intermitten overheating

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El caminnow

Junior Member
I have a 29 with a diamond block, runs good however overheats once in a while. Ill stop and idle, look under hood to check things out and then she settles down. I have a motometer to watch temp. it will run normal for 10 mi then suddenly shoot up. The other day i had to shut it down after boilover. Any way i removed pump, seems fine, impeller tight on shaft, very little end play and block and head are very clean inside, possible clogged radiator? Any thoughts anyone? THANKS, Sam
 
usually when an engine over heats on long drives or on a long gradual up hill grades, its the radiator that is the problem
 
Back flush it to remove the rust chunks that came from the block and are proudly sittin' on edge in the top of your radiator tubes.
 
it has no thermostat, what level is full? i usually fillr up to an inch or so from top. back flush it with the hose from bottom of radiator? thanks for replies! this site is great.
 
My 31 was overheating, I took the radiator to a rad. shop that deals with older cars, I watched them do a flow test, which it failed, They rec. I have it rodded out, which they did, The next day and $98 later it was done plus repainted, No more over heating.
I run my 50/50 mix. about 3" low.....Good luck, and let us know.
 
they make a back flush tool you can get at most parts stores, the radiator shops use it, it has a rubber cone on the front that sticks in the rad outlet tube or the hose, you attach an air and water hoses to it, the air causes turbulance in the rad tubes, dislouging any stuck particals in them, might and might not work, best bet is to have it rodded out if any dought of the rad being plugged
 
El caminnow said:
I have a 29 with a diamond block, runs good however overheats once in a while. Ill stop and idle, look under hood to check things out and then she settles down. I have a motometer to watch temp. it will run normal for 10 mi then suddenly shoot up. The other day i had to shut it down after boilover. Any way i removed pump, seems fine, impeller tight on shaft, very little end play and block and head are very clean inside, possible clogged radiator? Any thoughts anyone? THANKS, Sam
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If you are running antifreeze, drain it, save it and try water. Pure water absorbs much more heat than the same volume of antifreeze (remember all those specific heat calculations from chem class?). If that works, add a rust inhibitor. If that doesn't work (which is likely), remove the radiator and back flush it on a flat surface or upside down with a garden hose stuck in the bottom outlet. If a lot of debris does not come out, don't waste time reinstalling it. Take the radiator to your local radiator shop and see what they can do with it. If they can't fix it, buy a new one. It's money well spent. If a ton of debris is flushed out, reinstall it and see if it works. Motometers look nice, but are next to useless to monitor coolant temperature. Go to Tractor Supply and buy a cheap Coolant temp gauge. Put the probe in the upper radiator hose (you can use a couple of large washers to sandwich the hose where you cut a hole for the probe) and you will have more accurate temp info.
 
I'd bet the radiator needs to be cleaned out. Also, the coolant just needs to be over the tops of the tubes, otherwise the flow will usually push it out the overflow tube until it reaches that level.
 
My roadster was having boil over issues, cleaned head & block, had radiator cleaned and flow tested filled with 50-50 Sierra brand anti freeze. Still had minor issues, added a quart of napa engine Kool and it lowered my operating temp by about 30 degrees. No boil over now. A's others stated, just over tubes in radiator.
 
Paul from Maine said:
.... Pure water absorbs much more heat than the same volume of antifreeze (remember all those specific heat calculations from chem class?). ....
Click to expand...

Sorry to be picky, but two things: First, specific heat refers to "per gram", so to compare effectiveness on a per volume basis (i.e., the way radiators are filled) densities need to be taken into account. At normal operating temperature (~160 F), the specific heat capacity of 50/50 antifreeze is about 85% of that of water. But, it is also about 7% more dense than water at the same temperature. So, the heat capacity of 50/50 antifreeze would be about 8% less than an equal volume of water. So, my second picky is whether or not 8% difference qualifies as "much more".

On the other hand, in water's favor, its thermal conductivity--the rate at which heat can move through it--is nearly twice that of 50/50 antifreeze.

On the third hand, antifreeze's higher boiling point reduces the risk of localized vaporization at hot spots or when the going gets rough, at which point both heat capacity and thermal conductivity really do become much less.

Steve
 
If it overheats with 50/50, it will overheat with stright water, water wetter, or any other chem mix.
Take it to the radiator shop, It's not that hard of a job to remove and reinstall a model "A" radiator.
You'll be a happy guy, JMHO ;).
 
Steve,
Thanks for that great info. Very interesting. Im glad you took the time to post it, Thank you.
 
TIP # 319*****Intermittent overheating is often caused by intermittent LOW water level. Just drop a large head nail in your overflow tube to prevent "splash over" loss of water.
Bill W.
 
Pick up an infra red temperture gauge and shoot it at your radiator when warm. ($30 at Harbor Freight)
You will probably discover "Cool Spots" and such indicating blockages in the radiator.
This will help you determine about whether you need to repair/replace the radiator.
 
Louis said:
Steve,
Thanks for that great info. Very interesting. Im glad you took the time to post it, Thank you.
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Thanks, Louis. It turns out that aqueous ethlyene glycol's properties are very sensitive to temperature and concentration, so you really have to be careful making comparisons with straight water. I was surprised by the thermal conductivity data. Here's the most detailed source I found with Google:

http://www.meglobal.biz/media/product_guides/MEGlobal_MEG.pdf

Steve
 
Does the engine start running rough right as the temp is climbing? I saw this problem once and was blaming it on a head basket but found a crack between the cylinder and the water jacket on #3 cylinder... we also noted bubbling in the radiator from combustion entering the coolant system.
 
El caminnow said:
I have a 29 with a diamond block, runs good however overheats once in a while. Ill stop and idle, look under hood to check things out and then she settles down. I have a motometer to watch temp. it will run normal for 10 mi then suddenly shoot up. The other day i had to shut it down after boilover. Any way i removed pump, seems fine, impeller tight on shaft, very little end play and block and head are very clean inside, possible clogged radiator? Any thoughts anyone? THANKS, Sam
Click to expand...
Make sure you are using the timing lever correctly. I see many people driving A's that never touch the lever and have the timing drastically retarded. Makes more work and money for me but, I would just as soon not see motors destroyed like this. Sometimes they are not repairable.
 
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