International Full Size Jeep Association
Home Forums Reader's Rigs Tech Library Trail Stories FSJ-List
International Full Size Jeep Association  

Go Back   International Full Size Jeep Association > Tire Kickin' > General FSJ Tech

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 06-11-2004, 08:38 AM
roadgrime roadgrime is offline
Master Mechanic
 
Join Date: Apr 17, 2003
Location: boise ID
Posts: 1,438
Post

hey don S feel free to slap me about with your knowledge!

so I have always questioned how much good or bad a thermostat can do for your cooling system. Now let me clarify this. I am not questioning if you need one. I wouldnt run my rigs with out on. but here is where the question comes in.

as I understand it the thermostat doesnt really regulate the temp of the engine but rather regulates the flow of coolant through the cooling system they open and close at some setting say 185 to allow fluid from the engine into the radiator for cooling. now lets say you have that 185 thermostat in a system and the temp above the thermostat is 215.
question 1. is that reading (above the thermostat) the tempof the fluid entering the enging or exiting the engine for the cooling sysle.
question 2 if you are reading 210 would not at that point you be close to thermo runaway... where the thermostat is open all the time and the fluid no longer pauses enough in the radiator to cycle the temp cooler so the temp keeps rising?

question 3. are you going to be more pron to thermo runaway if you go to a lower thermostat. for instance i have considered going to a 165 or 175 in the summer since its a carburated model and not controlled by a computer the engine is not as sensitive to the temp except at extremes.(high or low)

qestion 4 i see people talk about drilling holes in the thermostat. while the holes them self re not big enough to allow coolant to flow fast enough to cool and engine in the event the thermostat breaks closed. wouldnt drilling holes in the thermostat move fluid again through the radiator faster therby decreasing the amount of time the coolant has too cool?

lastly I know that the answers to these questions coule be based toward a perfectly functioning cooling system but lets face it how many of our rigs are optimum when it comes to that. the best we can hope for is to get them better than where they are at by modify/improving them closer to that optimum range.
Reply With Quote
  #2  
Old 06-11-2004, 09:19 AM
89grand's Avatar
89grand 89grand is offline
Resident ***hole
 
Join Date: Feb 23, 2003
Location: Phoenix, AZ
Posts: 5,667
Post

Those are some good questions, I look forward to some responses. I've often wondered about the usefullness of the thermostat myself once engine temperature exceeds the thermostat temp rating. In the summer, mine is always above my thermostat temp of 180 by 20-35 degrees. At that point, what good is the thermostat doing? I see the need in cold weather but not hot.
__________________
Steve

1989 Black Grand Wagoneer, BJ's 4" lift, ProComp ES3000's
31x10.5x15 BFG AT KO's,MSD 6A,TFI upgrade,360,727,229,2.72 gears.
2006 Dodge Magnum R/T
2000 Jeep Wrangler
1988 Cadillac Brougham
1966 Dodge Monaco 500 383
1965 Pontiac Tempest 326
Reply With Quote
  #3  
Old 06-11-2004, 09:36 AM
carrotman carrotman is offline
Gear Head
 
Join Date: Oct 21, 2003
Location: Colorado
Posts: 716
Post

1. Coolant enters from bottom (block). The thermostat sensor is on the bottom.

2. The thermostat opens, but not that much.

3. I think it runs best at 180.

4. My 76 already has a bypass hose that comes off the thermostat housing to the water pump, so it doesn't need any drilled holes.
__________________
76 Chief, T18, 3.54, HEI, Carter AFB.
Reply With Quote
  #4  
Old 06-11-2004, 09:54 AM
roadgrime roadgrime is offline
Master Mechanic
 
Join Date: Apr 17, 2003
Location: boise ID
Posts: 1,438
Post

the coolant enters the block from the bottom?

and my temp sensor is on the thermostat housing above the thermostat. the stick is on the intake manifold.

[ June 11, 2004, 03:55 PM: Message edited by: roadgrime ]
Reply With Quote
  #5  
Old 06-11-2004, 10:43 AM
Ralph Rogers Ralph Rogers is offline
Master Mechanic
 
Join Date: Jul 29, 2003
Location: Queen Creek AZ
Posts: 1,494
Post

I run a 160 thermo in all of my wags for AZ temps. No problems what so ever, infact, they run cool. 110 air temp with AC and they get don't get to boiling until the engine is off and the water no longer circulates so it boils in the radiator. When and if I install electric fans that will prably end too.
The lower the thermo temp the sooner it opens and allows water to begin cooling in the rad and will stay open until the temp drops below that temp.
The thermostat allows the water to come up to temp for engine temp purposes. Then it pretty much stays open at normal driving. At that point it is petty much worthless except as a restrictor, which is a good thing. It is not a switch. It will not open and close instantly as temps fluctuate, which in a good system they shouldn't that much. It takes time.
Drop one in a pan of water on the stove with a thermometer and watch it as you increase/decrease the temp a bit.
Your temp gauge reads temps at the output of the engine, as this shows what temp the engine is running at, then it cools through the radiator and enters again at a lower temp. The thermo also controls water speed, as does the pulley size on the water pump. In most cases, not all, removing the thermo will make you run hotter as the water moves too fast, as does running to many RPM with a small pulley, it can also cause cavitation. A lot of racers run no thermo, only a restrictor, and they have ones with different hole sizes to customize the flows. You don't want it too slow
as the heat in the engine increases faster than
the radiator can dissipate it. And if it's too
fast it isn't in the radiator long enough for
heat to transfer. A water pump is not a positive
pressure pump, it will not increase in pressure
or speed as the RPM goes up beyond a certain point. It onlys moves water. Just look at all the
space around the impeller.
I'm not sure I get the thermo runaway thing you asked about at all. Maybe in a nucular ( that's
nuclear to all none Presidents)system, but not ours.
The waters maximum movement will be when the thermo is fully open and the water pump is running within a specified RPM window. Assuming the cooling sytem is up to standards of the heat you need to remove, air temp remains the same, the water will drop the same %of degrees regardlessof it's temp.
This is what the system was designed to operate at. If you see and increase in temp over time, changing the thermo won't solve this, unless of course your thermo is already at boiling point.
Every water pump I have ever seen has a bypass. If it didn't your circulation at start up would suck, pressures would funk out your thermo until temps came up, and your thermo would take longer to open. And there isn't a huge difference between
the diameter of the bypass and the hole in the
thermo.
My guess they drill holes for pressure differences. I don't understand that one either. Pressures can also effect regular thermos.
Think about this, water enters the engine at the bottom and flows to the top then back to the radiator and so on. The top of the engine is where most of the heat is generated as this is
where the little explosions are taking place.
Water is the coolest at the bottom of the
radiator. I know, it's bassakwards.
So why not put the cooler water into the top where it is needed most? It's called reverse rotation, it's results are exciting to say the least. Race cars run this way. Try it, you'll
like it!
Ralph
Reply With Quote
  #6  
Old 06-11-2004, 12:51 PM
roadgrime roadgrime is offline
Master Mechanic
 
Join Date: Apr 17, 2003
Location: boise ID
Posts: 1,438
Post

my definition of thermal run away is the point where due to the nature of the cooling system the amount of heat being added to the coolant is greater than the amount of heat able to be removed by the cooling system which then causes the temp to increase continually
Reply With Quote
  #7  
Old 06-11-2004, 03:14 PM
Don S's Avatar
Don S Don S is offline
Geriatric Doctor of FSJs
 
Join Date: Feb 06, 2002
Location: Burleson TX
Posts: 5,611
Post

Quote:
Originally posted by Ralph Rogers:
110 air temp with AC and they get don't get to boiling until the engine is off and the water no longer circulates so it boils in the radiator. When and if I install electric fans that will prably end too.
..
Ralph Rogers:

... What heat is applied that causes the water to boil in your radiator?

Have a good one and CUL Don S..
__________________
Sold our 1976 Wagoneer 406, MC4300, TH400, QT, TruTrac, 2" lift, 31x10.50s, duel Optimas,
It’s took us over 161 Colorado Mountain Passes, 3 Jeep Jamboree USAs & 2 Ouray Invasions from 1985 to 2010
ACRONYMS & ABBREVIATIONS HERE
Reply With Quote
  #8  
Old 06-11-2004, 04:13 PM
Don S's Avatar
Don S Don S is offline
Geriatric Doctor of FSJs
 
Join Date: Feb 06, 2002
Location: Burleson TX
Posts: 5,611
Post

Quote:
Originally posted by roadgrime:
my definition of thermal run away is the point where due to the nature of the cooling system the amount of heat being added to the coolant is greater than the amount of heat able to be removed by the cooling system which then causes the temp to increase continually
..
roadgrime:

... To me a thermal run away is is when the engine gets a 'steam pocket' that the coolant can't cover. Once the cooling system is boiling then it is a thermal run away until more cool coolant is added. Then you have to be careful how fast you cool a very hot engine.

Quote:
Originally posted by roadgrime:
question 1. is that reading (above the thermostat) the tempof the fluid entering the enging or exiting the engine for the cooling sysle.
..
roadgrime:
... The reading is at the spot where the temperature sender unit is and that is close to the place the coolant is exiting.

Quote:
Originally posted by roadgrime:
question 2 if you are reading 210 would not at that point you be close to thermo runaway... where the thermostat is open all the time and the fluid no longer pauses enough in the radiator to cycle the temp cooler so the temp keeps rising?
..
roadgrime:

... Do to all the restrictions of flow in the cooling system the coolant does not flow to fast to be cooled. The coolant does not boil at 210 degrees when the system is equipped with a pressure cap.

Quote:
Originally posted by roadgrime:
question 3. are you going to be more pron to thermo runaway if you go to a lower thermostat. for instance i have considered going to a 165 or 175 in the summer since its a carburated model and not controlled by a computer the engine is not as sensitive to the temp except at extremes.(high or low)
..
roadgrime:

... No. I run a 180 thermostat and I will replace it with a 185 or 190 next time I change it. The higher temperature thermostats help 'cook' the condensed moisture out of your oil to help prevent sludge.

Quote:
Originally posted by roadgrime:
qestion 4 i see people talk about drilling holes in the thermostat. while the holes them self re not big enough to allow coolant to flow fast enough to cool and engine in the event the thermostat breaks closed. wouldnt drilling holes in the thermostat move fluid again through the radiator faster therby decreasing the amount of time the coolant has too cool?
..
roadgrime:

... The flow configuration for the coolant (depending on engine design) is that the water pump puts a little extra pressure in the block due to the restriction of flow caused by the thermostat.
... The block distributes coolant though the cavities into the heads. Block pressure must be consistent from front to rear to insure uniform coolant distribution to reduce steam pockets that can cause water pump cavitation and over heating. Less pressure can result in less flow around the rear cylinders. When we boil this fact down it simply means the thermostat is a useful tool in maintaining the block pressure. The pressure between the water pump and the thermostat should be slightly higher than the radiator pressure.

... If a thermostat suddenly slows the coolant flow, a sudden increase in the water pump differential pressure can happen. The primary cause of cavitation is differential pressure change i.e. sudden change in flow rate.

... High quality thermostats that operate smoothly and slowly can reduce the probability of cavitation. Cavitation erosion can often be seen under the water pump on the timing chain housing on AMC V-8s.

For the most part thermostats only can cause overheating is if they are bad and stick in the closed position or mounted upside down.

link> THERMOSTAT TECH 101

Have a good one and CUL Don S..
__________________
Sold our 1976 Wagoneer 406, MC4300, TH400, QT, TruTrac, 2" lift, 31x10.50s, duel Optimas,
It’s took us over 161 Colorado Mountain Passes, 3 Jeep Jamboree USAs & 2 Ouray Invasions from 1985 to 2010
ACRONYMS & ABBREVIATIONS HERE
Reply With Quote
  #9  
Old 06-12-2004, 12:25 AM
SpruceMoose SpruceMoose is offline
Master Mechanic
 
Join Date: Nov 01, 2000
Location: Williamsburg, VA, USA
Posts: 1,424
Post

the thermostat sets the lower end of the "fully warmed up" operating range of the cooling system. the heat removing capacity of the fan, radiator, and waterpump system, working against the heating capacity of the engine, sets the upper end of the range. a properly setup system should run at the thermostat setting under "normal" operating conditions. i have to assume "normal" means under 100 or so degrees outside temp, less than MGVW, level ground, less than about 70 mph. lots of things will raise the operating temp: overloaded rig, long uphills, too slow or wayyyy too fast, etc.

i do know that mine runs at thermostat temp all the time, but i dont overload it, etc.

sm.
__________________
88 Grand Wagoneer<br />\"Spruce Moose\"<br /><br />See the Moose at:<br /><a href=\"http://www.fsjworld.com/mygallery.asp?id=3294\" target=\"_blank\">http://www.fsjworld.com/mygallery.asp?id=3294</a> <br /><br />AMC 360, DANA 44 F/R 2.72, TF 727, NP 229<br />Jacobs Pro-Street Ignition, Edelbrock 4bbl Intake with Holley 2bbl Analog Pro-Jection<br />Flowmaster 2.5\" 50 Series Delta muffler and tubing<br />K&N cone air filter, Amzoil fluids all around<br />31x10.5 BFG A/T KO<br />Rusty\'s 4\" lift<br />Home-made tube nerfs and bumpers<br />BJs Muscle grill<br />HF,VHF,UHF ham rigs and too many antennas (not)<br />8-Ball shift knob from college (1975)<br />Hella fog and driving lights<br />Kenwood MP3 HU, Orion sub amp, Jensens all around<br /><br />Mileage? We don\'t need no stinkin\' mileage!
Reply With Quote
  #10  
Old 06-12-2004, 05:32 AM
Don S's Avatar
Don S Don S is offline
Geriatric Doctor of FSJs
 
Join Date: Feb 06, 2002
Location: Burleson TX
Posts: 5,611
Post

Quote:
Originally posted by SpruceMoose:
the thermostat sets the lower end of the "fully warmed up" operating range of the cooling system. the heat removing capacity of the fan, radiator, and waterpump system, working against the heating capacity of the engine, sets the upper end of the range. a properly setup system should run at the thermostat setting under "normal" operating conditions. i have to assume "normal" means under 100 or so degrees outside temp, less than MGVW, level ground, less than about 70 mph. lots of things will raise the operating temp: overloaded rig, long uphills, too slow or wayyyy too fast, etc.

i do know that mine runs at thermostat temp all the time, but i dont overload it, etc.

sm.
..
SpruceMoose:

... Very well said !!!

Have a good one and CUL Don S..
__________________
Sold our 1976 Wagoneer 406, MC4300, TH400, QT, TruTrac, 2" lift, 31x10.50s, duel Optimas,
It’s took us over 161 Colorado Mountain Passes, 3 Jeep Jamboree USAs & 2 Ouray Invasions from 1985 to 2010
ACRONYMS & ABBREVIATIONS HERE
Reply With Quote
  #11  
Old 06-12-2004, 03:15 PM
JeepKahn JeepKahn is offline
Master Mechanic
 
Join Date: Mar 21, 2002
Location: Winston-Salem,Triad, NC
Posts: 803
Post

Throwing out a coupla points that I know about the subject, thermal runaway can be when the water moves to fast to pull the heat from the hot metal due to no thermostat or one that is stuck open, so you get water temps that are within limits but the metal itself is actually much higher because the heat isn't transfering from the metal to the water(you can get the same effect by running too much antifreeze, the antifreeze may be 180 degrees but the engine itself can be 280 degrees...
The hole in the thermostat, the hole that many people including myself drill in the thermostat is to allow trapped air under the thermostat to bleed past so that the "pill" is immersed in coolant and can operate properly, it doesn't take much air to "dry out" the pill that actuates the tstat, and jeep engines are notorious for developing the air pocket under the thermostat...

It's all about transfer effeciency and a synergistic approach is the best way to approach it, a good working 190degree stat, coolant capable of transfer heat effectively(30% AF during the summer/ 50% in the winter)plus water wetter or problend 40 below, a good radiator, and a fan/shroud setup that flows enough air to transfer the heat into the air out of the radiator...

As a side note, the reason multiple core radiators cool better has more to do with the velocity of the water moving through it than the surface area does... But the combination allows the improvement of both factors...
__________________
\"Smoke\'m, They\'ll Stick\"<br /><br />Got Heat Problems???Want Free HP???<br />Check This Out!!!<br /><a href=\"http://www.ifsja.org/ubb/ultimatebb.php?ubb=get_topic;f=3;t=024412\" target=\"_blank\">http://www.ifsja.org/ubb/ultimatebb.php?ubb=get_topic;f=3;t=024412</a><br /><br />Jeremy Kahn Jeepkahn@yahoo.com<br />79 J10Honcho \"SickPuppy\"<br />360,Th400,D20,D44s@4.09,35x12.50s <br />Mobi-Arc on board welder<br /><br />Winston-Salem,NC<br /><br />!!!Will Weld for Gas!!!
Reply With Quote
  #12  
Old 06-12-2004, 04:30 PM
Don S's Avatar
Don S Don S is offline
Geriatric Doctor of FSJs
 
Join Date: Feb 06, 2002
Location: Burleson TX
Posts: 5,611
Post

Quote:
Originally posted by JeepKahn:
The hole in the thermostat, the hole that many people including myself drill in the thermostat is to allow trapped air under the thermostat to bleed past so that the "pill" is immersed in coolant and can operate properly, it doesn't take much air to "dry out" the pill that actuates the tstat, and jeep engines are notorious for developing the air pocket under the thermostat...
...
..
JeepKahn:

... I appreciate your beliefs about drilling those holes and it shouldn’t hurt anything. I've been doing auto repair off and on for over 50 years and worked the line for many different dealerships. I have changed probably over a thousand thermostats and never found the need to drill one.

... Right now, here on my desk, are two thermostats. A Stant 54mm 'superstat' 195* #45359 and a Robertshaw 'extra performance' 180* #330-180. Neither of these have 'breather holes' but I have seen and used some that did. It is 74 degrees at my desk and both of these thermostats will pass air while in the closed position.
Most people think the Robertshaw is the better built thermostat.

I would like to debate some of the other ‘facts’ you have described but not at this time or thread.

Have a good one and CUL Don S..
__________________
Sold our 1976 Wagoneer 406, MC4300, TH400, QT, TruTrac, 2" lift, 31x10.50s, duel Optimas,
It’s took us over 161 Colorado Mountain Passes, 3 Jeep Jamboree USAs & 2 Ouray Invasions from 1985 to 2010
ACRONYMS & ABBREVIATIONS HERE
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 02:33 AM.


Powered by vBulletin Version 3.5.4
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
corner corner