Thermostats/cooling mods/Air Cond./Etc.

[Mike Pope]

Hi.

I've been reading posts that I dug up via a search for the last hour or so about cooling mods and which thermostat to use (180 vs. 195). Seems that opinions seem to vary, so I still have some questions. Sorry, I know this has been beaten to death, but lots of the posts I've read were from a year or more ago.......perhaps opinions have changed and/or are application specific?

We use our '95 Suburban mostly as my wife's daily driver, but do occasionally tow with it........right now only about 3000-4000#, but may get a "toy hauler" if we can ever afford it that would be more like 8000-9000# loaded. It gets very hot here (South Georgia), so we run the dual a/c a lot. The suburban runs pretty warm, but doesn't "overheat."

I am considering doing the '97 cooling upgrade and/or the fan clutch/fan mod. as well as doing some performance mods such as intake, exhaust, chip, +/- turbomaster.

So my questions are:

1. Will the cooling mods help with the A/C in the summer heat during those in-town trips? Right now, the A/C is useless at an idle, and marginal at slow speeds during peak heat of summer, although it does work pretty good at highway speeds. (I have already removed the radiator and cleaned it and all of the junk out)

2. Do I need (will I benefit) from doing both the cooling mods? (water pump/dual stats AND fan clutch/fan)

3. It seems that the general consensus is that 195* thermostats are better? Do you agree or disagree, especially for our application? (Fuel economy IS important as well)

4. What is the thought process for having a 180* AND a 195* thermostat in same vehicle? Has this been proven to be effective?

Thanks for any help!

[JoeyD]

I would say do the cooling mods and the Kennedy Clutch kit. Then get the intercooler. If you plan on towing with this truck the intercooler is very important. I say the intercooler is more important than the chips, exhaust and air filters.

[john8662]

I agree with what was posted above, install the upgrade then go directly to the Kennedy Fan Clutch and fan. I did the mods on my 95, and was running 180 stats, and it would still run hot pulling and the A/C wouldn't work that well at idle, etc, just like you're describing. The new fan clutch keeps my water temp at 180, and the A/C worked better in town. Too bad I didn't do this sooner, as I the last trip I took to NM in the mountains pulling a trailer is what cooked mine.

Both 180 and 195 in the same system? I don't agree with this practice! I would think that the 180 would be open all the time where the 195 would be closed most of the time. You would be running just like the single stat while under no load or light duty. I like the safety margin of the 180 stats, and I want them working as a pair, and flowing more water through the system, instead of half.

[rjwest]

Get FULL FLOW Thermostats, If you put them in boiling water, You can see the Full Flow Have much more area opened than stock.

[hug]

Since the thermostat deal was brought up. I have recently installed regular 205 thermostats in my 6.5. I was going to post after I seen how my fuel milage done. So far I have seen a gain of 1-1.5 mpg. My temp gauge runs at 210 but the scan tool shows 199-206 as the themostat opens and close. I do tow around 3000-5000lbs some Alot more in the summer time(mowing season). I will keep you posted on towing temps as I start doing more of it. As for your ac the duramax fan gave me a 5 degree drop in vent temperture just by installing the fan. The next biggest thing I did was install a self adjusting orfice tube in my ac system. This gives me vent temps somewhere between 34 -38 degrees at idle in 90+ heat. :D

[CareyWeber]

Originally posted by hug:
The next biggest thing I did was install a self adjusting orfice tube in my ac system. This gives me vent temps somewhere between 34 -38 degrees at idle in 90+ heat. :D Where does the orifice tube go in the system and does the system have to be evacuated to be installed?

Carey

[Mike Pope]

Originally posted by CareyWeber:
</font><blockquote>quote:</font><hr />Originally posted by hug:
The next biggest thing I did was install a self adjusting orfice tube in my ac system. This gives me vent temps somewhere between 34 -38 degrees at idle in 90+ heat. :D Where does the orifice tube go in the system and does the system have to be evacuated to be installed?

Carey </font>[/QUOTE]Yeah, I'm interested in this too. I know where the orifice tube is (at least I think I do.......and yes, you would have to evacuate the system), but don't know what a "self adjusting orifice tube" is, or how it differs from others.

[hug]

Aa the flow of freon slows the orfice becomes smaller and as rpms increase the orfice becomes larger so that the system does not get to cold and freeze up . This can also be done with using a ford style orfice but it is fixed. I tried one of the self adjusting orfices in duramax and it did not work because the orfice is located so close to the evaporator but I did use the ford style in it and it works great but not as good as my 6.5. I dont the exact sizes of the orfices but gm uses a larger one then ford.Also ford has 2 diffrent sizes but both smaller than gm.

[DmaxMaverick]

Terminology....

An orifice tube is fixed size. They don't change orifice diameter, no matter what you do, other than natural expansion of the metal due to the tempurature, which is negligible.

What you are talking about is an expansion valve. I've never had to break into the system (knock wood) on a '95, but I think it has an expansion valve already. If the system has R-134A, I'm almost positive it does. 1995's could be either R-12 or R-134A. Mine is R-134A, with an expansion valve, OEM.

My '85 has an orifice tube and R-12. The tube is in the pressure line, approx. 1/2 the distance between the condensor and evaporator. The tube is a plastic housing with strainer screen, with a brass smaller tube running through it.

Not sure what the Duramax has. Mine's not broke, and I ain't gonna' fix it!

[hug]

With the aftermarket one the orfice inside the tube is not fixed it self adjust to flow. All gm uses orfices tubes except in the rear air system then some of them use expansion valves in the rear. The duramax also uses the orfice tube. Your 95 also has an orfice not an expansion valve. Gm and ford uses fixed ones because they are cheaper and can regulate pressures on the system easier. An expansion valve does the same thing but has diffrent design. Also some of the pre 1973 models used expanion valves.

[Wheat Whacker]

When I installed the 97 cooling upgrades I did notice the A/C working a little better with the new fan clutch and Dmax fan. What really helped was installing a high idle switch this way the fan is spinning a little faster and pulling more air. Mine has always worked good at idle but with it idled up it gets ice cold inside while idling. Just a thought.

[JohnC]

$.02

If your AC is weak at low speeds, your fan clutch could be the problem. This can also cause overheating under heavy loads, but you may have never gotten to that point in your driving.

The thermostat sets the low operating temperature and when working correctly has little effect on the maximum temp; in otherwords, if you overheat with a 195, you'll overheat with a 180 too.

I cannot understand why one would want to install 2 'stats of different ratings. Seems to me it would just increase the temperature spread the engine operates in since they will start opening at the setting of the lower one but won't be fully open until above the setting of the higher.

DP testing years ago denonstrated a significant advantage in flow capacity between the Delco and Robertshaw stats and all others tested. I don't know if this carries over to the dual 'stats as well.

[rjschoolcraft]

Originally posted by DmaxMaverick:
Terminology....

An orifice tube is fixed size. They don't change orifice diameter, no matter what you do, other than natural expansion of the metal due to the tempurature, which is negligible.

What you are talking about is an expansion valve. I've never had to break into the system (knock wood) on a '95, but I think it has an expansion valve already. If the system has R-134A, I'm almost positive it does. 1995's could be either R-12 or R-134A. Mine is R-134A, with an expansion valve, OEM.

My '85 has an orifice tube and R-12. The tube is in the pressure line, approx. 1/2 the distance between the condensor and evaporator. The tube is a plastic housing with strainer screen, with a brass smaller tube running through it.

Not sure what the Duramax has. Mine's not broke, and I ain't gonna' fix it! The 95's are all R-134A and use an orifice tube. Suburbans with rear air use the same thing in the front, but use an expansion valve mounted to the evaporator core in the rear.

For trucks and the front A/C on Suburbans, the freeze protection comes from cycling the clutch on the compressor. These systems are called Cycling Clutch Orifice Tube (CCOT) A/C systems in the manual.

[Billman]

hug

Please share the Manufacturer/Part Number on the thermostats.

I will install these immediately.

[hug]

billman
I got these thermostat from carquest pt# 300-205 3.99ea
They are regular themostats not high flow. But for testing fuel mileage I think they will work fine. I plan on getting the high flows if these work out well. I'm going to run these on into summer to see how my truck does w/air and towing and then switch. At my shop we keep the high flow 195 and 180 in stock but the supplier can not get the 205. But I think Greg (lube specialist) said he could get some 205.

[ace58]

I have never heard of, or can not see an advantage to, running different temperature tstats within the same dual housing.

Many members have reported having problems associated with the rear cylinders over heating while using the dual housing and 180 or 195 degree tstats, let alone adding potential flow restriction.

I can not understand why GM did not use some form of cross over at the rear cooling ports instead of block of plates. I read about Hummers having such a kit and drilled, tapped, and installed my own. It has to improve flow and keep the block from having hot areas.

[norm]

ronniejoe's on the money! Just to add a bit about what these parts do, the variable metering device is typically called a "thermostatic" expansion valve (or TXV) and will regulate the flow of refrigerant based on the temperature of the suction line.
This would be why the rear air would have it in the 'burbans - to keep the evaporator from freezing up when the fan is off and it is not collecting heat from the vehicle.
The "cycling clutch" is typically done with high and low pressure switches - the low on the suction line will protect the (front) evaporator from freezing because, when the system is correctly charged, low pressure = low temperature. (this switch also protects you from low refrigerant levels) If you are not flowing enough air over the condenser, it can get too hot and alow pressure to be too high, cycling the high pressure switch off, to protect the compressor.
So on that super hot day in traffic on the way home from the beach you'll shut down and get hot if your fan is not doing its job. I have also seen improvement with my fan and clutch from JK.