H3 Thermostat Shim For The I-5

[EndeavoredH3]

Ive come across a couple threads to find a 180* thermostat, and no luck. I dont know if Im terrible at finding 180* thermostats or its apart of some ancient stock covered in dust on a shelf somewhere. Just past gutting the lower thermostat and installing an inline thermostat on the upper radiator hose, Ive come across a 355Nation post about shimming the I-5 thermostat.


Link to the tutorial:
[FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]https://www.355nation.net/threads/how-to-shim-your-thermostat.188762/


The first thermostat lasted for 10 years and was a 180*, the one that replaced it is a 194*. During the summer Im seeing temps of 225*+ climbing grades. The highest value ive seen is 227*. Before with the OEM 180* t-stat I wouldn't see these temps this often. Everything in the cooling system was replaced,

(Besides the radiator),​

when the new 194* t-stat was installed.

I'm hoping to find a good solution for us I-5 guys, not sure if shimming the t-stat is a good idea or not. Haven't heard of the practice until coming across the 355nation thread. Any input is appreciated!
[/FONT]

 

[alrock]

I remain in the camp that the thermostat opening value, 180 or 194, does not affect the maximum temperature or sustained temperature of the radiator. Once the stat is open, it no longer affects the cooling process. Your cooling is determined by airflow across the radiator and flow of coolant through the system. Since a 194 thermostat is just as open as a 180, it is not a factor above 194.

A 180 thermostat may slightly slow down the truck from reaching 200+ by a few minutes, but that's really the only difference.

You'll probably see a bigger difference by making your your a/c condenser is not full of dirt and debris, that your coolant is the proper ratio and that you have quality components. I saw a temp drop going back to an OEM radiator vs. an eBay one.

That's my :2cents: on how to keep your H3 cool, and the whole t-stat thing. But many of course will disagree so pursue whatever works best for you.

 

[amrg]

+1 on what he said!
Bottom line, a cooler thermostat will let you ect go lower IF your system has the capacity to, But wont affect how high it goes.

 

[JPaul]

My understanding is they went to the higher opening temperature for emissions, the cooler temp was keeping the engine from operating at a more effective temperature when not being pushed very hard (idle, low cruising, etc).

I know performance minded individuals will opt for the lower temp thermostat with the idea that cooler temps will help with performance, but that probably came from back when engines got all of their air from within the hot engine bay. The H3 has a proper cold air intake from the factory, as do most modern vehicles made since the 2000's. On top of that the intake is fully plastic which has a very low heat transfer so unless you're idling for long periods of time the intake charge picks up very little heat. Under power the air moves too quickly for it to absorb any real heat from the engine and underhood, even if it was an aluminum intake.

When it comes down to it, if you're reaching the max of the cooling system to keep the engine cool then the thermostat opening temperature doesn't matter anymore, either will be fully open by that point. The 180 will be fully open at 200, and the 195 at 215. But overheating doesn't begin to be an issue until past 230 degrees which is well above either thermostat's fully open temperature.

If you are reaching that temperature then the problem is with the load being placed on the engine and/or you have maxed out the ability for the cooling system to be able to transfer heat out of the coolant quickly enough. Maxing out the cooling system can be due to several factors: excessive engine load, cleanliness, coolant condition, ambient temperature and humidity, system design, damaged or poorly constructed parts, air in the system, obstruction in the airflow through the radiator, etc.

Lower temperature thermostats are in my opinion another holdover from the old carburetor days when engines were nowhere near as well designed and understood as they are today. I say save yourself the trouble of mucking around with trying to fit a lower temperature thermostat and just make sure that the rest of the cooling system is in good working order.

Sent from my SM-N975U using Tapatalk

 

[scoreh3]

+1 on JPaul , when I asked the dealer ship why they only have the hotter T-stat now ? He said it was an emissions requirement now .

 

[amrg]

Just a small note, with cooler thermostats and cooler ECTs you can get more performance. The stock ECU has a static value set for timing between 187* and 200* then starts retarding timing once temps go above 200* to reduce the chance of detonation, which as a result reduces hp. If the system can reduce temps and the tstat is now whats holding the system from doing so, you are missing out on some hp (a tune will allow you to advance timing as the lower temps to improve that powet).
Now obviously there is a point where going much cooler wont help you get much improvement, but generally around 185-190 is were max power can be achieved with pump gas.
FYI, running the ac adds alot of load on the cooling system, an older system probably runs at a lesser efficiency and puts alot of heat at the condensor infront of the radiator.

 

[EndeavoredH3]

I remain in the camp that the thermostat opening value, 180 or 194, does not affect the maximum temperature or sustained temperature of the radiator. Once the stat is open, it no longer affects the cooling process. Your cooling is determined by airflow across the radiator and flow of coolant through the system. Since a 194 thermostat is just as open as a 180, it is not a factor above 194.

A 180 thermostat may slightly slow down the truck from reaching 200+ by a few minutes, but that's really the only difference.

You'll probably see a bigger difference by making your your a/c condenser is not full of dirt and debris, that your coolant is the proper ratio and that you have quality components. I saw a temp drop going back to an OEM radiator vs. an eBay one.

That's my :2cents: on how to keep your H3 cool, and the whole t-stat thing. But many of course will disagree so pursue whatever works best for you.

Great points, the radiator is definately a napa aftermarket and is one of the last things not replaced in the cooling system so maybe Ill be changing that soonish. Ill try to go with an OEM next whenever the time comes. Thanks for laying it out for me, makes more sense now.​

 

[EndeavoredH3]

My understanding is they went to the higher opening temperature for emissions, the cooler temp was keeping the engine from operating at a more effective temperature when not being pushed very hard (idle, low cruising, etc).

I know performance minded individuals will opt for the lower temp thermostat with the idea that cooler temps will help with performance, but that probably came from back when engines got all of their air from within the hot engine bay. The H3 has a proper cold air intake from the factory, as do most modern vehicles made since the 2000's. On top of that the intake is fully plastic which has a very low heat transfer so unless you're idling for long periods of time the intake charge picks up very little heat. Under power the air moves too quickly for it to absorb any real heat from the engine and underhood, even if it was an aluminum intake.

When it comes down to it, if you're reaching the max of the cooling system to keep the engine cool then the thermostat opening temperature doesn't matter anymore, either will be fully open by that point. The 180 will be fully open at 200, and the 195 at 215. But overheating doesn't begin to be an issue until past 230 degrees which is well above either thermostat's fully open temperature.

If you are reaching that temperature then the problem is with the load being placed on the engine and/or you have maxed out the ability for the cooling system to be able to transfer heat out of the coolant quickly enough. Maxing out the cooling system can be due to several factors: excessive engine load, cleanliness, coolant condition, ambient temperature and humidity, system design, damaged or poorly constructed parts, air in the system, obstruction in the airflow through the radiator, etc.

Lower temperature thermostats are in my opinion another holdover from the old carburetor days when engines were nowhere near as well designed and understood as they are today. I say save yourself the trouble of mucking around with trying to fit a lower temperature thermostat and just make sure that the rest of the cooling system is in good working order.

Sent from my SM-N975U using Tapatalk

That's probably why the information that ive come across has been so conflicting, being based on the old carburetor days. The water temp only spikes out like that on the uphill climbs, then comes back down after. I have always seen this swing in temperature, was thinking about the "solution" of finding a lower temp thermostat but you guys have laid it out well for me that it wont do much.

Im not looking for straight line performance or a bunch of horsepower, and I don't mind the higher temps for the thermostat (ex: the 195* t-stat). Its always been the swing in temps that has me thinking.

 

[EndeavoredH3]

Here's another idea id like to throw at you guys. There has been a handful of people that have gutted the lower thermostat and then installed an in-line thermostat on the upper radiator hose. They have run either a 180* or a 190* and do not see a big swing in temps. MSC on club hummer offroad and a gentleman in spain (No clue on his username, hopefully he'll chime in) are two that I have found to have the most testing and success with this modification.

When the thermostat was relocated to the upper radiator hose, the temps stayed within 10-15 degrees of the rating of the thermostat. In the same situations where the OEM thermostat would give the higher temps like I've mentioned. ​

I haven't seen many vehicles with the thermostat on the inlet side of the motor and I'm not 100% on how it operates. From what im finding it cycles since the coolant temp of the motor opens the thermostat, coolant from the radiator rushes in but is cooler, then the thermostat closes. And its a constant cycle. Could be wrong, but would like to know if im getting there.

Let me clarify I do understand how a thermostat functions, its just this type of application is throwing me for a loop. The thermostats ive replaced have been in the water outlet.​

What are your opinions on this type of modification?

 

[JPaul]

Pretty sure the thermostat should never be on the inlet side since it's not going to really cool the engine. If it is on the inlet side then the moment the cooler fluid flows past it the thermostat will close and stop the flow. You can actually overheat the engine this way. With it on the outlet side then you keep hotter coolant flowing past it (keeping it open) until all the hotter coolant has been purged out and the temps are back down and the thermostat closes. Then the heated coolant can spend time in the radiator cooling off for the next cycle.

The coolant needs to spend a proper amount of time in both the radiator and the engine for maintaining proper engine operating temperature. Keeping the engine too cold or too hot will result in damage. Putting the thermostat on the inlet side of the pump will keep the coolant in the radiator and the engine for far too long, especially in colder ambient temperatures.

I have spent enough years looking into and trying various "aftermarket" modifications to understand that the engineers at the OEM know what they are on about, especially with modern cars (anything built after the mid 90's generally, and the newer the car the less you can tweak on it without spending big bucks). Generally the only times you really see issues is either when they were trying something new or the spec was marked down because of budget constraints. But something like the thermostat position is a pretty tried and true solution that is not something to be mucking about with.

Unless you're looking at changing the powerband of the engine, using forced air induction, nitrous, modifying the flow of intake and exhaust gasses, or changing the fuel and spark maps, you won't really see any improvement to the performance of the engine. At the least you'll just waste time and money for no benefit, at worst you'll trash your engine.

Sent from my SM-N975U using Tapatalk

 

[08H3]

... The stock ECU has a static value set for timing between 187* and 200* then starts retarding timing once temps go above 200* to reduce the chance of detonation....

Not sure I totally follow what you are saying. Timing is not static within that temperature range. Unless my Scangauge is just throwing out made up numbers, timing certainly does fluctuate within that temperature range. I agree it begins to retard timing based on high temperatures, but I'm not sure why you say it's static within the 187-200 range. Clear up my confusion.

 

[amrg]

By static I mean the ECU will not modify the timing values based on ECT. Once ECT goes north of 200*, the timing tables start getting affected by an ECT multiplier that reduces its final value.
On my Alpha, I used to feel a big difference in engine power between 190* and 210*. Once I got hptuners and went into the timing tables I understood why

 

[alrock]

Wanna reduce heat under the hood? Go back to 32s, get rid of roof racks, UCP and other heavy or mods that add weight or hurt aerodynamics. I bet these vehicles that used to run cooler also used to get better MPG. But once you start burning more fuel you're also creating more heat under the hood.

I would add that with these theories of a lower temp stat, modified stat or relocated stat, then a removal and bypass of the thermostat would simply give you lower temperatures all of the time. The vehicle would come up to temp more slowly (like any vehicle with a stat that's stuck open) but it would more clearly give the lower temps sought if those other theories are true.

 

[Exodus]

don't know how realistic this hint is as i haven't had the pleasure of replacing my t-stat yet
Use to drive a 71 ford truck with a mercury 410 in it,strictly a city driver,that dam thing ran hot all the time
So i drilled 3/16 holes in the flange of the t-stat,problem solved

 

[amrg]

I forgot to add that someone in saudi arabia modifies a tstat housing to bolt tp the h3, and it accepts a Hyundai tstat, I see on instagram customers posting good reviews about the temps dropping back to half or below with the current ambient temps of 100*. Iirc one of his customers posted it on a fb hummer page but as with everything on fb, its unorganized and difficult to find again.

 

[EndeavoredH3]

Wanna reduce heat under the hood? Go back to 32s, get rid of roof racks, UCP and other heavy or mods that add weight or hurt aerodynamics. I bet these vehicles that used to run cooler also used to get better MPG. But once you start burning more fuel you're also creating more heat under the hood.

I would add that with these theories of a lower temp stat, modified stat or relocated stat, then a removal and bypass of the thermostat would simply give you lower temperatures all of the time. The vehicle would come up to temp more slowly (like any vehicle with a stat that's stuck open) but it would more clearly give the lower temps sought if those other theories are true.

I have a tendency to overthink the simple stuff, never had the A/C OFF or Engine power reduced due to too hot of coolant temps. Even with the 33's, roof rack and various other stuff ive tacked on. Should be good then.
​