Most common reasons that A's overheat?
 

As newbie I need some help. Took the truck on a ride last night and over heated. Where should I start? Water looks good and clear when drained. I did notice that the Moto-meter may not have been seated properly on the top of the radiator. Could this be part of the problem? Anything else I should start with?

Thanks for any assistance.

Re: Most common reasons that A's overheat?
 

Generally the reasons are these in no particular order:

Retarded Ignition Timing.

Too lean of carburetor fuel mixture.

Radiator tubes clogged.

Radiator fins fractured from tubes and cannot dissipate heat properly.


Your system is not under pressure so a loose Motometer is an unlikely cause. Also, too full of a radiator tank can allow water to overflow giving the appearance of overheating out the overflow. Make sure your water level is about an inch above the core or baffles and try again. If it is indeed pushing water out the overflow, then start by checking the ignition timing and fuel mixture. If the problem persists, use an infrared temperature gun to determine if there are cool spots in areas of the radiator core which would indicate heat from the water is not being dissipated correctly.

There are other less-common things that could cause overheating but for now as not to confuse you as a "newbie", lets get the basics covered first if you like and we'll explore other areas if this doesn't produce results.

.

Re: Most common reasons that A's overheat?
 

Did it boil over or was it just the motometer reading high?

Re: Most common reasons that A's overheat?
 

Great colors on the pickup. Almost same as my coupe. I have been chasing this gremlin for a couple of weeks. Are you running straight water or a mix of antifreeze? How long did it take to overheat? Were you driving 40mph or faster? Do you have a temp gauge or just the motometer?

I spoke to another barm member down in Dallas and while he is not overheating he is running the same temps as me. At the temps we are seeing in OK and TX we don't know if we can get them to run any cooler.

Re: Most common reasons that A's overheat?
 

The clue here may be that you mentioned you are a newbie. One thing that most newbies do not realize or forget, and some that are not so new, the Model A cooling system is NOT a pressurized system like the modern cars. Is it spitting water out the cap and/or overflow, or is it steaming?
Did you fill the radiator to the top? If so, the water will expand when heated and it will overflow, this is normal the radiator is just seaking its normal operating level. Try running with about 1/2 inch water over the top of the tubes. If you did fill your radiator to the top, that is most likely your problem. Otherwise what some of the others said might be the problem.

Re: Most common reasons that A's overheat?
 

The truck actually boiled and steamed. I started with the water about two inches below the neck, or just above the fins. I had been driving about 10 minutes at 35 MPH in 85 degree weather. Truck otherwise running well. As far as the amount of actual anti-freeze that was in the mix, I am not sure. I have not changed it since I have had the truck in the last 3 months. It smelled like it had a little anti-freeze in the mix, but not really sweet.

Re: Most common reasons that A's overheat?
 

Looks like Brent has the correct things to check for. If you go down the list, you should come up with the problem.

Re: Most common reasons that A's overheat?
 

Of course, Brents list is perfect :)

Check ignition first (fast thing to do, but i guess its not the prob)

Check carb (fast thing and if it responds to your adjustments and the
spark-plugs look ok, the carb should be ok too ).

From your info i guess most important point on that list should be:
- Radiator tubes clogged.

As there is no good test for the radiator-flow:

Dont struggle to buy a new HD radiator ( and keep the old one )

Let us know about ...

Best regards
Christoph

radiator of my car looked really nice, car overheated while running
fast or running uphill. After changing the radiator, it NEVER again
overheated and it could even run without fan....
running with wrong timing reduces power, and for sure it will produce
more heat, but i guess it wont overheat once the radiator is good.
Bad news - lots of work to change the radiator

Re: Most common reasons that A's overheat?
 

I always check the simple things first. Is your fan belt loose?

Re: Most common reasons that A's overheat?
 

CPL,
From what you say I would remove the rad. and take it to a rad. shop that deals with older car rad's. They can do a flow test and rod it out if necc.
You say your truck is running well, then the timing is not that far off, and if it has anti-freez or stright water, it still should not overheat.
CpL, you got a rad. problem. Dont knock yourself out chasing grimmlins.
98% of the time that an "A" model over heats... is the rad. JMHO. ;)

Re: Most common reasons that A's overheat?
 

One common cause is rust flakes from engine stuck on end in the top end of radiator tubes. "Back flushing usually belches them out.
My dog just said, "Hush up, let's go to bed!"

Re: Most common reasons that A's overheat?
 

I installed a thermostat on mine and she's been cool as a cucumber ever since.