Cooling issues 69 Dart GTS 340

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Keyeserin

Keyeserin

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Oxford, Wi
Things I've checked out.
stock 2 core radiator
7 blade fan
fan 2 1/4 inches from back of radiator
crank pulley 5.2 inches dia.
fan pulley 6.5 inches dia.
180 thermostat high performance
I have heater core supply line plugged (heater core leaks)
What else should I check or what do I need to change?

Temp climbs if idling
turn off engine temp climbs
 
Last edited:
Bypass the heater core so that coolant flows through the intake. Most cooling issues are due to lack of flow! You may also want to get a hi-flow water pump, it will make a significant difference. 65'
 
Keyeserin said:
turn off engine temp climbs
Click to expand...
Normal.
Keyeserin said:
Temp climbs if idling
Click to expand...
Under what circumstances?
What is the normal temperature driving at 35 mph or more for at least half hour, and what is the temperature range when idling?

Fan shroud helps at idle and low speed
Not holding rated pressure will cause a lower boiling point.
Certain idle settings of the timing and fuel/air ratio but more heat into the cooling system. Some emissions era vehicles had coolant temperature overides so this wouldn't get out of control. Don't think that was used in '69.
I wouldn't start with this as the cause since if it was a problem, it would have been a problem in 1969 when the car was new. But definately don't want it to have less timing or leaner mix than the factory specs.
 
Keyeserin said:
Things I've checked out.
stock 2 core radiator
7 blade fan
fan 2 1/4 inches from back of radiator
crank pulley 5.2 inches dia.
fan pulley 6.5 inches dia.
180 thermostat high performance
I have heater core supply line plugged (heater core leaks)
What else should I check or what do I need to change?

Temp climbs if idling
turn off engine temp climbs
Click to expand...
Water pump integrity? Also, the temp is initially going to increase after shutting down because the flow and fan are no longer cooling to whatever little degree they were.
 
I had a similar issue with a car I bought that had no shroud. Could be a number of things, but on mine, it was simply not enough air through the radiator. I put a new fan clutch on and installed a shroud and the car now runs nice and cool.
 
abdywgn said:
fan shroud?
water pump impeller slipping on shaft?
Click to expand...
Fan shroud ...Yes
Water pump hasn't been off. But I can check that.
I have a 7.lb radiator cap on it.
Radiator has a new core and flows well.
At idle the temp keeps climbing Driving it will come down but not stay there. Saturday drove it for 20 miles eventually it climbed up to 215. when I parked it overflow hose spraying.

Thanks for all the replies. I'm going to pull water pump and check that.
 
PRC said:
I had a similar issue with a car I bought that had no shroud. Could be a number of things, but on mine, it was simply not enough air through the radiator. I put a new fan clutch on and installed a shroud and the car now runs nice and cool.
Click to expand...
PRC......How far was your fan set back from radiator?
 
I'm with QWKSLVR. A 7lb. cap! You must be loosing coolant. You need a 16lb. radiator cap for sure. I purchased a 79 Z28 years ago that had a 13lb. cap. (owner didnt know why it was overheating) When I would turn the car off I would here it purge/release from the cap a few times before it cooled off filling my overflow. This could be one of you problems.
 
SpeedyDart68 said:
I'm with QWKSLVR. A 7lb. cap! You must be loosing coolant. You need a 16lb. radiator cap for sure. I purchased a 79 Z28 years ago that had a 13lb. cap. (owner didnt know why it was overheating) When I would turn the car off I would here it purge/release from the cap a few times before it cooled off filling my overflow. This could be one of you problems.
Click to expand...
My 69 340 owners manual recommended an 18lb, damn now I'm going to have to check.
 
I agree with the posts above.

As far as temperatures. 210* 190 to 210* is normal while driving. Actually pretty good. It means oil temp while driving is also in that range and that's also good. Helps remove condensation and combustion moisture from the oil and the viscoity is in the right range at those temperatures.

As far as dumping coolant when shut down. Yup. Eventually the amount in the radiator when cold will be just enough not to dump when shutting down hot. My recollection is either an inch above the tubes or an inch below the fill neck is about where it should be. I've added an overflow on mine so its been a while since dealing with the drip tube system.

I'm not saying it can't be better or the isn't a problem, but its in the ballpark of what to expect.
 
Keyeserin said:
I use Peak 50/50 coolant
Click to expand...
Don't see that as a contributing to the problem.
However down the road, if its their universal, it won't protect copper and solder as well their 'Conventional green' which uses 'inorganic' corrosion inhibitors.
 
'69 Dodge FSM says 190* thermostat and 16 psi cap. 14 -17 psi acceptable when testing.
 
You have both an idling issue and a highway issue. Neither is real bad.

Is the 340 stock or has it been rebuilt? Any performance upgrades? The 2 core should be fine if totally stock. The suggestions above of a shroud and a 15lb+ cap will help for sure. If that doesn't do it and you've done some upgrades, that might be pushing an oem 2 core to it's limit.
 
Do you have your crank pulley and fan pulley sizes reversed in your first post? Looks kind of odd. Usually the crank is bigger than the wp.

is your fan on the right direction? Stupid, but it happens. Don’t ask how I know.....
 
Keyeserin said:
Things I've checked out.
stock 2 core radiator
7 blade fan
fan 2 1/4 inches from back of radiator
crank pulley 5.2 inches dia.
fan pulley 6.5 inches dia.
180 thermostat high performance
I have heater core supply line plugged (heater core leaks)
What else should I check or what do I need to change?

Temp climbs if idling
turn off engine temp climbs
Click to expand...

underdriven water pump , ur pulleys.
 
Mike69cuda said:
Do you have your crank pulley and fan pulley sizes reversed in your first post? Looks kind of odd. Usually the crank is bigger than the wp.

is your fan on the right direction? Stupid, but it happens. Don’t ask how I know.....
Click to expand...
The pully measurements are what is on the motor. I have 2 different pullies for the crank that I could try. One measures 6 1/4" and the other 7".
 
Keyeserin said:
The pully measurements are what is on the motor. I have 2 different pullies for the crank that I could try. One measures 6 1/4" and the other 7".
Click to expand...

That may be part of your problem. The water pump should be spinning faster than the crank I think. That means your crank pulley should be larger than the water pump pulleys.

Folks smarter than me here may have more exact info.
 
Keyeserin said:
PRC......How far was your fan set back from radiator?
Click to expand...


The more important thing is how much of the fan is inside the shroud and how much is outside??? A good starting point is 50/50, half in - half out...
 
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