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Why do some guys do this...


LawnSite Platinum Member
Northern KY
Ive seen lots of trucks, gas and diesels with cardboard taped over the front grill, blocking off the radiator, why do they do this in the winter? Just curious, lots of delivery trucks seem to have this too? Wouldnt this block off the air intake?


LawnSite Senior Member
Central Illinois
Too keep the truck warmer, just keep an eye on your temp gauge. Some people also say it keeps your engine compartment warmer to help keep oil and fluids thin. I dont know how true that is though. Its also not neccessary to cover up a gassers radiator. If i'm wrong somebody correct me. This is why I cover up my diesel in negative temps.


LawnSite Platinum Member
My Dad put cardboard over the radiator of our family car during winters, back in the 50's. Just driving around town, the engine would not heat up eniough to make the heater work well. In the days of manual chokes, it also helped the engine get up to normal operating temps. a lot quicker.
I currently have half of the radiator on my 97 Powerstroke diesel covered up.
Sure helps get it warmed up quicker on these cold mornings.


LawnSite Senior Member
Somewhere in FL
My buddy drives a Kenworth tractor trailer and was telling me how he has to put cardboard over the grill to get engine temps up in really cold weather. He was saying he was on the interstate and the engine temp wouldn't climb over 90 degrees. With the cardboard the engine got up into the 150 range.


LawnSite Bronze Member
Kitchener, ON
Covering the rad on diesels is commonplace in sub zero temps. Most diesels would take about an hour of idling to get up to operating temp at 0F, or about -15C. best way to warm up a diesel is to drive it, gets the boost up and the engine warms up as much as a gas does. However, the larger radiator used to cool the engine can work against interior heat in the winter, especially on the highway. The intercooler will operate at max efficiency in colder weather at least, but it also cools combustion air and thus the block cools down the colder it is outside. Blocking off the rad aids in keeping engine operating temp at an efficient setting, and gives the operator some heat.


LawnSite Senior Member
On a gas engine I wouldn't even think about covering the front up, too much excess heat is already being produced. On a diesel it's mainly to help the engine get to oper. temp. faster and help them stay up at that temp. I do this on on my 92'. Took a piece of cardboard and cut it the size of the radiator, cut about a 10" hole in the center to allow cool air to flow to the fan clutch so it doesn't burn up, cover the cardboard with duct tape to somewhat weatherize it, and then slide it down in front of the radiator. It works great, gets the truck warmer faster and helps it hold the heat it's built up a lot better. On my 06' I have the factory Mopar cover that goes under the hood and covers the entire front end...radiator, intercooler, all that stuff. It's made of a vinyl like material and has a large probably 10" x 16" opening that has 4 triangular flaps that can be closed or open to control how much air flow gets to the engine. I usually run with about 2 closed in anything below 45 degrees when I'm unloaded. Loaded I take it off because the truck has no problem maintain heat then, plus the cover covers up the trans cooler and that wouldn't be a good thing to do when towing.