Good day all, having an issue with my 1940 1/2 ton, 216 engine. Will start it up and let it idle. Engine fires great. After idling for a while (so not immediate) the temp will climb into the red zone (200-216).
It will also do it if i drive it for a short while, so not just while idling.
drained all coolant from the petcock at the rear of the engine and the bottom of the radiator. Came out fine, not plugged up, no sediment or anything suspicious. Put in new 160 degree thermostat with a 1/8" hole in the flange. Buttoned everything back up, new coolant, 50/50 mix, etc.
Still did it. Removing radiator cap - can clearly see the coolant is moving when the engine warms up. Wondering where else to look here. Too infrared heat gun and measure the following when the gauge on the dash was 200+. It has not boiled over or anything (coolant is filled to the bottom of the upper tank of the radiator), but the gauge has pinned all the way to 216.
Valve cover (so right on top of engine pointing down) - 140 Directly between each spark plug - all at 156, all the way back Thermostat housing - 195 Top of radiator - 195 middle of radiator - 186
Where the wire from the temperature gauge enters the head, which on this one is literally right next to the manfold which is interesting - temp was 230-240
Temps across the engine, particularly right between the plugs, looks good, but the thermo housing and where the sensor goes in seems overly hot. Any ideas here?
I did pre-boil the t-stat with a thermometer to verify it opens and works at 160.
Tiny’s advice is right on target. On my ”˜37 my IR gun will read the same as the temperature gauge when I aim the laser pointer directly at the fitting that holds the capillary bulb in the head.
On my engine the gauge and my IR gun read at least 10 degrees hotter than the thermostat temperature. That is normal due to the way the coolant is routed through the engine and head.
I also expect that you are dealing with some crud/rust accumulation in the block and head unless you have had those hot tanked and then manually dug stuff out.
With a 160 thermostat my gauge shows 170 when driving and will go to about 185/190 when sitting at a light on a hot day. The temperature reading drops back to 170 very quickly when I start driving. Or if I use the hand throttle to add a little engine speed.
When the gauge is reading 170 my IR gun shows 160 at the lower side of the thermostat housing.
Where the capillary line goes into the head it reads 230-240 when the gauge is up in the red. When I drained the head out the petcock it all came out clean with good flow and the petcock operated smoothly (no crud, didn't have to stick a wire in it or anything). I'll try draining it again and removing both hoses on the rad and using a compressor air/water flusher I borrowed from my father see If I can blast anything out. Definitely not sitting at 170 moving to 185/190 stationary
Thanks for the additional details. That is pretty hot.
The problem could be partial blockage in the passages between the head and block. That drain plug is for obvious reasons at a very low position in the block.
I agree with your plan to flush things using water and air pressure. I made multiple adapters and various hose fittings so can flush and drain a cooling system from multiple directions. For example, I have adapted an upper radiator hose so I can force water through the thermostat housing (thermostat removed of course) backwards through the head and block. I let water come out the block drain and then close it and make the water come backwards through the water pump inlet. I removed that hose so I do not push crud I into the radiator. I also push water into the block through the block drain.
I also connect to the lower radiator hose and push water up through the radiator. I let it come out the upper outlet.
You might want to check the timing or even advance it a little as long as no pinging is present,. Also check the temperature on the radiator both at the top and bottom to verify it is working properly.
All right so I I think it was just rusted up cooling passages. Ran a system cleaner seems to be working much better now, but I think the cleaner dislodge something or got rid of some rust that was preventing leaks because I seem to have a leak at the water pump. The leak seems to be right behind (coming out the backside of) the fan pulley. It flings all over the inside of the engine compartment when running. Do you think a whole new or rebuilt water pump is needed, or just the backer plate on the water pump may have rotted out? Chevs of the 40s seems to sell just the fan Mount and pulley, but my understanding is the water pump shaft with pressed into the original one so that's not something that you can just replace the one part of. 41-54 water pumps seen to be plentiful and reasonable but man the 37-40 ones are some crazy money. Anyone got a good source?
If you were to see the water passages in the block it would not be unusual to find a couple of inches of rust. Todays cleaners are very mild and will never do a good job.
Coolant flying off the back of the pulley almost invariably means the seal between the impeller and housing is leaking
To verify, with the engine OFF, poke your finger in behind and over the bottom edge of the pulley and touch the bottom of the water pump housing. If it is at all wet, you have a leaking seal. If it is dry, check the gasket area between the pump and the block.
Unfortunately the only cure for a leaking seal will be a new/rebuilt water pump.
I can't for the life of me seem to find any good aftermarket or replacement pumps for 1937 to 1940. Plenty from 41 to 54, but 37 to 40 seem to be very very hard to find and very expensive. Any good sources for aftermarket ones that fit? All I really found is chevs of the 40s which is like 250 bucks plus a 150 core charge
My January 2021 Filling Station catalog shows 37-40 water pumps (supply limited) for $195. Not great, but better. Also a rebuilding service for $145. Hope this helps.
There was a significant change in the water pump for 1941. You are correct that the 1937 - 1940 water pumps are not as plentiful.
There are plenty of rebuild kits out there. It is not that difficult to rebuild one. The only tricky step is removing the pulley without damaging it. You will need to fabricate some type of puller. I think I paid $35 for a rebuildable core and a kit for about the same price.
I found replacing the water pump on my 38 to be a difficult job. I could look in with a light and see the front of the block but when I put my hands in there with the pump, I was working blind. I ended up suspending the pump with mechanic’s wire from bracing rods and then bolting it on.
I put a spare on and sent my old one away to get rebuilt.
Last edited by old216; 07/14/2110:20 PM.
My 1951 1 Ton is now on the road! My 38 Master 4 Door is also now on the road .
I agree that installing the water pump on these engines is pretty much done by feel. Even getting one bolt installed is a major victory. By the time the second one is in place things are ok.
For the mechanics amongst us we find that a lot of repairs are done by feel "braille" as the modern car never has enough room for a work light and leave room to be able to see around your hands to do he job. Tony
The small hole basically allows air to escape from the head when filling an empty system and also allows for a small circulation when cold and the thermostat is closed allowing heated coolant to operate the thermostat earlier. Some modern thermostats have a small valve that closes with a high coolant flow. There are other theories as well. Tony
I drill that hole in almost every thermostat I put in an older engine. It pretty much eliminates the air pocket/overheating problem when you refill the coolant and start the engine.
If you look at the engine and cooling system on your truck you immediately will realize that the thermostat housing is about the highest point on the engine. When you refill the cooling system even with the engine running you get an air pocket just beneath the thermostat.
The coolant in the block and head heats up but that air pocket stops the heat from getting to the thermostat. The thermostat will not open so the engine overheats. Typically if you turn the engine off and let it cool down the system will "burp" itself. Coolant will eventually get to the the thermostat so it will function.
That small hole is more than enough to let the air bleed out of the head and the thermostat housing. So you will have coolant against the thermostat immediately when you refill. If you are patient the coolant will bleed though that hole and even fill the upper radiator hose. When you start the engine there will even be a small amount of coolant circulation past the closed thermostat as Tony noted. It is not enough flow to interfere with the operation of the thermostat as it regulates engine temperature.
I bought a 40 with original engine in 2006. Two years later the engine needed rebuilding. The machine shop boiled the block but I decided to check the passages in the lower part of the block. The engine had a history of running hot. I found out why. The crud was deep and hard and untouched by the hot bath. It took several hours with a clothes hanger, dishwasher concentrate, and trisodium phosphate to clean it out. Always ran with the temp needle straight up afterwards. Head has to be off though. Water pump grease, rust, and minerals in water make an excellent concrete.
A major positive factor is that the engine “concrete” settles in the lower portion of the water passages of the block. That is the cooler portion of the block. Most of the heat from combustion is in the head and the upper 1/3 of the water jacket in the block.
a. All the recommendations of cleaning the block are sound. You might blow compressed air back up through the block while water is flowing into an empty thermostat housing. While you're at this, use the air supply to blow back up through the radiator. Have a flow of water going into the top of the radiator whilst you're doing this. More than likely this will force enough flues in thee radiator to open to satisfy the need for sufficient cooling. If you have a radiator shop nearby then either get the core boiled and rodded or a new core installed. Most of the shops will tell you to get lost, but a few may still have the skill to do the job. They will tell you the core is rotten. Do it anyway and have them solder shut the really bad flues and to solder the flues that are merely leaking some air while in the ten lbs or so test tank operation. If the core has some flues eliminated by cutting them off and welding with solder and you have all the big leaks stopped then you are good to go. Just get you some Solder Seal or equivalent and put it in the clean cored radiator. That will take care of the minor/tiny leaks that showed up during the vat test.
b. The water pump is more than likely shot. The gasket from it to the block is not likely the problem. There is a factory hole in the pump casting to allow the water to drip when the seal is not holding the water back anymore. You need a rebuilt pump or a new one. I have never rebuilt a 41 pump or a 47-40 but I have heard over time that they are not the best way to go. Get a factory or NOS one instead. Bite the bullet and pay the price. Compared to gasoline, it's not all that expensive nowadays. No don't sell a pig to pay for the pump. Meat is up too.
c. If the fins in the core are badly bent then straighten them and make sure the bottom hoses are not collapsing owing to a vacuum effect.
d. The hole in the thermostat eliminates the need for the burping of the engine. You can count on the engine temp rising well above the thermostat opening degrees. Also, to the best of my knowledge, steam does a poor job of conducting heat to the thermostat but will eventually get past the thermostat lips to cause that baby to burp.
Good luck with it.
Charlie
BTW: I have some NOS radiators left. Don't PM me. I don't monitor that flashing thing. It hates me. Also, if any of you run across a Kalamazoo tool that hooks up to a water hose and air hose for reverse flushing a radiator and block , get it. They are great tools. I'd like to have one again myself.
BTW2: As long as there is water in the cooling system sufficient to reach the water pump you're not likely to do any significant harm.
You might want to dive into the investigation a little deeper by removing the head and inspecting the water passages. Especially around the back half of the engine. That's where crud builds up.
With the head off, you can poke around, loosen the crud, and vacuum it out.
When I first got my '28 Canopy Express, I took the head off to do this type of inspection and I found lots of rust and crude in the head waterways.
I also found also that the previous owner put so much sealant on the head gasket that ALL the water holes that carry coolant from the block to the head were SEVERELY restricted. I kept that head gasket hanging in my carport and shake my head every time I pass it. See the pic.
Dean
Dean 'Rustoholic' Meltz old and ugly is beautiful!
