Heavy Duty Cooling vs. Severe Duty Cooling

[YipMan_Style]

I'm looking at the Chrysler website, and noticed there are Heavy Duty Cooling and then Severe Duty Cooling.

Are they anything special? Or just marketing?

[schexy1]

I believe heavy duty is for towing, severe duty is for all day stop and go type driving like taxis and cops.
Don't quote me unless I am right!

[MattRobertson]

There are four radiator grades, unless they have changed them.

Heavy Duty
Severe Duty I
Severe Duty II
Maximum Duty

Heavy Duty is just another name for base level. 0.5" radiator core thickness. Severe Duty I is the slightly larger radiator you get if you order the tow package for an RT. Severe Duty II is the SRT radiator and significantly larger (1.75" core thickness). Maximum Duty is export-restricted and reportedly for vehicles bound for the Middle East. Getting one is a real pain and its nonstandard fittings make for an epic install. I know as I have one of the very few here in the States.

Edit: The cop cars get one or the other of the Severe Duty rads, plus the oil cooler and a bigger ps cooler.

[YipMan_Style]

So "Heavy Duty" is just regular standard.

Is more cooling always better? Cooling only works if the car is moving, right? If they offer Max Duty Cooling in the Middle East, it gets just as bad in the Southwestern U.S. AZ heats up to 120 degrees in the summer. So good idea to have it? Or waste of time, $$$, and research??

[MattRobertson]

More is always better assuming you have a working thermostat :-)

Here's the short version of the radiator saga, along with a lot more on best-practice LX cooling options.

You can also search for a thread entitled "radiators revisited" here. But the link above was written up specifically to boil down what is known out there.

The hand-lathed fitting was manufacturerd by Bob@SVS, a vendor here. He's the only one who has made them, and he's done three that I know of. He may need the actual radiator in hand to be able to do it as this is a custom fab job and there are no jigs in existence for this. The upper hose, BTW, on the Maximum Duty rad (assuming you also use the Mopar Police Oil Cooler) is a GM part.

[2005rtmag]

More is not always better. A larger radiator keeps the engine from warming up as fast in the winter. You could get a check engine light if it takes too long. I had this problem on my F150 that had a larger radiator.
The radiators are sized for quick warmup and also to keep the engine hot enough for low emissions. The engine also lasts longer when it is warmer.
I bought the Severe Duty I radiator with the expectation of pulling my 3000 lb. boat 600 miles. However, I proscrastinated and my job in FL ended before I got around to it. The new radiator is still in the garage. Hope to get around to it soon, since I still have the boat and I also tow a uhaul fairly often.

[Hemi31]

It could be the largest radiator on the planet and not affect the engine warm up time if the thermostat is sized properly.

[MattRobertson]

More is not always better. A larger radiator keeps the engine from warming up as fast in the winter. You could get a check engine light if it takes too long.

No. More is always better.


[EDIT]...SNIP...[/EDIT]


EDIT: NEVER MIND AS USUAL ERIK SAID IT BETTER AND FASTER.

[2005rtmag]

It could be the largest radiator on the planet and not affect the engine warm up time if the thermostat is sized properly.

The thermostat is a very crude temperature control device. It does have some bypass flow. You give it too much credit.

[MattRobertson]

Sorry but you are simply wrong. At least on an LX platform. Maybe on a Ford but not a Chrysler LX.

I have a secondary sensor attached to my cooling system and the tstat regulates temperature at *precisely* the degree its supposed to. In freezing temperatures it allows a 2-degre variation before it closes. I bought it in 2006, maybe 2005. Either way its had plenty of time to fail.

[2005rtmag]

Sounds like you know your car. Have you timed warmup time before and after a radiator size change? That is what we are talking about.

I experienced too slow warmup with my truck in the winter in Wisconsin after installing a larger radiator and got a check engine code. I solved the problem by cutting a piece of card board about 2 ft. square and dropping it between the radiator and the ac condenser and this fixed the problem for the rest of the winter.

My Mark VIII Lincoln ran a little cooler according to the gauge when I installed a large transmission cooler that was connected in series with the cooler inside the radiator. So, these and other experiences I have had are what I'm basing my opinions on.

[MattRobertson]

I didn't time the time-to-warmup, no. But from general observation I would say its no different. Even when the temperature has been in the teens and 20's the car warms up fast enough to dodge that sub-178* CEL, which I have never seen on this car. But guys who use sub-180 tstats do report that issue on occasion, so its not like the cars are immune to it... you just have to have the right tstat if you don't want the CEL.

Interesting you mention the tranny cooler issue. I took my stock tranny cooler out of service for a few months and went to an external stacked-plate cooler. That dropped water temps by about 20 degrees, from the low 200's to the 180's. That was the stock radiator. Still no cel and I had the 180 tstat. Nowadays I have the stock and the aux tranny cooler in play along with the big rad and a water-powered oil cooler (Mopar police oil cooler). No overcooling issues thanks to tstats regulating things.

I do road course racing a lot which is why I have all the cooling capacity.

[redbullssg]

Well that's cool, I have a Severe Duty in mine. I guess that is one more advantage to getting an AWD SXT. But I still have those pesky styling issues the AWD faces.... I just don't have to worry about my tranny being to weak or my cooling system, LOL....

[jatee]

thanks for the info matt. when i got my build sheet back on my '06 AWD, i did not understand the severe duty engine cooling listed until now.

[2005rtmag]

Interesting you mention the tranny cooler issue. I took my stock tranny cooler out of service for a few months and went to an external stacked-plate cooler. That dropped water temps by about 20 degrees, from the low 200's to the 180's. That was the stock radiator. Still no cel and I had the 180 tstat. Nowadays I have the stock and the aux tranny cooler in play along with the big rad and a water-powered oil cooler (Mopar police oil cooler). No overcooling issues thanks to tstats regulating things.

[/quote]

The RT tranny cooler is separate from the radiator. So, why would using a different, larger, separate transmission cooler drop the engine coolant temperature? I'm confused.