Change Your Thermostat!

[Nick1994]

Many people won't change their thermostat unless they suspect it is bad, but I've concluded its a good measure to change maybe every 5 years regardless if you have problems or not. My reasoning is below:

My mom has a 2003 Buick Rendezvous w/ the 3.4L. She was stuck in the middle of traffic moving slowly on the freeway. She looked down and the temperature gauge started moving towards H pretty quick and she tried to pull over but in traffic it took a while. There was also no room to pull off on the shoulder so she took the next exit and it was onto the next highway and the next exit on there was 1 mile up. She pulled off into a gas station parking lot and turned it off and it read something to the effect of "HOT ENGINE" on the display as well as the temperature gauge maxed out. I drove out to her and looked at the car and started it after it had cooled off for about 1/2 an hour and started it and turned on the heater, the heater did not blow hot at all even though the temperature gauge was at 3/4 of the way up, and the electric fans were working perfectly. No matter what it kept climbing toward Hot very fast so we towed it to my mechanic buddy.
He found that the thermostat was stuck closed (original thermostat) and he replaced it. Now, it does not overheat but the upper radiator hose is full of air, and there is a bleeder screw he opened up and it NEVER stops blowing air out with the engine running. He has concluded that the stuck thermostat overheated the engine and caused the head gasket to blow and is letting exhaust into the antifreeze. I have driven it around town and on the highway and it doesn't overheat at all anymore but obviously it still has major issues.

Replace your thermostat, you never know what situation you will be in if it goes and you can't pull over to turn off the engine. She probably could have blocked a lane and turned it off on the freeway but a blown head gasket is better than being run over on the freeway and dying.

I'll see about doing a compression test too.

 

[WobblyElvis]

I hope things are not as bad as it looks for your mom.
All cars should have some visual and audible warnings that alert you to an overheat before it's to late.
Flashing lights and a buzzer would help.

 

[HTSS_TR]

OE thermostat should failed open not close, when it fails the engine running cold which may pollute a little more than spec but will not damage the engine vs failed close.

 

[OVERKILL]

Originally Posted By: HTSS_TR
OE thermostat should failed open not close, when it fails the engine running cold which may pollute a little more than spec but will not damage the engine vs failed close.


This. Plus, if the heater was not blowing hot air, that's not a sign of a bad thermostat, that's a sign that there's no coolant in the heater core. It probably ate a head or intake gasket, dropping the coolant level and overheating.

 

[cjcride]

Switched a thermostat on a Toyota I had years ago with one called Failsafe if IRK. It was designed so if it failed it failed open not closed. Engine would run a bit cooler. Lot better than overheat damage.

Mentioned it to a Toyota tech. once and he felt it was a waste of money. Said he would just replace with a genuine Toyota thermostat and call it a day.

 

[Nick1994]

Here's the thermostat. I boiled it in a pot of water for 5 minutes and it didn't move at all.

 

[Nick1994]

Originally Posted By: OVERKILL
Originally Posted By: HTSS_TR
OE thermostat should failed open not close, when it fails the engine running cold which may pollute a little more than spec but will not damage the engine vs failed close.


This. Plus, if the heater was not blowing hot air, that's not a sign of a bad thermostat, that's a sign that there's no coolant in the heater core. It probably ate a head or intake gasket, dropping the coolant level and overheating.
After replacing the thermostat the heater blows hot now.

 

[BigCahuna]

This is a timely post for me. I noticed on my '02 Ford Explorer what looks like an antifreeze leak where the thermostat goes. My mechanic said I have to change out the housing that holds the thermostat, not just the thermostat and gasket. He also said the housing costs $145, and an hour labor.Does anyone believe this needs to be done?. It's more of a weep then a leak of any size, has anyone here done the housing replacement?.,,

 

[WobblyElvis]

Hot coolant circulates through the heater core regardless of thermostat position.

 

[OVERKILL]

Originally Posted By: Nick1994
Originally Posted By: OVERKILL
Originally Posted By: HTSS_TR
OE thermostat should failed open not close, when it fails the engine running cold which may pollute a little more than spec but will not damage the engine vs failed close.


This. Plus, if the heater was not blowing hot air, that's not a sign of a bad thermostat, that's a sign that there's no coolant in the heater core. It probably ate a head or intake gasket, dropping the coolant level and overheating.
After replacing the thermostat the heater blows hot now.


I imagine after adding coolant the heater blows hot now

On any vehicle I've ever wrenched on the heater core is on the engine side of the thermostat. Whether the thermostat is open or closed is irrelevant to it.

Now, some vehicles have control valves on the flow to the heater core as well but again, that's in response to coolant temperature not the operation of the thermostat.

 

[HTSS_TR]

Some years ago my neighbor gave her 1991 Mercury Tracer to my daughter, after few months the coolant temperature gauge was at near minimum after 15-20 minutes drive, turn the heat to max and barely warm air came out of the vent even in summer. Changed thermostat with el cheapo aftermarket and it fixed the cold running engine, MPG improved by more than 10% from 22-23 MPG to 25-27 MPG.

 

[OVERKILL]

Originally Posted By: HTSS_TR
Some years ago my neighbor gave her 1991 Mercury Tracer to my daughter, after few months the coolant temperature gauge was at near minimum after 15-20 minutes drive, turn the heat to max and barely warm air came out of the vent even in summer. Changed thermostat with el cheapo aftermarket and it fixed the cold running engine, MPG improved by more than 10% from 22-23 MPG to 25-27 MPG.


Yup, had the same issue on the Expedition when we first got it. The thermostat pooped the bed and it would barely get warm (massive 4-core rad). New T-stat and away we went

 

[cjcride]

Originally Posted By: BigCahuna
This is a timely post for me. I noticed on my '02 Ford Explorer what looks like an antifreeze leak where the thermostat goes. My mechanic said I have to change out the housing that holds the thermostat, not just the thermostat and gasket. He also said the housing costs $145, and an hour labor.Does anyone believe this needs to be done?. It's more of a weep then a leak of any size, has anyone here done the housing replacement?.,,
Long time ago I had an old Dodge Omni and the mechanic said he would try a double gasket and sealant as the housing was corroded. It held till I sold the car a couple of years later.

 

[MNgopher]

The lack of heat from the heater was because you lost a bunch of antifreeze somewhere and there was no antifreeze circulating through the heater core. The loop for the heater core is on the hot side of the thermostat specifically so you get heat, not on the radiator side.

You have heat now because the system was now refilled with the thermostat replacement. No heat is often a symptom of a stuck open thermostat or no coolant going through the heater core (through blockage or because there was not enough coolant!)

All that being said, I've had bad thermostats out of the box and I've had vehicles that have gone nearly 200,000 miles without changing it and no issues. You may win and you may lose...

 

[MNgopher]

BigCahuna, yes, that is a common problem on the 4.0l. Its a thermoplastic housing for the thermostat, and it eventually gives up the ghost. Check out some of the Ranger and Explorer boards and it is a very common issue.

 

[Pop_Rivit]

Originally Posted By: Nick1994
Change Your Thermostat!


No, I think I'll decide when and if the thermostat in any of my vehicles needs to be changed.

Originally Posted By: Nick1994
I've concluded its a good measure to change maybe every 5 years regardless if you have problems or not.


Another no. I've never had one fail in 5 years, and unless it's part of a timing belt change, I don't think I'll just randomly change a part that isn't faulty or causing problems.

Given all the issues with your mommy's vehicle, especially the past overheating, intake manifold gasket issues and running straight water in the cooling system instead of the correct coolant mix, I can't help but think your current thermostat problems are a result of inept maintenance.

 

[friendly_jacek]

last time i had a failed thermostat was in a 84 renault encore. it was stuck closed with steam billowing from the engine compartment. fortunately it was in a city and i wasn't stranded.

 

[01rangerxl]

Originally Posted By: BigCahuna
This is a timely post for me. I noticed on my '02 Ford Explorer what looks like an antifreeze leak where the thermostat goes. My mechanic said I have to change out the housing that holds the thermostat, not just the thermostat and gasket. He also said the housing costs $145, and an hour labor.Does anyone believe this needs to be done?. It's more of a weep then a leak of any size, has anyone here done the housing replacement?.,,


Your mechanic is correct...it's often the housing that leaks.

You can get just the t-stat, seal, and water neck that comes off the housing, but if that doesn't fix your leak, you are out $35-50 or so plus labor. Shops prefer to just do the assembly so they don't have a comeback. I'd only try partial replacement if you are doing it yourself and it won't be a big deal if you end up having to do the housing.

Ask what brand his part price is for. That's steep for Dorman.

If it's not leaking much, you probably have a while before it's a real issue, but it will almost certainly get worse. I have seen some trucks were the whole lower intake is just covered in coolant from the t-stat housing.

 

[Lolvoguy]

Originally Posted By: Pop_Rivit
Originally Posted By: Nick1994
Change Your Thermostat!


No, I think I'll decide when and if the thermostat in any of my vehicles needs to be changed.

Originally Posted By: Nick1994
I've concluded its a good measure to change maybe every 5 years regardless if you have problems or not.


Another no. I've never had one fail in 5 years, and unless it's part of a timing belt change, I don't think I'll just randomly change a part that isn't faulty or causing problems.

Given all the issues with your mommy's vehicle, especially the past overheating, intake manifold gasket issues and running straight water in the cooling system instead of the correct coolant mix, I can't help but think your current thermostat problems are a result of inept maintenance.


+1

 

[Nick1994]

Originally Posted By: Pop_Rivit
Originally Posted By: Nick1994
Change Your Thermostat!


No, I think I'll decide when and if the thermostat in any of my vehicles needs to be changed.

Originally Posted By: Nick1994
I've concluded its a good measure to change maybe every 5 years regardless if you have problems or not.


Another no. I've never had one fail in 5 years, and unless it's part of a timing belt change, I don't think I'll just randomly change a part that isn't faulty or causing problems.

Given all the issues with your mommy's vehicle, especially the past overheating, intake manifold gasket issues and running straight water in the cooling system instead of the correct coolant mix, I can't help but think your current thermostat problems are a result of inept maintenance.
Actually, I was wrong with the intake manifold gasket as previously thought. It is still ok for the time being. The coolant leak before was from a leaky heater hose which I fixed a couple weeks ago.