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Cooling System Mystery

MilspecE6

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i bet a hundred good-running 70s-80s 318s are out there sitting in rust bucket cars and trucks all around the US .. I have kept all but two trucks working on a rotation of salvage engines for the last 45+ years .. One of the jeeps had its original engine machined but it never got reassembled nor bearings, pistons, etc... The bare block and crank have been encased in grease in a crate since 1982.. Three $100 to $200 junkyard replacements have kept it alive since.. As it did way back when, the cost of rebuilds far-surpass my time and cost of dumping a used motor into them every 10-15 years or more
It isn't a bad option, we have a good supplier of used motors in this area. I was given the wrong t-stat from the parts store so I am stuck waiting for the correct one to arrive tomorrow. I asked for a 195 for a '77 Dodge W200....they gave me a 180 degree out of 6 cylinder Dart. Parts stores are not what they used to be.
 

MilspecE6

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Well, on my way to pick up that thermostat. The plan is going to be to drill a pilot hole in the t-stat this time around. I used to run Robert Shaw brand t-stats on my Jeeps and they came with pilot holes to prevent any steam pockets from forming. There remains a chance that my problem is coming from some air bound issues so it might help bleed it out before resulting in a volcano at the radiator. It should also allow combustion gas to reach the radiator while the coolant is still mostly held back so I can use the gas test liquid before I risk getting coolant everywhere again (I am so sick of smelling and wearing coolant right now).

I hope to luck out on this one, because I just purchased a reman carburetor that was too good of deal to pass up. I installed a kit on my current one, but it still isn't very responsive to adjustments and the throttle shaft bushings were a bit worn. With luck, I will be able to eliminate both a cooling and fuel issue in one week.
 

MilspecE6

New member
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Location
Nebraska
Received a Murray 3479 t-stat, which shows the correct application, but it feels really cheap. Anyone running these or should I look elsewhere?
 

87cr250r

Well-known member
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You can always change it later. Now that the t-stat housing is open I strongly suggest filling the engine to the top of the t-stat housing, removing the water pump belt and running the engine.
 

MilspecE6

New member
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Location
Nebraska
Well, I may have some good news on this front.

I drilled a 1/16 hole in the thermostat to help vent pressure and to allow me to use the combustion gas tester without the full flow of a open thermostat (in theory anyway). I then filled the block up to the t-stat housing and installed the t-stat. Fingers crossed, I ran the engine at idle and monitored temps with an IR thermometer as it warmed up.

Remember, the last time, the t-stat (180 degree) opened up after 3 minutes, on this 195 unit I was still only at 165 degrees after 5 minutes. I was able to remove the radiator cap without pressure and see some movement of the coolant and the level lowering about an inch. There was a little bit of flow happening via that bleeder hole.

Assuming that combustion gasses would pass through that bleeder hole (it should anyway) I used the liquid combustion gas tester on the radiator....stayed blue, no gas detected and this device is supposed to be very sensitive to even the smallest amount. I topped off the radiator with about a quart of coolant and continued to allow the truck to idle.

After 20 minutes, it still never reached the 195 degree level so the thermostat remained closed. It was running at 179 degrees and no hotter. The good part was that it was running very smoothly and zero smoke as always. I was also happy to see that I didn't mess up on my handiwork as there were no coolant leaks anywhere either.

So, I will have to take it out for a drive tomorrow to put a load on it and get the temps up higher. I wanted to do it tonight but it was already dark and do not want to spend time dealing with any issues in the dark before a work day. I do feel pretty confident in saying that I might very well have a good motor after-all.

dodge lives 011.jpg
 

87cr250r

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I recently had a Cat 3512 blow a head gasket. Despite a constant flow of bubbles through the tester it never turned colors. I even had the special diesel fluid.

Were you getting bubbles through the tester? Here is one bubbling furiously and here is the head with soot stains where it was leaking.

Screenshot_20230816-203028.pngScreenshot_20230816-203105.png
 

MilspecE6

New member
17
24
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Location
Nebraska
The only bubbling I got came from squeezing the bulb. It was stable otherwise.

The tester I borrowed has dual chambers to avoid a false reading (so they claim). The mechanic I borrowed it from said that it was great for gas engines, but he had never seen a positive result on diesel engines despite having gasket failures. You might have just confirmed his observation.
 

87cr250r

Well-known member
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Location
Rodeo, Ca
Diesel engine testers need to be more sensitive because they have more excess air in the exhaust and less CO2. They require special fluid as a result.

Otherwise, no bubbles is a good sign. I don't think those 318s were prone to head gasket failures. No bubbles is a more valuable result than no color change.
 

msgjd

Well-known member
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Location
upstate ny
I don't think those 318s were prone to head gasket failures. No bubbles is a more valuable result than no color change.
Dead-on.. Owned seven 318's over a span of 47 years ... Three of them were pounded hard and experimented on throughout the 80's ... Four of them are still running to this day.. Never had a head gasket failure with any one of the seven ... (and no cracked heads either)
 
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