Overheating at idle?

MN Stumpjumper

MN Stumpjumper

Senior Member
I just got a 50 2 door sedan with a stock v-8. It runs good, temp gauge shows 160-190 out on the road. When I stop and let it idle, the temp rises quickly. I didn't let it get past 195, as soon as I start driving, the temp goes down.The PO had the radiator rodded out.
Any ideas to start diagnoseing this problem would be appreciated.
This is my 1st flathead. Thanks.
 
Actually 195 isn't that hot. It can go above 212 with a pressure cap before boiling, but it shouldn't get that high.

Stock fan in place? Belts not loose? Pressure cap in place?

What happens if you speed up the idle just a little (spin the pumps and fan a little faster)

Checked the timing? (Might be retarded)

Water (coolant) level ok?

What sort of ambient temps you experiencing there at the time of testing?

Check the coolant level and belts, check it has thermostats, look inside the rad for water circulation when revving (above thermostat opening temp), check the timing, and then just let it idle and see what it gets to. It might go higher than 195 and steady out.

Congrats on your first flathead. May it be a long and joyful relationship.

Mart.
 
Overheating at idle indicates insufficient air flow. Over heating on the highway indicates insufficient coolent flow...
 
There should be an air baffle that seals the space between the top of the radiator and hood, and another below the rad between the frame rails. If these are not in place the fan can pull air around the rad instead of through it. ..B.
 
with all the 5 of the 50s cars i have owned, that normal.
reduced air flow at idle as indicated that the temp goes down when you start moving again. just make sure you have a good cap on it and you keep the radiator clean and you should be good to go.
if you feel uncomfortable, when you come to a stop just pull the choke out just enough to increase the idle a little and that will increase the airflow a little and slow the heat creaping up a bit. you can also put a 6v electric fan on a switch in front of the radiator and that will increase air flow in traffic when stopped.
that worked best for me.
don
 
MN Stumpjumper ..................
I do not think that you have a "problem". It is natural for a flathead to be a little warmer at idle. Naturally, there is less air moving through the engine compartment, to carry the heat away. I would not worry, until it gets close to boiling. I think this is "Normal".
Just setting up your idle speed, might fix your "problem".
MIKE :)
 
As I understand it, Flat heads don't like to parade in the summer due to overheating at idle. We did the Memorial Day parade yesterday in DC with 6 Model A's. We peed a bit but all made it thru the 96 deg heat. I had trouble at a 7 minute red light afterwards.
 
The 77 year old mechanic showed me something on an engine stand after he had overhauled my engine. At a slow idle no water circulated into the water tank he used as a radiator. At a fast idle the water circulated. Since then I have had Skip Haney rebuild my pumps and they may now circulate at a slow idle, I don't know.

I just drove my `35 last evening with the ambient temperature hovering near 90 degrees. On the road it does super with no heating problems, but once I sit at a traffic light, the red dye goes upward, even at a relatively fast idle. I installed an electric fan and it helps thru town.

I just had Skip set up a spare distributor for me. I have one of his rebuilt coils that will be used also. I am anxious to see if that helps cool the old gal down.

Shadetree
 
if possable when your gauge goes 3/4 or higher shoot it in several places with one of those thermo guns . i have 7 flathead fords with stock gauges . 3 with the fluid type 4 with the elect type. when i use the heat gun it reads much lower than my gauge,s say so i guess either my gauges are at fault or the thermo gun is. in any event they don,t boil over so i would take a reading & see what you have. may be just gauge reading higher than actual eng temp
 
Thanks for the info Guys, I'll do some more driveing and idleing. I'll let it "go" at idle to see how high the temp goes. It does have a mechanical gauge.
 
The fans on the early Fords do not provide enough air for stop and go traffic or long idle periods on hot days. I recently purchased a 39 convertible and drove it 45 miles home. It was 92 out, the car ran good and has Skips pumps. I went 5 miles and the coolant temperature was 162 through light traffic. Came to a large intersection with a long delayed red light and the temperature went to 178. Going through town for few miles it dropped back to 165 and when I got on the highway for the next 25 miles it dropped to 160. When I got to my town we stopped for a late lunch and when I came out in 35 minutes the temp dropped to 135. Drove 7 miles to my new shop at 160 degrees and left it idle for maybe 10 minutes while I made room to park the 39 and when I came out to pull it in the temp was 200 and a cup of water was on the ground. This is typical of any stock Ford in 90 degree temperatures. There are 3 things that are important in cooling. Amount of coolant in the system, the flow per minute through the system and the amount of air through the radiator. This car had the full capacity of coolant, more water through the system provided by Skips pumps and driving or moving forward plenty of air was moving through the radiator as indicated by the temperature driving home. When parked at idle there was not enough air and the temperature went up. To prove the point I also have a 39 pick/up that has Skips pumps for more water flow, a shroud and a modified 6 blade industrial fan for more air flow through the radiator. This truck was run at a fast idle for over 2 hours at the National V/8 meet in Maryland 5 or 6 years ago when it was 95 degrees in the flea market for all to see. It never got to 180 and when I raced the engine a little the temperature came down a few degrees. I went to lunch for close to an hour and left it running while Ken,Ct watched it for me. If I put 170 thermostats in it in 85 or 90 degree weather it runs 15 degrees warmer then with no stats. g.M.
 
I can run my stock 34 for 2hrs at a fast idle with a 14" household fan in front of it .the temp stays around 170 .What does that tell you ?? .
 
FlatheadTed said:
I can run my stock 34 for 2hrs at a fast idle with a 14" household fan in front of it .the temp stays around 170 .What does that tell you ?? .
Click to expand...
That you'll need to carry a large drum of electrical flex, and keep your trips slightly shorter than the length of the flex? :D:D
Oh, I slay me.....
 
All the tests we ran years ago testing Skips pumps were run with a house type electric fan against the grill. This simulates driving on the road with throatle set at about 40 MPH. The engine temperatures you get will be very close to driving at that speed at the same outside temperature as the test. Another thing of interest is on a hot day driving into the wind at the same speed as with a tail wind the engine temperature can be as much as 15 degrees lower even though the engine is working harder going into the wind. Even though you get low temperature with the fan test or driving at highway speeds, with stock fans the early engines will still run hot at long idles. The later cars improved with sheet metal ducting, seals and shroulds that directed all of the air flow though the radiator. The pressure cap also helped by blocking the over flow tube which keeps the water from excaping due to the restriction of the radiator tubes. This allows the water to be forced through radiator and the radiator to remain filled and cool better with a filled system. G.M.
 
GM,
I enjoy your posts, always informative. I have to wonder why someone doesn't come up with a more effecient replacement fan blade for our old Fords. They could sell a bunch of them.

Shadetree
 
Shadetree, the crankshaft mounted fans blow a lot of air but are poorly located. I have modified several generator mounted fans and put a lot of miles on them. I constantly check them so they don't come loose. I used grade 8 bolts and lock-tite but I still watch them. They do make quite a differance in cooling and the ones I used don't make a lot of noise. I just installed a new hard drive in this lap top and haven't transfered my pictures yet. When I do or get on my desk top I'll post a few pictures of 6 bladed industrial fans I modified to fit the old Fords. G.M.
 
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