M37 Runnung Warm

[SasquatchSanta]

My M37 is giving me fits! It's below zero and it's running @ 205 degrees with a 180 degree thermostat.

Last week I replaced the existing thermostat because the engine wouldn't get above 150 degrees. The only thermostat I could find didn't look like the stock M37 thermostat that releases water flow from the top. The unit I installed was a newer design that looks like the planet saturn. It was a 195 degree unit. Because of the design I was afraid it wouldn't operate correctly with the M37's bypass system so I ordered a new stock thermostat from Midwest Military. It is a 180 degree unit.

I installed it today along with a military style winter front. I left the flap open on the winter front, set the emergency brake and fired up the engine. I'm running an electric radiator cooling fan instead of a stock water pump fan so when the temperature gauge, which is a new mechanical gauge, got a little over 180 degrees I set the electric fan switch so it would come on. The problem was that it stayed on. With the winter front flap open, @ 2 below zero the electric fan couldn't keep the water temperature fron raising to 205 degrees. The fan ran constantly until I turned on the heater blower, then it was able to shut off every once in a while. Always before, when the engine was in the other truck, even in the summer, the electric fan was able to quickly lower the temp of the engine to 180 and shut off. It couldn't do it today --- even at 2 below zero.

When I drove home tonight the temp stayed at 205 while runnng down the highway & 45 to 50 MPH. One would think that the cold air flow alone whould have kept the temp down to 180 where the thermostat would kick in. It always did before --- even @ 80 degree summer weather. I ran the electric fan on the gray M37 for several summers with no problems.

Soooo --- what has changed?

1). I installed a head off a 1950 civilian Dodge pickup that had it milled .040.

2). The installation of the winter front.

I thought that it may be timed a little too fast so we retarted it a little this evening. No change.

I've heard that milling heads can cause engines to run hot. I wouldn't think they would run hot while idleing. I guess I don't know what to think. Any insight would be appreciated.

 

[hole]

Maybe the T stat ? I put a new one in my CJ that was defective, wasnt completly opening, swapped it out then she was fine. Another thought is ( I'm not familliar with M37/ old Dodges ) but are water ports within the civiy head the same as military head?

 

[rizzo]

I think bad new thermostat.

did you check the temp of the water in the radiator?if the stat is staying closed until 205 the fan will keep running and it will maintain 205.

 

[Stan]

Could gook that was in the radiator shifted about during the rebuild and be clogging it? What about trying it with no t-stat.

 

[citizensoldier]

Take the front cover off and see what it does too.. Water pump functioning? How old is the radiator? Bad maybe plugged up? Keep us posted..

 

[Stan]

Verify that the gauge is correct.

 

[Carter]

You might try checking the new T-stat to see at what temp. it opens. Remove it and place it in a sauce pan of water on the stove along with a thermometer, I use a candy thermometer. Slowly bring the water temp up and note at what temp when or even if the new stat opens. A 180 stat begins to open before, and should be fully open at, 180. If that's not what happens the new one is defective.

 

[Capt.Marion]

The temp. gauge sender is a plug that is located in the back of the block, just below the head, on the driver's side of the motor. It is hard to get to because of the oil filter.

Mine is a strange plug thing that is screwed in the top of the bypass elbow on the top of the water pump. It is connected to an aftermarket mechanical gauge screwed onto the bottom of the dash. You can see it in this picture, just follow the black cable running over top of the head.

EDIT: It was added by the previous owner, since the stock thermometer was not working. This one is a 180º and it works pretty well. I believe the reason the military did not have them there is that they believed the fan blowing air right at it would keep its readings erroneously lower than the actual water temp. I have not had any problems.

 

[Jones]

The Chrysler and Dodge flat-head sixes have this thing called a Water Distribution Tube. It runs down the inside of the block from the backside of the water pump back and carries water to the rear cylinders so that it circulates completely through the engine, not just around the first 2 or 3 cylinders. These tubes are sheet metal and DO rot out occassionally. If you still have the overheating problem after you've determined the thermostat is the right one and is doing it's job, you might want to pull off the water pump and relplace the tube. I use a piece of welding rod with a hook bent into the end to fish the tube out. Compare what you remove to the new tube to make sure you get all of it. A dose of radiator cleaner first will break down any rust and scale and may make the R&R easier.

 

[SasquatchSanta]

Thanks for the insight everybody.

I removed the winterfront today and everything appears to be working fine.

The temp gauge shows 190 degrees but I guess it could be off by ten degrees.

Without the winter front the electric fan is now able to control the temperature when highway speeds are too slow to supply ample ram air to the radiator.

Given that I had the flap open on the winter front PLUS given the cold air temperatures I would have never suspected that the winter front could cause engine heating concerns. Guess I was wrong.

"IF" I were running a conventional water pump fan I'm sure it would be a different story. I'd like to get rid of the electric fan and go back to an original fan BUT I fear the stock water pump fan zaps a lot of horsepower AND fuel.

Once again, thanks for the insight.

I installed a rebuild Carter carb today. The old carb was getting about 3MPH. When I pulled the old carb the intake manifold was flooded with a pool of gas. The new, rebuild carb seems to run a LOT better.

My next tinkering project is going to be re-jetting the Carter. Todays gas requires a lot more air to burn than did gas fifty years ago. Having said that, it stands to reason carbs jetted for yesterdays gas are running too rich. I've got to do some research on how to go about it. Any insight on modifying a "civilian" carter would be appreciated.