OK, so a little back story. Engine/truck was sitting for 20+ years. I had to clean the block cooling jackets extensively for sludge and rust. I installed new expansion plugs after the cleaning along with a new water pump,hoses,thermostat (180 deg), radiator ect.
I got it running Thursday night with no issues that i could tell. But I did notice the engine never got over 160 deg. Today I drove it around in first gear for about 45 min, again nothing over 160d engine temp. I parked it and noticed the lower half of the radiator was cold along with the lower radiator hose. The upper half of the radiator was hot (no boil over or steam) I'm assuming the upper half was hot from heat transfer from upper radiator hose. When I opened the radiator cap there was definetly no coolant cycling. There is coolant present at every port and drain, hoses are also not obstructed. I'm going to pull the thermostat again and check for function. Ambient temp here was about 60 degrees today. Other then change the thermostat to a 160 I am kinda at a loss. Radiator is not clogged and oil is clean no coolant leaks. I guess my question is how is this possible? How could the engine not be cycling coolant throught the radiator and not be overheating Any suggestions or help would be great.
I think you're fine, probably the thermostat is opening too soon. The coolant has to be circulating for the upper hose to be hot, you can't tell just by looking in the cap. If it wasn't, it would overheat. Sounds like your cooling system is doing its job.
a bad connection can give false readings on the gauge. did you check the temp with a inferred gun ?
the lower hose and bottom tank are often cool to the touch @ 15c.(5 blade car fan, stock pulleys, shroud and belly pans. open heater circuit, always a needle width from 180 on a stock gauge).
are you running a waxstat thermostat or a ? or a newer style with a bypass ?
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No infered gun yet, just checked thermostat and it's good. I'm running a stant 13928 no bypass. The lower radiator and hose felt cold like it had not been run. Maybe it is working fine. But my Willy's mb has never acted like this.
Bad water distribution tube made mine overheat. Overheating is not good, check the temperature of the coolant in the radiator, or with an infrared thermometer at the thermostat housing. I think you don't need to worry about it.
The truck has never overheated. Used an IR thermometer today systems run cold but talking to other M37 users I'll monitor my systems. Thanks for everyone's help.
a bad water distribution will reduce the amount of cold water going to the back of the block.
sounds like your cooling system is working great. how do your plugs look ? can it be leaned out a bit ? how conservative is your timing ? can it be bump up a bit ?
is the heater port on the back of the head feeding the lower rad hose ?
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if you have a 160 thermostat then its great! dodges are cold blooded. the reason is because they have water jackets the full length of the cylinder. same on the mopar v8s as well. most other brands do not have full length water jackets. also the M37 radiators are huge and work really well. so water should be cool by the time it gets to the bottom. in fact the tube design is similar to a modern design they call "high performance" in the rad core biz.
Rms, Kaegi thanks for the input. The back of the block is cooler than the front when I checked to my relief. Also the lower radiator and hose were right at the numbers RMS told me. I still have the 180deg thermostat installed.
Plugs are new and don't have much signs of use yet I'll pull and check again. When I checked Sunday morning they were still pretty clean.
I have not checked timing yet since it was running so well. I did discover the homemade tube to cylinder head for the temp gauge probe is running 20 degrees cooler than the head in that spot. (It has a civilian head) I assume that's why I thought it was running cold. I'll continue to monitor in case something pops up and post here. No my heater port on the head is blocked off. Should I have it running to the lower radiator tube?
so the temp gauge probe isn't inside the head? that is probably why the low reading. don't need to plumb heater outlet to rad hose. its a great system that is superior to anything I have been around in the real world. I used to do lots of wheeling in the mts. in the summer time and on really hot days I was the only one with zero heat issues. the Toyotas would overheat first if rad was dirty. then the chevies with autmatics were next. I used ot bring water and always had to give it away never needing for myself.
Kaegi, thats correct on the temp unit. The civy head has a small port that will not fit even a jeep style probe. I am out of ideas for one unless I pull the head off and put a DT one on. I guess I could always drill and tap but also tricky. She is sporting a 12v system.
the heads aren't too hard to find. probably good till one pops up. I probably have one here in WA don't know where you are. you might have a later higher compression head from a car. if so I would keep it. but the truck heads can be shaved down a whole bunch for higher compression as well.
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Any suggestions or help would be great.
