Thermostats and Thermostat Housings

[Dynomite]

Here is How My Day Went

After a New Fluidyne Radiator Install I thought I should go all the way and put in a New 180 deg Thermostat. Marc answered a question I had in that regard. The thermostat for all LT5's is the same. The temperature rating is 180 degs F. In detail, the thermostat begins to open at 175 and is fully open at 185 degrees. A thermostat with over 50k miles generally opens 5 degrees later and opens about 80%.

So.....why not. I checked my New 180 deg Thermostat in Hot Water and it started to open at approximately 175 deg. Ready to go...and I had my Post on LT5 Thermostats on hand

Post 7 - LT5 Thermostats
Post 237 - Blocking TB Coolant, Fluidyne Radiator and Thermostats

Well......the New Fluidyne Radiator Drain Port worked perfectly. Now to separate the Thermostat Housing Halves. OOPS!!!!!

It all went down hill from there on.....

1. Bottom Bolt on Thermostat Housing was frozen Solid. Broke it off.
2. Had to remove Belt Tensioner, to get my hands in to move AC Dryer and to get to Lift Thermostat Housing.
3. Also removing Belt Tensioner gives access to the Spring Clamps on both ends of the Radiator Hose connected to Water Pump.
4. The Hose from Water Pump to Thermostat Housing is the only Coolant Hose I have yet to replace.
5. Disconnected Passenger Side hose to Heater Nipples on Thermostat and got it free (what a corroded mess).
6. Cut the Coolant Hose going over rail to Thermostat Housing.
7. Finally got Thermostat Housing up and out after moving the Top Coolant Hoses connecting Each Injector Housing.
8. Once the Thermostat was lifted up so I could get to the Drivers Side Heater Nipple....Disconnected that Heater Hose.
9. The Water Pump Spring Clamp was completely turned impossible to get a pliers on it so I used an Air Grinder.
10. Oh...ya.....Got the Hose Clamp cut but all I did was cut a piece out that allows you to compress the ends together. Now what a mess
11. After a couple hours with a razer blade and screw drivers finally got that hose off the water pump.
12. OOPS.....forgot about the frozen Bolt in Thermostat Housing which I had to use Acetylene Heat.
13. After heating finally got the stud showing to move back and forth and 30 minutes later got the stud out of the Thermostat Housing.
14. Chased the Threads in the Thermostat Housing.
15. The Drivers Side Heater Nipple on the Thermostat Housing has an "O" ring and the inside where the "O" ring resides was corroded.
16. Thanks to Jerry having much more foresight than myself I ordered a New and Improved Thermostat Housing Heater Nipple.

THIS ALL STARTED THIS MORNING AT 9:00AM AND ENDED AT 5:00PM THIS AFTERNOON !!!!!!!!!

This should be titled "You think you got Problems"

Oh......Checked that Stock Thermostat (must have been stock since the bolts in the Thermostat Housing were frozen solid) for Function.

I suspect it be a 180 deg Thermostat. It started to open at 195 deg and never opened all the way as far as I could tell.

So....what started off a great day with great idea had some tuff spots but ended up solving several issues including Corroded Thermostat Housing, Old Water Pump Hose that needed replacement, Corroded Heater Nipple on Thermostat Housng, and finally found out that what Marc had suggested about Thermostats was exactly what I found with the poor condition of my Stock 180 deg thermostat.

Installed the NEW Jerry's Thermostat Heater Nipple on the Thermostat Housing. After Cleaning up both Heater Nipples and with the New Heater Nipple installed I popped on the Heater Hoses. I acutally used just a tad of Permatex on the nipples for ease of insertion and a bit of additional leak protection. I also installed one new Water Pump to Thermostat Housing Coolant Hose. Fired up the LT5 after filling with Coolant and took it for a spin. No Leaks and Coolant Temperature stayed about 15 deg cooler than with the worn out Thermostat that actually opened at 195 deg (the New 180 deg Thermostat opened at 175 deg).

Just a Heads Up......if you ever have to remove the Thermostat Housing for any reason, have on hand one of Jerry's New Heater Nipples to replaced the old Heater Nipple on the Thermostat Housing. Jerry's New Heater Nipple

As an aside See Item #9 Post 237 - Blocking TB Coolant, Fluidyne Radiator and Thermostats..........My thinking is that the whole purpose of the Dual Opening Thermostat Housing (Thermostat can open at the Temperature side or on the other end at the Pressure side) is to keep Radiator Pressure to acceptable limits. In other words the Thermostat functions when the engine is cool and when the engine is at high rpm.

When the engine is at high RPM, the Bypass on the thermostat will be open completely do to the water pump developed coolant pressure on the bottom of the Thermostat. This Higher pressure being developed at the bypass end of the thermostat because the Thermostat is closed on the Temperature end or because the high water pump RPM is developing too much pressure on the radiator on the Bypass end of the thermostat.

In other words the Thermostat can open on either end (one end temperature controlled and the other end differential pressure controlled). And even if the Temperature End of the Thermostat is fully open, HIGH water pump RPMs may develop greater pressure than the radiator can stand on the Bypass End and the Thermostat would then open on both ends to allow more coolant to recirculate rather than ALL of the coolant flow being forced through the Radiator . 7,000 Engine RPM does that to you

[efnfast]

Lernt me some stuff about thermostats. Thanks Dynomite.

[XfireZ51]

Thermo housing is definitely a candidate for 3D printing.

[Tripler]

Awesome update and tips Dynomite . Sounded like a hell of a job .

[5ABI VT]

Looks like ill be getting that nipple ! Planned to pull apart the shroud and rad for cleaning and tinkering with the thermostat soon. Btw does anyone make a 170 or something slightly cooler than the 180 factory thermostat?

[Dynomite]

Originally Posted by 5ABI VT

Looks like ill be getting that nipple ! Planned to pull apart the shroud and rad for cleaning and tinkering with the thermostat soon. Btw does anyone make a 170 or something slightly cooler than the 180 factory thermostat?

I think you can find cooler Thermostats down to 160 deg but my theory is the LT5 engine operates best with 180 deg Thermostat and both a 160 deg and 180 deg thermostat will be fully open at say 185 deg F.

The 160 deg just opens sooner but does not keep the engine cooler than a 180 deg thermostat once the 180 deg Thermostat is fully open. The 160 deg thermostat will keep the engine down to say 165 deg on cool days which is too cold I think. The cooler Thermostat will set the bottom temperature but does nothing to set the top temperature once both thermostats are fully open.

[Paul Workman]

Originally Posted by Dynomite

I think you can find cooler Thermostats down to 160 deg but my theory is the LT5 engine operates best with 180 deg Thermostat and both a 160 deg and 180 deg thermostat will be fully open at say 185 deg F.

The 160 deg just opens sooner but does not keep the engine cooler than a 180 deg thermostat once the 180 deg Thermostat is fully open. The 160 deg thermostat will keep the engine down to say 165 deg on cool days which is too cold I think. The cooler Thermostat will set the bottom temperature but does nothing to set the top temperature once both thermostats are fully open.

I never took 'thermal dynamics', so I don't know the proper physics terms for it. But, you're right: The greater the heat differential between the radiator (coolant) and the ambient air, the greater the rate at which (therms or calories or whatever) will transfer (to the air, in this case)*.

*Plotting the temp over time, the graph would describe the change over time according to the natural log of decay. This would explain why it usually requires a lager capacity radiator and sometimes increased (fan) air volume coupled with a lower temp thermostat to bring the coolant temperature down to the lower 'stat opening point. IOW, the closer the coolant is to the ambient air temperature, the slower the coolant temperature falls (unless and until the motor adds more heated coolant to the radiator), all else being equal.

[Dynomite]

Originally Posted by Paul Workman

I never took 'thermal dynamics', so I don't know the proper physics terms for it. But, you're right: The greater the heat differential between the radiator (coolant) and the ambient air, the greater the rate at which (therms or calories or whatever) will transfer (to the air, in this case)*.

*Plotting the temp over time, the graph would describe the change over time according to the natural log of decay. This would explain why it usually requires a lager capacity radiator and sometimes increased (fan) air volume coupled with a lower temp thermostat to bring the coolant temperature down to the lower 'stat opening point. IOW, the closer the coolant is to the ambient air temperature, the slower the coolant temperature falls (unless and until the motor adds more heated coolant to the radiator), all else being equal.

I took Thermal and other stuff but much easier to explain with just plain logic. When both the cooler and hotter Thermostats are fully open (assuming both allow the same flow) there is NO advantage using the cooler Thermostat. When it is HOT outside and you are operating above the full open Coolant Temperature of the Hotter Thermostat.

There is a DIFFERENCE however when operating on COOLER Days when the Coolant Temperature does NOT rise to the FUll OPEN Conditiaon of the Hotter Thermostat. Then you are operating with a PART OPEN 180 deg Thermostat and maybe a FULL OPEN 160 deg Thermostat. Or when really cool outside. A PARTLY Open 160 deg Thermostat and a CLOSED 180 deg Thermostat. In OTHER WORDS your Coolant Temperature is Held Below 180 Deg which is NOT GOOD for the LT5.

The LT5 is designed for 180 deg I think as that is the Thermostat it comes with albeit my 95 had a 190 deg Thermostat which I changed out for a 180 deg (I think the 180 deg original Thermostat just drifted to a higher opening temperature with age as Marc suggested).

[Hog]

Originally Posted by Paul Workman

I never took 'thermal dynamics', so I don't know the proper physics terms for it. But, you're right: The greater the heat differential between the radiator (coolant) and the ambient air, the greater the rate at which (therms or calories or whatever) will transfer (to the air, in this case)*.

*Plotting the temp over time, the graph would describe the change over time according to the natural log of decay. This would explain why it usually requires a lager capacity radiator and sometimes increased (fan) air volume coupled with a lower temp thermostat to bring the coolant temperature down to the lower 'stat opening point. IOW, the closer the coolant is to the ambient air temperature, the slower the coolant temperature falls (unless and until the motor adds more heated coolant to the radiator), all else being equal.

Yes Paul, your explanation is correct. IOW The rate of heat transfer is directly proportional to the heat differential

A house with an internal temperature of 80ºF and outside temp of 40ºF will lose heat at a faster rate than a house with an inside temp of 70º and outside temp. of 40º.(of course when all else is equal)

[Hog]

Originally Posted by Dynomite

I think you can find cooler Thermostats down to 160 deg but my theory is the LT5 engine operates best with 180 deg Thermostat and both a 160 deg and 180 deg thermostat will be fully open at say 185 deg F.

The 160 deg just opens sooner but does not keep the engine cooler than a 180 deg thermostat once the 180 deg Thermostat is fully open. The 160 deg thermostat will keep the engine down to say 165 deg on cool days which is too cold I think. The cooler Thermostat will set the bottom temperature but does nothing to set the top temperature once both thermostats are fully open.

Emphasis mine.

I think the bolded statement pretty much sums up thermostats with various opening points.
The purpose of a thermostat is to allow the engine coolant to circulate through the engine without it being cooled, this allows the engine coolant temperature to rise. Without that thermostat, the cold engine coolant while being heated by the warming engine block, will be simultaneously cooled by the radiator. We want the engines heat to warm its engine coolant as quickly as possible to be able to warm the cabin as quickly as possible and also to get the engine up to operating temperature for both decreased wear and fueling concerns.
Once the engine coolant has been heated enough, the thermostat opens allowing engine coolant to flow through the radiator circuit for cooling. Once that rad circuit is opened the only way control the engine coolant temperature is to either:
1) Change the amount of heat being introduced into the engine coolant (turn off engine, slow engine revs)
or conversely
(increase engine revs, increase engine power output etc)

2) Change the amount of heat being taken from the engine coolant: increase airflow across the rad via fans/roadspeed, engage the cabin heater/fan
or conversely
disengage the rad fans, physically block airflow across the radiator etc.

Of course this is over simplified, there are other things at play such as bypasses, thermal shock and many other things at play, but the basic purpose of the thermostat is simple. Delay the cooling function of the radiator until enough heat has been produced by the engine.