Last summer in the heat my ac wasn't keeping up unless going down the highway. I didn't feel like doing the ac mod where you change around a bunch of vacuum lines. It messes with the controls. I don't feel its a big deal to open the hood and turn a valve. I'm sure enjoying the cold air but also am wondering about the design of Ford putting the heat exchanger next to the ac coil? Was it to take a little heat away from the coolant helping keep the coolant cooler? The reason I'm asking is because I left Tucson, AZ it was 104° and when I got to Lake Havasu City to drop the Geo off it was 112°. My temps were scary high, the aux gauge was up to 240° and the stock gauge was past the L, 3/4 of the way over! This is my third OBS and I haven't seen temps like that before but I haven't been in the heat like this before either. Today on the way to Vegas same thing, pretty hot and I wasn't pulling the Geo behind the 5er! Oil was 233° and for the first time with the 6.0 32 row trans cooler I saw 188°. I just don't know how far it can be pushed before trouble happens? Heading to Salt Lake City tomorrow or the next day and it will be cooler up there. Maybe I'm just worrying to much? So, in your opinion, is the valve not a good idea or is it OK? Basically doing the ac mod is the same thing so I'm been assuming its OK.

 

that valve open wont help with cooling unless you have the heat on


do you hear your fan kick in? possible the fan clutch isn't working when it should

 

ya, I forgot to mention that. About 3-4 years ago I bought a motorcraft clutch from RockAuto. Pulling these hills its really hard for me to hear the 'roar' of the fan so I can't say for sure. These old railroad engineer ears aren't what they used to be either, lol. Spinning the fan by hand it has resistance, feels normal.

 

does that resistance increase when its getting hot?


if it doesn't then the clutch might be failing


have you done a hygrometer test on the coolant and check SCA level?

 

I don't think that dead heading the line is the best idea. The AC mod still makes the loop but doesn't send it through the core. I don't understand the concern about the vacuum lines. You can tie into a line that is less than 12" away from where the valve goes. It was a pretty easy install. I can grab a pic of where I tied in if it would be helpful

 

Are you sure your oil cooler ain't plugged Glenn? What about an aftermarket oil cooler?

 

I'm not sure with the flow of coolant on these motors but I'd probably try and avoid dead heading the lines as well. It probably isn't too big of a deal, but maybe it's part of the cooling issue.

I've used an explorer (from a 99 or 2000) heater core bypass valve. It has four connections for coolant, and one vacuum connection. All you have to do is tap into the vacuum line that goes to the valve in the far passenger side corner for the MAX AC setting. That way when the MAX AC setting is on, the vacuum pulls on the valve so coolant circulates before the heater core instead of going through it.

 

I never checked the resistance after its warm, I'll try that. The antifreeze is new precharged with a new dieselsite WP and filter. The oldest thing is the clutch, which is probably now that I think about it is four years old. I wouldn't think a expensive motorcraft clutch would go out that fast.


Your probably right about the dead heading isn't the best idea. After putting it on I've wondered about it. On the mule that burned I did the ac mod and I still have links to that. I guess I shouldn't be lazy and do it right.


I'm sure the oil cooler is fine, at the thrashing we put new O rings on it and lots of experienced eyes looked at it.


I have one of those heater core bypass valve's someplace, I'll have to look for it. Like I said above, I was just being lazy.


Thanks for the replies!

 

Glen, I'm wondering about your cooling fan also You have the a/c condensor in front of the radiator, and that big tranny cooler between the condensor and radiator. Both if those are a heat source. It would probably take quite a bit of air moving across those to cool them in 112 degree temps. Also, if the condensor is not being cooled enough, your a/c wont cool correctly. Seems like you should hear that fan roaring all the time.

 

There's gotta be an h-style valve (through vs. bypass) that's operated by a manual lever vs. vacuum. Otherwise, you could fab your own bypass system with two tees, three valves and some hose and clamps.

 

only need two tees and two valves shown in red


one valve open, other closed to change flow

 

I think you'd still want a third valve in the other line to the heater core. Otherwise the coolant in that line would get warm and eventually so would the core.

 

might get some turbulence in the first foot of hose, doubt it will heat up that much but it wont hurt to have an extra valve in it

 

This is what I used





This mod will stop the flow of hot water through the heater core when the AC controls are in the MAX setting and the OFF position providing cooler temps and preventing the hot pocket of air down by your feet. I went to NAPA and asked for the 'hot water shut off valve' from a 1990 Ford Ranger with a 4.0 V-6, I also got 4 - 5/8 hose clamps, a couple feet of 1/8" vacuum line and a 1/8" plastic "T" for the vacuum line. To begin the install loosen the cap on the radiator overfill to remove pressure from the system (do this while the engine is cool). On the passenger side of the engine compartment there are two 5/8" hoses that come from the firewall and continue to the engine, these are the heater hoses. Cut the hose closest to the drivers side (It doesn't really matter where, I did mine about 6 inches after the firewall). Then holding the 'shut off valve' with the vacuum controller towards the passenger side install the portion of the heater hose coming from the cab to the top left nipple on the 'shut off valve'. Tighten the clamp. Install the portion of the heater hose coming from the engine to the top right nipple and tighten the clamp. Next cut the heater hose closest to the pass side in the same location as the previous. Install the portion coming from the cab on the lower left nipple, tighten the clamp. Now install the portion going to the engine on the lower right and tighten the clamp. Measure out how much of the 1/8" vacuum line you need to reach from the bottom of the vacuum canister on the shut off valve to the white vacuum line on the pass side that goes to the vacuum operated door underneath the pass side cowl. Cut that white vacuum line and splice in the 1/8" plastic "T". Then run the 1/8" vacuum line you measured out from that plastic "T" to the nipple on the bottom of the vacuum canister on the shut off valve. It sounds more complicated than it is. Once you do it the job will seem real simple.

 

Brian, I definitely know that there is a lot of heat producing things in there. Four things, IC, ac condenser, trans cooler and radiator. Maybe its 'roaring' all the time and I just don't hear it any more pulling that load. Or, it isn't. I've been looking for another motorcraft one and summit has one for almost $300, ouch! Maybe someone knows of another brand that's good. When I get to SD I'm thinking I might have a spare there worth trying. I guess we are staying in Vegas for a few more days but I'll be darn if I'm going out to work on it in 105°. I just turned the valve open for now so I don't hurt anything. The line I tapped into is off the passenger side head and I'm thinking now that was a pretty dumb idea not letting that head get circulated coolant. Maybe my ARP head studs saved the day!


Thanks for the other replies guys. I think I might have one of those valves you talked about Mike. When I get out of this heat I'll search the camper basement for it or just buy another when I get to cooler weather. Thanks