The Stovebolt Site Forums The Shop Area Engine Shop Possible Coolant flow issue

I recently converted the 261 I got over to the short water pump with adapter and the wide groove harmonic balancer, so all pulleys are for the wide belt. Other than a couple small spots, I did not notice any significant coolant leakage after initial fire up and running of the engine. I went to my first show a couple weekends ago and on my drive home. I did encounter a traffic back up and got into stop and go traffic for about 10 to 15 minutes and the temperature gradually rose to just under the red line, I’m guessing that’s around 200°? As soon as I got out of that, it cooled right down. After parking the truck for the night, I did notice some coolant leakage. Upon running it at idle, I noticed the overflow tube would puke out a stream of water. When revving it up above idle, the stream would stop. no water in the oil or coming out of the exhaust. Might I have exhaust gas leaking into the coolant possibly .or could this setup just not be enough RPM related to water pump speed with this adapter plate to flow the water properly. Any suggestions on this issue would be greatly appreciated.

Do you have the original radiator and a "zero pressure" cooling system? It's possible you've got the radiator over filled. There should be a couple of inches at least of free space below the radiator cap for expansion. If you're not having to add coolant frequently, it's not likely you've got an actual "overheat" problem. The short shaft pump puts the fan too low on the radiator for good cooling at idle speed or in traffic.
Jerry

When you say “adaptor”, do you mean the adaptor plate that relocates (raises) a 216 water pump to the proper position on the radiator or just the short water pump that fits in the original position on your 261?

HRL, as noted above I definitely used the adapter plate from Davis to move the water pump up. I did take the thermostat back out and drilled an 1/8” hole in it to prevent vapor lock as someone had suggested elsewhere. I am definitely filling the radiator completely up. I guess I didn’t know any better. The radiator seems to look like an original in excellent condition. The funny thing is the radiator cap looks like the oldest rusty colored thing on this truck. i’m guessing it is what you would call a zero pressure cap? I didn’t know about overfilling the radiator. Are you saying that once the excess water purges itself I might be good to go and keep an eye on it from there?

That is exactly what Jerry was referring too. Once the engine comes up to temperature, the coolant expands purging out any excess coolant. After it cools, you will only see coolant just above the cooling fins. Some put on an expansion tank to remedy this.

I have the same setup as you, only on a 235 and don’t experience your issue. I had my engine boiled out as well as the original radiator when it was rebuilt, run a 180° thermostat (also drilled with a 1\8” hole) and a 4 lb. radiator cap.

If it continues to overheat, in traffic, you’ll need to look elsewhere.

Some "zero pressure" cooling systems have a canister on the top tank of the radiator with the overflow tube attached to it. It's about the size of a small cat food can. Others have the overflow tube incorporated into the filler neck, and the radiator cap does not have a spring loaded center piece that allows cooling system pressure to build up. Then there's the pressurized system, with a gasket surface below the overflow tube, and a spring loaded centerpiece on the cap. Every pound of pressure on a cooling system raises the boiling point of the coolant 3 degrees (like a pressure cooker)- - - - -so a 4# cap keeps the coolant liquid to 224 degrees F. A 7# cap gets the boiling point up to 233, and a 15# cap will raise the boiling point to 257 degrees. (all at sea level). The downside is that most stovebolt cooling systems won't handle over about a 7# cap- - - - -the heater core is the weak point.

It's also possible to mount an overflow tank up close to the top radiator tank level, put the overflow tube into it, and keep the end of the tube submerged under the liquid level in the overflow container. As the coolant expands and contracts, the liquid isn't lost- - - -it cycles in and out of the recovery tank.
Jerry

You say the temperature rose to just under the red line. What is that? 200 F is not overheating.

Purchase an infrared thermometer from Any parts store for $20. When the engine is at operating temperature, shoot the thermometer at various places around the engine - in particular the T stat housing, upper rad hose at radiator, top of radiator, bottom of radiator, temp sending unit, etc.

You'll see what's normal for your engine.

Carry the tool with you and if you think its overheating again, shoot the temps in all the usual places to verify what the temp actually is.

My engine runs at 180 all the time with a 160 T stat and 4 lb cap. When the dash gauge says 180, the top of the radiator and water outlet read 179-183. Bottom of ther radiator reads around 154 or so most of the time.

This truck came to me with an overflow tank installed and I opted to leave it. This way I can fill the radiator all the way to the top. The plastic tank level goes up when hot and down when cold. They are available from any parts store or Rock Auto.

I('d also buy a new zero pressure or 4 lb radiator cap if you are unsure of your current cap's efficacy.

I had found using my infrared pyrometer at work, that putting a strip of matte black (electrical) tape on anything you want to shoot gives the best results, some surfaces reflect such that readings are less reliable.
Chuck

I will borrow my infrared temp gauge from work and give that a try. And I will consider changing the radiator cap. I would like to add an overflow jug, but hate to distract from the original engine compartment, but I need to have functionality also.

I've seen a WWII vintage military canteen used as an overflow canister- - - - -quite a conversation starter when the hood gets opened up at a show & shine!
Jerry

That canteen would make an interesting choice. After looking on eBay, I’ve seen some aluminum cylindrical pieces, and a universal style. Nothing trips my trigger yet.

For instance:

www.ebay.com/itm/205465200723?

Pop rivet the cup to the core support and slip the canteen into it at about the level of the top radiator tank.
Jerry

I use an antique freezer jar that’s clamped in place with an old fire extinguisher bracket. Not sure if I have a pic handy. It looks pretty cool, IMO.

I did find a new version of the military canteen already made into an overflow tank. They’re a bit proud of it at $75.

Found a pic:

For a quick fix to try, I got this small universal overflow tank to try. ($11). It maybe mounted lower than I would have liked, if necessary I will relocate later, The infrared thermometer I have needs a battery so I will check temps later also.
Thanks for the comments and help on this topic.
I tried to get a new cap but at the parts store , their system only goes back to 1950. Of course the one they showed and didn’t have a rating. I‘ll keep looking.

Can you post a picture of the radiator neck with the cap removed, and the attachment point of the overflow tube? A late design radiator with the fill neck designed for a pressure cap will have two gasket surfaces- - - -one above the overflow tube nipple, and another one below it. That design can use a universal fit cap with whatever pressure rating you choose. I'd suggest a 4# cap.

www.ebay.com/itm/186041735906?

Jerry

Your radiator will take the same cap as a 1950.

My truck has a 1941 radiator and takes a 4 lb cap that will fits all the AD and AK trucks.

Hopefully these pictures will show you what you want. Inside the filler neck there is a lip, but it is a very thin ledge. The overflow tube is at the center top of the tank, not near the radiator neck. Shown is the picture of the radiator cap that was on this truck.

That one's a real "zero pressure" system. The best you can do without swapping radiators will be to install an overflow tank and recycle whatever coolant gets pushed out of the top tank when the engine gets up to operating temperature. You can check the accuracy of your temp gauge by immersing the sensing bulb that is installed into the cylinder head in a pan of boiling water and see what it indicates when the coolant boils. It may (or may not) give you an accurate reading on the actual coolant temp. It would be possible to super glue a thin piece of rubber gasket material to the current radiator cap to be sure there's no leaks at the filler neck.
Jerry

You can buy one from classic parts here. Shipping will be more than the price of the cap so you may want to look to see what else you need.

Take your old one to Tractor Supply. They fit a lot of farm equipment like John Deere tractors.

Jerry: Given that this is a zero pressure system, wouldn't any new radiator cap that would provide a good seal at the top of the radiator filler work instead of trying to fix the current cap?

Yes, but if the OP wants to preserve the patina, it's an easy fix to add a new gasket to the old cap.
Jerry