VCCA Home Forums TECHNICAL - GENERAL Trucks and Vans 37 Half ton pick up - Coolant Overflow??

I recently had engine work done on my 37 half ton pick up. I had cylinders bored to clean 'em up, bearings installed on the crank, new valves, etc.

Driving it around for the first 100 miles or so I seem to be having a coolant overflow problem.

Symptoms: When the engine gets good and warmed up I seem to get a rush of antifreeze flowing out of the radiator overflow tube. It seems especially prominent when breaking (as if the momentum is forcing more fluid out of the block).

Does anyone have any possible explanations and a solution??? I'm wondering if I could have a faulty thermostat.

Thanks.

The problem is most likely either insufficient radiator capacity or air being drawn into the coolant. The air comes past the packing on the water pump. Tighten the packing nut a bit to see if that helps.

An air pocket in the cooling system can easily be the cause of this kind of problem. It can happen when a small amount of fluid runs out of the overflow tube and air is sucked into the system through the overflow when the system cools down. Over a period of time, the amount of air captured can be enough to continue to make the system burp. The best way to stop this is to install an overflow tank so when the fluid comes out, it can be captured and than drawn back into the system when the system cools down. No air is drawn in and the system works well as a "closed system".
Another problem could be air which is captured deep into the system and will not exit, instead forcing the liquid in the system to come out. A trick to stop this is to drill a small 1/8" hole in the flange of the thermostat. By doing this, the air can escape without forcing liquid out to escape through the thermostat, which usually closes as the system cools down, holding air and water in.
While both of these ideas are not ideas that are part of 1937 technology, they will work and no one except you will know what you have done.
The capacity of a 1937 pickup truck radiator is not a large amount, but should work. The "big truck" radiator is a heavy duty radiator and will help, if you need it. They will bolt right into your truck in place of the "thinner" 1/2 ton radiator.

The non recovery system (used on most cars of this era) will always have a coolant level about 1" below the radiator cap, this is caused by coolant expansion when heated.
To use the overflow tank idea you will need a radiator cap that seals at the top of the radiator neck as well as the base of the cap.
Tony

My 37 pickup cooling system does not seal. The water level stays about 1 1/2" down and it runs about 180 deg. It will go up to 200 in a parade then cools back down when I pick up speed.

Bruce.
Do not over fill the radiator. When cold the level can be just covering the core. It will expand to mid-tank when hot.The engine will run hotter than normal during the break-in process. Give it a few hundred miles and see if it improves.
Was the radiator boiled out when the engine was rebuilt?

I doubt if his water pump has a packing nut. While the original 1937 did the replacements had a sealed bearing. The original 1937 pumps usually gave up by 20,000 miles.

Chev Nut
Thanks for the tips and the insight from the others above.
Im curious now to find out if i have the original water pump and if it has packing.
My temp gage seems to work but it rarely moves up any more than just off the bottom. I let it sit ideling for about 25 minutes one time and the gage did show a temperature reading more towards the 180 degree mark but it didnt quite get there. It also "burped" then as someone from above called it.

I was wondering if there was just some pockets of air somewhere in the block. I took the temp probe out and there did not seem to be any air right there.

If you let it idle for longer periods of time pull out the hand throttle and bring it up to a fast idle. It will then cool better and it forces the oil into the tight engine parts better. A lot of idling is not good for the engine during break-in and I don't advise it for any engine,
Compared to modern cars these engines have very marginal cooling and it dosen't take much to bring up the temprature.
I run 160 degree thermostats in my cars.
I just did my hoe work on the 1937 water pump. They had self adjusting packings and no nut, The is an oiler on top of thee pump just behind the pulley. Later new and improved Replacement pumps made by Chevrolet has no oiler, grease cup ot grease fitting. Some after market pumps had a grease fitting.

No Sir, you do not have to have a radiator cap that seals at the base of the cap, just at the top of the neck!
A zero pound (stock) radiator cap, with a good seal at the top opening of the radiator, will seal the top of the neck well enough to make the coolant go into an overflow tank through the overflow tube. As long as there is more coolant in the overflow tank than the amount that has been displaced by the engine when running, the system will pull all of the displaced coolant back into the system when cooling off. I have been running a system like this on my 37 for 20 years by running a secured rubber hose from the bottom of the discharge tube of the radiator. I have a tank under the bottom side of the baffel (which has the crank opening in it) with the hose running into it and it works perfect! I just check regularly to be sure there is at least 2"-3" of coolant in the tank all of times!

The only time a perfect seal is required with an over flow tank is when a pressure cap is used. A paper gasket was included with the tank installation kit for the later models.

6Cyl,
I gather from the previous discussion comments that there maybe a kit for the overflow tank idea. If so where might I look for one to fit?

Alternatively, or in addition to the overflow tan Idea, what part number or model and year should I look for for the "big truck" radiator that someone suggested would fit right into my '37 half ton.

Thanks

Bruce,

Not to complicate the matter, or in any way dispute any of the other posts, I have a 37 1/2 ton whose original motor I just rebuilt last summer. Prior to the rebuild, the cooling system had a lot of oil in it, but it seemed to cool the engine OK. After flushing the system and using a Prestone radiator flush treatment, the radiator started leaking, so I had a new original-style V-cell core installed. I drove the truck from Reno to Flint and back last summer in temperatures near 100 degrees every day, and the engine hardly ever went above 185 or 190, even when idling in traffic. It climbed over the San Rafael Swell on Interstate 70 in Utah in 100 degre weather and stayed under 190 (though I did have some trouble with fuel vapor lock on that climb). At no time has my radiator ever burped or overflowed, as long as it is not over-filled. Like ChevGene said, fill it to just cover the core when cold, and it will expand as the system heats up, so that at operating temperature, the level will be over the top of the core, but still well below the fill opening.

Mark

MArk,
Thanks for the additional info... That sounds like an impressive trip!!!!

I have seen some reproduction coolant recovery tanks on ebay that were reasonably priced and was thinking about getting one for my 37,I used a radiator from a school bus and had it recored as a 4 row and never get hotter then 180 even sitting in traffic. I also picked up a big truck shroud top but I got it because it was available and not really needed.

Hi All,

I have been writing about coolant overflow.

My question today is just how can I determine if the engine is in fact running hotter than it should? My dash temperature gage doesn't seem to be working although it did a short time ago.

With regard to my coolant overflow problem - I suspect that the newly rebuilt engine is running hotter than it should. The coolant overheats and expands out through the overflow tube.

I have an infra-red thermometer and I was checking the block and radiator core at various locations for temperature. I haven't yet recorded the temp. readings but I was wondering what temperature values I should be looking for to either verify or disprove that the engine is running hotter than it should.

I am seeing the left rear side of the block away from the exhaust manifold reading around 240 or 270 degrees F and that just seems too hot in that area.

Does anybody have information on what I should be seeing for temperature on various areas of the engine block surface for a normal or acceptable running engine on a 37 1/2 ton pickup?

I will record temperatures today after I give it a give it a warm up run.

I do have a 180 degree thermostat installed. Would it be OK to try running it without the thermostat in place to see if there is a temp difference?

My next question is about checking and cleaning out the core and the block. How best can I have this done? Just to make sure I have good flow and there is no gunk lining the walls inside somewhere.

Thanks for all your help and advice!

I'll make three comments and yield to others for input.
I don't think removing the thermostat will help you solve your problem. I would not do that for any reason. You need to get the temperature right with the thermostat IN the block.
I don't see how your block could have any blockage in it if it has been rebuilt, BUT you might want to reflush the block before you do anything else that could be more expensive.
Finally, you need to get the temperature gauge working correctly or get it repaired because, on the road, it is the only way you can correctly measure you engine temperature.

I wont comment on temps at various points around the engine as I dont have any readings to compare with.

As part of fitting a new or rebuilt engine I have the radiator "rod cleaned" which involves removing 1 (generally the top) of the tanks, flowing water into the still fitted tank until water spills out the tubes, any tubes that dont flow water have a suitable sized rod poked through until water does flow but this only works on straight tubed radiators.

If the engine was built with a thermostat I would not discard it.

Reverse flushing the engine will do no harm but with the lower radiator hose disconnected or the muck will collect in the radiator to cause the same problem again.

Tony

A tight new motor will put more stress on a old radiator then a worn motor will so did you have the radiator checked out before putting it back in.