Running hot with extended idle time.
 

My 54 Meteor with the 255 Flathead (Canadian car, we got the flathead one more year) has a new Champion radiator, 180 thermostats, 15lb cap, new water pumps and otherwise completely stock. Engine runs like new, in normal driving it never gets hot.

It does get hot if you leave it idling for more than about 10 minutes. Had it happen two years ago at a construction site on the highway, it approached hot on the gauge, but once we got the green flag, it cooled down in about 1 minute, maybe less once driving.

From what I'm told this is normal behavior for the old flatheads.

Recently I was on a car cruise with my wife in the car. I warned her it was going to run hot, and I might have to run the heater sometimes. Well we ended up idling and barely moving for about 45 minutes! The gauge was in the hot zone the whole time. I was holding my foot on the gas to keep the idle speed up, and that would bring the needle just above the "hot" line on the gauge.

It never boiled over, didn't lose any antifreeze at all. I shut it off when we parked, opened the hood to let it cool, and two hours later when we left it fired up and has been running just fine since.

Has anyone built a shroud for the rad fan? I'm thinking when I get time next summer I would build one, I'm really curious as to if that would fix this issue. I really wish I had my infrared temp gun with me, because I don't really know what temp that engine was actually running at.

Re: Running hot with extended idle time.
 

i would be hoping to find a slightly loose fan belt or better yet, a kink in an old coolant hose.

Re: Running hot with extended idle time.
 

From everything you've said, I think it's time to come up with the $10-$20 it takes to get one of those infrared remote thermometers. Then you can find out what's really happening. They're useful for other things, too. I was able to determine the little lady's oven was consistently 20 degrees too low a few years ago. It was the only car-related thing I had that she ever appreciated.

Re: Running hot with extended idle time.
 

Fan belts are tight enough, and no kinks in the hoses.

Took the car to town tonight, and when I came back, I let it idle. Took a long time, more than half an hour to even get close to the hot mark on the gauge. Brought out my infrared thermometer, and the hottest temp I could find was 209 at the thermostat housings. Most of the cylinder head(s) surfaces were around 200, with one area that was 212 next to a spark plug.

So, I have a feeling, the gauge on the dash is a bit more sensitive than I thought, and my guess is that when the gauge needle gets ON the hot mark, its probably close to 220, maybe not even that much. I didn't have enough time tonight to mess with the car more but it is a cooler evening and it just wouldn't get any hotter.

Might have to keep one of these temp guns in the car on my next road trip when I think I can let it idle for a while and verify what my gauge is showing. At this point I'm not too worried.

One interesting note, is that even though my thermostats are 180, they seem to run at 160 or so at normal operating temp.

I could swear I read on this forum somewhere, that as long as it doesn't boil over (any engine) it's still transferring heat into the cooling system (no air in the system) and there is no harm done. That makes sense to me.

I feel better now after taking these readings, and I'm actually quite impressed at how well that new radiator keeps it cool. Still want to put a shroud on it someday...

Re: Running hot with extended idle time.
 

I would fit an electric pusher fan in front of the radiator. You might not want to do that or it may not be easy if you are still 6V.
While marginal, it does sound like your car is still coping.
Mart.

Re: Running hot with extended idle time.
 

I've had lots of early Mustangs that would overheat if I was caught in a traffic jam on the freeway on a very hot day. I replaced the two-row radiators with three-row's and that cured them. You could also try a fan shroud or an electric fan. You might crank the idle speed up just a little and see if that helps, there's just not enough air going through the radiator when it's idling.

Re: Running hot with extended idle time.
 

I have a 50 Ford with stock 239 cu in motor. It has a I think Champion radiator. Running temp on the heads are around 165. I have never let it run an extended period of time. It runs fine.
My question is why does the radiator stay hot so long. I came back from town yesterday. The radiator was still pretty warm after a few hours. Maybe it has did that all the time and I haven't noticed.
I bought the car about a year ago. What lb. Cap should be on it.

Re: Running hot with extended idle time.
 

you can have the best radiator in the world and if your not moving air through it its useless. you need a fan shroud. how far is fan from radiator?? maybe you can get it closer to radiator.

Re: Running hot with extended idle time.
 

Some thoughts: The right and left banks of flat head engines tend to run at slightly different temperatures due to differences in the casting of the engine blocks, so you may see different readings on your hand-held sensor. The dash gauge and/or its sensor s in the block could be causing high side readings. A mechanical gauge would lilely be more accurate. I have adjusted my dash gauges but that's for another story. Aside from making sure the radiator cores are clean/clear ..... If there's too much space between the fan blades and the inner face of the radiator, the fan will tend to thrash the engine compartment air around and not draw much air if any through the radiator when the car is sitting still. This happened with my '47. I tried an electric fan .... had to increase the size of my alternator and got no substantial improvement. Options (1) shim the blade closer to the radiator (one inch minimum clearance and/or (2) better, having a sheet metal worker/person made an inner shroud so the fan will draw air through the radiator when the car is sitting still.

Re: Running hot with extended idle time.
 

Re: Running hot with extended idle time.
 

One thing to remember about fan shrouds, while they help your fan pull air at low speeds, they are a restriction to air flow at higher speeds. What speeds do you normally drive your car? Set the car up for those conditions.

Re: Running hot with extended idle time.
 

Curious what the ambient temp was when you experienced the over heating. I've only boiled my Merc once due to stupidity and having the rad covered on a cold winter day. The rad did boil and blew out the seam on the top tank. No thermostats in this one and I went with a 7 pound cap. They do tend to warm up a little if left idling too long on a hot day. Different fan blades options on these were available. Mine with the Mercomatic came with more blades than the 53 parts car I bought. Maybe the 3 blade fan was original with the standard trans.
Edit: my heat gauge "normal" is just a needle's width above the centre line.

Re: Running hot with extended idle time.
 

Here are some measurements to get you started……….Mark

Re: Running hot with extended idle time.