging the heat from the coolant to the air. I almost gurantee this will solve your problem.


I agree about the flex fan, ditch it. They were designed more to reduce loss of overall HP. They are not for street driven cars. It's a ticking time bomb. 


also, a radiator not being leaky is not necessarily a sign of a good rad. It's jsut a sign that the rad does not leak. The tubes get clogged up over time from rust, calcification, mineral deposits, etc... Flush that bad boy out or have it cored. Your rad is pushing over 40 years old and you stated that it sat. When things sit, they settle or if it had jsut water in it, seperte into their individual components.

[cudamadd]

Have used the flex fan in the past and they are complete rubbish IMO l think all cars should use a shroud. When I got my can it was running hot done the radiator and got a shroud has been good now so far .

[cudamadd]

I have a 160   Thermostat 22 inc radiator and a 16 lb cap

[bennydodge]

Mine stays cool with the factory 22 inch radiator and a 180 T-stat. Putting a shroud on made a big difference at low speed.

[YellowThumper]

You stated the radiator lost pressure when tested.
Isolate it from the motor. Cut off the hoses short and clamp in some plugs. I have used pvc plumbing caps clamped on. If it drops it is radiator. If not then as others have said you have an internal engine leak.

[MOPAR MITCH]

Regarding comments on the flex fans, my experience showed the thin blade type as a bad cooling decision... made matters worse.. changed to a wide blade flex fan and much improvement!

However, in my racing ... with the SCCA (Autocross, road race, etc)... the SCCA has banned the usage of flex fans as they claim they are dangerous and eventually fatigue and break.. so, I'm now using a clutch fan with an aluminum blade OE fan (added almost 2 pounds).

[cuda hunter]

Good idea on plugging the lines that way.  Easy way to isolate the radiator. 

Looks like I will be buying a clutch fan.  No one has answered my wanted ad here so where do I find a clutch fan new? 
Should I just call roseville or is there a better location to purchase from?

[Strawdawg]

get a kit to test for exhaust gases in the coolant.

Most older radiators are severely blocked with sediment and precipitates from the coolant.

Shroud and hd clutch and fan.

Personally, I like 180 deg temps in these older cars but that does not seem to be your problem at the moment.