LS thermostat talk

redneckengineered · Oct 14, 2015

Interested to hear what thermostat you guys are running in your LS motor, your cooling setup, and what temps you run. My LS 402 stroker had a stock 195 stat and would run 205-210 max all day long no matter how you treated it. We recently rebuilt that motor and threw a little more compression at it and HP. Same 195 degree stat. It now runs 210-220 and will climb to 230 when you're beating on it but then come back down to 210-220 fairly quickly. Rear mounted 31x16 Griffin, dual fans. I have a plenty of cooling capacity. Mast suggested I switch to a 160 degree stat. I ride a lot during the winter so I was also considering a 180 but wasn't sure if that even would make enough of a difference. I'd like to run around 200-205 degrees all the time ideally. How much of a change can you actually expect going from a 195 to a 180 or 160 temp wise? My fans run with the ignition so they do not cycle on/off with temps.

tommy450r · Oct 14, 2015

I run a washer with a 1 inch hole with my fans on the ignition an I run right around 180 unless I'm in really tight trails easin around a lot then it will creep up to around 200 and I can rev it up good an drop it back down..

If I ever let it get to about 230 it will create a air pocket an I gotta bleed the system?? I haven't figured that out yet..

JRowe · Oct 14, 2015

Not an LS, but 5.7 vortec. I noticed a good difference when I switched from 195 to a 180.

John Galbreath Jr. · Oct 14, 2015

redneckengineered said:
Mast suggested I switch to a 160 degree stat.

I would do what they say.

On Solo Buggy (Gen1), I run a thermostat only during the winter. Just put it in after the last ride.

crawlin85cj · Oct 15, 2015

Both mine have a freeze plug with a hole drilled in the middle. I think that's how Turnkey does them all. WFO will warm up if you treat it real bad for a long time.

2012 Jim's Garage YJ
2013 Wide Open Design WFO
Next one is in the oven!

tallnate · Oct 15, 2015

I might be telling you stuff you already know but I have done a lot of research on this... definitely don't consider myself an expert by any means. I fight coolant temp issues in mine at times but my problem is 100% a capacity issue.

1. Air / fuel ratios can easily influence your coolant temps. Does your engine run on a closed loop system meaning does the ECU receive O2 sensor readings so that it can constantly modify it's timing and fuel maps?
2. The correct temp thermostat is important especially with LS motors running on a closed loop system because the ECU is tuned to keep the engine coolant temp at the factory operating temp based on the factory thermostat temp.
3. It is important to run a thermostat as opposed to no thermostat at all. Running without a thermostat will allow coolant to circulate too quickly which can result in fluid cooling too much after a period of easy running or not cool enough under periods of heavy throttle. Again, this is necessary because engines are tuned and air / fuel tables are set at full operating temp. A closed loop system will run on the lean side until it sees the coolant temp at the set thermostat temp.
4. Are your steam ports hooked up? I know mast likes to block them but I've read a lot of articles on the effectiveness and importance of leaving these hooked up.

Now if you run an open loop (a pre-set loop tune based on rpm's alone) it's hard to say. Since you're sure you have plenty of cooling capacity, and you were getting a little warm when just cruising around, my guess would be that your tune runs a little on the lean side in the 2-3k rpm range. Lean air / fuel ratios make big power but also make big heat.

croes · Oct 15, 2015

redneckengineered said:
Mast suggested I switch to a 160 degree stat.

Before I had my new rad setup custom built I had issues, my buddy that builds and tunes lsx's made the same recommendation to give it a "head start". I did go from a 180 to a 160 but don't know if it helped since I went to a 3" dual pass with a fully shrouded Spal HD. I can't force it to go above 220, and it stays right where the fan settings command it to be.

tonybolton · Oct 15, 2015

Re:

Are any of you that are running this 160° thermostat having troubles in the winter time with them?

croes · Oct 15, 2015

Re:

tonybolton said:
Are any of you that are running this 160° thermostat having troubles in the winter time with them?

No, first trip was in December after I got it back together.

tonybolton · Oct 15, 2015

Re:

Well that sounds good. I think mines got a 180 degree in it or whatever is stock and was thinking about switching to a 160 as it will get up to around 220 if I sit and beat on it for about 5 or 10 minutes.

It actually got up to about 235 or 240 one time when it was about a hundred and five or so degrees out and I was running it through the trail pretty good on a consistent climb up the mountain. Only did that one time though but I think the lower stat would be a little better for it

patooyee · Oct 15, 2015

tallnate said:
3. It is important to run a thermostat as opposed to no thermostat at all. Running without a thermostat will allow coolant to circulate too quickly which can result in fluid cooling too much after a period of easy running or not cool enough under periods of heavy throttle. Again, this is necessary because engines are tuned and air / fuel tables are set at full operating temp. A closed loop system will run on the lean side until it sees the coolant temp at the set thermostat temp.

I don't know about that. As long as the O2's are working it should not run lean. Yes, the main VE tables are tuned at op temp but there are a bazillion modifiers that modify the base fuel tables based on ECT. The main VE tables are only like 1% of the overall fueling calculations. Even in open loop there are fuel modifiers to compensate for ECT.

I ran my LS2 without a t-stat and was very happy with the results. It always stayed around 200-210. Maybe over the lifespan of 200,000+ miles not running a t-stat could affect something in an OEM vehicle. But the average LS in a dedicated offroad rig probably doesn't even see 10,000 miles in its lifetime.

cdemart2 · Oct 16, 2015

crawlin85cj said:
Both mine have a freeze plug with a hole drilled in the middle. I think that's how Turnkey does them all. WFO will warm up if you treat it real bad for a long time.

2012 Jim's Garage YJ
2013 Wide Open Design WFO
Next one is in the oven!

What size freeze plug and how big is the hole? Does it go in the back of the water pump or does it go where the thermostat goes?

I've had problems with stock thermostats sticking shut. Rear radiator 31x19 CBR, stock gen IV 6.0. One day it'll be fine, run 210 no matter what. Get in it a few weekends later, goes right to 240 into limp mode and the radiator is cool to the touch. Put a new stat in it and all is well until it sticks again.

I made a restrictor plate with a 1/2" hole that goes in place of the thermostat but I haven't had a chance to drive with it yet. I just did a few heat cycles in the garage to bleed it.

muddinmetal · Oct 16, 2015

y'all do realize that a stock ls going down the highway runs in the 220s, right? The factory cluster is calibrated to show much lower so it doesn't freak the old timers out....

shrek tits · Oct 16, 2015

cdemart2 said:
What size freeze plug and how big is the hole? Does it go in the back of the water pump or does it go where the thermostat goes?

I've had problems with stock thermostats sticking shut. Rear radiator 31x19 CBR, stock gen IV 6.0. One day it'll be fine, run 210 no matter what. Get in it a few weekends later, goes right to 240 into limp mode and the radiator is cool to the touch. Put a new stat in it and all is well until it sticks again.

I made a restrictor plate with a 1/2" hole that goes in place of the thermostat but I haven't had a chance to drive with it yet. I just did a few heat cycles in the garage to bleed it.

Not all water pumps have the same size hole. I drilled a 3/16" hole in the top of the plug. Plug goes in the back of the water pump.

redneckengineered · Oct 16, 2015

tallnate said:
I might be telling you stuff you already know but I have done a lot of research on this... definitely don't consider myself an expert by any means. I fight coolant temp issues in mine at times but my problem is 100% a capacity issue.

1. Air / fuel ratios can easily influence your coolant temps. Does your engine run on a closed loop system meaning does the ECU receive O2 sensor readings so that it can constantly modify it's timing and fuel maps?
2. The correct temp thermostat is important especially with LS motors running on a closed loop system because the ECU is tuned to keep the engine coolant temp at the factory operating temp based on the factory thermostat temp.
3. It is important to run a thermostat as opposed to no thermostat at all. Running without a thermostat will allow coolant to circulate too quickly which can result in fluid cooling too much after a period of easy running or not cool enough under periods of heavy throttle. Again, this is necessary because engines are tuned and air / fuel tables are set at full operating temp. A closed loop system will run on the lean side until it sees the coolant temp at the set thermostat temp.
4. Are your steam ports hooked up? I know mast likes to block them but I've read a lot of articles on the effectiveness and importance of leaving these hooked up.

Now if you run an open loop (a pre-set loop tune based on rpm's alone) it's hard to say. Since you're sure you have plenty of cooling capacity, and you were getting a little warm when just cruising around, my guess would be that your tune runs a little on the lean side in the 2-3k rpm range. Lean air / fuel ratios make big power but also make big heat.

Closed loop. Engine was broke in/tuned on a dyno, I'm confident the tune is solid. Steam ports hooked up. Funny thing, before this rebuild they were blocked but I never had any problems. Mast suggested I go to the 160 stat, they've never steered me wrong before. Just wanted to hear some real world experience with it. I got a Lingenfelter one coming from Summit.

muddinmetal said:
y'all do realize that a stock ls going down the highway runs in the 220s, right? The factory cluster is calibrated to show much lower so it doesn't freak the old timers out....

I'll actually be the first to explain to people going from an old school motor to an LS they need to get used to looking at a temp gauge that hangs out between 200-220. It is where these motors like to be for the most part. I'm ok with that. My issue is by no means a big problem and it hasn't stropped me from riding. I just know I have enough cooling capacity and need to take about 10 degrees out of the overall temps. Like I said, before adding a point of compression and some more HP I'd stay at 205-210 no matter what. If you got it over 220 you better get out and check around because something is wrong. That's how solid it was. That's kind of where I'd like to get back to.

altfuel1991 · Oct 16, 2015

On a stock LS truck engine the thermostat is designed to keep the engine above 195 degrees. When the engine is cold the ecm adds extra fuel to keep it running and heat it up quicker, basically you have an electronic choke. The ecm has to see at least 187 degrees in the engine before it will go into hot-run mode and lean the mixture out. That function needs to be programmed out if running a colder thermostat. On trucks we see at the shop if the thermostat is stuck open the engine will not get above the 187 degree level.

jsg1113 · Oct 17, 2015

I had a lot of issues with mine heating up, especially if I was on a hill. Still running a stock (195 deg) thermostat but I went with larger coolant lines and it made a big difference in operating temps as well as how quickly it cools down. I initially ran -16 AN lines from front to rear and I now run 1.5" flex radiator hose and it works much better. Just my experience....

fl-krawler · Oct 19, 2015

I've always ran the stock thermostat with a 1/8" hole drilled in it. 22x19x3 Griffin radiator with a taurus fan. Never gets above 200 via autometer gauge unless I am really not nice to it for more than 10-15min solid at a time (playing in the mud at sustained WFO the whole time).. Even when the tem creeps up I can back out of it a little and the fan brings the temps down quick

tallnate · Oct 19, 2015

altfuel1991 said:
On a stock LS truck engine the thermostat is designed to keep the engine above 195 degrees. When the engine is cold the ecm adds extra fuel to keep it running and heat it up quicker, basically you have an electronic choke. The ecm has to see at least 187 degrees in the engine before it will go into hot-run mode and lean the mixture out. That function needs to be programmed out if running a colder thermostat. On trucks we see at the shop if the thermostat is stuck open the engine will not get above the 187 degree level.

This is a much better way to explain what I was trying to say. ^^

redneckengineered said:
Closed loop. Engine was broke in/tuned on a dyno, I'm confident the tune is solid. Steam ports hooked up. Funny thing, before this rebuild they were blocked but I never had any problems. Mast suggested I go to the 160 stat, they've never steered me wrong before. Just wanted to hear some real world experience with it. I got a Lingenfelter one coming from Summit.

Cool, I'm interested to see how it does. If it keeps it cooler than the expected normal op temp it may run a little on the rich side but that's definitely better than getting hot.

hokie_yj · Oct 19, 2015

fl-krawler said:
I've always ran the stock thermostat with a 1/8" hole drilled in it. 22x19x3 Griffin radiator with a taurus fan. Never gets above 200 via autometer gauge unless I am really not nice to it for more than 10-15min solid at a time (playing in the mud at sustained WFO the whole time).. Even when the tem creeps up I can back out of it a little and the fan brings the temps down quick

This makes me feel a whole lot better about the chances of my setup working if I ever get it done. I have a 1/8" hole drilled in my thermostat, and a 22x19 PRC radiator with a fully shrouded Volvo fan. Glad to hear it's working for you.