29model A overheats when I drive over 50

M

mrphil

Junior Member
I have a 1929 model A that runs great. I put an overdrive in it that increases output by 30%. ever since I bought the car about 15 years ago, and even before I added the overdrive, it has overheated whenever I push the spead past 50. (with the overdrive, 50 is the equivilent of 42 mph in direct.) I can watch the thermometer in the radiator cap climb after driving about 8 or 9 miles, and when it gets close to the top, if I do not back off and slow to 45, it will boil over. I had the radiator cleaned, and have tried driving with more and with less timing advance, and that does not seem to make any difference. any thoughts? I drive this car every day, and next year, my wife and I had hoped to drive it from MN to TX. that is the reason for adding the Mitchell overdrive.
 
mrphil ;

I suggest you do a search on overheating . This topic has been addressed many many times . Usually the problem is the radiator . Where in TX. do plan to end up ?
 
I did have the radiator cleaned, and I can order a new one for about $600.00, but if I do that and it still over heats, I will be back where I started. My wife and I own a home near Fruitvale, which is about 50 miles east of Dallas. Anyway, I would like some to say that they had the same problem and they did this or that to fix it. but so far, all I hear is that it is a model a problem. I have had the head and the block magnafluxed and can find no reason for the overheating, but you may be right, in the end, I may just have to spring for a new radiator and hope that it solves the problem. Or drive the car 45 mph. at that speed, it never overheats.
 
Keep it at 49 mph. Just kidding. Have the radiator backflushed. Crap from your engine block could have coughed up and clogged your clean radiator
 
What exactly do you mean by having it cleaned? Was it a professional radiator shop and it was rodded out? Or was it just flushed out with some type of cleaner?

In the restoration of my truck I "cleaned" my radiator with 1 gallon of straight simple green. I capped off both of the inlet / outlets for the radiator hoses, plugged the overflow tube and sloshed it around two or three times a day for about a week and then flushed it out. I was amazed at the amount of crud that came out. Don't know if over heating would have been a problem as it hadn't run in 50 years prior but it runs 170 ish now with no problems.

Are your fins straight and attached well to the tubes. If not it won't transfer the heat well.

Get an infrared thermometer from harbor freight and play it over the radiator to see if you have any unusual differences in temperature. Should be evenly warmer across the top than the bottom.
Dave
 
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mrphil

When you do the search you will find many reasons ( radiator ,leaking head gasket,loosing water out the over flow, engine not broken in , baffle missing from radiator, air flow blocked from getting through radiator ,etc.etc. ) for over heating . Also I think Les Andrews covers this in one of his books.
 
My friends 29 Tudor did exactly the same thing, and a new radiator fixed the problem.

As Dave asked, what did they do to clean it? I'd try running straight white vinegar for a few days to see if that helps. If not, then have it rodded out. If it's too bad to rod out, then spring for a new core from Bergs.
 
I have a 3 row modern core called a VT core. It's not original, but you really have to look to see that it's not original. A lot of people here in Texas use them. I hear some people have a problem with water "flowing too fast" through them to cool, but I have it pressurized so I have no experienced this problem. At 65 in overdrive with AC on, it runs 170-175. If you decide to go this route, and water flows too fast, you can install a 160* thermostat, or shave off some of the water pump impellers. If i were you, I would install a temp gauge so you know exactly what's going on in that engine.
 
If the car overheats only under load or at higher speeds, you may want to see if you have a subtle leak in the head gasket that is burping a little combustion gas into the coolant systems. I did a test for this with my car by putting the front wheels against a high curb, putting the car in third gear and giving some gas while a friend checked for bubbles in the coolant. BAMB! I had bubbles. If the coolant looks like bear foam on the top, this may be the problem. Sometimes this can be fixed by just retorquing the head. For my car, I replaced the head gasket AND had a radiator shop clean (not rod) out the radiator with multiple backflushings and acid washes.

Keep us posted.
 
hey guys,
thanks for all the ideas. And to answer some of your questions, yes, I had a radiator shop rod and clean the radiator. they said that there are some fins that are not attached. I have checked for leaks, and have had the head off a number of times replacing the head gasket. we had the head magnafluxed and found no cracks. I will probably end up replacing the radiator, but it concerns me that when it heats up, and I back the speed down below, say 47, it will cool right back down. to me, that does not seem to be a circulation problem. Anyway, I appreciate all of your ideas, and it is great to hear from other A owners. I will have to get a photo of mine in here when I get a minute. thanks again.
 
Timeing too slow will cause major overheat.Make sure the lever when moved all the way down is increasing the timeing to max on the distributor .
 
If the radiator is functioning then I ditto Seth`s assesment . Starting to sound like a weeping head gasket . When you had the head off I assume you ensured that the head and the top of the block were flat . You might want to retorque the head and add some BARS LEAK .
 
The gradual overheating as you drive faster is not really a mystery. The faster you run, the increase in firings generates MORE heat! Fins that are LOOSE from the tubes means that the core IS junk.
A QUALITY core IS essential. I ran an earlier Walker 10 fin per inch core and NEVER had problems, even at 112 degree temps. Bill W.
 
The more I drive it, the more I think that "THE ASSISTANT GURU OF STUFF" is right. I think I will go ahead and order a new radiator and see what that does. Thanks to all, this is a great place to look for Model A answers!
 
I read another post on the Net where a person said he found acorns inside his engine water compartment. Just a wild idea, but if you want to pull your radiator hoses and then run a flush though your block/head, it may find something blocking the water flow in this area of your system. Just a wild idea but may not be to much of a effort and a lot less expensive than as new radiator. You may need new hoses anyway and a good time to change them. Good luck.
 
Fred K-OR said:
I read another post on the Net where a person said he found acorns inside his engine water compartment. Just a wild idea, but if you want to pull your radiator hoses and then run a flush though your block/head, it may find something blocking the water flow in this area of your system. Just a wild idea but may not be to much of a effort and a lot less expensive than as new radiator. You may need new hoses anyway and a good time to change them. Good luck.
Click to expand...
Fred,
Friend Dennis bought an "A" with lower hose missing. The head, the block, and the lower radiator tank was COMPLETELY stuffed with cotton!!:eek: No cotton in the upper tank, as it had the cap on and a thermostat installed. Took him FOREVER to get it all cleaned out! He thought a COTTONMOUTH snake did it!!:eek::eek: Bill W.
 
Is it "overheating" as in getting above 212 degrees?

Or is water just coming out because you have it overfilled? Water coming out does not mean your car is overheating.
 
you mit want to look at cleaning the inside of the engine block. Have a radiator shop check for tubes in radiator that mit be plugging to restreck the flow of colant. my 2 cents
 
My Model A was overheating at times, and I took the suggestion of Tom Endy and took the radiator to a shop that knew how to rod it. Simple cleaning and flushing will often times not clean out plugged tubes...they need to be rodded by someone who knows what they are doing. In my case, over 20 tubes were totally plugged...after rodding, the car maintains temperature perfectly.
 
Tow your fast car hehind the Model A and change when speeds over 50 are required. Other than that, enjoy it for what it was and is and not what you would like it to be ! Not nasty, just realistic !
 
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