Hey Mechanics. Thermostat in a radiator hose

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my5thmopar

my5thmopar

Life Long MOPAR Owner
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Is there a kit or OEM vehicle that has a thermostat in the radiator hose? My son's 99 Isuzu Rodeo 3.2 V6 has the thermostat under the intake manifold. What dummy thought that was a good idea. The truck has marginal heat and the engine stays cool because it is stuck open. It will cost too much to have fixed and I'm not going to do it. SO besides the cardboard infront of the radiator, I thought why not put it in the hose. I thought about 2 housings back to back with a thermostat sandwiched between. Any ideas? Thanks
 
If the OE stat returns to working order, you’ll overheat.
 
I've seen a floating housing on some farm equipment.

A long long time ago, don't laugh,I had a slightly-used 84 Hyundai Pony .......
The only way to even keep the windshield defrosted was; to fully block airflow to the rad, remove the fan, and blanket the engine with insulation. The heater was the bypass, and it ran wide open. That was an annual thing. Well bi-annual I guess cuz come summer, I had to undo it,lol....................I do not miss that car,not even a little bit. But the easy buy-in and great mpgs, got me thru some tough times.
 
Gm had a thermostat under the rad cap. Cant remember what car.
I cant see why it wouldnt work.
My nissan uses 2 thermostats one in upper hose and one in lower. Also a stupid idea.
 
rumblefish360 said:
If the OE stat returns to working order, you’ll overheat.
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Nope. If the stock one starts working at the normal temp and the new one also works at normal temp, no overheating will happen. Both will be open when they should be.
 
Tooljunkie said:
Gm had a thermostat under the rad cap. Cant remember what car.
I cant see why it wouldnt work.
My nissan uses 2 thermostats one in upper hose and one in lower. Also a stupid idea.
Click to expand...

I "acquired" a fiero GT with a V6 about a year ago. It had a funky thermostat under the radiator cap. There was a handle on the thermostat to pull it out. I was so happy when that car left my driveway.
 
Ddaddy said:
Nope. If the stock one starts working at the normal temp and the new one also works at normal temp, no overheating will happen. Both will be open when they should be.
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Let me know when you have some cash to loose because I’ll take that bet it won’t work as you think.

Once the OE stat starts working again, the water trapped upstream will cool and close the upstream thermostat. The water trapped in between the two thermostats will not beat up quickly enough to open the upstream thermostat. The water in between the two stats will not cycle around like if you were rotating your coffee cup spoon around.

That’s the way I see it.
 
rumblefish360 said:
Let me know when you have some cash to loose because I’ll take that bet it won’t work as you think.

Once the OE stat starts working again, the water trapped upstream will cool and close the upstream thermostat. The water trapped in between the two thermostats will not beat up quickly enough to open the upstream thermostat. The water in between the two stats will not cycle around like if you were rotating your coffee cup spoon around.

That’s the way I see it.
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Physics disagrees with you.

Think of it a different way, which direction does the heat come from that conducts through the coolant to open the thermostat?

It isn’t the radiator side.

And how much time or temperature differential will it take to heat a pint of water between the two to open the other thermostat?

Not enough to cause an overheat situation.
 
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I was working on a dodge Dakota last summer and I remember the rad cap being in the top hose, but not sure if the thermostat was there or not. Kim
 
Ddaddy said:
Physics disagrees with you.

Think of it a different way, which direction does the heat come from that conducts through the coolant to open the thermostat?

It isn’t the radiator side.

And how much time or temperature differential will it take to heat a pint of water between the two to open the other thermostat?

Not enough to cause an overheat situation.
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I’ll take that bet!
 
Depending on the thermostat, i’d drill a 1/8” hole in the plate,to pass air and some coolant will flow, so if original stat starts working(when a wax pellet fails its done) it will still open secondary thermostat.
 
rumblefish360 said:
I’ll take that bet!
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You would lose because your assumptions are predicated on false assumptions.

For just a moment, rethink the situation based on the physics of water heat conductivity and how the system is designed to work.

The downstream stat opens when the engine reaches the temperature it is rated for (which is well below the full operating temp of the cooling system). That opens the path to the upstream stat that contains a small mass of water between the two that is already rising in temp as the engine warms. A few minutes later, the upstream stat opens and the system operates normally.
 
Tooljunkie said:
Depending on the thermostat, i’d drill a 1/8” hole in the plate,to pass air and some coolant will flow, so if original stat starts working(when a wax pellet fails its done) it will still open secondary thermostat.
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Or change the temp rating of the second stat to be below the OEM one.
 
Dave has a point here. If thermostat is closed,in rumblefish’s world it would never open as the coolant isnt flowing.
Placing thermostat as close to outlet will reduce the chance of this.
 
Tooljunkie said:
Dave has a point here. If thermostat is closed,in rumblefish’s world it would never open as the coolant isnt flowing.
Placing thermostat as close to outlet will reduce the chance of this.
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That’s how I see it but moving a second thermo stat closer to the problem one...

Ddaddy said:
You would lose because your assumptions are predicated on false assumptions.
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What is it you think I’m assuming?

For just a moment, rethink the situation based on the physics of water heat conductivity and how the system is designed to work.

That opens the path to the upstream stat that contains a small mass of water between the two that is already rising in temp as the engine warms. A few minutes later,
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The way I see it, the water trapped in between will not heat up fast enough to open up the second thermo stat. Your assumption is the water caught in between the two thermo stats will heat up in time to prevent over beating the system.

You assume that the thermo dynamics will work in your favor. I just don’t see that or the fluid dynamics working in your favor.

Now who is assuming?!?!?!


Look here, I’m backing out of this argument discussion and I’m walking away. This is all based on an assumption. We are all guessing. I gave my thoughts on it. You can come back all you want, knock your self out, have fun.

I’ll just leave with, I’ll take that bet. As in you’ll over heat before it works correctly.

But we’ll never know.

Good day gents.
 
my5thmopar said:
Is there a kit or OEM vehicle that has a thermostat in the radiator hose? My son's 99 Isuzu Rodeo 3.2 V6 has the thermostat under the intake manifold. What dummy thought that was a good idea. The truck has marginal heat and the engine stays cool because it is stuck open. It will cost too much to have fixed and I'm not going to do it. SO besides the cardboard infront of the radiator, I thought why not put it in the hose. I thought about 2 housings back to back with a thermostat sandwiched between. Any ideas? Thanks
Click to expand...
Do the job right and do it once.
 
rumblefish360 said:
That’s how I see it but moving a second thermo stat closer to the problem one...



What is it you think I’m assuming?



The way I see it, the water trapped in between will not heat up fast enough to open up the second thermo stat. Your assumption is the water caught in between the two thermo stats will heat up in time to prevent over beating the system.

You assume that the thermo dynamics will work in your favor. I just don’t see that or the fluid dynamics working in your favor.

Now who is assuming?!?!?!


Look here, I’m backing out of this argument discussion and I’m walking away. This is all based on an assumption. We are all guessing. I gave my thoughts on it. You can come back all you want, knock your self out, have fun.

I’ll just leave with, I’ll take that bet. As in you’ll over heat before it works correctly.

But we’ll never know.

Good day gents.
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Ok, goodbye.
 
Do the job right, do it once.obviously Isuzu doesent follow that mantra.
I use those words often.
Thermostat failed,its not going to unfail.i have seen many fail in different ways. Spring breaks,cage breaks or they just stick open as a result of getting hot and lock open.
Convection or thermal conductance or whatever term one uses will open a second thermostat. May cause a longer heat /cool cycle, but gm did use a remote thermostat. It worked, but the thermostats were junk.
 
The problem with mounting a stat "higher in the system" is "IF" the coolant level gets a bit low..........Don't know the vehicle or hose routing, but if it can generate an air bubble in the stat vicinity, it could overheat before the stat can absorb enough heat to open.

This is also a problem with a higher mounted sensor for the gauge.......I've seen them a time or two mounted in a top tank bung. If the coolant gets a bit low, the gauge will read low, and you will be "behind the curve" so to speak on engine temp
 
I have had an inline thermostat ever since I installed the blower. It works great. I used it because the blower made it impossible to get at the thermostat without taking the blower off. Heres a photo of it.

Jack

BLOWER SETUP006.JPG


BLOWER SETUP007.JPG
 
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Ddaddy said:
JEGS has them...

JEGS 53260K2: In-Line Thermostat Housing Kit with 195 Degree Thermostat | JEGS
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That's it. I agree, always do the job right. This truck has 200k+ miles. It has stuff broken, uses oil and probably to the point of not worth putting money into it. He is just trying to get a few more miles out of it and not freeze on the way to work. Also, I have taken the intake off this engine and I won't do it again. It was not fun...I don't like working on modern vehicles. If it fails or overheats, then we'll address it. Thanks for all the discussion.
 
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