Overheating issues on a 383 Polara

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MopaR&D

MopaR&D

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My cousin and I were looking at a 1969 Dodge Polara with a 383-2V (converted to 4-bbl. and dual exhaust) for sale up in Fort Collins today. For $1000 and the condition it's in it's quite a bargain but the engine overheats after a half-hour or so of driving (started cold). The owner said he replaced the thermostat, hoses, water pump, and had the radiator flushed but the problem still existed. Since he had it done by a shop I'm wondering if there might be the classic "Mopar block corrosion" going on and the system is plugged up with deposits. If this is the case would there be any way to at least partially clean it out so we could drive the car on the highway for about 1 1/2 hours?
 
check for head gasket. aside from an obstruction, its the last viable cause for heat up
 
I doubt it's a head gasket as the engine has only 69,000 miles on it and I'm pretty sure the heads have never even been off. Also the oil is still a nice light honey color, barely any combustion deposits and certainly no "chocolate shake" in there.

One thing that might possibly be the culprit is an odd block heater (coolant heater really) that was "spliced" into the lower radiator hose. I have never seen one like this so I have no idea how it works. Time to go look up my old Mopar Action tech articles on cooling, haha!

EDIT: Just thought also, could overly retarded ignition timing make it heat up? The engine had kind of a stumble when you'd step on the gas and wasn't quite as strong as I expected a 383 4-bbl to be, even in a 4500 lb. C-body. Come to think of it I sure hope the timing set isn't starting to wave goodbye...
 
A lot of the inline block heaters have a pump in them to circulate fluid for a total warmup rather then the traditional in the block kind that only warm up a small portion of the coolant in your block.
 
Dan201 said:
A lot of the inline block heaters have a pump in them to circulate fluid for a total warmup rather then the traditional in the block kind that only warm up a small portion of the coolant in your block.
Click to expand...

So could that possibly have failed somehow and obstructed flow?
 
Does it actually boil over on you, or does the dash temp gauge just indicate that the engine is hot? If you aren't actually boiling over it could just be temp. gauge problems.
 
Radiator partially plugged even after flushing, fan clutch weak, retarded timing.

If it is a good deal, rent a U-Haul trailer and drag it home or drive it home while it is raining or snowing.
 
Disclaimer: I have a low post count so pay no attention to me as apparently one's post count determines the knowledge level of the individual

The block may be full of sediment as well, usually a reverse flush thru the drain plugs in the block will fix it.
 
I had a field mouse croak in one of mien that did that. But the radiator flushing would have taken care of Mickey. My money's on the restriction in the lower hose. I also would verify it's really overheating with a temp gun to rule out the gage.
 
440Ken said:
Does it actually boil over on you, or does the dash temp gauge just indicate that the engine is hot? If you aren't actually boiling over it could just be temp. gauge problems.
Click to expand...

Well the thing is the car doesn't have a coolant reservoir ("catch can") like my Duster so the small hose coming off the radiator cap just empties onto the ground. After driving the temp would continue to creep up and then the cap would start releasing water and it would start to form a puddle. Also the owner said the last time he drove the car it did overheat; there was proof of this as the radiator was about half-empty when we first checked.

I have a small infrared temp gun (more like a small stopwatch-looking thing) that should work but where is the best place to point it?
 
Infrared thermometers are freakin awesome for troubleshooting clogged rads.
Check the temp at:
The inlet neck.
The outlet neck.
Various places on the front of the rad - ( look for "cold spots" ) will tell you if some of the tubes are clogged. The biggest variation in temp will be on the first cycle of the t-stat

From you last post it sounds like it's overheating just sitting at idle?

Take a look at this...
I know it's from a ( GULP, prepares to duck and run ) "honda" site, but the concepts are the same. (just replace the "fan not coming on" with "bad fan clutch" :)
http://www.tegger.com/hondafaq/overheating/index.html
 
MOPEkidD-3 said:
So could that possibly have failed somehow and obstructed flow?
Click to expand...

That inline heater, if it's the one I'm thinking of, has a check valve in it so as the glycol heats up it'll open the valve and move thru it till cold glycol hits the heating element. Get rid of it and get a one piece hose and make sure the spring is inside the hose, which was probably removed to make room for the heater.
 
Thanks again guys. Unfortunately my cousin is having second thoughts about the car, as he's worried about distractions and whatnot that might affect his studying next semester. I'll make a note of your guys' suggestions though if we do end up going to look at it again.
 
See, I'd think he would be worried that the studies would get in the way of the project :lol: ah the priorities :)
 
Wow it's amazing how anytime I search a mopar issue it brings me to this great site that I'm a member of. This car seems to be having the same issue I'm having. I bought a 65 polara for dirt cheap. Runs great, drives great. After about 30 minutes of driving it gets hot, doesn't over heat though. I drove it a lot during the winter and had no problems
 
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