Thermostat

[Topsterguy]

I put a new Mr Gasket HiFlow thermostat in my '69 340  and after a couple of short trips to the coffee shop it overheated bigtime and puked all over my shop floor! I put it in a pan of water and brought the temp up to about 200 and as far as I could see it didn't open, the overall "appearance" didn't change. Could it be a bad one that soon?  Do I really need a thermostat on a car that's only driven if warm / good weather?

[416Ford]

Yes and Yes.
I have been told to check them before you install them to make sure it work out of the box.
As for running without one, or old cars like to have some heat to run better.
This is all here say...

[enjenjo]

the hotter you can run the engine without overheating, the more horsepower you get, and the better the fuel mileage becomes. So a thermostat increases horsepower to a certain extent.

I like Robert Shaw thermostats available from Summit and others.

[Topsterguy]

Sounds good!  Thanks guys!

[Topsterguy]

the hotter you can run the engine without overheating, the more horsepower you get, and the better the fuel mileage becomes. So a thermostat increases horsepower to a certain extent.

I like Robert Shaw thermostats available from Summit and others.

That's the type I had in there except it was from Mr Gasket. I tested it twice yesterday and it wouldn't work. So, they can go bad after next to no time in the car.  Best to check 'em before they go in, but even then you never know cuz they're probably all made in china!

[enjenjo]

The Robert Shaw is the same type, but much better quality. As far as I know they are still all american made.

[wayne petty]

FYI...

i worry that it did not open in 200f water... what temp is stamped into the bottom of the brass bulb???

160F, 180F, 192F  or is it metric.. a 192F will be marked 95C..  or something like that..

when a thermostat is severally overheated..  it can open far enough that it moves the rod all the way out..  and the wax is still expanding and it pushes past the crimped area and escapes.    this prevents the thermostat from working again as there is not enough wax left to overpower the spring..


with a 160 or sometimes with a 180 thermostat  you can reach radiator temps that exceed the turn on temp of the thermostatic fan clutch if equipped.. this causes a runaway cooling system ..

if your radiator cap does not hold pressure..  you will have cooling system problems.  check the disc in the middle of the cap.. if its spring loaded to the rubber seal. thats good.. there are a few cap part numbers out there that have a loose center disc that requires coolant to push and hold it closed..  these cause so many overheating issues i cannot possibly count the ones i have had to perform major repairs because of the cap spec..

dodge V8s have an almost question mark shaped coolant bypass hose.  some replacement bypass hoses have a straight bend..instead of the question mark shape.. these usually end up with a KINK that blocks coolant bypass flow..  

in a normal system.. the thermostat is closed.. coolant flows from the water pump.. into the block.. around the cylinder walls.. up thru the back of the block and into the heads.. where it goes forward picking up more heat until it goes into the crossover where its blocked by the closed thermostat.. the mechanical pressure created by the water pump on the coolant in the engine will push it all the way thru the heater hoses and also push it thru the bypass hose where it will go around and around until it picks up enough heat to open the thermostat...

at that point the hot coolant will exchange with the cooler coolant in the radiator..   the cooler coolant will close the thermostat and start the  flow thru the bypass and heater core again..

the hot coolant in the radiator will if equipped turn on the thermostatic  fan clutch..  when the air flow thru the radiator cools off below 170F. the fan clutch freewheels again..

this is the cooling system operation..

if you don't have a big enough radiator.. or too small blade size on the fan..  you won't cool the radiator before the thermostat opens again.

when this happens the thermostat opens and does not close. the coolant circulates so fast thru the radiator that it cannot be cooled..

if you have the wrong radiator cap as i described above.. you won't have the additional 13 or 16 pounds of cooling system pressure.

each pound of pressure increases the boiling point 3F..  15 pounds = 45 degrees..

the mechanical pressure created by the water pump and blocked by the mostly closed thermostat creates pressure above cooling system cap pressure in the block and heads to keep the hottest spots around the exhaust ports, exhaust valve seats and exhaust valve guide from exceeding the 250 to 265 boiling point of the cooling system under heavy load.

i have not measured the pressure. but it must be significant..  without a thermostat and the top hose off.. you can rev the motor and throw water out at least 10 or 15 feet..

[Topsterguy]

FYI...

i worry that it did not open in 200f water... what temp is stamped into the bottom of the brass bulb???

160F, 180F, 192F  or is it metric.. a 192F will be marked 95C..  or something like that..

when a thermostat is severally overheated..  it can open far enough that it moves the rod all the way out..  and the wax is still expanding and it pushes past the crimped area and escapes.    this prevents the thermostat from working again as there is not enough wax left to overpower the spring..


with a 160 or sometimes with a 180 thermostat  you can reach radiator temps that exceed the turn on temp of the thermostatic fan clutch if equipped.. this causes a runaway cooling system ..

if your radiator cap does not hold pressure..  you will have cooling system problems.  check the disc in the middle of the cap.. if its spring loaded to the rubber seal. thats good.. there are a few cap part numbers out there that have a loose center disc that requires coolant to push and hold it closed..  these cause so many overheating issues i cannot possibly count the ones i have had to perform major repairs because of the cap spec..

dodge V8s have an almost question mark shaped coolant bypass hose.  some replacement bypass hoses have a straight bend..instead of the question mark shape.. these usually end up with a KINK that blocks coolant bypass flow..  

in a normal system.. the thermostat is closed.. coolant flows from the water pump.. into the block.. around the cylinder walls.. up thru the back of the block and into the heads.. where it goes forward picking up more heat until it goes into the crossover where its blocked by the closed thermostat.. the mechanical pressure created by the water pump on the coolant in the engine will push it all the way thru the heater hoses and also push it thru the bypass hose where it will go around and around until it picks up enough heat to open the thermostat...

at that point the hot coolant will exchange with the cooler coolant in the radiator..   the cooler coolant will close the thermostat and start the  flow thru the bypass and heater core again..

the hot coolant in the radiator will if equipped turn on the thermostatic  fan clutch..  when the air flow thru the radiator cools off below 170F. the fan clutch freewheels again..

this is the cooling system operation..

if you don't have a big enough radiator.. or too small blade size on the fan..  you won't cool the radiator before the thermostat opens again.

when this happens the thermostat opens and does not close. the coolant circulates so fast thru the radiator that it cannot be cooled..

if you have the wrong radiator cap as i described above.. you won't have the additional 13 or 16 pounds of cooling system pressure.

each pound of pressure increases the boiling point 3F..  15 pounds = 45 degrees..

the mechanical pressure created by the water pump and blocked by the mostly closed thermostat creates pressure above cooling system cap pressure in the block and heads to keep the hottest spots around the exhaust ports, exhaust valve seats and exhaust valve guide from exceeding the 250 to 265 boiling point of the cooling system under heavy load.

i have not measured the pressure. but it must be significant..  without a thermostat and the top hose off.. you can rev the motor and throw water out at least 10 or 15 feet..

It was a 180. I got a buddy to test it after I did just to make sure and it wouldn't open for him either.  I took it back and wound up getting a "Super Stant" 180 because I liked the idea that if they fail they automatically fail open which I thought was a good idea.  I run a stock clutch fan and a 7#  rad cap. Seems to work fine so far but I'm wondering if it might boil easy with that cap on a road trip where it's hot ?  Thanks, great info on how it all works!

[wayne petty]

"If a man is alone in the forest and speaks, and there's no woman around, is he still wrong?"


off thread..

a few years ago.. a storm here knocked down a tree in the next block.. it smashed a ford taurus wagon..

i walked down there.. ask the crowd standing around if anybody had heard this happen..  nobody had.. i said.. well. that proves it ... several of them ask what it proves... oh.. .. That if a tree falls on a taurus.  it does not make any sound..


that tree blocked over half the street for several days..  the city crews finally showed up just as i was driving past.. i told them the taurus tree joke..  then i said.. its amazing..  that somebody left that tree double parked there and that the parking enforcement was not crawling up in the branches looking for a license plate or Vin number so they could write a ticket and get it impounded..  they laughed.. they said they would handle the impound personally as they started their chainsaws..


a few weeks later.. the large object trash crews were out picking up big items on the streets people had put out ..  i slowed down and said loudly to them.. say .. if you keep picking up the good stuff.. how will i ever get my apartment furnished..  they laughed like nobody had ever said that to them.

[Arnold]

"If a man is alone in the forest and speaks, and there's no woman around, is he still wrong?"


off thread..

a few years ago.. a storm here knocked down a tree in the next block.. it smashed a ford taurus wagon..

i walked down there.. ask the crowd standing around if anybody had heard this happen..  nobody had.. i said.. well. that proves it ... several of them ask what it proves... oh.. .. That if a tree falls on a taurus.  it does not make any sound..


that tree blocked over half the street for several days..  the city crews finally showed up just as i was driving past.. i told them the taurus tree joke..  then i said.. its amazing..  that somebody left that tree double parked there and that the parking enforcement was not crawling up in the branches looking for a license plate or Vin number so they could write a ticket and get it impounded..  they laughed.. they said they would handle the impound personally as they started their chainsaws..


a few weeks later.. the large object trash crews were out picking up big items on the streets people had put out ..  i slowed down and said loudly to them.. say .. if you keep picking up the good stuff.. how will i ever get my apartment furnished..  they laughed like nobody had ever said that to them.

  If a woman's truck has a tree fall on the box of her truck..(a Ford Diesel that she thinks is pretty big and strong)..
   She gets $45K
   Which she puts towards a GM Diesel truck..

[Arnold]

FYI...

i worry that it did not open in 200f water... what temp is stamped into the bottom of the brass bulb???

160F, 180F, 192F  or is it metric.. a 192F will be marked 95C..  or something like that..

when a thermostat is severally overheated..  it can open far enough that it moves the rod all the way out..  and the wax is still expanding and it pushes past the crimped area and escapes.    this prevents the thermostat from working again as there is not enough wax left to overpower the spring..


with a 160 or sometimes with a 180 thermostat  you can reach radiator temps that exceed the turn on temp of the thermostatic fan clutch if equipped.. this causes a runaway cooling system ..

if your radiator cap does not hold pressure..  you will have cooling system problems.  check the disc in the middle of the cap.. if its spring loaded to the rubber seal. thats good.. there are a few cap part numbers out there that have a loose center disc that requires coolant to push and hold it closed..  these cause so many overheating issues i cannot possibly count the ones i have had to perform major repairs because of the cap spec..

dodge V8s have an almost question mark shaped coolant bypass hose.  some replacement bypass hoses have a straight bend..instead of the question mark shape.. these usually end up with a KINK that blocks coolant bypass flow..  

in a normal system.. the thermostat is closed.. coolant flows from the water pump.. into the block.. around the cylinder walls.. up thru the back of the block and into the heads.. where it goes forward picking up more heat until it goes into the crossover where its blocked by the closed thermostat.. the mechanical pressure created by the water pump on the coolant in the engine will push it all the way thru the heater hoses and also push it thru the bypass hose where it will go around and around until it picks up enough heat to open the thermostat...

at that point the hot coolant will exchange with the cooler coolant in the radiator..   the cooler coolant will close the thermostat and start the  flow thru the bypass and heater core again..

the hot coolant in the radiator will if equipped turn on the thermostatic  fan clutch..  when the air flow thru the radiator cools off below 170F. the fan clutch freewheels again..

this is the cooling system operation..

if you don't have a big enough radiator.. or too small blade size on the fan..  you won't cool the radiator before the thermostat opens again.

when this happens the thermostat opens and does not close. the coolant circulates so fast thru the radiator that it cannot be cooled..

if you have the wrong radiator cap as i described above.. you won't have the additional 13 or 16 pounds of cooling system pressure.

each pound of pressure increases the boiling point 3F..  15 pounds = 45 degrees..

the mechanical pressure created by the water pump and blocked by the mostly closed thermostat creates pressure above cooling system cap pressure in the block and heads to keep the hottest spots around the exhaust ports, exhaust valve seats and exhaust valve guide from exceeding the 250 to 265 boiling point of the cooling system under heavy load.

i have not measured the pressure. but it must be significant..  without a thermostat and the top hose off.. you can rev the motor and throw water out at least 10 or 15 feet..

  That was a tough one for me to learn..overheating with no thermostat..
  They used to sell restrictor plates that fit in place of the stat. Don't know if they still do.

[wayne petty]

they do still sell restrictor discs...

in most cases you can just knock the guts out of the thermostat and just install the disc without the valve if you want to go that way..

one must slow the water down from speeding thru the radiator.  or it will never cool..

want to know why..  water pumps move a lot of water... at higher engine speeds.. they could probably keep up with a firehose.  

there is so much water flow that it backs up going thru the radiator.. but the pump still keeps building pressure.  it will expand the top tank till it blows off the radiator header panel.

something else... i have only seen talked about..  there are not really any nascar tracks around so cal where i can get at them..

racers have to throw out the aluminum radiators at the end of some races.  they say there is enough debris that garden hose water won't flow between the tubes front to back... i saw a picture..  the oval tubes were expanded until they blocked all the airflow.  this was either because of the extreme amount of coolant flowing thru them building pressure. or the 30 pound racing radiator caps..  perhaps both.

the thermostats that seem to have the bottom 3/4" of a soda can as a valve instead of a disc in the middle are not as effected by the mechanical pressure built up behind them when closed by the water pump..

[Arnold]

they do still sell restrictor discs...

in most cases you can just knock the guts out of the thermostat and just install the disc without the valve if you want to go that way..

one must slow the water down from speeding thru the radiator.  or it will never cool..

want to know why..  water pumps move a lot of water... at higher engine speeds.. they could probably keep up with a firehose.  

there is so much water flow that it backs up going thru the radiator.. but the pump still keeps building pressure.  it will expand the top tank till it blows off the radiator header panel.

something else... i have only seen talked about..  there are not really any nascar tracks around so cal where i can get at them..

racers have to throw out the aluminum radiators at the end of some races.  they say there is enough debris that garden hose water won't flow between the tubes front to back... i saw a picture..  the oval tubes were expanded until they blocked all the airflow.  this was either because of the extreme amount of coolant flowing thru them building pressure. or the 30 pound racing radiator caps..  perhaps both.

the thermostats that seem to have the bottom 3/4" of a soda can as a valve instead of a disc in the middle are not as effected by the mechanical pressure built up behind them when closed by the water pump..

  I played around a bit many years ago with an adjustable restrictor set up I made. Basically just bored through the t.stat housing and put a valve in  there that I could open and close from the outside.
  Yes..I did have an inline water pressure gauge..but to be honest I cannot remember those values.

[Mikej]

Don't believe restrictors are much good for normal driving.