ICPete Posted August 31, 2015 Report Share Posted August 31, 2015 Today my Volvo began overheating as I pulled my 16,000-lb trailer up US 16 headed west out of Buffalo, Wyoming, towards Ten Sleep, eventually over a 9666-foot pass in the Big Horn mountains. The first warning was the A/C started blowing warm air; I hadn't gotten very far out of Buffalo, and was at around 6000 feet at that point. I wondered if the compressor had failed, and looked at the temperature gauge, and saw it was up to almost 210 degF. Normally the temp runs rock steady at 180F (just above the mark at 170). I had just started the climb out of town and was going perhaps 40 to 50 MPH, while the speed limit was 65. I pulled over as soon as I came to a pull-out and parked to let the engine idle to cool down, of course turning off the A/C. The radiator overflow tank had plenty of coolant and there were no signs of any leaking. After about 5 minutes of idling the temperature gauge was still reading about 200 deg. I wanted to check the oil, so I shut off the engine and checked it and it was fine. I waited another 5 minutes hoping the engine would cool off some more. When I restarted it, the gauge showed about 190 (about halfway between the indications at 170 and 210), so it had cooled off a little. I continued on with my trip but took it very slow up the steep grades. Based on the downhill signs descending into Ten Sleep, after the summit, I would guess the grades I was climbing were about 6%. I was getting passed by several pickups hauling livestock and horse trailers, and they were having no problem going at least 55, while I was chugging along as slow as 20-30 MPH in some parts, trying to keep the temp gauge below 200. Possibly I was being too conservative, but I was very concerned about the temperature gauge. The ambient temperature was about 80F, and when I restarted after my initial stop I turned the cab heat up full blast and kept the A/C off, and of course opened the window. My right foot, in an open sandal, was frying all the way to the top of the mountain. I can't know for sure what would have happened if I had tried to go faster; perhaps the temperature rise was simply due to the fan clutch thermostat setting. I did notice, since the window was open, that every time the temperature hit about 200F the engine fan noise came on loudly. My best analysis is that since the fan doesn't engage until about 200F, up to now I was never climbing a steep enough hill to employ a lot of horsepower while not going very fast. So the truck speed had always caused enough air flow over the radiator to keep the temp down around 180F. I have to admit that the only symptoms that made me think my truck was overheating were that the A/C stopped blowing cold and the gauge read almost 210F. I backed off the accelerator enough to prevent it from going higher, but maybe the fan would have been sufficient as well. Any ideas? BTW, as to recent service, in March I had the cooling system flushed and refilled, and the two thermostats were replaced. I haven't done any service to either the water pump nor the fan clutch. I'm wondering whether my radiator is perhaps not flowing freely due to age and corrosion, or is it possible that the water pump impeller might be eroded and not pumping the full volume it should? Finally, the end of the story is that once I got to the top of the pass (9666 feet) and started down the west side towards Ten Sleep, the temperature stabilized at 180 and never climbed again. I held a steady 65 MPH after Worland, all the way to Cody (no longer climbing much). I even turned the A/C back on and it worked fine once again. A year ago I had the engine on a dyno, and the result showed it made the specified HP and blow-by was right at the factory limit for needing an overhaul. Mileage is about 914,000 right now, 7,000 miles after the dyno test. There is always visible blow-by coming from the hose under the engine, for instance when I stop and idle during a short rest stop-- there is actually quite a bit of smoke or oil vapor getting pumped out that blow-by hose (though the engine doesn't appear to consume oil). Could the overheating be evidence this engine is simply old and tired? My typical towing mileage averages about 8.0 MPG; the 350 miles I drove today brought that average down to 7.8 MPG, and there was already about 400 miles on the clock going into that 8.0 average before today. So if I'm doing the math right, today I averaged maybe 7.5 or 7.6 MPG, which maybe isn't so bad considering the very long, very steep climb over the Big Horns. I just don't think this truck should be having so much trouble pulling a light trailer, even up a very long 6% grade. It doesn't feel like it has the power it should have, although I've never driven any other HDT. The temperature rise during the climb especially bothers me, making me think SOMETHING IS WRONG. What would be the appropriate diagnostic tests to ask for? Does anyone know a good diesel shop near Cody, Wyoming? We were planning to sit here until Thursday, then drive down to Elko, Nevada over two days of travel. I haven't studied yet what kind of hills or mountains we will encounter between here and Elko. If there's no serious climbing, I could wait until Elko to get the diagnostics done, or possibly find a shop near Salt Lake City. Wondering how worried I should be......; Pete Link to comment Share on other sites More sharing options...
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