High altitude driving

[runaway parents]

Heading over north cascades high way (high way 20) in Washington state drove over it two years ago truck seemed to run a little hotter than usual at that time did not know why. Cense then I have been told the hotter engine temp was caused buy the thin air at high altitude. Truck was starving for air. and to prevent this I need to back foot out of throttle and not to push it so hard..Can any body confirm this? 

 

 

 

 

 

 

 

 

 

 

 

 

 

[SKP101479]

At 5,477' elevation it's nearly the same as many other areas of Montana,Nevada, Arizona and much less than Colorado. If your truck struggles with this altitude I suggest having it looked at. We live just a few feet off WA.20 in Mazama.

[mr. cob]

Howdy runaway parents,

We just yesterday drove east to west from Twisp to Rockport over Hwy 20, and had NO heating problems.  As has been stated the passes in Washington are NOTHING compared to some we have driven over in Colorado.  If you truck is struggling or over heating while doing Hwy 20 in Washington, I'd suggest getting it checked out.

Dave

[MrSeas]

22 hours ago, runaway parents said:

Heading over north cascades high way (high way 20) in Washington state drove over it two years ago truck seemed to run a little hotter than usual at that time did not know why. Cense then I have been told the hotter engine temp was caused buy the thin air at high altitude. Truck was starving for air. and to prevent this I need to back foot out of throttle and not to push it so hard..Can any body confirm this? 

 

 

 

 

 

 

 

 

 

 

 

 

 

Yes yes yes yes

[crazybanshee]

I run over 10,000 ft passes every other weekend without issue. My gross is 47,500 lbs and it has been an overly hot summer.

[lenp]

I find my ISL will get a little warmer if I let the RPM drop below 1600.  Seems that is where the Allison wants to run but I always drop down a gear to keep the RPM around 1800-2000 when climbing and it seems to keep things a lot cooler.  More air flowing through the engine which (I believe) keeps the exhaust temperature down which helps with keeping a cooler engine.

Lenp

[beyerjf]

You didn't specify if the temp increase occurred while pulling a grade, or just rolling hills at an elevation of say 5500 ft. The elevation itself will have little effect on the cooling systems ability. But usually you will be changing elevations, sometimes significantly, and normally engine temps will rise while pulling a grade. 

On the flat, most class 8 diesels run in the 180-190 degree area, pulling a hard grade(6%) with a significant load (75K lbs) mine will run up to 210 or so, then the fan kicks in and pulls it back down some. Ambient temp at the time also has an effect. The cooling system is designed to keep the temp of the engine at about 100 degrees above ambient, with thermostats and other controls helping in the lower ambient temps to maintain proper operating temps. But above 90 degrees ambient with a heavy load, something most HDT folks here won't see, the systems approaches its maximum cooling capacity, and higher temps would be normal, and precautions taken not to damage something. 

[Dollytrolley]

Before clutch fans heavy trucks often had "shutter-stats" that were louvered shutters in front of the radiator core and the shutters opened and closed as needed to keep the engine in the normal coolant operating temp range. 

Grumps had a manual over ride valve that allowed him to fully open the shutters BEFORE he started to climb a grade on a hot day and it made a substantial difference in lowering temps since the coolant did not have the initial substantial heat load needed to trigger the auto shutter operations.

 

I tend to use the Grumps method with the manual fan clutch switch and it works well in that I never see more than 190 f on a long grade IF I engage the fan clutch manually before the climb.......

 

Perhaps I have too many decades of aircraft engine operations where the pilot IS totally in charge of engine cooling or engine melting or ........fires.......

Aircooled aircraft often have Cowl Flaps and the pilot is charged with adjusting the cowl flaps as needed and not paying attention IS very very very bad juju.........

 

Drive on..........(Keep your......cool)  

 

[runaway parents]

13 hours ago, beyerjf said:

You didn't specify if the temp increase occurred while pulling a grade, or just rolling hills at an elevation of say 5500 ft. The elevation itself will have little effect on the cooling systems ability. But usually you will be changing elevations, sometimes significantly, and normally engine temps will rise while pulling a grade. 

On the flat, most class 8 diesels run in the 180-190 degree area, pulling a hard grade(6%) with a significant load (75K lbs) mine will run up to 210 or so, then the fan kicks in and pulls it back down some. Ambient temp at the time also has an effect. The cooling system is designed to keep the temp of the engine at about 100 degrees above ambient, with thermostats and other controls helping in the lower ambient temps to maintain proper operating temps. But above 90 degrees ambient with a heavy load, something most HDT folks here won't see, the systems approaches its maximum cooling capacity, and higher temps would be normal, and precautions taken not to damage something. 

Yup pulling a grade fan kicks in around 210 cools it back down to 185 from what your are saying I am in the ball park with the temps.  Temp has never gotten any hotter. just didn't want to over work any thing.

[DJohns]

When I had my motorhome with the 5.9 cummins I could go over any pass in Colorado without heating. I would watch the temp gauge and when the temp started to climb I would drop down one gear and no more temp rise. Is this how I should run the Volvo or should I  keep lugging it until the temp rises to 210 when the fan clutch kicks in?

[beyerjf]

If you know you are going to see higher temps, most of these trucks have a manual fan switch. No harm in turning the fan on ahead of time. Just remember to turn it off. You won't damage anything but it is noisy and tough on fuel mileage. 

[pethier]

Cooling systems do not work as well at altitude because fewer air molecules are contacting the radiator fins.  I suppose the answer is more fan capaicity, but I have no training in thermodynamics.

[DJohns]

I do not have a switch to turn on the fan so isn't downshifting one gear which speeds up the fan and doesn't pull the motor so hard do the same as locking on the fan? I just notice when pulling hills on hot days temp is rising by the time I am getting to the hill top so my instinct is to down shift.

[Scrap]

Not long ago that used to be how you'd drive truck at elevation.  Follow your gauges, shift your few gears leading into the hill, then lock fan on at the low RPM's just before that last shift you make to settle into the hill.  When you hear the turbo ring you'd back out some.  General rule of thumb then was 1% per 1000ft for just about everything.  1% less cooling efficiency per 1000ft, 1% faster turbo speed per 1000ft, 1% less boost per 100ft, etc, etc.  10000ft was considered high altitude and to spend any real amount of time there you'd have to recal your pump, etc, etc

But now it is all different.  Your truck knows its turbo speed and will change the VG to get it to where it needs to be.  You also have to deal with EGR.  It has many different modes that change at elevation among many other things.  You'll feel this as you drive.  EGR cooler also puts a slug of heat into the rad early in the hill which, of course, changes depending on what mode you are in.  Just about the time you get it figured out it changes on you, but watch close during your lead in and you'll see temp climb non-proportional to the hill .  An on/off fan hub totally misses the mark on this, then has a programmed minimum on time that keeps it locked on way past the EGR surge.  So yea, you'll see a lot of fan time and 210 deg where you don't expect it.  You don't really see it every day but it becomes very apparent at elevation.  DEF motors aren't quite as bad as they don't have as much of a EGR surge to cool.  This is why the electronic viscous fan was invented.  The ones of the last few years can see the rate of temp change, among other things, and can ramp up enough to pull out that EGR surge without hitting full on.  It'll then end up at full on if you really need it for cooling.  If the on/off fan drive drives you nuts then it is a worthwhile upgrade.  Adding a fan switch is a worthwhile upgrade as well as it is pretty hard on things for a fan to come on at 1800 rpm.  Sure the big fat 10 rib poly-vee belts of today can do it, but it is just one of those things beat in your head when learning to drive truck long ago that just makes you wince when an automatic truck does it today.

10,000ft is still considered high altitude for a truck, so go easy on her up there.  There's just so much going on with them nowadays all you can do is sit back and let it do its thing.  They want you to 'lug' to 1100 RPM for fuel mileage, but if you look out your windshield and have a big ol mountain you are settling into and you have the right gear for it then I settle into 1500-ish.

 

[runaway parents]

Made it over high way 20 with no problems. at a temp of 210 fan kicked in cold it down. figured I was pushing it to hard back her down a gear got my foot of the throttle a little. never got over 200 fan did not kick on .pulled over the sumit with no issues went to Everett and then back home over Stevens pass  made for a good run .