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OH NO, ANOTHER THERMOSTAT PAGE

MrMarty51

MrMarty51

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Location
Miles City, Montana
I have been looking over thermostat questions and answers.
I have read to run the 195s, I have read to run 185s or whatever the 180 range comes in.
I have on the shelf a pair of brand new GM original set of 190s.
The reason I ask.
Ambient air temp was 66 degrees.
Driving to Church last Sunday. There are some fairly steep hills in this area but about the longest climb would be 3, maybe 4 miles.
Running two coolant temperature gauges, aux gauge at the back of the Right hand side cylinder head.
That aux gauge is the more accurate and easier to read than the factory dash gauge.
Cliimbing the hills I noticed the electro viscous fan clutch indicator light had came on.
Both temp gauges were barely over 200* F.
Vehicle speed was 80 MPH and tachometer, IIRC, about 2700 to 2750 RPM.
The temp remained at 200 for a very long time even after getting on the flat stretches of road.
Slowed vehicle speed to about 70 and temp gauges came down and electro viscous indicator LED bulb extinguished.
I run it at about 70 the rest of the way home.
I have never tried running 80 MPH before so I dont know if the coolant pump on the old engine would have performed the same.
I am in need of getting this truck totally ironed out befor the 19th of June when I travel over to My brothers in Ohio. I will be towing a 8X12 single axle trailer going both directions.
I have a total disliking to draining prestone so I want to take just one shot at this.
I am thinking pulling the NAPA pump from the old engine, about 12,000 miles on that one, maybe less on that coolant/water pump and also installing those 190 thermostats.
I wont be hauling much of a load on the trailer, less than 2000 pounds but I do not want problems with the cooling system.
Oh yeah, the cooling stack was cleaned out when I had the engine removed.
The radiator is the nice aluminum unit thats recommended and it made the side journey through Chris shop for the coating.
The water pump was ordered from Rock Auto and was suppose to be the AC Delco recommended pump but when it got here it was some chinese knock off that I had to auger the mounting bolt holes on to get them to align with the holes in the block. It was a POS to get installed proper:
Thank You for the suggestions.
 
The temperature of the thermostat is not always what temperature the engine will run at, but what temperature the coolant starts going through the radiator.

The engine is considered running cold when it is below 160°- the timing will advance and the idle RPM will raise. DS4 ECM is programmed emissions control priority, not Engine life priority. Some people have done testing and found better mpg at 195 than 180. The biggest improvement I ever saw in all the testing we did from 160° vs 205° was 0.10 mpg improvement, but we also saw 0.08 mpg improvement from 160°-180° so most was being at 180.

Watch any performance show, talk to any dyno shop and they pefer to do dynos at 135° because the colder it is the more power they produce. The few ponies extra are not why I prefer 180°, but when there is something that loads the engine - be it my foot on the floor, up a steep hill, etc. Or bad stuff like a hose blows- there is a lot more headroom before the engine suffers damage. Imagine a hose blows and you dump all the coolant- if temperature raises 5° per 30 seconds and you are starting at 200- you have 2 minutes to have it shut off before you are smoking your rings. At 180° starting point I have double that.

I found that 6.2/6.5 tends to run within 5° of the thermostat under normal use and 10° working harder. This is using block off stat- using the dual which doesn’t block off- can be anything.
 
Think I’m going to go with the two 190s, both are new AC Delco stats that I’ve had on the shelf for about six or so years.
Then see what temps the engine runs at with these and possibly go warmer if I’m not happy with these results.
I’ll try to get these changed before Sunday when I drive over to Rosebud for church and see what kind of a difference these makes.
I do have another trip to take to the lake on May the 9th. I’ll be pulling over a fairly heavy boat and I guess that will judge what happens next.
 
MrMarty51 said:
Anyone want to comment on using 190* thermostats ?
Its got 195s in it now.
Would five degrees cooler make a huge difference in performance ETC ?
Click to expand...
Your operating temperature can be above 190 and 195 so what is the use of changing out your thermostats? If you are suspecting that your engine isn't cooling effectively enough then have the radiator looked at. You can take an infrared temp gun and check the the top and bottom of the radiator. Is there a fan shroud? The boiling point is raised by the pressure cap so I don't think that you should have too much to worry about.
 
Mine is a single stat setup and has a 180 installed. I have gotten it up to almost 200 running over 70 on the freeway in the summer time here. IDK what temp stat the 93 has in it, but both trucks temp gauges will climb rather quickly when accelerating up hill. both trucks have the factory aluminum core plastic tank radiators in them. with all the cooling upgrades the 95 has I don't think it's the pump flow or stats that cause the temp to go up but the lack of capacity on the system as a whole, that or once the stat is open the coolant just flows too fast to cool down in the rad.
 
I have the single t-stat and loaded up a little in the hills of southern Ohio with A/C on and 90-95 degrees out, I didn't need to turn off the air conditioner. That is with an OEM which I believe is 195. It didn't really offer to get much warmer than typical unladen.

An internally plugged Radiator will result in a different story as I experienced before replacing mine.
 
Radiator is a new Champion with the Twisted Steel Performance thermal coating stuff.
I had the radiator out when installing the new engine and did clean out between all the components in the stack.
When I installed the new engine I did not do anything with the thermostats. The cooling system was functioning real well. Even on days of 112 degrees the temperature gauges would climb to only 200* on a pull.
And so now the 190s are in and the system is topped back up.
Tightening the bolts holding down the upper intake manifold and the last bolt, giving it the last little bit of tight, felt this slip, oh 💩.
Okay, didnt go any farther. Enough for one day.
I have plenty of heli coils. The repair will be a snap. No, not a snap a bolt. A snap real quick getting that hole fixed. 😹😹😹
I am leaning more towards that screwed up water/coolant pump I got from rock auto.
When it got here it was a GM part instead of the AC Delco, which is what I actually ordered and the shipper must have been out of the AC Delco and sent me this made of chinesium POS that I had to auger the holes on to get it all to line up and bolt to the engine.
 
Completely agree with Will that in the 180 - 195* range there is not much noticeable difference in fuel economy and the only true factor is amount of buffer from operating temperature to overheat. If only cruising and never towing past 2K#, 195's will probably work just fine. If looking to get better mpg, focus on a tune which keeps RPMs in good ranges and locks the TCC more frequently and in lower gears.

With only towing ~2K#, just focus on making sure the cooling stack is good. Looks like the truck is on a good path for health.

In terms of towing closer to the GVWR limits, other factors come to play such as managing RPMs for maximum coolant turnover and throttle position to limit amount of heat generation. Failure to do this will quickly get a very hot stack when pulling up grade. With a slushbox, the OE shift tables will let the coolant temperature quickly rise into the unhealthy zone (and beyond) when pulling heavy up a long grade by letting the RPMs drop too low. Even with an excellent cooling stack, this is when limiting EGT's via the throttle, manually downshifting to keep from lugging, and riding the trucker's lane at 20 - 30 mph (maybe less?) are critical to controlling coolant temperatures. While it's been a few years and the memory is getting fuzzy on numbers, IIRC the EGT targets for the Burb (with an ATT) was 1,000 - 1,100 and no less than 2,500 RPMs when pulling hard up a grade. On level ground and minor hills I was good to cruise at highway speed with the AT in OD or the MT in Direct. Although I did limit speed to 55 mph. Different trucks with different builds will likely need to use different target numbers.

Oh, and fun fact. When towing heavy, don't fill the overflow bottle past the "COLD" mark when the system is actually cold. The thermal expansion of coolant will puke any coolant above that line out of the tank. Don't ask how I know... ;)
 
When pulling heavy taxing loads I never run over 60. Probably do the same with dragging that boat to the lake next Thursday.
Yeah, was going to go over on Friday but another couples plans changed so now there will be three truck, draging three trailer headed to the cabin on Thirsday.
 
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