Advice Needed To Solve Another Overheating Mystery

S

sgwilson904

Member
I'm glad to see I'm not the only one with overheating issues, although I'd wish this problem on no one. I've read the other recent and archived threads and followed all advice but no I'm stymied as what could be wrong.

My 29 CCPU (which is new to me) seems to run all day around town and 35-40 mph. Over 40, the problems started. Cruising at 45 even in just 80 degree weather here in FL prompted boiling and soon water came out the top.

Club buddies thought the therm inside the upper hose was blocking flow and unneeded in hot climate. I not only removed it, I took off the radiator had it fully rodded and pressure tested by experienced Model A guy who assured me although he found it to be 30% blocked, it is now clear and fully flowing...yet that did not solve the problem.

A real pro told me since my radiator does not have a baffle, it isn't really hot but just splashing hot water up onto the MotoMeter sensor to make it SEEM hot...but that can't be it because the water IS hot--you can hear it boiling inside and thermometer confirms temp is 210+ when it gets that way.

Next guess was bad head gasket or crack in the block or head causing hot gasses to get into the water, even though there is no sign of water in the oil. So then we removed and inspected the head and the block and saw no signs of cracks.

We thoroughly cleaned both head and block and replaced the old copper-style gasket with a new silicon model. It ran 40-45 no problem and MotoMeter showed only slight bit of mercury...but then, sitting in the driveway idling (with spark at 9 o'clock position or maybe a little more advanced and idle set somewhat fast) it was boiling up a storm in about 8 minutes with water and steam pouring out the overflow pipe.

With the (slight?) possibility that the 8-minute idling caused the overheating, next plan is to let engine cool overnight, retorque the head and go run it at 45-50 and see what happens. If it starts to heat up, I'll slow it down...but then what?

The timing is perfect, so it's not that. The carburator is also properly adjusted--in fact after cleaning plugs and re-setting gap, it's never started easier or run more smoothly, at least until it overheats. It's got a new head gasket, so it's not that. There's no obvious cracks or sign of water in the oil. So what in the world could be causing this and how can I fix it?
 
How many cores in the radiator? If it is not a 3 core radiator you are wasting your time on it. It will not keep up. Sounds exactly like the problems I had last summer. Search the barn for my posts and you can see the extensive work we did to solve this.
 
Recore your radiator and add a proper baffle. 99% of Model A overheating problems, if the engine is tuned properly (fuel and timing correct), are due to a poor radiator and owner denial about the condition of the radiator.

Can you verify heat transfer from the radiator tubes to the fins (one eventual mode of failure)? Full flow (what exactly is that?) means nothing if heat transfer to the fins is not occurring.

Swap in a known, good radiator and prove it to yourself.

A motometer is a nice period accessory but is a poor diagnostic tool. You might try using a remote IR thermometer to determine if you in fact have a heat gradient in your radiator (uniformly hot at the top, uniformly cooler at the bottom) to at least support the assertion that the core is capable of cooling.

I recored my original radiator and can run at 50+ mph all day at 100°+. I added a thermostat to keep the coolant temperature above 180° for more efficient combustion otherwise most of the year it would run at 140-160°.
 
Rich has it right. If all else you say is true, it's your radiator. I faught overheating for years until I finally installed a good radiator. I even found a new one from Snyder's that didn't work. I suspected plugged tubes from a poor soldering job. Get a good radiator and your problems will be over.
 
FIRST, go to a smog shop and have them sniff for hydrocarbons in the radiator, you gotta' rule this out first or you may be just like a dumb cat chasing his tail!! Bill W.
 
What is the condition of the water pump vanes/impellars?? You rodded the radiator, what's the inside of the block look like??
Paul in CT
 
Thanks to all so far. One of my trusted experts has said from the first that it is the radiator, though the man who rodded it swears it is working as it should and this is NOT the cause.

Regarding the water pump: we inspected this carefully and it turns freely and the impeller seems to fine. No sign of any obvious problems here.

As to the condition inside when we pulled the head: The gasket was the old copper type so we didn't see much from that. We did see some sign of what could have been a little water leakage between the #2 and #3 cylinder due to coarseness on the head in a couple of small spots. We were hoping this was a sign of a little leak which may have been the culprit, even though there was never any water in the oil.

Also, we noted original Ford script valves but each cylinder was stamped "100," so we're thinking some bore job sometime has left us with thinner walls and perhaps there COULD be a crack inside there somewhere allowing exhaust gasses to over heat the water?

Other ideas? I sure hate to pay $500 for a new radiator only to find that is NOT what it is.
 
If someone with a new radiator could post some temp readings using an IR temp gun, that would give a good baseline for comparing your radiator. Shoot the temps across the top of the radiator, then across the middle, and then across the bottom. This is just a guess, but you might find something like 190* across the top, 175* across the middle and 165* across the bottom. The top half should give up a few more degrees than the bottom half because it's a larger temperature difference with the air than the bottom half. Anyway, this would give us a good baseline to check radiators that are in question.
 
I highly highly doubt it it anything besides your radiator and the fact u don't have a baffle inside stopping air from getting pulled down the fins and causing an air lock you. if it was a pressurized cooling system you wouldn't need one. i just had a cooling problem with mine i though my radiator was clogged up ect. turns out i just kept having the same air lock in the radiator. my uncle took put the front wheels on ramps and burped it for a while and she ran fine (air is a funny thing)
 
the compression seems good, so that leads us back to, slow timing, weak water pump worn vanes in it, or the most likly a bad radiator, either restricted or not enough enough cores, need at the least 3, 4 row is a lot better
 
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