3rd Gen Tech: Colder AC in under 25
 

This Bomb has been floating around the internet and the trucking industry for years. I got the idea to apply it to my truck from CBrahs, who also did a little write up here on it earlier this year.

My hope is this tech article may be a little more comprehensive, leaving little doubt, if any about what is needed, or how to do it. This modification was performed on an 2007 5.9L. With some variation, it should be adaptable to the 6.7L, and also other makes and models. For the purpose of this article, I’ll limit myself to considerations for the 5.9L only.

As the title suggests, this Bomb can be done for under $25.00 and 25 Minutes.

By completing this modification, you will lower your Air Conditioning air output temps about 10-15 degrees, by preventing coolant flow into the heater core.

The parts for the modification can be obtained at Home Depot, Lowes, Ace Hardware, or just about any other hardware store. What you will need to obtain is:
1- ¾” Ball Valve
2- 5/8” barb X ¾”NPT adapters
3- ¾” to 1 ¼” hose clamps
Roll of Teflon tape

I decided to only do one valve, placed into the supply line of the heater core. If appreciable “Heat soaking” occurs thru the coolant in the return line to the coolant in the heater core, I may later go back and install a second valve in the return line to isolate that from happening.

The tools required to perform the modification are quite simple also:

Standard screw driver, or socket and ratchet that fits your hose clamps.
Razor knife, or anything else that you can cut the hose with. (I used Tin snips)
12” crescent wrench, or the correct size wrench that fits your valve and adapters
A vise. (A second Crescent or wrench can be substituted for the vise.)

Here’s a couple pics of the parts I bought from Home Depot The total was $22.38

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Ok, Let’s get to work. The correct location for installation is in the 5/8” coolant supply line coming off the top of the head, on the passenger side. Here is a pic of me pointing to the proposed location of installation.

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The other side of the Heater core is the return side. It drops into a “T” that is supplying the liquid to liquid heat exchanger for the transmission. Here is a pic of that line, the screwdriver is pointing to the “T” location for reference.

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It is because of this “T” that no provision need be made for a bypass loop on the 5.9L.
The Heater core is effectively on its own loop, so the ball valve only affects flow to the heater.

The first step is to assemble the barb adapters and the valve. To do this, begin by wrapping the threads on the adapter with Teflon tape. Note the orientation of the fitting and the direction of the wrap. Wrapping it the wrong way will cause the tape to unravel, and may cause a leak. (I didn’t feel it was really necessary to wrap a brass on brass fitting, but with my luck, it would leak… lol!)

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Next, screw the barb adapters into the ball valve. If you use a vise to hold one end, while you tighten the other, you will want to put the fitting in the vise, NOT the valve. The wall thickness of the valve will not tolerate much clamping pressure without deforming, and causing a leak.
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When you are done, it should look like this

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The next step is to cut out a section of hose at our installation location. You may want to put a bath towel sized rag to catch the little bit of coolant that will come out. I removed 3” of hose from my supply line. Here is the section removed, compared to the valve and fittings I installed. From this pic you can determine how much needs to be removed by measuring your assembly, or “eyeballing” it, as I did.

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Next place the hose clamps over each end of hose, and install your valve. Be sure to orient your clamps so you can tighten them up.

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This is what my valve looked like after installation. It is shown in the closed (Summer) position. Start the truck and check for leaks with the valve both opened and closed. Top off the coolant level, if necessary.

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Questions and comments are always welcome!

Dang Bill that is awesome, i might actually have to try that modification though I don't live in Arizona

lol Ty, If you use AC in Montana, you are a NANCY!! :tttt:

Excellent Job :U:

Thanks, Luke! :c:

Nice mod :U:

The only thing I would do is open that valve 2-3 times a month and let fresh coolant into the heater core. I would suspect letting that old coolant sit in the core for months would start to become corrosive and cause the core to fail come winter time. Like it used to do on the older cars.

hey Bill you've obviously never been to Montana, not only do we get as hot as Arizona it also gets as cold as Alaska or colder I don't know, but yeah we have both extremes rather than just HOT:c:

ok... I take my "Nancy" comment back... :pals:

Now that I'm workin on "single" I might actually get to do some traveling...

been doing this for years on cars, it a good idea to do this on any vehicle, but like stated i would recommend opening the valve every once in a while and circulating the coolant so it dosent become stagnant and start to eat away at the heater core and cause a wet floorboard........

How often do you think it should be open, Logan?

Redpatcher0481 thinks 2 or 3 times a month... I think that might be excessive, maybe once a month or once every 2 months... any thoughts?

Not only does my first gen have one stock, but it's electric-over-vacuum controlled. :tttt:

Well I did the mod, and it turned out great. The only thing I did different was I found a 3/4" valve with 3/4" barbed ends (all one piece). I let the truck sit for awhile then went out there cut the hose, put on the hose clamps, and put the valve in. Worked like a charm. The valve cost me about $7.50 at Lowes. It took longer to wait for the truck to cool down enough than it did to put the valve in. I saw a 14* drop in temp coming out of the vent.

Thanks Wildcat:U:

NP man.

I too looked for an "All in one" valve. I couldn't find one with 5/8" barbed fittings. I figured if I was having trouble tracking down a 5/8" valve, or a 3/4 valve with 5/8" barbed fittings, others might also, so I would just cover the assembly of something that would work.

Did you have trouble getting the 5/8" hose over the 3/4" fittings?

Glad this helped you! :U:

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lol

I "wonder" if it leaks by... Most of them do.. (By design, I think)

5,000 to 10,000 miles, about your typical diesel truck oil change.....on a newer truck i wouldnt worry, on something 10 years old i would worry more about it......and 14 degrees is a HUGE drop in air temp......what was the before and after temps and what was the outside air temp at the time you did the measuring.....

my cab tractor has a valve you close heater line off. i dont think new veh. close clear off by design. a ball valve will stop it dead. its got to help ac

Thanks Bill, I'm going to try this when I get home. :U::U:

No I didnt have any trouble getting the 3/4 onto the 5/8 hose, the motor and that hose was still pretty warm so the hose was pretty flexible and the barbs just kinda slipped right in.






Logan, I bought the temp gauge and put in the air vent on the drive home approx 20min, it never got below 55, I pulled in the garage and sat there about 10 min at idle still never went below 55, I did the mod went for a 20min drive and it got down to 41* sat in the garage for about 10min at idle and it stayed at 41 never went lower than that. The outside temp was hoovering around 100*.

Right on, Red :U:

Hey Logan, Thanks for the input on the periodicity of opening the valve. I think the oil change interval will work well. :U:

This is very interesting i would like to do this to my 6.7 the a.c. does not blow cold enough for this texas heat. does anybody know if this will work on my 6.7 or not/:humm:

I looked at a 6.7L briefly last Saturday. It seemed like it would be complicated, not just a drop in, but ultimately, could be worth it.

A couple problems I saw right off were the hose you need to cut the valve into isn't as accessible as on the 5.9L. Also your turbo is water cooled, and that would need to be addressed.

So, you would probably need 2-3 valves, and a Tee or 2 to plumb in a bypass for the heater core.

I guess I should have looked at it closer, but then it was hot outside and the thought of cool beverage and fellow diesel enthusiasts were calling me in...

Maybe if someone wants me to do one here local, I can take another look at what it would take... They will have to buy everything tho'...

This should work on almost any vehicle to some degree.

On most vehicular air conditioning systems, all air goes through the air conditioning evaporator. From there, it can take two paths; one path leads straight to the vents, the other goes through the heater core. The amount that takes either path is determined by the "blend door" or "mix door". When the slider or knob is all the way in the "red" position, the blend door directs all of the air through the heater core; when it's in the "blue" position, the blend door directs all of the air around the heater core.

Even if the door directs all of the air around the heater core, the heater core is still hot and warms the air up a little bit through heat soak. Some vehicles (like 3rd gen Dodges apparently) have more problems with heat soak than others. Older vehicles (like 1st gen Dodges) tended to use valves that shut off the heater core automatically; I don't know why they went away from them.

A 15 degree decrease almost makes me think that these trucks are having problems with the blend door not closing all the way; that's a lot of heat soak, and a poorly designed air box if it has that much heat soak.

Hey wildcat, nice post. Is anyone else worried about having the coolant dead-end at the valve. My last car was a blown Cobra and they have a known problem with trapping heated coolant at the back of the head. So much that they sell kits to route coolant from the back of the heads back in to circulation. I'm not sure if it would cause any problems but it sure makes me nervous to block off a coolant path, especially dealing with our summers in Phoenix. I've thought about adding more valves, a crossover or something to that effect. Heck, even a quick disconnect system may work. Your thoughts?

you could put a valve in each line and T the lines together so it completely bypasses the heater core when you shut off both valves.......

i did this on my 12v and it works wonderfull, i did the ball valves on both lines so that it keeps cerculation threw the lines

65Stangboy, On the 2005 -2007, the heater core is a parallel path, so no worries. You also have the liquid to liquid tranny cooler off the back of the head... Might be like that on other years as well.

Good to know. You better believe I'm going to do this this week. My A/C is adequate, but I want to freeze. I read about this awhile ago, if I was smart I would have done this before it got stinking hot.

anybody ever done this on a 2nd Gen? is the process pretty much the same?

ya i posted up earlyer that i did this on my 12v

i dont have this mod on my truck(yet)...but i noticed that my passenger floorboard has been getting wet recently...could this be the result of my heater core going down the ol' poop hole??? anybody else had this problem?

yep your heater core is shot

thanks man....ill get er fixed asap! those arnt to bad to replace are they? :humm:

Dash has to come out

no kidding? the whole dash??? i cant just remove the glove box and all that stuff in there??? man thats alot of work for a darn heater core....is it a one man job or 2 man job??? haha :booo:

Wait a second, fellas.

redneckcummins85,

When you say your floorboard has been getting wet, is it with the AC on? Has it been pretty humid in Springfield? Could it be condensation from your AC?...

I know it's Apples and Oranges, but my Chevy work truck will "wet the floor" when the AC is on and it's really humid (Well, really humid by Arizona standards, anyway...)

I would suggest you try to find out if it's coolant on the floor before recommending tearing apart your dash...

Either way, good luck!

well im pretty sure its coolant...and when i say the floors wet i mean its soaked!!! from the front to the back floor

lol

Well I guess you got your work cut out for you then!

I know this is an old thread but I just wanted to say that I did this last weekend and got a 12 degree drop in air temp.

It was 92 degrees out with 81% humidity so I was very happy with the results.

Thanks for the tech tip guys :rocking:

If you like AC for what the part costs I would change the evaperator core while you're in there, unless you want to tear the dash out again next year:c:

Are you having to add coolant?

If you are not having to top the coolant system off then it probably is not coolant.

You say the floor is soaked, seems to me that would take a gallon at least.

when you stop do you still see the acumulation of fluid from the condesation collection, usually shows up by the front passanger tire. If not your tube may have come unconnected or is plugged and the fluid is running into the passanger compartment. The condesation amount is quit alot of fluid, sitting in my driveway for 15 min in florida (90-100% humidity in summer) i will see about a 2 foot diameter puddle of condesate on the ground under my truck.

You guys need to wish this thread HAPPY BIRTHDAY ... its a year old :w2: