Thread Tools Display Modes
Old 02-11-2020, 01:43 PM
Machine Elf is offline
Join Date: Feb 2007
Location: Challenger Deep
Posts: 12,732

Why do diesel-powered vehicles need a windbreaker in cold weather?

In northern parts of the US in the winter (and I presume Canada as well), it's common to see diesel-powered vehicles with some kind of fabric shield across the grille, blocking most of the incoming air that would otherwise pass through the radiator. Is that wind blocker a solution in search of a problem? Can the coolant thermostat really not close down enough to prevent the engine from being overcooled while out on the highway?
Old 02-11-2020, 02:08 PM
engineer_comp_geek's Avatar
engineer_comp_geek is online now
Robot Mod in Beta Testing
Join Date: Mar 2001
Location: Pennsylvania
Posts: 26,316
It's not just diesel engines. Gasoline engines can also be over-cooled in cold weather. I've had it happen to my pickup truck on really cold days. I have also seen people wedge cardboard in front of their radiators (between the radiator and the grill) on really cold days to prevent the problem. Most commonly though you see the covers on big diesel trucks that you refer to.

With both gasoline and diesel engines, running them too cold can make the oil a bit sluggish, which can cause a bit of extra wear and tear on the engine, especially on the piston rings (or so I've been told). You can compensate for that by using thinner oil. Some people who live in very cold areas will put different oil in their vehicles in the winter than the summer.

Colder diesel fuel tends to clump more than colder gasoline, so diesels are more prone to unburned hydrocarbons causing buildup inside the engine if they are run too cold for extended periods of time. As I understand it, gasoline engines don't suffer from this as much.

Last edited by engineer_comp_geek; 02-11-2020 at 02:08 PM.
Old 02-11-2020, 03:20 PM
smithsb's Avatar
smithsb is offline
Join Date: Sep 2002
Location: mid-Pacific
Posts: 3,042
My old Toyota Camry (1984 w/1.8L turbo diesel) had a problem with the fuel gelling; not in the tank but in the filter/water separator. I had to Rube Goldberg a shield with a clothes dryer duct running from the vicinity of the exhaust manifold to keep things running on below zero days.

So keeping the engine up to temp and fuel gelling problems.
Old 02-11-2020, 09:07 PM
Toledo Jim is offline
Join Date: Nov 2013
Location: Toledo
Posts: 136
As a general rule a Diesel uses more of the heat energy to push the piston (which why you get better mileage with a diesel) and thus sends less of the heat to the cooling system. Add to that the great big honkin radiators in large trucks and in really cold weather the thermostat never opens. Diesel locomotives in colder climates will have a winterization hatch which blocks off part of the radiator. Diesel and gas engines both run better when warmed up.

When I was younger (early 1960's and such) small Fords were overcooled. It was common to see a Falcon or early Mustang or even a Fairlane with a piece of cardboard over about half the radiator.

Old 02-12-2020, 08:22 AM
slaphead is offline
Join Date: Feb 2005
Location: nowehereistan
Posts: 2,921
As Toledo Jim says, diesel engines generate less waste heat, especially the reasonably modern ones.

I have a turbodiesel panel van from 2007 (so not particularly new) and live in a cold climate, it actually has a supplementary a supplementary diesel-burning heater that kicks on automatically to warm the coolant enough to provide cabin heat. With temps around freezing this doesn't kick in and it can take the engine 10 mins of driving to hit 80c / 180F. On a cold day at say -20c / -4F the extra heater is whining and whooshing away otherwise the engine would be very unhappy indeed.
Noooo! The hamsters ate my masterpiece!
Old 02-12-2020, 01:51 PM
mmmiiikkkeee is offline
Join Date: Feb 2001
Posts: 1,610
Originally Posted by engineer_comp_geek View Post
As I understand it, gasoline engines don't suffer from this as much.
I'm assuming this was a problem with older gas engines but not so much now. I live in northern Alberta and the temperature this morning was -40C. I drive a plain old 2008 GMC pickup and the engine temperature was up to 100C in less than 10 minutes driving. I've seen cardboard in the grill of older trucks years ago but I don't see it at all where I live now, which is full of newer pick-ups.

Last edited by mmmiiikkkeee; 02-12-2020 at 01:52 PM.
Old 02-12-2020, 02:43 PM
kanicbird is offline
Join Date: May 1999
Posts: 20,165
I had a V8 gasoline car which had a always spinning fan connected to the water pump. The darn thing would not give heat worth a dam in winter without putting cardboard in front of the radiator. Since it didn't have a temp gauge I can't comment on the engine temperature aspect for that car.


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump

All times are GMT -5. The time now is 01:56 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

Send questions for Cecil Adams to:

Send comments about this website to:

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Copyright 2019 STM Reader, LLC.

Copyright © 2017