I have a 1969 Charger with a 440. I have been having trouble with it overheating. To this point, I pulled the radiator and had it pressure tested, replaced the thermosat with another 190 deg, and replaced the radiator cap. Still, it begins to overheat. If I am driving the temp will hover between 220 and 250, but eventually leads to the radiator boiling over. I replaced the water pump three years ago along with the fan and clutch, it ran fine up until this overheating problem. I do not see any water in the oil, therefore, I don't think it's the head gasket. I recently read in the serveice manual that it could be the heat control valve on the passenger side manifild. When I looked at it, it appears rusted and the outer spring is broken off. The valve was all the way to the left, counter-clockwise position when I inspected it. Is that the closed position? Is it possible this is the cause of my overheat? Any help you can provide is appeciated. Thanks.

 

I am running a 50/50 mixture.

 

If that were the case, how can I get the air out? Is there a bleeder plug?

 

the tubes in the rad might be clogged.

are you using a rad shroud?

using a 160 thermo can actually make the water flow too fast and make it run even hotter as would a thermostat being stuck open or removed.

check your timing.

heat riser causing the overheating is possible but not likely. i can't tell you if it's stuck open or closed. if you free it up it may leak exhaust when the rust on the shaft comes loose. try to find out if it is open or closed before you free it. mopar may still have rebuild kits.

440's do run on the hot side but over 205 in gentle driving is not normal.

make sure the lower hose has a spring in it to prevent the hose from collapsing from suction.

 

Could be the rad tubes. If it is, what is the best way to tell if they are clogged, how would I unclog?

No shroud right now.

The heat riser is not stuck, it moves freely (spring broken). I guess this would have to be stuck in order for it to cause me a problem, correct?

Lower hose does have spring in it.

 

to check the tubes a laser thermometer is the best way. you can warm the car a bit until the water is just getting warm and then carefully feel the rad tubes. you might notice that some are cool and some are hot.

the corrosion adds a lot of weight. if the bottom of the rad weighs MUCH more than the top (you have to factor in the trans tubes in the lower tank if it's an automatic) you might have clogger tubes. the lower part of the tubes clog first.

if you have green spots on the tubes, it usually indicates corrosion.

with the water level just above the tubes, try looking into the rad while the car is warming up and look at the water flow. you should see a rush when the thermostat opens and the water level should not rise waiting for the water going down the tubes.

if you pull the lower hose, hold your hand over the bottom and fill the radiator. stop filling the rad, pull you hand away and the water should just flow out very rapidly. if it starts fast and slows, the upper tank is draining slowly because the tubes are restricted.

much of the testing comes from experience but i hope it helps.

you can tie the heat riser open with the slower warmup as tim said.