Radiator Overflowing Question

Hi all, 

Is the engine getting hot or just losing some coolant? How much is it actually losing? A Dixie cup full looks like a lot when it spits from the overflow and runs across a clean shop floor, LOL.  You may be simply suffering from parts mixing?  I cannot remember when the B went to pressurized radiators? but our 38Band 41C are both non-pressurized.  Does your radiator cap look like gas cap underneath? or does it have a rubber seal and spring like a "normal" radiator cap? The non pressurized systems didn't have thermostats originally and dont like them added, I would remove it. Instead they used shutters out front and you adjusted them per need.  Any of the non pressurized systems will lose coolant if filled to the top when cold thermostat or not. Let them lose what they want to lose and dont fret it. if the core is covered cold you are good to go. If your tractor has been converted to a pressurized type radiator and cap you may have other issues, Bs and Cs are not noted as warm runners, usually a person has troubles getting them up to temp.


Edited by Butch(OH) - 19 Dec 2016 at 8:42am

A gallon is a LOT and definitely abnormal. The later  tractors with that engine platform had a thermostat by-pass hose, do you have one? Not sure when that was added, a B and C expert will have to chime in. I know the D-14 and 15 had them and have seen them on CAs. Again you may be suffering from parts mixing

I gallon is abnormal. My uncle used to tell me to leave an inch or 2 empty from the top of the radiator for flow. If you fill I all the way, you will overflow a little, BUT not a gallon, you'll maybe lose a pint.

I would lose that pressurized cap and put a standard cap on it. If there wasn't a thermostat in there, I would leave it out. The coolant will warm up faster with it out because there is no restriction in the system to slow the coolant down in the radiator. A lot of people get that backwards. If you have a overheating problem, you want the thermo in to slow the coolant down in the Radiator so the Rad can do its job. If you're having a problem getting the engine to warm up, remove the stat so the coolant goes through the engine faster and picks up heat from the engine block. As Butch mentioned, if your B is a 38/39 I don't think they had thermo's in them till later on in production. Sometimes if you have a little bit of coolant being pushed out, it may have been from a air pocket and the cooling system is just leveling itself out. A gallon is way to much. A small cup like Butch mentioned would be more normal to me. I think its because you pressurized the system. Just my 2 cents...
Steve@B&B

Oh, okay. This is a B tractor, as fas as I know. I do not know what kind of radiator is has, but I do know that it is pressurised. 

It is a 180 degree thermostat. It seems a tad high, but that is the only temperature that I could find.

the long side is generally facing the head or opposite direction of water flow.

CAL(KS) wrote: the long side is generally facing the head or opposite direction of water flow.

BenGiBoy wrote: Hi all,  So I recently got my B running again, the only thing is that when the thermostat gets up to temp and lets antifreeze through, it dumps a whole bunch out of the radiator overflow.  So.....does this mean that the radiator cap is dead? I could get a new cap, or it would be better just take the thermostat out. I wanted to leave the thermostat in, because it will never heat up in the winter, especially like the winters we have had for the last few years with temps under -20 degrees F..... The thermostat was just installed during the rebuild. It didn't have one for a while.

I use a thermostat that fits into the recessed part of the thermostat housing on a WD45 and do away with the rubber portion, I then drill a 1/8" hole at the base of the thermostat to allow fluid to flow by. Maybe this would also work for this situation, especially with no bypass.

Dick L wrote: BenGiBoy wrote: I do not know exactly how much it loses, but I had to pour at least a gallon into it after the one time that it dumped. It is a '39, but has been converted to a pressurized radiator at some point, and it has a regular pressurized cap on it.  I could take the stat out, but I would rather leave it in... I do have a set of the shutters but I do not know if they will fit on this radiator, I will definitely give it a look though. You do not need a pressure cap on these tractors. They did not come with a pressurized cap.  The C I mow with has not had a radiator cap on for two years. It popped off in a rough hay field and I have not put the one on that I bought to replace it.

looks to me if you lost a gallon you must have a head gasket or some internal problem.

Read the last paragraph of the shop manual page I posted above. It says those B and C that are pressurized have a 7 psi cap. Its from a scan of Allis Chalmers form SM-3, I didn't find a date.

Gerald J.

If you lose that much coolant on a repeated basis you may well have compression going into the cooling system. Some compression leaks don't show up until the engine gets hot. If this is the case the exhaust gets trapped under the thermostat on warm up and the coolant is forced through the lower rad hose and out it comes at the top. If a compression leaks only occurs (like in a cracked head) while hot you wouldn't have the problem running the engine cold (without a thermostat). Secondly, without a thermostat any compression leak is able to escape immediately through a non pressurized cap. What I have described here is exactly the problem I had with a Perkins diesel. Once I put a little spacer in the thermostat and had the rad cap loose I did not lose coolant BUT the problem turned out to be a cracked liner.