I'm thinking of adding a second cooler for the coolant. I want to mount it in the back of the truck somewhere and wire a fan to it as well.

Which coolant line would be best to tap into for this? And where would you put the return line?

I'm hoping this will help drop my temps more than the inline t-stat mod. I'll be dropping a 180* stat in as well. Below is the link for the cooler I'm looking at. It's a trans cooler, but it should help out quite significantly.

What do you all think?

 

Bail. You're creating a great increase in leak chances. Forget the secondary coolant cooler idea and instead retrofit a full size Chevy truck radiator. It's been done before. Should be easier and will achieve what you're looking for. That's what I'm going to do whenever I need to replace my radiator.

 

NEW DIRECT FIT COMPLETE ALUMINUM RADIATOR - 100% LEAK TESTED RAD FOR 4.8L-5.3L

And it's cheaper.

 

I have experimented a lot trying to add a second cooler that actually would work & drop the temp, what you have in mind will not help, since I tried similar mods, reason is there isn't enough flow trough reservoir tubes to. Be sufficant,
Best is a larger capacity all aluminum rad for sure,,,,
BUT, since both my D2 had new radiators & I didn't want to change them I kept experimenting & finally found the solution,,
First, any trans cooler is not sufficant enough for coolant, because the inlet & outlet's are very skinny & wont flow enough coolant,,
What I finally used was a heater core that was the right size & placed it on top of trans cooler, so it sits between A/C radiator & main radiator,, then you put a T right b4 the upper hose connects to rad inlet,, the T branch should acomidate a 5/8" heater hose,, run that hose to inlet of newly installed heater core,,
Then make 2 aluminum tubes aprox 20" long taper the ends so 5/8" hose can be attached to it securely, (of course need to make brackets for everything to hold them in place securely) secure the aluminum tubes on the cavity below the front grill slightly below front bumper, parallel to each other, (there is an opening below bumper that will provide cool air to those tubes) this is to provide enough time for coolant to cool off & be worth anything,, attach the ends of aluminum tubes to each other creating a "U" ,, now attach the outlet hose from new heater core to upper aluminum tube so coolant will go trough it, now attach a 5/8" hose to other end of those aluminum tubes and bring it to inlet hose to engine block, (use another T connector right b4 radiator outlet attaches to engine inlet octapus piece & connect your 5/8" hose there,,
In my setup this extra assembly holds about 1 quart of extra coolant, but the coolant traveling trough this section is much cooler than coolant traveling trough main rad,, so when it mixes with coolant coming from main rad b4 entering the engine makes a significant difference,,
I have to mention you will not notice much difference in low cruising speeds or in lower ambiant temps,, because main rad can handle that easily,, But you will notice a significant difference in high ambiant temp, specially if driving in higher speeds in fwy where main radiator starts giving up keeping it cool,,
B4 this mod my temp at low speeds were fine 182 to 188*,, but in 90 to 100* ambiant going long uphill in fwy it would get to 210*,,
After this mod, the absolute worst temp I have seen in a cross country road trip was on a long uphill (I-40 in Arizona, ambiant 119*) & engine temp hit 198*, with A/c on,,,
On average it dropped the high tempretures by 10*or more,,, & it only works well when it's really hot outside,,, when it's cool it really doesn't change the engine temp that much,,,
(I do have an inline T-stat mod done)
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All this said, if I had to replace my radiator next time,, I would buy a much bigger capacity all aluminum radiator,, as they say "There is no replacement for Displacement),,

 

This is a direct for for the factory rad?

 

No, that's direct fit for a Silverado. I'm assuming you can do a little fenangling to make it work though since you're talking about retrofitting an extra cooler and fan anyway.

 

What vehicle should I look for a heater core for? I was thinking a Suburban since the interior is so massive, but the core doesn't look like it's very big at all.

 

My trucks don't have oil cooler, (03 & 04),, but still there is limited space on top of factory trans cooler to fit an extra heater core,,
I went with (Spectra 93012, same as Spectra 394187) those are same as (Spectra 398336),, but last one has slightly longer connecting tubes , which is better but costs twice as much,!! I don't know why, since it's exactly same core,, 7.1"X8",,
Height is the critical issue, weight you can go even 5-6" more, but I couldn't find anything else, with a reasonable price,,
But you need to make sure to get all Aluminum version (not the copper) or it will start eating aluminum parts that are connected to it trough coolant, (Electrolyses)
Those are not huge cores, but with the 2 aluminum tubes I added, it did the job for me,
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Note: not only core need to fit in that space, but in order to fit the inlet/outlet tubes need to cone out of one side & straight, & at least one tube (inlet) be very close to top, so it will bleed the air out,

 

Hey Alex I've read you talk about this before. What kind of temps were being talked about after this radiator is installed. I dont really run that hot at all but I don't like seeing 198-200... makes me nervous. And when I'm out keeping up with the club driving at 70 miles uphill on the freeway it happens often. Think this would help the creep when climbing?