My 1972 Duster is running VERY HOT!!

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Paladin06

Paladin06

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Hello all it's been awhile. I took my Duster out yesterday for drive and noted immediately it was running very HOT. Initial indications were a stuck thermostat. I replaced it. Let the car run for about 10 minutes in the garage and the temp got over 200. I noted water flowing in the radiator so I assume the thermostat is working.

When I shut the car down I could hear water boiling in the engine. Any ideas much appreciated.

PS - The clutch fan is working.
 
What engine? What size radiator? Are you running a fan shroud? Is this a new problem- ie, did it work before with this same combination? Or is all of this new?
 
72bluNblu said:
What engine? What size radiator? Are you running a fan shroud? Is this a new problem- ie, did it work before with this same combination? Or is all of this new?
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It's the factory 340, and radiator been rebuilt once 5 years ago. Yes it has a shroud. It worked fine until yesterday
 
Paladin06 said:
It's the factory 340, and radiator been rebuilt once 5 years ago. Yes it has a shroud. It worked fine until yesterday
Click to expand...

Ok, so, you're looking for something in the "catastrophic failure" category instead of a general cooling mismatch then. I assume you checked the coolant level.

You already replaced the thermostat and you can see water circulating in the radiator, so, the thermostat probably isn't the issue. But, what temperature is it and did you test it before install? If it's not opening all the way it could be restricting flow.

Next would be to check if the lower hose is collapsing, if there was a spring in there before it could have rusted out (old ones weren't stainless). Then the water pump. You're circulating water, but if there's something going on there you might not be circulating the amount you need- bad bearing/shaft would reduce water and air flow. You also say the clutch fan is working, but what type do you have? If it's not spinning fast enough you could be losing air flow. And of course something could have broken loose in the engine (big old chunk of RTV, or rust, or...) and plugged something important.

I would just start checking the general condition of things. Hoses, belts, play in the impeller shaft, do a coolant flush on the radiator, that sort of thing. Looking for stuff that's worn out, out of place, etc.
 
72bluNblu said:
Ok, so, you're looking for something in the "catastrophic failure" category instead of a general cooling mismatch then. I assume you checked the coolant level.

You already replaced the thermostat and you can see water circulating in the radiator, so, the thermostat probably isn't the issue. But, what temperature is it and did you test it before install? If it's not opening all the way it could be restricting flow.

Next would be to check if the lower hose is collapsing, if there was a spring in there before it could have rusted out (old ones weren't stainless). Then the water pump. You're circulating water, but if there's something going on there you might not be circulating the amount you need- bad bearing/shaft would reduce water and air flow. You also say the clutch fan is working, but what type do you have? If it's not spinning fast enough you could be losing air flow. And of course something could have broken loose in the engine (big old chunk of RTV, or rust, or...) and plugged something important.

I would just start checking the general condition of things. Hoses, belts, play in the impeller shaft, do a coolant flush on the radiator, that sort of thing. Looking for stuff that's worn out, out of place, etc.
Click to expand...
Thanks. I had the pump replaced last year due to a leak. The fan rotates freely by hand and has no wobble. I'll try replacing the lower hose as it does look bad but it has a spring in it. The radiator has not been flushed in 5 or 6 years at least. Well I got work to do but not today, it's Easter Sunday.
 
72Dart6pack said:
15 psi.
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16 psi according to the 1972 factory service manual.

Paladin06 said:
Thanks. I had the pump replaced last year due to a leak. The fan rotates freely by hand and has no wobble. I'll try replacing the lower hose as it does look bad but it has a spring in it. The radiator has not been flushed in 5 or 6 years at least. Well I got work to do but not today, it's Easter Sunday.
Click to expand...

Check the impeller with the fan belt removed. A tight belt can hide a little play in the shaft. Plus you can take a better look at the belt and tighten it if necessary anyway.

And I haven't mentioned it yet, but there's always a gauge problem too. You said you heard boiling on shut down so that's probably not it, but it might be worth checking with one of those infrared thermometers to see if it's in the same ballpark as the gauge readout.
 
Paladin06 said:
I'll try replacing the lower hose as it does look bad but it has a spring in it.
Click to expand...

Check it first.

Fire up the engine, let the coolant get flowing and with the system sealed up operate the throttle by hand under the hood and rev it a couple times while watching the bottom hose.
 
Paladin06 said:
Thanks. I had the pump replaced last year due to a leak. The fan rotates freely by hand and has no wobble. I'll try replacing the lower hose as it does look bad but it has a spring in it. The radiator has not been flushed in 5 or 6 years at least. Well I got work to do but not today, it's Easter Sunday.
Click to expand...


On a thermostatic clutch That's a bad sign.
On a viscous clutch it could go either way, which is why I never run one anymore.
Did you test it with an IR gun, or a meat thermometer?
Working in your driveway, with the cap off,you can get her hot, then cool it by watering the outside of the rad. The temp should begin dropping almost instantly.
If you see bubbles in the water, or foam, or smell exhaust, well you know what that is!
Sometimes , when you blip the throttle, you can hear it bubbling in the heater core. Reverse the hose connections and try again.

At idle in your driveway, with the engine hot, the fan should be noisy and moving huge amounts of air. If you have A/C, the condenser is, or can be, a huge PITA. They get clogged with dirt and debris and insect nests/eggs.
 
Last edited:
AJ/FormS said:
On a thermostatic clutch That's a bad sign.
On a viscous clutch it could go either way, which is why I never run one anymore.
Did you test it with an IR gun, or a meat thermometer?
Working in your driveway, with the cap off,you can get her hot, then cool it by watering the outside of the rad. The temp should begin dropping almost instantly.
If you see bubbles in the water, or foam, or smell exhaust, well you know what that is!
Sometimes , when you blip the throttle, you can hear it bubbling in the heater core. Reverse the hose connections and try again.

At idle in your driveway, with the engine hot, the fan should be noisy and moving huge amounts of air. If you have A/C, the condenser is, or can be, a huge PITA. They get clogged with dirt and debris and insect nests/eggs.
Click to expand...
My fan is moving air but i would not say huge amounts. Perhaps I’ll replace the clutch.
 
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