The Stovebolt Site Forums The Shop Area Interiors Overflow problems using 1949 Harrison radiator

Fellow Bolters... I am having some overflow/overheating problems when using an original 1949 Harrison radiator with my 1955 Chevy 235 and would like some advice/guidance. My 235 was bored .060 inches over and I'm using a short shaft water pump with Fenton dual intake and headers. I have the dual carbs semi-adjusted and the truck will now idol on it's own. My original temp gauge is reading about 185 degrees F after about 5 minutes of run time and then within about 5 additional minutes, the antifreeze will begin flowing out on the ground via the overflow tube. I am currently using a 50/50 antifreeze mixture with a 4# radiator cap. I've been testing with no thermostat as the thermostat that the local parts place sold me was a 195 degrees F thermostat which I think is much too high of a temperature and I don't think I'm ever reaching 190 degree F. A friend mentioned that the addition of either a single or double electric fan unit should help alleviate this problem. I look forward your responses and appreciate your help in advance!!

first off, coolant pushing out of the rad is most likely a sign you're filling the rad too full, it MUST be down at least an inch warm, more when cold, so that as the coolant expands with heat it DOESN'T push out, having the top tank down by half should work fine

next, DO NOT run it without a thermostat, ever, for any reason - a 195 is better than nothing, and until you put a stat in there's no point in trying to figure out if it's working correctly or not

lastly, considering the above, you don't have a problem to alleviate - except for needing a stat

Bill

When water boils (212 degrees at sea level), it turns to vapor and expands rapidly. The only place for it to go is out the overflow pipe. That's why the overflow pipe is there. If you did not have an overflow pipe, boiling water would crack your block every time.

Many in this forum have reported overheating problems with 235 engines. Search on the word "overheat" and you will find a ton of information.

I have my own theory on this, which you probably won't find using the search tool. Start by measuring the size of your fan. I believe the original fan from a 1949 216 engine is about 16.5-inches in diameter. About the same time GM switched to full pressure engines (1954), they also increased the size of the fan. The fan on my '59 235 is 19.0 inches in diameter. Now, this might not sound like a big difference, but consider this. A fan with a diameter of 19.0 inches has 33% more surface area than a 16.5-inch fan. What's more, as the diameter of the fan increases, the tips of the fan blades move faster at any given rpm. The tips of the blades move 15% faster on a 19-inch fan compared to a 16.5-inch fan at any given rpm. The bottom line is, the 19-inch fan pushes a LOT more air, probably around 50% more air when you combine surface area and blade speed.

The bolt pattern on the larger blades also changed. The short-shaft pumps that I've seen are designed for the smaller 16.5-inch blade. I installed the 19-inch blade on a short shaft pump, but I had to drill new bolt holes in the blade.

With the larger blade, a 180-degree thermostat, and a 7 psi radiator cap, my 235 will idle indefinitely at 185 degrees, even when the outside air temperature is 110 degrees. I can't speak to the effects of the dual carbs, but I imagine more fuel translates to higher engine temperature. If you are using a 16.5-inch blade, you will never push enough air to keep the engine cool.

P.S. You should probably take this topic over to the "Engines and Drivelines" forum, where you will get many other opinions.

not quite so 49er - water expands much before reaching boiling, and the overflow is there to prevent overpressure due to either overfilling [common] or overheating [unusual], and the coolant in a properly maintained [and filled] system will never use it [freezing will crack your block, extreme pressure from boiling will split the rad] - note the fact that there is a specified pressure for the cap and a specified temp for the thermostat AND the operators manual that came with all these ol trucks specifically states:

"volume in a Chevrolet cooling system expands about 1 quart when temp is changed from 32*F to 160*F -
therefor the solution should be left 1 pint to 1 quart low if filled cold to prevent loss of solution through the overflow pipe"
further on discussing antifreeze it specifically states coolant loss through expansion "is a result of overfilling"

also the standard thermostat is 160*F on all models, and the cap is 4# pressure on early trucks, 7# on later years
check your operators manual

Bill

Bill,

Good information, especially about coolant level and coolant expansion in the radiator.

However,
" . . . also the standard thermostat is 160*F on all models, and the cap is 4# pressure on early trucks, 7# on later years
check your operators manual"
is a very sweeping statement.

- on all models ?
- early trucks vs later years ?

The thermostat settings and radiator caps differed over the Advance-Design years and over the model of trucks in given years (and over the years of 216/235/261 engines, 1937-1963).

However, as you state, a 160 degree thermostat is the most common or "standard" setting for trucks, especially in later 235/261 years; however, 0-7 degree pressure caps

I think that light duty & medium duty trucks had 0 (zero) pressure radiator caps until 1954. However, earlier COEs had pressure caps - check the 1951 Chevrolet Truck Operator's Manual.

Also, a 151 degree or 160 degree thermostat was recommended many years (at least for A-D trucks) but I think that warmer thermostats were recommended in some years for some models of trucks and/or for some types of service and/or for some types of coolants/anti-freeze.

It should also be noted that in the same years (1954 and later), passenger cars had different specs than trucks for the "standard" radiator pressure-caps (at least up to 13 lbs) and for the "standard" thermostat temperature (at least up to 180 degrees).

You advice about checking manuals is on the mark. Would you suggest that the safest reference for radiator-cap pressure and thermostat setting would most likely be the Owner's/Operator's Manual and the Shop/Maintenance Manual for the year of the truck/radiator (to match the pressure capabilities of the radiator and heater system)?

Tim

http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0688.htm

http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0682.htm

http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0684.html

http://chevy.oldcarmanualproject.com/shop/1942_47/4247csm647.htm

http://chevy.oldcarmanualproject.com/shop/1955truck2/55ctsm06s09.htm

http://chevy.oldcarmanualproject.com/chevyowner/58om29.htm

Ahh. My two cents.
I run a 185 in my truck. I like the 185, as it makes more heat in the cab. It has dual carbs, doesn't get more fuel, just better mixture. I have a zero pounds radiator cap. Even running with a load, in all the heat we've been having, it never overheats, it never actually moves from 185.

I would suspect, that as stated earlier, the rad is over filled, and pukes out the excess, as the coolant expands. I know thats what my truck does.

If your carbs are lean, your truck will overheat. But that's a different problem.

Get that thermostat in there, and then see whats what.

True, water expands when it gets hot, but not much. Four percent to be exact at 200F. The capacity of 1949 engine and radiator is 15 quarts, which becomes 15.6 quarts at 200F.

However, as soon as water reaches its boiling point, it expands rapidly, and the weakest part of your cooling system will blow. The pressure cap on the radiator is designed to blow first. If it's not working the radiator will split.

Keep in mind that water boils at different temperatures depending on conditions. The higher the elevation, the lower the boiling point. The more antifreeze you use, the higher the boiling point. Finally, the higher the pressure, the higher the boiling point. Modern cars/trucks have higher ratings on pressure caps to increase the boiling point of the coolant.

well, yes Tim, I got a little general there, which is why I added to check your own year manual - the operators manual gives the basics in terms of how the system works, but most years don't have all the exact specs, not sure even the shop manuals indicate pressure cap ratings, and while there are variations with model, it's usually with special equipment and the majority here are dealing with 1/2 and 3/4T basic trucks, few automatics or odd models or car rads

I believe in all years after 48, 160 was the standard stat for light truck 235's, if antifreeze is used, the common practice now although it was a new idea then so the "standard issue" would have been lower - I know the Deco years and before were no pressure systems [and much larger rad tanks], the 4# cap I thought started with the 'full pressure' 235 .... at any rate, I'd say the 55 under discussion should have a 4# max with a 49 rad, but with a later rad could use a 7# .... part of the problem with our mixing original year parts

my particular point has to do with overfilling, as I believe it to be the real problem many folks call "overheating", and the misconception stems from modern systems with a remote tank, the assumption being the rad itself is full to the brim and should be in all cases - with rads that usually have virtually no tanks except the remote [expansion] tank .... also use of a modern pressure cap [12-15#] on an original rad is the cause of more than a few leaky rads as they weren't designed for the pressures of higher temps

the case at issue here is simply the truck telling the operator what the correct water level is by burping out the excess - although of course there's no chance of evaluating the cooling performance with no thermostat .... the fact that the [apparent] temp never got above 190 indicates there's no overheating going on

Bill

Hi, I just read the above posts and I went out and measured the the level in my stock 49 1/2 ton. It was about 3 1/4" below the top of the rad filler neck, just below a deflector plate in the rad. It looks low but it is not. When I first got the truck I topped up the rad to about 1" below the neck and took it for a drive and it pushed out some antifreeze and then stabilized at that level. My truck runs at a steady 180deg. idle or at warp speed of 50mph, so if your truck will idle for 1/2 hour at a steady 185deg. the cooling should be ok.Let it cool down and check the level.