Heater core bypass in 88-95' fullsize trucks?

Hey guys and gals,

Any of you bypassed the heater core during the summer months on an 88-95 fullsize truck to increase A/C performance? Those of you familiar with the system know the heater core sits just below the A/C evaporator (heat rises, what the hell were they thinking!) and is always hot regardless of climate control settings.

I'm thinking that this comprimises the A/C efficiency a tad, and bypassing the heater core altogether would result in increased A/C performance. So...............

1) Anyone try it? 2) Did it work? 3) Did you fabricate or buy an aftermarket bypass valve?

Thanks,

Doc

Reply to
"Doc"
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tad,

Yeah I have done this for years. Just go to a hardware store and get a water valve and two short sections of pipe or tubing that match the valve and the inside diameter of one of the heater hoses. Cut the hose, insert the valve, and turn the water on or off as needed. Q.E.D

One word of caution, make sure that you have the right mix of water/antifreeze in the cooling system, because without hot water circulating through the heater core, in might freeze up from the A/C. You know that "heat rises" but also remember that cold sinks.

Reply to
Diamond Jim

Jim, did it make a difference in A/C performance? If so, how much?

Doc

Reply to
"Doc"

Hi!

No. I've never tried that and didn't know you could do such a thing. But I did notice that the heater core (or at least a "hot spot") was right near that area.

I wonder if it results in an improvement for all trucks. My dad's '94 went to Missouri in the blistering heat of the summer and never had a problem freezing us out if we left it turned up.

William The Guesser

Reply to
William R. Walsh

my '87 Toyota MR2 had a valve from the factory that cut off flow through the heater when the temp setting was on full cold. now if you guys want to talk about one MF'er of a complicated cooling system... THAT car takes the cake.

-Bret

Reply to
Bret Chase

Better yet, go to the parts store. Get the cooling parts book and look for a valve made with the correct size connectors. Some vehicles used them. Cutoff valves that is.

And, no, I've never done this. I've always used the heater as an extra way to cool the engine off. Had some vehicles that would overheat because of the amount of boost I'd run on the turbo and I used the heater to keep me within limits.

"Either the engine overheats or we overheat" From "The Gumball Rally", the yellow camaro.

Reply to
C. Vaughan

I've done that on my 92 Explorer. There is a valve ford sells and which also seems to appear quite regularly on ebay for this purpose and it shunts the water around in one position, and thru the core in the other.

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It's supposed to be vacuum operated to shunt it when you put it inMAX ac. I just move it manually twice a year (It wasn't originalequipment).

As to whether it helps, it helps a lot. Temp readings of the air from my vents when the AC is off (controls set to vent position) show that even with the heat/cool level in the full cool position, all the heat buildup from the hot core raises the air temp by at least 5 degrees. Without turning the hot water off, there is no way to ever get truly cool air thru the system with the AC off. So you know that it's got the same hurdle when the AC is on. When you have the vehicle warmed up and then park it for an hour and that hot core heat soaks all the stuff around it you are just adding a huge load to the AC system. I can definitely tell it makes the AC air cooler in the middle of the summer.

-- Elbridge Gerry, of Massachusetts:

"What, sir, is the use of militia? It is to prevent the establishment of a standing army, the bane of liberty. . . Whenever Government means to invade the rights and liberties of the people, they always attempt to destroy the militia, in order to raise a standing army upon its ruins." -- Debate, U.S. House of Representatives, August 17, 1789

Reply to
AZGuy

It's nothing compared to a 78-81 Mercedes.

Reply to
Celica Dude

tad,

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It's supposed to be vacuum operated to shunt it when you put it in> MAX ac. I just move it manually twice a year (It wasn't original> equipment).

Thanks AZ, I'm gunna give her a whirl this weekend................

Doc

Reply to
"Doc"

a

A number of years ago I lived in the high desert of Calif., 29 palms to be exact. I had a black Chevy. I couldn't leave the windows down or even cracked during the day because of the dust and sand blowing around. And yes, I think the heater cutoff made a big difference. One problem was early in the morning it would be cold and by the middle of the day it would be hot.

I can't think of the name of the valve but they are a ball type valve. They open and close when the lever is rotated 90º and are rated as 300WOG. WOG stands for Water Or Gas. You can buy then with male or female threaded ends, plane male or female ends or just about any combination of ends you want. They only cost a few dollars, no where near as expensive as the OEM one the stealerships sell.

Now the more I think about it, I am pretty sure they are called ball valves.

Reply to
Diamond Jim

tad,

Doc I made a setup for my 95 S10. Basically an "H" connector made with 1/2 brass pipe fitting and barbed connectors and a ball valve. The horizontal part of the "H" was a 1/4 orfice and the ball valve was on the inlet side of the heater core. When the ball valve was closed, coolant could circulate through the 1/4" orfice and return to the block. From what I could tell the heater core was the by-pass path for coolant when the t-stat was closed. If I shut off the heater inlet it looked like the coolant wouldn't circulate through the block until the stat opened. After this mouth-full, I really couldn't tell any appreciable difference. If you want to try something take a c-clamp and a couple pieces of wood and clamp the inlet hose shut to stop circulation. That should tell you if it's worthwhile If you have an accumulator I'd suggest wrapping with some extra insulation such as aluminum bubble wrap.

Reply to
DonW

I'd suggest a 4-core radiator....

~TLGM/KJ

Reply to
Lonely G-Monkey

I had a 1949 Mercury that I paid $50 for and drug out of the high desert near 29 Palms Ca. It had a flathead V-8 and it came with a valve to cut the water heater off. That old valve looked just like an outside water faucet. I understand that it was stock, anyway it was cast brass/bronze ??? and had the word Ford in a oval in it. We finally got it running after a fashion and sold it for quite a bit more than we had in it at a auto/motorcycle swap meet one 4th of July at the Dragstrip in Bakersfield Ca.

I had forgot all about that car until I saw some pictures of it yesterday. My wife took several pictures of a buddy towing me home in it. We were circling the house trying to stop it in the sand without hitting his Station Wagon as it didn't have any brakes. There wasn't much traffic in the desert in those days.

We went back to the same guy and bought a 1946 Dodge coupe. We got that old flathead six running too/ The Dodge was really in pretty good shape, after we cleaned the dirt off and out of it. Its no telling how many years those vehicles had set. The engines weren't froze up but they had some sand and dirt in them and had to be flushed and refilled with fresh oil before we tried to start them.

Reply to
Diamond Jim

I don't know about that. The most complicated cooling system/heater setup in any car I ever owned was in a 1956 Jaguar. No matter what you did it didn't work, and no human could get it to work. I guess the only reason I ever bought that car was because I had never owned or even driven a Jaguar. Once I had that one, I learned, that you don't drive old English cars in the winter or in the rain.

Reply to
Diamond Jim

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