overheating

[Maclab58]

Ok im a newbie Model A owner of about 3 months. I have a 28 AR Sport coupe that had set for 12 years. It runs great and is easy to start. Now my problem....... Whenever i turn it off it backfires add to that if I take it out and drive it more than 10 miles it overheats and boils over. Yesterday I took it for a drive a total of about 15 miles the first ten were no problem then it started to boil over and run like crap missing, sputtering and backfiring. I let it cool off, added water and it started and seem to run ok. So I headed back to my shop about 5 miles away and by the time i got there it was boiling over again. It was 105 degrees here yesterday to add insult to injury. It has a freshly cleaned out radiator, new waterpump and hoses. i do not have a thermostat in the cooling system. I have timed it checked the point gap etc and still have the backfire and heating problem. HELP!!!!!!!!!!!!!!!!!!!!

 

[Tom Wesenberg]

I would check the timing and add a thermostat.

Hopefully the muffler isn't plugged with animal crap or nests. Probably not, since you said it runs good for several miles.

 

[Gary WA]

Check for air around manifold (leak),cracked manifold air leak at wiper connections. Black soot will show up if any leaks are present around gasket.ensure carb has a gasket to manifold, and is tight. start here let us know what you find out.

 

[johnbuckley]

hey Tom Wesenberg , are you suggesting that a thermostat aids cooling?
Check for crud in cooling sytem has rad ben effectively flushed? , crud in water jacket?
back fire indicates posible weak mixture for various reasons which could also promote o/heating.

 

[Maclab58]

I rebuilt a zenith carb, has new manifold gaskets, the rediator was professionaly rodded out by a reputable shop. muffler is clear, no evidence of a manifold leak. i will ck the timing and point gap again. I doubt a blown head gasket.

 

[Tom Wesenberg]

hey Tom Wesenberg , are you suggesting that a thermostat aids cooling?
Check for crud in cooling sytem has rad ben effectively flushed? , crud in water jacket?
back fire indicates posible weak mixture for various reasons which could also promote o/heating.

A plugged radiator was my first thought, but the owner said he had it "PROFESSIOANALLY" rodded out, so that should eliminate that, unless he has too few tubes. My 29 Tudor came with a repro 2 row when I bought it, and that wasn't enough to do the job. And, it also wasn't enough area to allow the water to flow back to the block as fast as the water pump was filling the top tank.

The thermostat recommendation was just to help the engine warm up quicker and to help against coolant loss. At least it stopped the coolant loss on my 28 using an original radiator, fan and water pump, and stock engine.

 

[Old182]

If the backfiring doesn't start until you drive a distance, it doesn't seem likely it's from a vacuum leak; that would show up as soon as you start the engine. One way to check for manifold/vacuum leaks is to spray water or light oil around the suspected leaks and listen to the idle smooth out as a vacuum leak should give you a rough idle (when my wolf whistle horn loosens up, I can tell right away). You should also NOT fill the radiator to capacity - Model As have a unique ability to find their "happy" level of coolant, which will be a couple of inches down from the top of the filler neck. It seems all engines are a little different, and you'll have to find your sweet spot. If the radiator is overflowing coolant, it may not be overheating. When I first restored my car, I had a similar problem as yours and it turned out to be junk in the fuel line. The car would run fine for 25-30 miles and then run rough and quit. A few minutes later it would run fine again. I had used silicone caulk on my gas gauge and it turned into "snot" when the gasoline touched it. I found the problem on the way back from a long trip when I removed the fuel line (after changing carburetors, distributors, and just about everything else you can think of) and here was this long, snotty-looking mass hanging from the fuel line. Lesson learned! You might have rust or other stuff coming out of the tank after it sloshes around while driving - it's an easy check. BTW, leave the thermostat on the shelf until you figure this out - at 105 degrees you don't need a restriction in your cooling system. $0.02.

 

[kp]

Water is not flowing thru the radiator,mine did same thing,all ceased with new 4 tube radiator.Accelerate motor from idle and water would gush out filler hole with cap removed,with cap on, just run out over flow tube. New radiator core just ended my problem.

 

[Purdy Swoft]

The backfireing when you cut it off is caused by an air leak in the exhaust system it could be a loose manifold clamp or a poor fit between the exhaust pipe an the manifold. often the flared area on the exhaust isn't fitting up to the manifold and an air leak in this location will cause a backfire when the engine is shut down. Just because the manifold gasket was replaced doesn't always mean that it isn't still leaking. You could have a warped manifold, this is VERY common. The early style manifold gaskets are very narrow and if the manifold has the least bit of sag it may not be covering the gasket good. I always use the late 31 copper clad manifold gaskets because they are wider and less likely to leak. A Too rich mixture at the gav will contribute to the backfire apon shut down. What will happen is gas will collect in the muffler and a few seconds after shut down the temperature increases in the muffler enough to set the gas off and if air is present you will have an explosion, in some cases enough to damage the muffler. I run my gav one quarter turn off the seat with the model A zenith and closed with the model B zenith. The pot metal carbs usually have to be opened more because most are warped and leaking vacume.

Improper use of the gav or the spark lever will contribute to overheating.

 

[Paul from Maine]

I had my radiator cleaned out at a radiator shop. Infra red thermometer showed several cool spots after re-installation.Removed radiator, laid it on a table and filled it with draino. After four hours I backflushed and enough debris came out to fill an 8 oz cup. Re-installed and still had cool spots. Took it off again and filled with a gallon of that new rust eater you can get at Tractor Supply. Let it sit for a weekend and then backflushed it. Again enough debris came out to fill an 8 oz. cup. Eighty years of rust is probably too much for the standard radiator shop flush.