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

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tranniedoc

tranniedoc

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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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I forgot to mention, I checked the temp with an infrared thermometer, the gauge is correct. The lower hose has a wire insert and isn't collapsing. The Champion radiator was new and it has run hot since day one.
Thanks.
 
Your not moving enough air and may also need a larger rad..Where you live? i do have a used but good condition electric fan that move a lot of air and has built in shroud .Might be able to help you.
 
A electric fan with shroud should help as mentioned. A step further would be a mechanical fan with clutch and shroud. My Dodge ram has a 5.9 and it has a mechanical fan with shroud w/195 degree thermo. I had over heating problems in my cuda so I upgraded to a Griffin rad and a mechanical fan with shroud. This cured my problem. I just never had any luck with a e-fan . The fan I used moved 3650 cfm and still wasn't enough.

If you don't have a big trans cooler I highly recommend that as well.
 
Could the carb be too lean? Also, i don't have personal experience with the magnum (outside a few trucks) but isn't the pump a reverse rotation. I see you have the serpentine system, could you have gotten the wrong pump? Just throwing out some ideas.
 
fan shroud is needed as well as checking the plugs to make sure your not running lean as suggested above

if your heads/intake have been off it could be the gasket is blocking the coolant ports
 
I was having heating issues as well and some crusty old mechanic and I were bullshiting and he told me to get a shrouded electric fan off a 80's Mercedes. Found one at a wrecking yard for 40 bucks and that sucker could propel the car forward it moved so much air! Solved all my problems. Most of the new fans suck. Just another option to explore.
 
just a thought, it may sound redundant, but have you verified the electric fan blades are actually spinning the right direction?
 
If it gets hot on the highway no fans or shrouds are going to help. You need more radiator.
 
That mmile-long ribbed upper radiator hose isn't helping, either....Those things are horrible for flow!
 
After looking at the pic., it looks to me that the aluminum cover/mount you are using to mount your elect. fan could be limiting the amount of air flow across the useable radiator cooling cores. I say that because even with the holes cut in the mount you are still blocking the path of the air. I would try a full size shroud and a manual clutch fan. The standard shrouds have a funnel effect to direct the air to the fan which allows all of the surface area of the coils to have a smooth air flow across them to the fan, not just a small center area. Good Luck and keep us posted.
 
I had the same problem with my 73 dart. Running around town idling ect was fine. Get out on the highway and put some sustained load and it would get too hot. I had a stock 26" 2 core copper radiator. Replace it with a Griffin 2 core aluminum radiator and a Mrgasket high flow t stat and it barely gets warm now. Your radiator looks pretty good so I would look at getting max air and coolant flow through what you have. High flow t stat and seal all the holes in the radiator support so all the air has to go through the radiator. Fans and shrouds can actually block airflow on the highway. So you have to find a balance. AC condenser also blocks air and adds heat to the system.
 
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.
The fan is turning the proper direction, a sheet of paper stuck in front of condensor and the fan is moving a lot of air out the rear.
As stated, I've tried the timing all over the place.
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).
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.
 
In another post I had the same issues. I have a 408, High stall convertor, Pro Form electric water pump, fan shroud, and 3 electric fans. I could keep the car cool for a while, but then the temp would start creeping up. Read another post about air in the system, and decided it was cheap and easy to try that. I have a few holes drilled in the t-stat, so I lifted the front of the car as high as I could on jack stands and then ran the electric water pump. I saw bubbles coming out for quite a while, and I just kept topping it off.
Since then I can get the temp up and it never goes past 190. I have a 180 degree stat in also....
Give it a try, won't cost you anything.
 
I also have a 3 row Champion radiator on my 408 stroker Dart. I'm running 2 12" pusher fans right now and have the same issue with the temp slowly climbing. I'm not sure how high it would go because I shut it down if it hits 210. I'm going to add a large fan in a puller config next to see if that helps. I'm wondering if these radiators are just junk.
 
I have a 4 row Champion with 2 12" pullers and have the same issues-wondering the same thing. Mild built 360 close to stock.

Loosenutz said:
I also have a 3 row Champion radiator on my 408 stroker Dart. I'm running 2 12" pusher fans right now and have the same issue with the temp slowly climbing. I'm not sure how high it would go because I shut it down if it hits 210. I'm going to add a large fan in a puller config next to see if that helps. I'm wondering if these radiators are just junk.
Click to expand...
 
Ksipes1 said:
I have a 4 row Champion with 2 12" pullers and have the same issues-wondering the same thing. Mild built 360 close to stock.
Click to expand...

I thought about going with a 4 row but Champion rates the 3 row at around 700hp :roll:
 
schreecher said:
In another post I had the same issues. I have a 408, High stall convertor, Pro Form electric water pump, fan shroud, and 3 electric fans. I could keep the car cool for a while, but then the temp would start creeping up. Read another post about air in the system, and decided it was cheap and easy to try that. I have a few holes drilled in the t-stat, so I lifted the front of the car as high as I could on jack stands and then ran the electric water pump. I saw bubbles coming out for quite a while, and I just kept topping it off.
Since then I can get the temp up and it never goes past 190. I have a 180 degree stat in also....
Give it a try, won't cost you anything.
Click to expand...

I was helping with a late model Stratus - they have an air vent valve in the cooling system. We attached a hose and watched air bubbles come out for a surprisingly long time even after full temp was reached.

I suspect the rad is not the problem in a lot of cases.
 
Idaho said:
I was helping with a late model Stratus - they have an air vent valve in the cooling system. We attached a hose and watched air bubbles come out for a surprisingly long time even after full temp was reached.

I suspect the rad is not the problem in a lot of cases.
Click to expand...


Wish these guys would try getting all the air out of the system before bashing the radiators (any brand for that matter). The guy down the road has a Dart with a 500+ cubin inch motor with a smaller radiator and a 16" fan, and he has no problem with it. Although he does not drive it on the street, it would surely heat up very quickly just idling I would think....
 
I've been working on cars for almost 20 years and I'm well aware of how to remove the air from a cooling system. I even have air bleed valves installed on my 408 and small holes drilled in the thermostat. There's no air in it.
 
Mr.FT said:
After looking at the pic., it looks to me that the aluminum cover/mount you are using to mount your elect. fan could be limiting the amount of air flow across the useable radiator cooling cores. I say that because even with the holes cut in the mount you are still blocking the path of the air. I would try a full size shroud and a manual clutch fan. The standard shrouds have a funnel effect to direct the air to the fan which allows all of the surface area of the coils to have a smooth air flow across them to the fan, not just a small center area. Good Luck and keep us posted.
Click to expand...

I noticed that too .
Also I've heard where the electric fans can actually block airflow at highway speeds. That's why the old tech used the clutch fan for max airflow when the vehicles moving. My 2C.
 
Very familiar with getting the air out of the cooling system and have made sure that there is no air in my system many times. Not bashing the radiator, it is a 4 row but it just doesn't cool any better than the stock unit I took out.

schreecher said:
Wish these guys would try getting all the air out of the system before bashing the radiators (any brand for that matter). The guy down the road has a Dart with a 500+ cubin inch motor with a smaller radiator and a 16" fan, and he has no problem with it. Although he does not drive it on the street, it would surely heat up very quickly just idling I would think....
Click to expand...
 
Well if you have an over flow tank on the rad. This will remove the air from the system and add coolent as needed. The pic you have posted it looks like an air flow issue with the shrowd the fan is only pulling air through a small part of the rad. If you put the mechical fan on with a funnel shaped shrowd it should pull more air threw it and cool the engine down. I have just never had much luck with the electric fans.
 
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