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Overheating question


ICPete

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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

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A typical cooling system with a 50% mix of ELC coolant with a 15 psi cap (CAT brand in this case) is 265*F/ 129*C - https://parts.cat.com/wcs-static/pdfs/PEHJ0067-02.pdf - see the numbers on page 2

 

Your fan was coming on at 210*F? and kept the temp there? It was doing it's job. You could have a computer guy lower it at the dealer, I suppose, but why? The fan (remembered reading) is supposed to use 40 HP. If it is running, that power comes from your engine and you use more fuel to power it. Your also climbing in the mountains. That uses fuel that going downhill does not make up, some but no free lunch.

 

Your climbing a mountain, your truck weighs in a 20K and your trailer is 16K so your lifting 36,000 lbs, Your using 40 HP for the fan, your 450 HP just became 410 HP, mildly warm outside, Turbo was doing it's job, boost pressure rise??, exhaust gas temp rise??, Turbo's do help a lot but they are not 100%, but in a normal aspirated (non turbo) gas engine, you lose 3% power per 1000 ft, 10,000 feet you lose 30% of the engine, and you also lose cooling for the less dense air (another factor)

 

Yes you lost power, used more fuel, MY concern would be the A/C wasn't working.(but that less dense air cooling factor, also affects the A/C condenser efficiency)

 

Try this one. tooling along the road, turn off the air, as your pulling into a rest stop. The truck just lost it's cooling, no longer has that 60 mph air pushing through the radiator. Your temp will go up and the fan will cycle. People tend to forget that when the fan is cycling (at a stop) for the A/C at a stop that it is also cooling the engine.

 

These trucks are great, but there are laws of thermodynamics that they must adhere to.

 

By the way - my truck acts the same way and the trailer is 25K

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You did not mention (or I missed it) what the turbo boost was reading. If the boost was low you may have a boost sensor going out. Some of us have replaced them lately. Bill B hit everything else well. I can add that before replacing the fan clutch, check replacing the fan clutch solenoid first. I can speak from experience on this one and the solenoid is cheaper than the fan clutch.

 

Brad

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Evan though you have new thermostats. I wonder if one is bad or the wrong temp setting. I think you have a older freight shacker not sure about motor.

The newer trucks do run warmer. But my old 1997 Pete never runs more than 200deg.

Maybe take off the radiator cap when COOL. and as motor warms up check to make sure coolaint is circulating. Also possibly with cap on and motor warm use a heat gun to check lower and upper radiator hose for temperature difference to make sure thermostat is not stuck.

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I had a '91 Volvo with Cat 3406 that struggled with altitude lightly loaded. Climbing the hill behind Denver I was in lowest gear all the way up just to control the over-heating. Turned out to be leaky intercooler. Perhaps something else to check.

Jay

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Thanks guys for all your helpful replies.

I don't have a boost gauge nor an EGT gauge. I had installed those on my former truck (2007 Duramax), and indeed that was extremely helpful to keep an eye on.

I might go ahead and add them to my Volvo.

I do have a handheld IR temperature gun, so will compare top and bottom radiator hose temps after a hard run, especially as the fan is cycling on and off. I did observe that my fan clutch was cycling; I just didn't know at the time that it was supposed to stay off until about 210 degF. So it appears the clutch is working OK. Also the shop wrote on the work order that they installed 180-deg thermostats; I didn't inspect them before they installed them, but I guess I trust that is what they put in. Plus the truck has always held right at 180 under normal loads. As to radiator cap: both caps on the Volvo expansion tank above the radiator appear to be stock; they do not look like the kind most cars and small trucks have.

Now that I know that, I'm not so worried.

We just got back to Cody after spending two days in Yellowstone with just the car. We're at the Absaroka Bay RV Camp and I ran into John, the campground host, who is also a member of Escapees, this forum, and the Hitchhiker Owners' forum. His truck is a class 6 International, and his description of his fan behavior and temperature gauge readings while climbing has convinced me there's a very good chance there is nothing wrong with my Volvo/Detroit rig.

This may simply be a case of my inexperience with this truck climbing any REAL mountains up to this point.

I know I can keep the EGT lower by shifting manually (this is an autoshift), same as I used to do in my Duramax on very long climbs.

I'll continue to watch the temp gauge but will no longer panic when it hits 210. If it heads up to say 230, then it will be time to back off the accelerator pedal.

I'll also find a way to check the intercooler. Since that is pressurized under boost, is there a way to hear the leakage? Or does someone need to blank it off at both ends and set up a static pressure test?

Pete

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Hi ICPete - recent emission trucks don't display EGT to the driver because the variable injection timing, cooled EGR, and/or hydrocarbon dosing for DPF regeneration produces "different" EGT levels than just the response to engine fueling for the load... so the readings don't make "sense" sometimes so to speak...

 

which then triggers a call to the truck owner at 2 a.m.

 

and so on...

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"I'll also find a way to check the intercooler. Since that is pressurized under boost, is there a way to hear the leakage? Or does someone need to blank it off at both ends and set up a static pressure test?"

 

It needs blocked off and pressure tested. If it's pulling comfortably at a decent speed/gear, and the fan is controlling temps, it's all good. 210-220 is not completely unreasonable. Just back off a bit, perhaps a lower gear. Good luck, Jay

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I wish I saved the link. But sat radio host Kevin Rutherford from let's truck.com has a great way to build your Own inter cooler pressure test kit using home depote products. Yes you pressure test it and he says that dealers will tell you your ok with 20 psi lost. But he dosnt like more than 5 psi. I don't recall over how much time.

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Any loss is loss. It won't magically get better, or the hole shrink with age. I haven't seen anyone suggest cleaning the air-to-air and rad yet, either. Way easier to do than a pressure test. If LGT were passing you, I think we can rule out weather, load, and altitude. The newer variable vane trucks pull better, but the older ones could melt a set of exhaust valves in a hurry, if the driver wasn't paying attention.

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Hi ICPete - recent emission trucks don't display EGT to the driver because the variable injection timing, cooled EGR, and/or hydrocarbon dosing for DPF regeneration produces "different" EGT levels than just the response to engine fueling for the load... so the readings don't make "sense" sometimes so to speak...

 

which then triggers a call to the truck owner at 2 a.m.

 

and so on...

OK, but since mine is older (2000), presumably displaying EGT would be helpful to me. I'm an engineer and like lots of gauges!

 

Darryl, I was wondering about the inside of the radiator possibly being "gunked up", but I think you're suggesting to look at cleaning the outside of the radiator and air-to-air exchanger as well. That's an easy thing to check visually; it's on my list now. Thanks.

 

Pete

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Thanks guys for all your helpful replies.

I don't have a boost gauge nor an EGT gauge. I had installed those on my former truck (2007 Duramax), and indeed that was extremely helpful to keep an eye on.

I might go ahead and add them to my Volvo.

I do have a handheld IR temperature gun, so will compare top and bottom radiator hose temps after a hard run, especially as the fan is cycling on and off. I did observe that my fan clutch was cycling; I just didn't know at the time that it was supposed to stay off until about 210 degF. So it appears the clutch is working OK. Also the shop wrote on the work order that they installed 180-deg thermostats; I didn't inspect them before they installed them, but I guess I trust that is what they put in. Plus the truck has always held right at 180 under normal loads. As to radiator cap: both caps on the Volvo expansion tank above the radiator appear to be stock; they do not look like the kind most cars and small trucks have.

Now that I know that, I'm not so worried.

We just got back to Cody after spending two days in Yellowstone with just the car. We're at the Absaroka Bay RV Camp and I ran into John, the campground host, who is also a member of Escapees, this forum, and the Hitchhiker Owners' forum. His truck is a class 6 International, and his description of his fan behavior and temperature gauge readings while climbing has convinced me there's a very good chance there is nothing wrong with my Volvo/Detroit rig.

This may simply be a case of my inexperience with this truck climbing any REAL mountains up to this point.

I know I can keep the EGT lower by shifting manually (this is an autoshift), same as I used to do in my Duramax on very long climbs.

I'll continue to watch the temp gauge but will no longer panic when it hits 210. If it heads up to say 230, then it will be time to back off the accelerator pedal.

I'll also find a way to check the intercooler. Since that is pressurized under boost, is there a way to hear the leakage? Or does someone need to blank it off at both ends and set up a static pressure test?

Pete

 

I'll state that I tend to agree with this. Before you do any thing else other than visual inspection, make another trip thru the hills and do some diagnosing. Your initial description in your opening post is about the most complete and one of the best ever observations ever written on the internet.

 

Next time you on a hill and stop for a break, listen to the other trucks on the road. You'll hear their fans howling so loud you'd think they are going to come thru the radiator any second. There's a difference between the automobile type fan system and the class 8 system, in that the air clutch is either full on or full off. The coasting when off, is only that, coasting. So there has to be a temp cut off point that engages the fan to full on, then another switch point to turn it full off.

Whereas an automobile fan system has a viscous fan drive that is infinitely variable in it's speed selection based on temps coming from the radiator to the viscous clutch actuator. Plus they are usually a flex fan blade to reduce the noise levels. A class 8 truck is used for work, so they tend to be a little more crude as function is prioritized over fashion.

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Last spring on our trip north to Montana our N-14 Cummins decided to get hotter than normal while going over a pass from Price Utah to Vernal Utah. It has always got a little warmer than I like but it never did like this time. We did pull over and let it cool down.

The next morning the air pressure would only build 10 psi. Replaced the air governor and now the air builds like it should and the fan comes on at a much lower temperature.

Do not under stand it but it works better.

 

 

Safe Travels. Ver

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You could also find a convenient connector in the power to the fan's air control and temporarily wire in a manual switch to test the fan clutch. Saves having to get the engine hot enough to activate it.

 

Some MDT folks wired the switch in permanently along with a light, not for more cooling but because the fan gave another 25 HP or so of engine braking when they were going down hill.

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Hi John! Enjoy your remaining stay at ABC!

 

Today I drove the rig over a few lesser passes, taking 120 down through Meeteetske and Thermopolis, then US 20 through Riverton and Lander; finally I-80 from Rock Springs to Evanston, where we are now camped. The Wind River Canyon was the largest test today, and the truck did just fine. There were a few points where the temp got near 210, and one of them I thought I could hear the fan come up to speed. I did make more use of the "H" (Hold) position on the Autoshift, so I could force it down into 9 as the speed dropped below about 55-60 MPH. The truck did just fine all in all.

 

All in all I think there was nothing wrong, and just my inexperience and lack of understanding about how the fan clutch is supposed to work. BTW, I think mine is "normally engaged", in the sense that when the engine is off with no air pressure yet, the fan feels totally locked. So I'm guessing my clutch operates with "reverse logic", meaning it takes air pressure to disengage it.

 

Thanks again everyone for your help and advice.

 

Pete

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