(3rd Gen, but others would be similar)
This isn’t going to be one of my usual over engineered solutions for things mostly because it’s something that I’ll probably really need to use a few weeks a year (yea, I know, that might be more than lots of stuff that I’ve way over thought and over built) and more importantly it’s brutally cold out and I didn’t feel like dealing with it. That said, lets get on with it…
Around here we have usually have 2 or 3 COLD but short cold snaps each winter that last a day or 2 at a time and that’s it. The rest of our winters are pretty mild, spending most of that time around freezing or higher.
The last couple of weeks have been different. It seems like we’ve spent most of that time below 20*F with most nights between 10 and 15*F and sometimes getting significantly colder (yea, some of you in the Midwest and Canada are thinking what, that’s cold???). Well I’ve found that driving the Cummins around below about 30* it takes it A LONG time to warm up enough to get good heat, and below 15* without a load it seems to drop below the thermostat temp when you start moving and doesn’t get fully warmed up without a heavy load. Considering the forecast for the next few days is colder than (expletives deleted for those with virgin… well… I’m just being civilized, for once), and getting down into the –5 to –10 range the next couple of nights, I decided to do something about it.
Even though I don’t entirely get it* I decided to take a page from what I remembered the school busses and trucks doing when I was a kid growing up in Buffalo- they used to drive around with zip-up covers for the radiators to cut down on airflow and warm them up faster.
I spent 10 minutes using some google foo and found that it’s a common thing to do or try to do with a Cummins Dodge, but there were a lot of people asking for ideas and pictures and none available, with the exception of commercial products (I wasn’t going to spend money on this, and I needed it now).
I grabbed a flashlight and tape measure and froze for about 5 minutes in the brutal wind trying to figure out what I would do. I decided there are 2 issues:
- Where to put it
- What to use
- How to attach it
Um, 3 issues…
1- The “where” was mostly a question of all the stuff in the front of one of these things, in order from the front: AC condenser, a BIG intercooler, oil cooler and a big radiator, all with an assortment of brackets, supports and plumbing to get in the way. My thought process was:
“I just want the engine to warm up faster, in a perfect world I didn’t want to block the intercooler (and possibly hurt power), the AC condenser I didn’t care about and I figured the oil cooler (it may be a transmission cooler, I didn’t crawl under to check where the lines went) sort of fell in the 6/half dozen category- I may want it blocked, I may not.”
I decided that the most convenient and safest place was between the core support and the oil cooler, behind the intercooler.
I measured the radiator core and found that the finned area was 26” across, and I had 17” from the top of the core support to a cross piece (but something thin enough could sneak past that). I also found that a bracket and plumbing for the oil cooler was partially in the way on the driver’s side, so I couldn’t go all the way over to that side and because of some of the weird shapes in there it had to be about a 1/4” thick or less…
2- The “what.” I initially considered cardboard, until I realized that any precipitation would turn that into a soggy mess, I had some thin plywood ,which wouldn’t be that much better without some sort of finish on it (I wanted to get this done fast, I’ve spent 2x as much time typing this as it took me to do it). I also had the thought that any of the outdoor rated plywood that I had around would be heavy enough to beat up the fins on the coolers if I could jamb it in there at all…. I wish I had some waterproof cardboar…. AH HAAA!!! I remembered that I had a good size chunk of coroplast in the garage (it was the sign they used to label the lot before they built my house on it) in the garage.
For those of you that don’t know what coroplast is, it basically plastic molded shaped like corrugated cardboard that they use for making various signs. Lighter than cardboard, waterproof and durable… SOLD! (literally, it had a sold sign across it from when the lot was sold to build the house on it 
I pulled the tape measure out and it measured 24x18”… THAT IS ALMOST PERFECT… it will cover the top 1/2-2/3 of the radiator and leave a 1” gap on either side of the fins to make room for the mounting brackets and plumbing.
I ran outside and shoved it in the space. It fit perfectly, and even felt like the friction fit with the support 17” down was going to hold it, till I pushed it all the way down to the height of the core support and it just slipped down :-/
By the time I fished it back out my hands were cold and numb. I looked around and noticed some wiring, tubing and a couple of clips across the top of the radiator. I measured them out with a tape measure.
I ran back inside and marked to spots 3/4” down and 6-1/2” from either side, grabbed a hole punch and punched two holes and grabbed to zip ties (had to find black ones, I couldn’t have 2 obnoxious yellow zip ties front and center in my engine bay):
You can see the holes punched at the bottom of the picture. Yea, it’s a little beat up… the house was built in ‘99 and I’m pretty sure that this thing was run over by some heavy equipment.
At this point I ran back outside with my flashlight, my carefully calibrated (eyeballed) radiator airflow limiter (coroplast sign) and mounting kit (2 zip ties) and tucked it in it’s space:
Ran the zip ties through the holes and wrapped them around the assembly (wiring/tubing/brackets) on the top of the radiator and trimmed them off with my Kershaw Thermite:
Yea, it’s a little bit hokey, but it really fits perfectly and it will take 10 seconds to remove once it warms up again.
How does it work? Last night I took the truck to the gym, it was 18* according to the truck’s thermometer, and I road around with an infrared thermometer pointing at one of the heater vents. At right around 4 miles I was reading 88.1* at the vent (remember, this was after driving to the gym, letting it sit a little bit while I worked out and driving back, so this wasn’t a cold start, but the truck cooled off enough that the gauge wasn’t reading anything when I re-started.
Tonight I went to the gym again, it was 14*, and was at the gym 25 minutes longer (so the truck should have been significantly cooler). I hadn’t moved the heater controls from the night before. I checked the vent temps when I started the truck up and got very close to the same temp (33.8* last night, 34.5* tonight), and then drove the truck the same distance (it’s actually to the ramp getting off the “highway”).
117.9*! I’d say it works. Blue (the truck) wasn’t fully warmed up by the time I got back but I did have decent heat. I’m guessing on a longer trip it would warm up better than twice as fast.
If I was going to do it again, would I change anything? Well if I started with a bigger piece of coroplast or was buying one I would make it larger, probably the same width, 24” but I’d increase the depth to 20 or 24” hoping to get it to heat up a little faster. If I had any signs of overheating (I really doubt it) I’d trim it back down. Also, the bright white catches lights through the grill at night so I’d probably paint it back so it wasn’t visible from outside at all (I don’t think you’ll see it in the daylight without a flashlight, the inside of the grill has a pretty heavy shadow in it).
So why didn’t I take the time to make something to my normal over thought about, over engineered and over built standards that just slips in and has some lip that locks onto the top of the radiator or core support? Well, between the cold and the high winds I was freezing, in the time it took for me to slip the panel in and zip tie it down was enough for my hands to turn purple and my finger tips to start going numb, this was about 5 minutes after I got back inside:
* Even though blocking off some of the radiator has been used for years, in theory the thermostat is supposed to prevent any significant coolant circulation through the radiator below its opening temperature, so blocking off the radiator should have very minimal effect on warm up. My guesses why this works, without spending time testing it is that there is either significant coolant bypassing the thermostat and still flowing through the radiator and/or there is significant engine cooling just from the airflow through the engine bay and blocking the radiator cuts that down. Maybe some day I’ll have the time with nothing better to do to test it. Doubtful.
) from melting tips earlier.