Cooling System Towing Test Results, Before/After Mods

Grumpy Bear · May 27, 2018

4 hours ago, Jon A said:

See, that's the issue. The V8's have the opposite setup. The heat exchanger for the transmission fluid is in the hot tank of the radiator, the one for the engine oil is in the cold tank. And all V8's have an air/oil exchanger for the transmission fluid which, in this configuration, provides virtually all of the cooling for the trans.

Something I would not have known without further discussion. Thank you Jon. Learning winds my watch.

The six only gets the additional air/oil with the max tow package. I wonder why they are plumbed differently? The transmission doesn't know what motor is in front of it. In any event I'm glad I have the six then because that layout makes little sense. Think about it; 192 F thermostat in the transmission pumping fluid to the hot side which with the factory thermostat is around 207 F. That's a fluid heater not a cooler and now dump that to an air exchanger which is less efficient?

Have any data on your 160F trans stat yet?

Edited May 27, 2018 by Grumpy Bear

Jon A · May 28, 2018

3 hours ago, Grumpy Bear said:

that layout makes little sense. Think about it; 192 F thermostat in the transmission pumping fluid to the hot side which with the factory thermostat is around 207 F. That's a fluid heater not a cooler and now dump that to an air exchanger which is less efficient?

I agree. While I gave GM an attaboy for the general sizing of the cooling system overall, they get about a D- on this particular part of the layout. My stock trans thermostat was actually 180 (of course it never ran nearly that cool, even in the winter), so the conditions under which that heat exchanger will act as a cooler instead of a heater would be exceedingly rare. And since they put a thermostat on the transmission you don't even get the benefit of faster warmup times. The good news is the air/oil cooler is quite large for a 1/2 ton and will overpower the heater in the radiator in most conditions well enough it doesn't matter that much.

4 hours ago, Grumpy Bear said:

Have any data on your 160F trans stat yet?

Some preliminary stuff but no hard tests or anything yet. I'm not sure it would have made much of a difference on the test above as the stock thermostat was pretty wide open for most of the test. However, I'm not convinced the stock thermostat is the best design in the world, it simply may not work as well as the aftermarket unit at partial opening temps.

So far I've been doing some tests in more normal driving using and bypassing the radiator tank exchanger to decide whether or not I want to keep it in use at all. If it was in the cold tank, I'd definitely keep it and put the thermostat between it and the air/oil cooler for the best of all worlds (which is typically the industry standard way of doing it).

Grumpy Bear · May 28, 2018

38 minutes ago, Jon A said:

So far I've been doing some tests in more normal driving using and bypassing the radiator tank exchanger to decide whether or not I want to keep it in use at all. If it was in the cold tank, I'd definitely keep it and put the thermostat between it and the air/oil cooler for the best of all worlds (which is typically the industry standard way of doing it).

It would definitely be worth a replumbing and swapping sides with the oil cooler don't you think?

Just sharing some info to give you a feel as mine is already plumbed reverse of yours and keeping in mind I have the 170 F radiator thermostat and no air exchanger after the cold side tank:

Two hour test done today on I-39 at 60 mph with the AC on and in a light ENE breeze. 2 hours and bit over 100 miles. 4-6 PM peak heat of the day. Maximum grade along my route 3%.

Ambient 100 F

IAT 102 F

Water 173 F

Oil 199 F

Trans 158-160 F

Jon A · May 28, 2018

Yes, if more transmission cooling is needed that would certainly be a clean way of doing it. Clean for the transmission, but it creates an issue for engine oil. Even if a cooler in the hot tank would be good enough for the V8s (I don't think it would) it's unlikely to be usable. Typically you can't use a transmission cooler for engine oil as they are not built to handle the required flow rates--too much restriction causing a pressure drop across the cooler, which is the last thing you want for engine oil. So that would likely require installing an aftermarket engine oil cooler. Installing a cooler for the engine oil is probably a good 3-4 times as much time, effort and cost as installing an aftermarket transmission cooler. So if I did need more transmission cooling, I think I'd be inclined to install a larger (or another keeping the stock one) air/oil cooler for the transmission instead.

I'm hopeful nothing more will be needed though. I was pretty happy with the performance of the stock setup in the above test (with programmed fans and 180 engine thermostat) and I really think that's good enough for highway speed towing. The times I've had the biggest issues with transmission temps have been towing at low speeds (dirt roads up into the mountains) and that's really the only reason I'm messing around with things now. At low speeds, the air/oil cooler is obviously less effective but the radiator tank heater is not so you get less net cooling, at times probably net heating from the cooler circuit. A lower temp trans thermo providing a lower baseline temp, increased fans speeds and eliminating the tank heater will hopefully keep things under control to my liking.

Grumpy Bear · May 29, 2018

Question Jon. How low can the fans be triggered and how many steps to ramp it up? Also what is the factory initial setting to start the fans? I'd like to explore that more.

Jon A · May 29, 2018

I use HP Tuners for the tunes. The two charts used are in the first post. I haven't looked at any V6 files but I assume they're probably the same. 91 represents full speed (don't ask my why it's not 100) and 15 is the lowest speed the fans will actually turn. I've found if you put a big number in the first cell at 192 degrees, the fans just stay on all the time (bad for many reasons, especially in the winter), so 212 is the lowest temp you can realistically set the fans to be fully on without them blasting all the time.

On the modified run, the temp increase stops as the fans approach full speed, indicating some of the potential of the 180 thermostat is wasted by not being able to turn the fans up to full speed sooner. If there was another cell available around 200 degrees, I do believe max engine temps would have been held to a lower temp with the 180 thermostat. Conversely, with these same fan settings, I think a higher temp thermostat (such as the GM 194) would have ended up within a few degrees of the 180 results as the fans seem to be the limiting factor.

Grumpy Bear · October 10, 2018

For whatever reason I missed the above post. Thanks for the reply belated.

You have a part number for the GM 192F? Two dealerships and both swear there is no such thing claiming that only a 207F is available. I miss good parts people.

Crobinson16 · October 10, 2018

6 hours ago, Grumpy Bear said:

For whatever reason I missed the above post. Thanks for the reply belated.

You have a part number for the GM 192F? Two dealerships and both swear there is no such thing claiming that only a 207F is available. I miss good parts people.

That's why you can't always listen to the parts people. The part number is. 12674634 it's the complete water neck with thermostat.

Grumpy Bear · October 11, 2018

2 hours ago, Crobinson16 said:

That's why you can't always listen to the parts people. The part number is. 12674634 it's the complete water neck with thermostat.

So I looked this part number up and laughed myself silly. Corvette, Caddy 6.2 yes, Silverado 6.2 no. Like the part knows what vehicle the motor is in. Great find!! I have to ask....how to you find a part number GM doesn't what found?

I use to have a set of cross reference books for mid 70's Corvettes when I owned one that let me find things cheap. Like the center Universal for a two piece drive shaft for the 1 ton GMC/Chevy pickup of certain years is the $7 version in a blue box of the $90 red box version for the Corvette half shaft Universals.

Anyway....thanks.

Crobinson16 · October 11, 2018

Ive been following this new line of ecotec motors. I wanted to see what all changed, I was pissed when I learned the 6.2 incorporated afm, among other things. I knew the Corvette and Camaro had a lower temp thermostat, and more than likely shared the same water neck design. The 6.2 motor in the truck is pretty much the same as the Corvette and Camaro except cam, intake and vacuum pump along with some other things, but basically the same. And now I've be reading that GM has changed the recommended oil for the new Corvette and has also back specd for previous models to Mobil 0w 40 esp, not to be confused with Mobil 0w40 FS, but yet still recommend 0w20 in the truck that weighs nearly twice as much and can be put to higher oil temps in towing situations. My guess is you probably already knew that as I suspect you frequent Bob is the oil guy judging by some of your postings?. Just a guess though ? Not to get off topic but I'm still undecided on what I'm going pour in the valve cover next.

Grumpy Bear · October 11, 2018

15 hours ago, Crobinson16 said:

Ive been following this new line of ecotec motors. I wanted to see what all changed, I was pissed when I learned the 6.2 incorporated afm, among other things. I knew the Corvette and Camaro had a lower temp thermostat, and more than likely shared the same water neck design. The 6.2 motor in the truck is pretty much the same as the Corvette and Camaro except cam, intake and vacuum pump along with some other things, but basically the same. And now I've be reading that GM has changed the recommended oil for the new Corvette and has also back specd for previous models to Mobil 0w 40 esp, not to be confused with Mobil 0w40 FS, but yet still recommend 0w20 in the truck that weighs nearly twice as much and can be put to higher oil temps in towing situations. My guess is you probably already knew that as I suspect you frequent Bob is the oil guy judging by some of your postings?. Just a guess though ? Not to get off topic but I'm still undecided on what I'm going pour in the valve cover next.

I read Bob's original post and then haven't looked since. Not much need. Oil/Gas/Chemical was my work for 40 years. Actually wrote some of the refineries operating manuals. Chevron/Gulf, Chevron Research, Getty, Conaco/Phillips and Eastman. Not so much job hopping as big fish eats little fish. There were allot more players when I started.

A large percentage of what people know about oil or gasoline is what the advertising and marketing divisions WANT you to know about it. The Internet has made it all seem so infallible and quite trustworthy while being 99.9% pure drivel.

Simple concept. Viscosity is a function of temperature. The oil responds to the motors current conditions. Doesn't care about what's on a spec sheet. What conditions are in the bottle. It certainly doesn't care about what MIGHT happen, only what IS happening. Hot tip and to the point of this entire thread actually. Control the environment. Temperature.

Edited October 11, 2018 by Grumpy Bear

Jon A · October 11, 2018

After more data, I think I've changed my mind on oil selection. I had stubbornly stuck with 0W20 (Redline) for this truck due to the number of cold starts (sometimes way below zero) and short trips this truck takes and figured I'd just try and keep it really cool. But after towing a couple thousand miles this summer and collecting data more than I had in the past, I found oil temps still exceeded 240 on the hardest portions (harder that the test in this thread) even with my current mods. Peak temp recorded on the last trip was 246.

I'm fine with that temp using the 5W30 Redline that has been my go-to oil since Terry Dyson steered me toward it for my racecar 15 years ago. But 0W20 at that temp when the engine is working the hardest (and wearing parts at the fastest rate) just doesn't give me the warm fuzzy. I think I'll probably go with 5W30 for the next fill.

But that further reinforces what a good idea these cooling mods are...anybody with a stock truck doing what I did would have oil temps approaching 270 degrees. Just not a good idea on 0W20.

300 Blackout · October 11, 2018

I posted this in another thread but it’s worth bringing up here too. GM powertrain recommends Dexos 5W-30 when they sell these engines to OEMs for marine, industrial or recreational use. They clearly state their recommendations are only meant to be a starting point and the OEM must decide the correct maintenance based on the use of the engine. I’d say towing like that justifies upping your viscosity as you fall into the severe use category which they also state is a comparable to how they expect engines to be used by the OEMs they are supplying.

Grumpy Bear · October 11, 2018

Red Line's suggested oil temperature for the High Performance series is 200-212 F. Exxon/Mobil implies safety to 500F for there Mobil 1. NOACK test is carried out a 482 F. Viscosity markers are at a CCS temperature for the API grade, Pour point report, 104 F (40C), 212 F (100C), 302 F (150C) and on the MSDS flash and fire points. Something for everyone.

The only common point is that for each number and for a given API class viscosity changes. Very predictably between 104 F and 212 F. Enough so it is considered linear. Above and below those points....not so much. Truth, the viscosity between several API grades at the 302 F mark is measured in fractions of a Centistoke. Nil. On a percentage basis the difference can seem great (percentage is the adverts best friend) but in terms of absolutes (a marketing enemy) the difference between a 30 and a 20 API grades (weights in common speak) at 250 F is inconsequential. And yet by the masses comments made by 'experts' (in marketing) who claim safety to 500F lead, with intent, to the illusion that 250 F is a safe and acceptable operating number. You may feel free to hold that thought dear.

In general the onset for free radical oxidation is roughly 160 F (some sources claim 180F) and doubles with each 20 F. Yep Groups I and II. Group III gets a nice bump as the carbon bonds are fully saturated. But it isn't 250 F, still under 200 F. We live with it as do the design and mechanical engineers. It is accounted for in the change interval tables to give reasonable rates of exchange.

I take serous note of Red Lines suggested numbers in that these oils are PAO and Ester Blends which are both inherently more resistant to both free radical and thermal oxidation than a non-synthesized molecule. As with any breakdown mode it is not only temperature but also time. They will take 500F for like seconds, maybe minutes before high enough percentage of the can is degraded to become a problem. (thus the ridiculous claims). But not hours.

I know people will argue their points and beat horses long dead back to life. Each will believe as they wish and do as they like and that what is or isn't true is not much of a concern. So...that said. I set a hard limit at 212 F and add enough cooler to make that happen vs the expected and unexpected and an appropriate thermostat to set a reasonable floor.

If you feel otherwise I remind you that physics and chemistry care little and that extended intervals AND high temperatures for extended periods of time are keeping OEM manufactures, rebuilders in new Caddy's, Cubans and nice homes. If your going to accept 250F as 'normal' 10K oil changes might by a gamble??? Give it some thought.

John has done some GREAT work here and shown us the limits of the OEM systems in a practical way. It would be a shame to ignore such research.

Tammy20002500 · October 11, 2018

My truck is older ('00 2500), with a mechanical fan. Over the years,I've been debating putting in a 180 deg thermostat mostly just to run it at a lower temp around town.

The coolant itself has never exceeded 210, even when towing hard through the desert. The transmission however was another issue. when towing in summer in the desert, AC on etc. the trans would get up near the 200 mark, or a little higher on grades.

I wanted to cool the trans down, but I had two additional goals;

1. I did not want the trans to run cooler all the time (when not towing, or in the winter etc) or too cold period.

2. I did not want to add heat to the radiator stack. (putting an additional cooler for oil or trans fluid etc. in front of the radiator does make the target fluid cooler, but at the expense of adding heat to everything behind it).

My solution was to add a B&M Hi-Tek trans cooler with a fan and mount it horizontal under the truck. I built a rack from frame to frame just behind the transmission mount cross member and I tapped into the return line for the tranny for the fluid feed.

The results were amazing. Just adding the cooler (without its fan on and no air blowing through it since its horizontal under the truck) lowered the trans operating temp by around 20 deg in unladen around town driving. (It now warms up to about 140 on an 80 deg day).

Towing is even better. Without the cooler fan running, I'm at about 160 with the AC on and at freeway speed with a 4K lbs trailer on an 90 deg day. For hills, I can flip on the fan, and she'll stay around 160 on a 6% grade.

The unintended side effect is that with the trans operating at a lower temp, the trans fluid that is circulating through the radiator core and the factory auxiliary cooler, is much colder, which in turn does not transfer as much heat to the radiator core & oil cooler. The result is that my oil temp has lowered (i have a gauge) and from this, I can extrapolate that I now have some additional cooling capacity for the engine coolant (i don't know for sure because of the 210 thermostat.) but it makes sense.

Also, without having as much heat being fed to the engine bay, she seems to have picked up some horses when towing. (i know, its probably my imagination)

just a thought on skinning the the same cat a different way.