Not saying you are wrong but wouldn't it want to overheat with a stuck open t-stat? it never ever get's above 195
Diagnostic question - engine is extremely slow to get up to operating temp - 5.2L
- Thread starter tallhair
- Start date
Not saying you are wrong but wouldn't it want to overheat with a stuck open t-stat? it never ever get's above 195
live4theking
Old Man with a Hat
- Joined
- Nov 24, 2014
- Messages
- 12,722
- Reaction score
- 8,914
No, it would not want to over heat with it stuck open. Think about the hot water tank in your house. If the flow of water never stops or slows through it there is no chance for the water to get hot.
The thermostat being closed is the only thing that keeps the water from circulating from the engine to the radiator to be cooled. If the thermostat is stuck open the water pump keeps pushing the coolant from the block into the radiator. When operating correctly the thermostat stays closed until the coolant reaches the temperature it is designed to open at (160, 180, 195). Then it opens and the coolant flows to the radiator. This causes the coolant to decrease in temperature closing the thermostat again until it reaches the temperature that it opens at. If you drive for long enough, say an hour, the temperature of all of the coolant will come up to temperature and the thermostat will stay open all of the time.
I hope this helps and wasn't insulting.
The thermostat being closed is the only thing that keeps the water from circulating from the engine to the radiator to be cooled. If the thermostat is stuck open the water pump keeps pushing the coolant from the block into the radiator. When operating correctly the thermostat stays closed until the coolant reaches the temperature it is designed to open at (160, 180, 195). Then it opens and the coolant flows to the radiator. This causes the coolant to decrease in temperature closing the thermostat again until it reaches the temperature that it opens at. If you drive for long enough, say an hour, the temperature of all of the coolant will come up to temperature and the thermostat will stay open all of the time.
I hope this helps and wasn't insulting.
This is completely contrary to everything I've ever read or heard and my own mechanical understanding. The coolants job is to keep the engine cool. If it flows constantly through the engine it will become the same temp as the engine and perform no function and the engine will overheat eventually because nothing will be cooling it.
I could however see the result you propose in the short term/ i.e. limited short duration driving.
I hope this helps and wasn't insulting. Sorry I couldn't help myself. Seriously though thanks for your response.
Answer to both of your posts... sometimes, yes, if the opening is less than full flow. Otherwise the restriction of your thermostat opening is meant to be your maximum coolant flow... sometimes when we need to get one back running right away or for diagnostic purposes we may cut the center out of the old thermostat and reuse the plate... the circle track boys like these:
twostick
Senior Member
If you install a new thermostat you may discover that what you have read or been told was false or mostly false.
Put a new t-stat in it and it will hit operating temp in 10-15 minutes even at idle.
Kevin
Put a new t-stat in it and it will hit operating temp in 10-15 minutes even at idle.
Kevin
Mr C
Senior Member
My brother had a similar issue with a Dynasty. In winter, it could idle forever and not heat worth a damn. He found that after driving around a bit (to get a coffee) bam!, it heat just fine. By the way, everything was working properly on his car.
The only thing we figured was:
1) Electric fans on that car were cooling too well;
2) the additional heat of the ATF being cooled in the rad after a bit of driving was just enough to get the heater working more efficiently.
He put 500 000 on that little Dynasty before the rust monster got it. One of the best commuter cars I've ever seen. Drove it to the wrecker...still ran like a champ.
The only thing we figured was:
1) Electric fans on that car were cooling too well;
2) the additional heat of the ATF being cooled in the rad after a bit of driving was just enough to get the heater working more efficiently.
He put 500 000 on that little Dynasty before the rust monster got it. One of the best commuter cars I've ever seen. Drove it to the wrecker...still ran like a champ.
OK new t-stat - 195 in, reverse flushed heater core and lots of stuff came out, and refilled. It's 50 degrees right now so I'll report back on next cold morning and see how quickly it warms up and if it will do so after idling 10-15 min.
The old t-stat looks good and has stiff spring pressure but replaced with new 195 now.
I didn't do all that personally - took it to my local mechanic.
The old t-stat looks good and has stiff spring pressure but replaced with new 195 now.
I didn't do all that personally - took it to my local mechanic.
I was just going to say JP was probably on the money with the low coolant, with the air going the the highest point in the system. Not sure with the durango's but you need to be in the right mood to change the stat on the rams - not as straight forward as the older cars
Its behind / under the A/C compressor - yikes. I wasn't in the right mood at all. Glad I had someone local to do it.
stubs300
Senior Member
Kinda the same w/a 3.3. I should probably do mine, but you know the sayin about if it isn't broke thing cause I'm sure something would get dicked up.
The shop was reluctant to do the t-stat today because they were only working a half day and were afraid of broken bolts. Said a lot of times on the 5.2 of this vintage the bolts for the housing break in the manifold ... thankfully mine didn't. Also something that surprised me is they said later models have the t-stat lower on the engine.
65sporty
Old Man with a Hat
The 4.7 has the thermostat in the front cover and lower hose attaches to it
Update - had pretty frosted windows a few days ago and after about 10-15 min or so the windshield was mostly frost free ... basically in the wiper path was frost free and upper part had soft slush - I didn't have the wipers on, just a description of where the defroster had melted the frost. Also it's heats up normally now to operating temp at idle.
So whatever the issue was I'm glad I finally had it dealt with !
I now have another vehicle (2002 V6 Mercury Sable) with no trouble heating up to operating temp (coolant is full) but the heater will not put out much heat - at best its basically not cold but also not hot air. I'll probably be taking it in for a cooling system flush and a back flush of the heater core and a new thermostat. Lots of crap came out of the Durango's heater core when it was back flushed.
I've never had heater problems with vehicles before ... when I was driving older vehicles that is.
So whatever the issue was I'm glad I finally had it dealt with !
I now have another vehicle (2002 V6 Mercury Sable) with no trouble heating up to operating temp (coolant is full) but the heater will not put out much heat - at best its basically not cold but also not hot air. I'll probably be taking it in for a cooling system flush and a back flush of the heater core and a new thermostat. Lots of crap came out of the Durango's heater core when it was back flushed.
I've never had heater problems with vehicles before ... when I was driving older vehicles that is.
Just want to make a suggestion here... because you are going to a shop for this anyhow, please let them do the diagnostic. It was the bane of my existence when a customer came in with the idea that I would actually repair whatever they said to do.
As a professional I was responsible for the car to operate safely and correctly after a repair. Even when the customer was knowledgeable and correct in their diagnosis, I had a lot of CYA to take care of. For example, if the flush and thermostat(which the Sable doesn't need) did not correct your heating problem... would that be the shop's fault? Regardless of your answer, small claims court would nearly always rule against the shop.
The symptoms of the Sable could be the core (a flush doesn't hurt), is not the thermostat(calling it PM is ok), but also could be in the controls... I believe that one has an electronic control head and a electric motor with a potentiometer to feed back position. I don't have a "shot from the hip" answer for DIY... but could help more if you need it.
BTW... how often are you replacing the coolant in your cars? The old replacement interval was 3 years, but newer long life stuff may go considerably longer (I still don't believe in it too much). A cooling system PM service would involve new coolant and thermostat and possibly flushing... but that kind of servicing has fallen off. If the Sable has the 2 valve 3.8L I believe they all had corrosion problems in the cooling system... Ford told us it was cavitation... but they never solved the problem from what I could tell.
i had an 02 taurus with the same symptoms. in my case there were metal tubes along the rear of the motor that connected to the heater core. the tubes rusted internally and plugged the core. new tubes and a reverse flush of the core and all was well.
a word of caution if you change the tubes yourself, you WILL rip your hands to shreds on all of the pins and bolts sticking out of the firewall.
a word of caution if you change the tubes yourself, you WILL rip your hands to shreds on all of the pins and bolts sticking out of the firewall.
Yes it has this bypass deal ... wouldn't be surprised if it needs replaced.
I do. I diagnose myself if I can and discuss what I think with them and evaluate what they say. If they make me feel comfortable with their ability and honesty I stick with them and leave them to use their expertise.
MoPar Maniac
Well-Known Member
The new stat solved your problem by staying closed making the coolant stay in the engine until it came to temp. Then it opens allowing cooant to flow through the rad. Then cool water hits the stat and it closes.
My 92 Dakota had the same problem. Changed the stat and it didnt help. Changed it with a Stant brand and it works.
Tauruses and Sables are well known for clogged heater cores. Got one of those, too.
My 92 Dakota had the same problem. Changed the stat and it didnt help. Changed it with a Stant brand and it works.
Tauruses and Sables are well known for clogged heater cores. Got one of those, too.
Ripinator
Old Man with a Hat
Whuduhyuhknow . . It really was the thermostat !
saylor
Senior Member
the accursed mopar Blend Door. a hated feature. on my nitro i undid the motors and just spun the gear by hand when the blend door motors took a crap.
i know a guy that that did not work on his 1500 truck, and he had to cut into the heater box to reach the flap to flop it... then pooky the hole back together.
sheesh.
i know a guy that that did not work on his 1500 truck, and he had to cut into the heater box to reach the flap to flop it... then pooky the hole back together.
sheesh.
Similar threads
