After A/C Add On Engine Overheats Really Bad

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hotrod3forty

hotrod3forty

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I just installed an a/c only unit on my 69 340 Swinger. It's a Nostalgia Air under dash unit. It puts out cold air but the engine immediately overheats to the point of the temp gauge pegging past hot when cruising or sitting at a stop light. The water pump is new, the heater core is new, I have a stainless steel flex fan that really doesn't flex that much, a 3 core radiator, 160 degree thermostat, and the timing is about 8 degrees BTDC. After I shut the car off, it won't start. I have backed the timing off and when it does start, it backfires thru the carb. If I move it up, it runs extremely rough. It ran great before the a/c install. Oh and the 340 is bone stock. I'm really tired of messing with it and I just don't want to touch it anymore, and everybody I've talked to don't have a clue. Any ideas before I yank it off and complain that I wasted hundreds of dollars??

Thanks
 
A/C isn't causing your overheating, something that wasent doing great before the install has called it quits likely

have you checked for the flow in the radiator? is the clutch fan working good? have an 8 blade one on there?
 
A 160 degree thermostat isn't bone stock. That fan isn't stock, A/C without a shroud isn't stock either.
 
Not sure about the a/c issue but the starting after its hot I may know why. My Dart would refuse to start when it got hot. I talked to an old timer and he told me to put the fattest ground cable I could find on the battery. I thought he was crazy and continued jacking with everything I thought was wrong. After a day screwing with it I figured I would try his idea and I chit you not worked perfectly. I couldn't believe it.
 
Put a shroud on, Ditch the flex fan for a factory 7 blade or a factory clutch fan, check the thermostat and heater core. Try the thermostat first and change the fan and add a shroud.
 
Toss your fan and thermostat in the garbage.

Get a real clutch fan that moves some air. Get a 180 stat. Get a shroud. Make sure your hood to core-support seal is there.

Get the car properly tuned.

See where you are after that.

The stock cooling system on these cars would cool just fine in Arizona heat back in the 60.
High compression, AC and all....
It's when people think they are smarter than Mopar engineers that problems happen.
 
Yes it has a fan shroud. I have run a 160 degree thermostat and a flex fan for more than 30 years and the temp gauge never made it to the first mark. As far as I'm concerned it's bone stock, I'm not splitting hairs with fans and thermostats. And I don't think I'm "smarter than Mopar engineers" either. I'm just asking for some ideas and I appreciate the one's I got. Thank you.
 
Don't trust the factory temp guages. Get an infrared gun and look for the hot spots on the engine, hoses and radiator. Could be something as simple as the bottom radiator hose sucking shut/collapsing and slowing down the water flow.
 
Good grounds and increase the timing to about 14-16* initial. Get the timing right and then tune the carb.
 
Sounds like there's air trapped in the cooling system. If so, it'll create steam, and that will make the engine run HOT.
Fan shroud is a MUST. Nothing wrong with a flex fan. I have a 11.5-1 compression 440 that runs so cool, if I run it without the thermostat, the gauge won't move from the "cold" pin, and it has a stainless flex fan.

Good Luck!

George
 
George R said:
Sounds like there's air trapped in the cooling system. If so, it'll create steam, and that will make the engine run HOT.
Fan shroud is a MUST. Nothing wrong with a flex fan. I have a 11.5-1 compression 440 that runs so cool, if I run it without the thermostat, the gauge won't move from the "cold" pin, and it has a stainless flex fan.

Good Luck!

George
Click to expand...

very bad idea to run without thermostat, water circulates too quick to cool the back of the engine, can cause rear cylinder damage

nothing wrong with flex fans, but they definatly won't move the air a clutch fan will that has a proper thermo clutch on it

for the most part flex fans will keep a car nice and cool, but ma mopar put the parts that are on our cars for a reason; it worked and worked good
 
66plyValiant said:
very bad idea to run without thermostat, water circulates too quick to cool the back of the engine, can cause rear cylinder damage

nothing wrong with flex fans, but they definatly won't move the air a clutch fan will that has a proper thermo clutch on it

for the most part flex fans will keep a car nice and cool, but ma mopar put the parts that are on our cars for a reason; it worked and worked good
Click to expand...
Yes, they did and you're right; engineers knew what they were doing.

I only ran the car without the 'stat when I first put it together to ensure I got all the water in the system, and all the air out of it. Car runs a 180 'stat now, mainly because I drive it until the first snow, and I like heat! LOL

I came from Corvettes and as you may know, they run hot, especially big blocks. If you run anything other than a clutch fan on a BB Vette you'll have cooling issues. Also, ALL the foam seals MUST be in place.

Only thing about my car is, with a 440 there isn't enough room between the WP and the radiator for the clutch fan. Like I said, my car runs cold with a flex fan and no 'stat. With a 180 'stat, the gauge will stay at the first mark on the stock temp gauge whether it's 90º out, traffic, red lights etc.

I think his problem is air in the cooling system. I suggest removing the 'stat and running the engine like that to be sure there's no trapped air.

George
 
..if it overheats immediately it's probably a defective thermostat,or it
got installed backwards.
..just a thought.
 
An engine that operates at too-low a temperature is a bad thing ! If it doesn't get "hot" enough , it won't be able to burn-off unburned gasses and other impurities .

Please note that MoPars equipped with either an axle package or factory-installed air conditioning had :
- 22" or 26" wide radiator ;
- fan shroud ;
- 5-paddle or 7-paddle fan ;
- viscous clutch or torque-drive clutch (one-in-the-same ?)

160 degree thermostats have no place in any post-1965 vehicle ; same goes for less-then-12 lb pressure caps .
Run a 180-185 degree t-stat (get a "fail-safe" 'stat) and a 12 lb - 16 lb pressure cap .

The temperature gauge *should* read some-where in the low-middle to absolute-middle ; this is normal .
One of the reasons --if not thee reason--why your Dart's engine's operating temp is climbing so rapidly at idle / low speeds is because of that direct-drive flex fan .

Best of luck ! Is that your Dart in your Avatar ? If so , it looks quite nice !
 
* Also consider adding a "puke can" for the coolant overflow . You can get a "generic" bottle from NAPA (et al.) and mount it either in the engine compartment or hidden in , say , the wheelwell's underside .

Again , good luck to you !
 
Did the aftermarket A/C change any of the water pump pulley ratios?

There is now a condenser in front of your radiator that will impede some air flow. Even with the A/C off. Maybe that was just enough to get it hot.

Do you run the A/C water pump? IIRC, there is an A/C water pump and a non A/C pump.

There are some cruddy thermostats out there. The owner of Milodon during a plant tour told us that the Milodon thermostats that are built to his spec have two manufacturing plants: One in the U.S. and one in India. His contract specifies he will only buy thermostats made in the U.S.

I think it's a really good idea to invest in a $30 harbor freight inferred laser thermometer. That way you can tell what temperature of: t-stat housing, temp sensor, rad inlet hose, rad. outlet hose, various spots on your radiator. If you have certain areas of your radiator that are not consistent with other close areas, you have a blockage.

Also, many times temp sensor are incorrect. You can check that with a infrared gun. Like I think most new mopar temp sensors are wrong. Shannon at www.Redlinegaugeworks.com adds an resistor to get the correct resistance for the gauge to show correctly.
 
I borrowed a picture that would look exactly like my Dart for my avatar until I got mine finished. Now that it is finished I will be changing my avatar when I get some pics put up! The a/c belt runs around the compressor, a separate crank pulley, and a single side pulley. It doesn't involve the water pump pulley. However today I messed with the timing some more, tapped the key and it started right off, checked the timing, ran it without the radiator cap and checked for flow, which there is, maybe if there was some air in there, maybe it got out, then put the cap back on. I let it idle with the a/c on for a loong time, and the temp needle sat in the middle of the gauge. I also sat with it in drive for a long time and the temp didn't move. This was in my storage building with no air movement. I shut it off several times and it restarted each time. So I'll see how it reacts when I drive it again. Thanks for all the suggestions...I'm sure I won't be through with it!

So where do you find Milodon thermostats?
 
Problem solved! New thermostat was stuck shut. Replaced the thermostat.....everything works great now! Shoulda looked there first I guess.....
 
hotrod3forty said:
Yes it has a fan shroud. I have run a 160 degree thermostat and a flex fan for more than 30 years and the temp gauge never made it to the first mark. As far as I'm concerned it's bone stock, I'm not splitting hairs with fans and thermostats. And I don't think I'm "smarter than Mopar engineers" either. I'm just asking for some ideas and I appreciate the one's I got. Thank you.
Click to expand...

When I added aftermarket air to my friends 65 Plymouth it was the same thing. It ran really cool before the ac addition but sucked big time after. it ended up being a problem of the fan not pulling enough air through the radiator due to the condenser. we made a few adjustments to the shroud and installed a 7 blade stock clutch fan and life was good again. it did run a little warmer that he was used to but we put on a mechanical temp sender and it never climbed over 205 even in 95 degree weather(outside , inside was goooooood!)
 
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