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How To Climb A Grade Without Overheating


By Matt Chase

The blazing heat of summer is not here quite yet, but your engine can overheat anytime, especially when climbing grades. A couple of weeks ago as I was heading out of town with my load, going east on California Hwy 58 over Tehachapi grade, the all-too-familiar site of trucks, at least one every time, on the side of the road, overheated. What can we do to prevent this from even occurring?

Pretrip Inspection

First, our radiator (and engine of course) must be in proper working order. Secondly, our coolant level in our radiators and engine must be topped off. If all this checks out, let’s go climb a grade together, and see how most experienced drivers handle this climb without overheating their engines.

Uphill Pull

We have a full load on and we know we are going to go over a mountain grade that will tax our engine and transmission. The first thing I always do, is manually kick my engine fan on well before I hit the uphill pull. Secondly, I turn off my A/C. It might be like an oven for awhile inside the cab, but it’s better to sweat for a few minutes, than sweat all day long sitting on the side of the road.

Now as we start our uphill climb. Keep your eye on that temperature, never let it get into the red zone. Most engines red zone is around 250 degrees, if yours gets too hot, you should hear a warning buzzer or bell, your temperature light, and a shutdown engine light come on. When we downshift to a lower gear this in itself cools the engine, because your RPM’s rise, which creates your fan to spin faster. If you lug your engine or do not down-shift properly, and let your RPM’s drop too low this will heat up your engine faster for the opposite reasons. So, as you climb do not worry about your speed, or who is behind you that wants to pass, let them drive their own truck. Your job is to safely get to the top of the grade without overheating, no matter how long it takes.

Then we’re climbing, and let’s say were in 7th gear, and our RPM’s are at the range were we can keep it at the same speed as we climb. But then you notice that your temperature is climbing higher and it is close to that red zone or the danger zone where the bells and whistles will go off and the shutdown engine light will come on. If you notice this in time, slow down a little more until your RPM’s will let you down-shift to 6th gear, this will increase more spin on your fan motor, and might just be the trick to start that temperature to start coming down again.

If you’re driving a truck with a 10-speed transmission, you should know that to go from 6th to 5th, you have to move your range selector switch in the down position to go into 5th gear. This can be problematic while you’re climbing a grade. Be careful not to miss that gear. If you do, you will probably stall on that hill, and this is what you never want to have happen. My suggestion would be to just go ahead and pull the truck over to the side of the highway, let it cool down using the proper method.

If your engine overheats to the point where you must pull over, make sure to get completely off the road. Do not shut your engine down immediately, instead put it in neutral, set your brakes and keep the engine revved up to around1500 RPM’s to let the fan continue to cool your engine. Once it is cooled down to a normal range, then you can cut your engine and go check under your hood to find what may have caused the overheating. Look for coolant leaks, see where your coolant level is your reservoir. Call your dispatch or service tech if you need to.


In conclusion, you must always do a thorough pretrip every day. Switch on your automatic engine fan. Do not over-burden the engine with your A/C pump running. Keep your RPM’s up so as not to lug your engine. And if you must downshift to a low range gear, make sure you do not miss that hole. If you have to pull it over, do this safely and keep the engine revved up so the fan can continue to bring engine to normal engine temperature.


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