Kateck 174 thermostat

HarryK · March 13, 2022

Hi all, I read through all of the coolant/6L80 discussions I think...quite a bit of research and some very knowledgeable people spent a lot of time on it.

My high mileage 2014 4.3L 1500 4WD didn't light the MIL but the fans stayed on full even after engine shutdown. Dash coolant temp gauge was pinned left at 160.

Got new thermostat from GM, installed it and reset P0128. What a difference in the heat the engine was giving out (When ambient air was about 88 degrees and high humidity.

Never felt anything like that before. Put OBDLink on it and it was pretty steady holding the ECT at 208...dash gauge was at 12 o'clock...Found out new OEM stat is

207 degree.

Ordered a Katech 174 and installed it. Some findings: (all temp readings by OBDLink plug in.)

At idle in the driveway, while checking for leaks, the temp goes to 212 (takes a while) at which point the fans turn on and it cools it down to 185 +/-.

Fans appear to shut off about 210 or so..

Few days later, ambient is 62 degrees, test drive brings the temp down to 158 and steady there. Side roads about 5 or 6 miles. 30 to 40 MPH. Sometimes

goes to high 170s. At idle in store parking lot, temp rises very slowly to 200 or so and more. Didn't wait for 212 this time but turned on A/C to bring fans

online and temp began to lower almost right away..goes down to 170s or so while parked..this tells me that the radiator is extremely efficient with air flow

going through it. Now wondering if the ECT sensor next to the thermostat is a factor in this and needs to be changed because it became 'lazy' or is

just malfunctioning. Shouldn't temperature be holding about 178 +/-?

Will take some more readings but I'm wondering if they sent me the 160 one instead..I thought it was stamped with '79' but not sure......

......just starting the post with some basic info here...appreciate any thoughts or recommendations..Thanks!

Note: Going by remote OBDLInk MX and referencing the dash temp coolant gauge, the first small mark on the left past the 160 correlates to 125 degrees,

the next one correlates to 150 degrees, the next one to 168 degrees and when it reaches 12 o'clock (dash 210) the OBDLInk reads 185.

pokismoki · March 13, 2022

the fans have to be reprogrammed via a handheld tuner or HPtuners, i brought mine down to 193 on the fans, problem is our trucks dont have mechanical fans so you wont see too much cooling in stop ang go traffic or while parked, you need airflow with a katec thermostat, so until your driving on the highway you wont get any cooling. if you offroad climb trails in 4wd you need to bring the fans down to 190 in the software,

Another trick not many know about is you can override the cooling fans from the 210 programmed-on point, simply by activating the AC system from inside the cab, i dial my AC down to the lowest temp setting ,and full blast the blower. This causes the AC mode in the ecu to turn on the fans in a "low powered" setting to cool the Condenser and maintain cool AC temp, but it also has the benefit of cooling the radiator of the engine and will cool the motor down. only issue with using this trick is running the AC and all the fans draws about 1 hp from the truck. so your better off reprogramming the ecu

Edited March 13, 2022 by pokismoki

HarryK · March 13, 2022

Thanks..no offroading...just reliability as second vehicle at this stage in my life (close to social security age)...wondering on what you think about the Katech and how to see

if I received the correct one..

Grumpy Bear · March 13, 2022

3 hours ago, HarryK said:

Few days later, ambient is 62 degrees, test drive brings the temp down to 158 and steady there. Side roads about 5 or 6 miles. 30 to 40 MPH. Sometimes

goes to high 170s. At idle in store parking lot, temp rises very slowly to 200 or so and more. Didn't wait for 212 this time but turned on A/C to bring fans online and temp began to lower almost right away...goes down to 170s or so while parked...this tells me that the radiator is extremely efficient with air flow

going through it. Now wondering if the ECT sensor next to the thermostat is a factor in this and needs to be changed because it became 'lazy' or is just malfunctioning. Shouldn't temperature be holding about 178 +/-?

Maybe. See that line on the thermostat housing? That's a minimum flow bypass to keep the pump happy AND to get the 'heat' to the thermostat to make it function. Thing is, it moves a fair amount of water. Enough that on cooler days and under really light loads it may sneak a bit below the set point as the bypass amount is actually enough to get the job done.

Better test to find the 'throttling' temperature is a hour down the interstate or some other road where you can get a hours worth of clean drive time at 55 mph or better. It won't take that long but it will give you time to watch it in action.

It if truly is running under 174 F steady with a 'normal' load Katech will make it right.

HarryK · March 14, 2022

Interesting, thanks GB, I'll let you know as I run some road tests. I believe the P0128 trips after a certain amount

of drive cycles not reaching 168 degrees (from what I've read). Makes sense now for my last couple of years ,most

likely had thermostat failing slowly...(had truck for 4 years..bought it with 178,000 miles...dash temp was always around 11 o'clock/11:30 lately). With the new OEM stat installed, It seems to hang steady at the 210 degree 12:00 o'clock position.

Again, from everyone's input and my observations with the OBDLink, , it seems to be programmed to hang there for a 30

or 40 degree range, presumably to not panic people about normal fluctuations. I will say though that I love the coolness of the engine compartment compared to before...feels good to not subject everything under there to such high heat. An added benefit

would be that the trans fluid gets cooled down now when it goes through the radiator instead of heated (it's already at 192 when the trans stat opens (I know,,waiting to install sure cool bypass...one thing at a time). On to my testing...

pokismoki · March 14, 2022

whats the ambient temp in your climate?

the lower temps will make all the components last longer since everything under the hood is made of plastic, which gets brittle with heat. the plasticizers evaperate off the hotter it gets. you should see what happens to 8 year old BMW's after running factory thermostats, they disinegrate from the heat!

yes trans fluid gets cooled down , but not when you have the factory inline trans thermostat installed, you need to pull that out and either block off the cooler line bi-pass or reverse the thermostat , "pill flip" You can also buy the thermostat tsb update from GM it runs at 170 degrees i think. but i prefer deleted for improved flow , my trans operates at 145 even pulling trailers, with No trans cooler inline either

HarryK · March 14, 2022

I'm currently in south FL and the heat becomes oppressive here. We have a couple of cool days now before the run up to the summer. I did read that the

transmission stat opens at 192F. But before, with the stock 207F coolant thermostat, that 192 would get pumped into the 207F coolant. (Although I have the V6 4.3L

so the transmission cooler lines go to the passenger side radiator tank (cold side) so the coolant temp may be a bit lower there where the trans cooling lines

are inside.). Anyway, the Sure Cool delete kit for the trans stat arrived a couple of weeks ago. As I mentioned though, one thing at a time and I wanted to do the

Katech 174 first. As for the updated TSB on the trans stat, I believe GM changed the fittings in 2015 or 2016 that go to the transmission thermostat. My 2014 has C clips

going into it and the updated GM thermostat (which is rated at 158F) will not swap in. I would have to buy the entire line set with it. I hope to get the truck out this week for

the testing that GB recommended. I did check the packaging today and it was marked as the 174F coolant thermostat.

Thanks for the info...If you have thoughts on the ECT sensor right next to the coolant thermostat housing let me know. I was going to change it out.

pokismoki · March 15, 2022

i doubt theres anything wrong with the ECT sensor

Grumpy Bear · March 15, 2022

19 hours ago, HarryK said:

I'm currently in south FL and the heat becomes oppressive here. We have a couple of cool days now before the run up to the summer. I did read that the

transmission stat opens at 192F. But before, with the stock 207F coolant thermostat, that 192 would get pumped into the 207F coolant. (Although I have the V6 4.3L

so the transmission cooler lines go to the passenger side radiator tank (cold side) so the coolant temp may be a bit lower there where the trans cooling lines

are inside.). Anyway, the Sure Cool delete kit for the trans stat arrived a couple of weeks ago. As I mentioned though, one thing at a time and I wanted to do the

Katech 174 first. As for the updated TSB on the trans stat, I believe GM changed the fittings in 2015 or 2016 that go to the transmission thermostat. My 2014 has C clips

going into it and the updated GM thermostat (which is rated at 158F) will not swap in. I would have to buy the entire line set with it. I hope to get the truck out this week for

the testing that GB recommended. I did check the packaging today and it was marked as the 174F coolant thermostat.

Thanks for the info...If you have thoughts on the ECT sensor right next to the coolant thermostat housing let me know. I was going to change it out.

The pills will swap between the two trans thermostats sir. It will even swap into the 8L and 10L thermostats.

Gray line is the new GM 70C data I just started collecting. The other two are two different water thermostats. Currently I'm using the 170 C from Reische Racing in an IPSCO housing. I live in norther Illinois so supporting the bottom in winter is important to me. Or I thought it was. Enough to by the new valve anyway.

Powertrain wise we have the same truck.

Several yeas of data in this graph and yes driving faster will run up the temperatures

HarryK · March 15, 2022

That's a comprehensive chart GB. Remember, the temps I'm typing up here are for the engine coolant I'll deal with the transmission bypass shortly

by installing the Sure Cool kit when this is figured out. As for the transmission thermostat, yes the pill contents are interchangeable with the new 158 degree

replacement from GM bu the actual thermostat is not. The housings for the 2014 and I believe some 2015s have different fittings for the transmission lines

(C clip vs. a bolt pressing in a bracket.). So you can't just swap out your thermostat for the new one unless you buy the new lines if you have these

early build Silverados. You are correct though that you can take them apart and replace the new guts into your original housing. As I have the Sure Cool

kit waiting, I won't have to buy a new trans thermostat to do that (Each lowers the temp in it's own way, with GM I believe using an actual element inside and the

Sure Cool kit using a pressure system which I believe equated to about 160 degrees with a fail safe.

So much stuff to know for this thing. Hope to verify my coolant thermostat this week and then attempt the Transmission one.

GB thanks for the chart..impressive work.

HarryK · March 15, 2022

22 hours ago, pokismoki said:

whats the ambient temp in your climate?

the lower temps will make all the components last longer since everything under the hood is made of plastic, which gets brittle with heat. the plasticizers evaperate off the hotter it gets. you should see what happens to 8 year old BMW's after running factory thermostats, they disinegrate from the heat!

yes trans fluid gets cooled down , but not when you have the factory inline trans thermostat installed, you need to pull that out and either block off the cooler line bi-pass or reverse the thermostat , "pill flip" You can also buy the thermostat tsb update from GM it runs at 170 degrees i think. but i prefer deleted for improved flow , my trans operates at 145 even pulling trailers, with No trans cooler inline either

Pokismoki, yes you're correct, if the transmission thermostat remains, the fluid goes out to the radiator cooler at 192F and even if it is cooled and returned, the

transmission stat will keep it at 192. But it's better than the transmission sending it out at 192 into a 207 degree coolant enviornment and actually raising the temp

for the fluid's return to the transmission. At least I think with the coolant about 175 (and lower on that side of the radiator, it won't raise the transmission temp

as the factory set up would. Hope to know more about my Katech this week.

Grumpy Bear · March 15, 2022

Remember sir that you trans cooler is in the cold tank which can be MUCH cooler than the inlet temperature. Someday I will install a thermocouple in the pump supply and quantify that.

HarryK · March 18, 2022

Interim update:

I did two more tests. One was in the driveway cold start while monitoring temp with the OBDLink MX and keeping my hand on the upper

radiator hose. At about 156 to 158 degrees, the hot water started flowing in...

Second was at 50 to 55 mph for 5 to 6 miles after warmup. Temps fluctuated but always trying to get back to about 165 +/-

I called Katech and talked with Dan who was very helpful. He said that sometimes in applications the cooling system is so large and

efficient that it overwhelms a thermostat but mine is stock Silverado 4.3L. But it is possible I received the incorrect one.

I ordered a new one and will send the old one back in when I do the job upon new arrival. Katech was very accommodating but I had

to order a new one ($91), then they will credit me when I send the old back in. This way truck is not down for 2 weeks. Shipping is

very high ($18) for small item even though well packed, still small box. Even express mail would be less and it is sent regular UPS.

Oh well...will let you know...thanks for commenting/helping out....

By the way, it's still great to open the hod and feel the immense difference in heat when the engine is running 40 degrees cooler. As pokismoki said,

there's no way that 210 degree coolant system is good long term for all the parts under there, no matter how engineered they are

Thanks!

Grumpy Bear · March 18, 2022

2 hours ago, HarryK said:

He said that sometimes in applications the cooling system is so large and efficient that it overwhelms a thermostat but mine is stock Silverado 4.3L.

I have the same set up as you. The radiator for your 4.3 is the same as the radiator for the 5.3 non NHT. The get a different part number but the same. GM has done this for a long time. My 76 Corvette U joints are the exact same part as that years trucks middle drive shaft U joint. Different color box. Different part number. About $80 difference in price. There is/was an exchange book at one time for this sort of nonsense. This 'oversized' radiator is one of the 'special' things I love about the 4.3.

My Reische Racing 170 F stat in an IPSCO holder (in upper hose in photo below) will hover just under 170 F in the coldest days of winter and may take up to 25 miles to throttle on temp on those colder days. Patients grasshopper.

HarryK · March 18, 2022

Yes, absolutely. (Really like your setup). Remember though, if it is a 174F then then it should open right around there,maybe fully open a little higher (Katech lists +7 degrees as a tolerance so I don't know if it means it starts to open at 167 and fully open at

174). When I first changed to the factory OEM 207, the top radiator hose would get hot right there at 205/206 or so....the stat

in question on the truck now starts to open at 156/158F.

I would keep the one I have (which I really think is the 160) but I bought the 174 so the ECM wouldn't trip the P0128 and put my fans on full. I believe it will do this after too many <168 degree drive cycles. With a 160 thermostat, and no change to the electric fan schedule, the coolant may reach over 200F while stationary, occasionally taking care of this problem. However, in the winter when you're idling and the coolant doesn't reach past 168 for a few cycles the computer thinks your stat is stuck open. With a

174 it should be fine.

We'll see what the changeover brings...