Overheating during idle

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34DTaz

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Hi,
I have a 71 340 VS Duster and just got it started again after about 7 yrs of sitting. I changed the oil, ran a fuel line to a gas can so I knew it was fresh clean fuel, changed the water pump, lower radiator hose, radiator cap and flushed the cooling system. The car still gets hot when Idel. The water starts flowing well in the radiator at about 185 so I do believe the thermostat is working. I have not put coolant in it since it overheats and spits the water out. Any suggestions?

Thank you
 
That is what I thought I might hear. After doing the things I listed it is now idling at about 210 and if I am correct coolant boils at a higher temp. Do you know the volume of diluted coolant in a 340?
 
34DTaz said:
That is what I thought I might hear. After doing the things I listed it is now idling at about 210 and if I am correct coolant boils at a higher temp. Do you know the volume of diluted coolant in a 340?
Click to expand...

Coolant will only raise the boiling point 11 degrees. Don't need it in So. Cal.

That is not the core of your problem. Good chance you'll have to drain the liquid in the system to find/repair the core problem.

So it gets to 210 degrees, starts boiling over, and you turn it off? Have you actually driven the car since you got it running again?

What did the water look like the first time you drained it or flushed it? Have you drained the block itself at the drain plug in the block? Have you stuck a coat hanger wire in there to check for sludge rust? What did it look like when you removed the water pump.

Some probabable causes for overheating at idle.

Timing
carb tune
ignition tune (plugs, wires, points, advance)
fan shroud?
even though you flushed the system, there might be rust blockage and scale in the block

Do you have a laser heat gun? You can get them at Harbor Freight for like $35Check it at the intake manifold before and after your thermostat. Check the temp and various place all over the fins of the radiator. There could be tubes . You need one.

Check the temperature of the water at the top vs bottom radiator hose. that are blocked.
 
I have not driven it.
T
he water was solid rust color when I flushed it. I used a flush kit so I was putting water into the water pump/intake ports. I ran it, let it cool down, drained the radiator then repeated until the water came out clear. Thought it would not hurt to have the radiator hot tanked to be sure it is flowing well.

Water pump had some corrosion.

What do you suggest to figure out if it needs a new gas tank or just cleaned? Do I have to drop it or just pull the sending unit to inspect and remove old gas?

Thanks for all you help
 
34DTaz said:
I have not driven it.
T
he water was solid rust color when I flushed it. I used a flush kit so I was putting water into the water pump/intake ports. I ran it, let it cool down, drained the radiator then repeated until the water came out clear. Thought it would not hurt to have the radiator hot tanked to be sure it is flowing well.

Water pump had some corrosion.
Click to expand...

So did you take the radiator out to a shop to have it flow checked and rodded out?

Whenk you replaced the water pump, did you stick you finger or a coat hanger to see if you could get any more rust out.

Next is plugs, points, dwell adjustment, check intial advance, varify mechanical advance is working, varify vacuum advance is working.

Have you rebuilt the carb?

You have a timing light right?
 
34DTaz said:
...

What do you suggest to figure out if it needs a new gas tank or just cleaned? Do I have to drop it or just pull the sending unit to inspect and remove old gas?

Thanks for all you help
Click to expand...

Pull the sending unit, replace fuel line, drain all gas. Then try to look inside. Not easy to see. It's not going to look pretty and shiny. But look for loose scale. At than point you are a few screws and a couple of bolts from dropping the gas tank. Recently seen a 69 Dart sitting for 20 years cleaned out the loose stuff with a pressure washer. Of course let it set out on a hot day to evaporate all the water inside.

Typically your pick up screen/sock on the sending unit is disengrated. If so, replace it.
 
My 318 valiant does this.

I had a brand new 3 core high volume after market radiator, fresh engine, water pump, thermostat etc. everything is new.

It's nowhere near as bad since I changed to a 5 blade fan and put in a fan spacer to get the fan as close to the radiator as is possible.

(this bothers me as the 5 blade fan is HEAVYYY and will undoubtedly be robbing horsepower at high RPM)

My theory is simply that a modified motor will create more heat than a factory standard motor at idle and requires better-than-factory solutions.

One day I will build a fan shroud, swap to a flex fan and add additional electric thermo fans to the frontside of the radiator. In the mean time I just have to remember to not let it sit at idle for extended periods.
 
frosty_the_punk said:
My 318 valiant does this.

I had a brand new 3 core high volume after market radiator, fresh engine, water pump, thermostat etc. everything is new.

It's nowhere near as bad since I changed to a 5 blade fan and put in a fan spacer to get the fan as close to the radiator as is possible.

(this bothers me as the 5 blade fan is HEAVYYY and will undoubtedly be robbing horsepower at high RPM)

My theory is simply that a modified motor will create more heat than a factory standard motor at idle and requires better-than-factory solutions.

One day I will build a fan shroud, swap to a flex fan and add additional electric thermo fans to the frontside of the radiator. In the mean time I just have to remember to not let it sit at idle for extended periods.
Click to expand...

You need a shroud. And a 7 blade fan would help. That is why you had an improvement when you moved the fan closer to the radiator and changed from a 4?? to a 5 blade fan. You had a 4 blade fan on it before?

Stock 340's had a shroud and a 7 blade fan.
 
autoxcuda said:
You need a shroud. And a 7 blade fan would help. That is why you had an improvement when you moved the fan closer to the radiator and changed from a 4?? to a 5 blade fan. You had a 4 blade fan on it before?

Stock 340's had a shroud and a 7 blade fan.
Click to expand...

Cheers and thanked, I was not aware of that. Never noticed a 7 blade fan over here in Australia. It makes me wonder if i just haven't been paying attention!
 
Going to do the radiator have not rebuilt the carb.

Timing light is not working will get one this week.

What temp should I hope for at idle?

Not sure how advanced the timing should be?
Thank you
 
34DTaz said:
Going to do the radiator have not rebuilt the carb.

Timing light is not working will get one this week.

What temp should I hope for at idle?

Not sure how advanced the timing should be?
Thank you
Click to expand...

180 at long idle.

Sounds like you have tuning/timing issue. Is it fairly stock motor. Go by the book or don't run vacuum advance and set it to 34 degrees total advance at 3,000 rpm.

Having the radiator checked out is a great idea.
 
If you have access to the front of the rad, get it up to operating temp, thermostat open,, and just touch the front of the rad with the back of your knuckles, about half way down,, all across the rad.. What you're feeling for is cold (cool) areas, which will indicate plugged rad tubes.. If it's hot all the way across, which I doubt considering the rusty water, the rad isn't likely the prob... Laser temp gun is handy here, if you got one..

The bigger the cold area = bigger lost cooling capacity..

hope it helps..
 
if you have a fan clutch installed check to see if moves freely when engine isn't running, bad fan clutch has no resistance. If you're running a solid fan, this aint the problem.
 
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