Magnum in 70 Dart, can't keep it cool.

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tranniedoc said:
Okay, this is what I've already done...
I've checked the plugs and they don't show any signs of lean burn.
I changed the water pump (the first one was the original from the donor car, the second one has a omni-directional rotor, both ran hot.
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Do you have anymore information on this "omni-directional" water pump? I have never seen any reverse rotation type pump with such an impeller. Have a picture by any chance?


tranniedoc said:
If I'm going to change anything in the fan/shroud area, I'll be putting in a clutch fan and shroud, but honestly, I don't think that's the problem since it gets hot on the highway (I'll probably put the clutch fan on anyhow).
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Since it only gets hot on the highway, save some work & just pull the shroud & electric fan clear out for a highway test.

tranniedoc said:
The Champion is a 3 row and it's the largest dimension I can get between the frame rails. Has anyone else run into a problem with these? They do offer a 4 row now, that would be the only way it could possibly be larger.
I rebuilt the engine, the head gaskets were ordered for the magnum engine, could they be wrong?
Thanks for all the responses.
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With a heating problem at highway speeds it sure sounds like a radiator problem. Perhaps some tubes were blocked during furnace brazing? If opening up the ram air through the radiator does not fix the highway cooling I would probably try another radiator.

The wrong head gaskets? I can't say for sure, but usually problems like that are more localized, like a hot cylinder or two and pinging problems.

B.
 
Here's the latest update...
I took off the electric fan and shroud and put on an 18" mech fan and clutch. No shroud yet, it's all custom in there so I'll have to fabricate one.
I took the same long drive uphill that has always resulted in 225* temps at the top and this time (with the A/C on) it barely got above 195*, and that's without a shroud.
It really moves some air! I had it running yesterday with the car cover still kinda draped over the car and the hood open, and when I raised the rpm's the air from the fan filled the front of the car cover like a parachute. I had the door open and my leg out the door and I could feel a strong wind coming from under the car. It really moves some air!
It doesn't like sitting still and the temp climbs quickly at a stop, but I'm attributing that to the lack of shroud, since it never got hot sitting still before. I'll fab a shroud and see what happens. But this is a tremendous difference with the mech fan and clutch.
Everyone that said mech fan and clutch... you were right!
Everyone that has a cooling problem with electric fans... try a mech fan (not a flex fan), it made a huge difference on mine.
I'll get a shroud on it and post the results, but after all of the stuff I've tried to get this car to run cooler, this is the only thing that produced any results, and it's a big improvement.
Thanks for all of the reponses, this forum is the greatest.
 
tranniedoc said:
Hi, I've got a 5.9 Magnum in a 70 Dart that won't keep it's cool. It runs cool enough in the winter (around 200+) but in the summer it climbs slowly to 225+. The temp climbs when the engine is under a load, or with the A/C on. If I remove the load (go downhill or pull over and idle) it cools off right away. It's the same at highway speed, if there's a load, it heats up. It has never boiled over but I can easily get it to climb to over 225.

It's got a Champion 3 row radiator, anti cav water pump, 17" electric fan with shroud, it's a mild, carburated, low compression engine. I've got the timing set at 8* idle with 25* total advance (but I've tried the timing all over the place with no effect on the temp). Today I put an aux pusher fan in front of the rad... no change. I'm running 25% coolant and water wetter... no change. I've tried several different thermostats (160, 180, 190)...no change. Notice in the picture that I removed the shroud flaps when I added the second fan. With or without flaps... no change.
I'd really like to get this thing to run in the normal temp range, but I'm at the end of my rope, I don't know where to go from here. I would put a clutch fan and shroud on it if I thought that would fix it but it gets hot at highway speeds as well.

Thanks. ](*,)
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The air in your block could still be a problem. You have to make sure that the hose going to the top of the radiator will not hold air pockets. I use the same type of hose ad it worked great once it was going up hill the whole way to the radiator. I also put three small industrial 12V fans over the blow through holes. They move a lot of air and don't use as much power as automotive fans. Got them from Granger. There web has lots is choices and work great.
 
This thread is almost 4 years old and he solved his problem.
 
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