Overheating 1946 V8

46HARLEY

46HARLEY

Member
I have a lot to still learn about Flatheads. Today I would like to know the best way to track down my overheating problem. 15 mile drive and it overheated, pulled in the driveway and came out the over flow. What should my first task be ?
Thanks Larry
 
Has the cooling system been flushed recently?
What is the condition of the radiator?
What's in the radiator?
Are there thermostats? Do they open?
Are the waterpumps turning?

No magic, just some checking and trying.

Keep us posted on your progress.
 
FortyNiner is right on the money. Radiator, Radiator, Radiator. When you're done check the Radiator.

That was excessive however every single run hot situation I have had was because the radiator tubes were clogged with junk.

Having said that, you could have a head gasket issue or a block crack but I would start with removing the radiator and having it professionally cleaned.
 
It's not over heating unless it boils, and steam is coming out the overflow. Let it find it's own level. Some only fill the radiator a little above the cooling tubes.
 
It was definitely over heating. Removed thermostats and ran for 1/2 hour in the driveway, temp gauge in the middle. Read up about cooling system options. Some say have to have thermostats others say not necessary and some recommend restricting the flow with washers or other means. Curious about how others on this forum feel. Thanks Larry
 
46HARLEY said:
It was definitely over heating. Removed thermostats and ran for 1/2 hour in the driveway, temp gauge in the middle. Read up about cooling system options. Some say have to have thermostats others say not necessary and some recommend restricting the flow with washers or other means. Curious about how others on this forum feel. Thanks Larry
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That’s good news. Sounds like problem was with a stuck thermostat.
But in my opinion you should use thermostats so engine will come up to temperature quickly. Then when stats open you get just about the same coolant flow as with no stats.
Those washers were used to restrict flow in circle track racers running at continuous high RPM. For your usage, you don’t want to restrict flow.
 
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The 'Old Wive's Tales' about restricting flow so the "water picks up more of the heat" are just that - don't believe them. Flow is your friend - period. If you're ever bored - here is a link to read about coolant flow and this very subject:

https://www.stewartcomponents.com/tech-tips/tech-tip-3-thermostats-restrictors/

You should be running thermostats as they keep the engine operating in the correct temperature range. I would get some new ones first - preferably quality high-flow ones.

Also, have the radiator checked out - maybe cleaned and rodded out. Also, if you have stock pumps - then consider having them rebuilt by "Skip" here on the Barn - he has high-flow impellers that will increase flow and really help cooling.

If your block has a lot of rust and scale in it, that can also be a problem - read up on the various ways to flush out the rust/scale in a flathead (lots of posts on here).

Best of luck!
 
Thanks for all the replies. But more questions, suggestions on temp and which thermostats to buy and placement of the thermostats in the system. Some drill holes, some wire them in. What seems to be best practice ? Thanks again
 
46HARLEY said:
Thanks for all the replies. But more questions, suggestions on temp and which thermostats to buy and placement of the thermostats in the system. Some drill holes, some wire them in. What seems to be best practice ? Thanks again
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I use 180 degrees original style in my 39. With original style hoses they don’t move and are in the stock location.
 
180 degrees, Carquest 13848. I do like some others here and place a clamp on the hose above the thermostat. That holds it down on the water neck. I’ve never had the hoses with that oversized pocket for a thermostat.
 
Do drill two small (3/32) holes to let a little water bypass the thermostat. That is to let hot water down in the block get up in the neck of the heads where the thremostat bi-metal strip is. Otherwise, the temp gauge may go way towards hot, and then drop down when water near the thermostat finally gets hot enough to start opening. It is not really a big problem, just a little disconcerting,
 
A lot of good suggestions above, but I have to ask, do you have the top rad shroud and seal in place in front of the rad, and the same goes for the bottom shroud and seal. I had the shrouds in place but not the seals, when I bought my Coupe, and installing the seals helped reduce the engine temperature, especially at low speeds. I run 180 deg stats.
 

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51woodie said:
A lot of good suggestions above, but I have to ask, do you have the top rad shroud and seal in place in front of the rad, and the same goes for the bottom shroud and seal. I had the shrouds in place but not the seals, when I bought my Coupe, and installing the seals helped reduce the engine temperature, especially at low speeds. I run 180 deg stats.
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543381


543382
 
In addition to all the above good advice we need to ask how hot is your car getting? Some people get concerned when the factory temperature gauge goes past the half way mark. The 3/4 mark is 180 F, a completely normal running temperature. Full hot is 212. Also, some of the old gauges or sending units are no longer in proper calibration. I use a candy thermometer with the bulb in the coolant in the radiator to check the factory gauge.
 
Problem resolved, hopefully. 2 Carquest thermostats #13848 and 2 1/8 holes drilled in each. Temperature sits perfectly in the middle of the gauge. To answer was it really hot, pegged the gauge and boiled over. Thanks for the responses, Larry
 
My 1935 Ford pickup had a water boiling out issue, passenger side ran 20* warmer. Had the rad flushed, turns out the overflow tube was cracked in the upper tank. It would heat up then "syphon" out the upper tank very quickly, steam etc.
Rad shop fixed this & we run cool & no boil overs.
Both sides the same too
 

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Jeep09 said:
My 1935 Ford pickup had a water boiling out issue, passenger side ran 20* warmer. Had the rad flushed, turns out the overflow tube was cracked in the upper tank. It would heat up then "syphon" out the upper tank very quickly, steam etc.
Rad shop fixed this & we run cool & no boil overs.
Both sides the same too
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543681
 
A sticky thermostat is one of the first things to check. Another thing to check is the distributor to make sure that the flyweights are working to advance the spark and that the vacuum brake is functioning for load control. A plugged radiator can be checked with a infrared thermometer gun but it's not easy to tell if some tubes are plugged and some are open.

Moderate vacuum leakage or partially blocked carburetor ports can cause the engine to run a little lean and that will cause overheating.
 
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