Posted by Clint Dixon [172.68.58.86] on Thursday, May 17, 2018 at 20:54:30 :
The head gasket was money well spent. The old one definitely needed replacing and the carbon needed to be cleaned out. The coolant smell is completely gone now and it should not return anytime soon with all head bolt threads now coated in pipe thread sealant. During flushing and testing with straight water, and then again after changing to a 70:30 coolant/water mix, the 169 degree thermostat opened right up at 160 degrees and the temperature never went any higher while sitting stationary at a fast idle.
Tonight we took the first test drive, a 26 mile round trip. Within the first couple of miles the temperature had risen to about 180 degrees. 5 to 8 miles later and several hills, she was up to 200 degrees. The outside temperature was only about 82 degrees and I was taking it easy and never drove over 50 mph. With 4.89 gears and 9.00x16 tires, this truck should cruise at 55 mph all day with no problems, and it has countless times over the past 18 years. On the return I tried to hold it at about 40. The outside temperature had dropped to about 79 degrees. The truck ran cooler but still about 190 degrees.
So, no regrets on the head gasket. Now onto "Plan B."
The first thing I am going to check again is the timing. This time at various rpm's. When the problem was first noticed about a year and a half ago, it was on the return leg of a 150 mile trip. During the 75 miles out there were no problems. At that time I found that the timing was advanced a lot further than I would ever set it. I found that the distributor adjustment screws were just beyond finger tight. Problem solved I had thought at the time. Not. Tonight's trip was the worst yet, especially at these mild temperatures. If I find any erratic timing fluctuations, I am going to pull the distributor and may find a broken weight spring or two.
If I find nothing wrong with the distributor or timing then the thermostat will get replaced with a correct NOS 160 degree MoPar unit that is doing me no good just sitting on the shelf anyway. If that fails then I will move onto checking the water pump and distribution tube.
Junior
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