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Thermostat failed closed, happy I avoided disaster #4759716
05/17/18 09:35 AM
05/17/18 09:35 AM
Joined: Dec 2006
Posts: 8,451
Illinois
mrsilv04 Offline OP
mrsilv04  Offline OP
Joined: Dec 2006
Posts: 8,451
Illinois
Monday night, I had the thermostat on my 2000 Sierra 5.3 fail in the *closed* position. I had been driving for about a half an hour, with the A/C on, and I got a whiff of something that didn't smell quite right. I shut off the A/C and rolled down the window, and smelled more of what didn't smell right.

I took a look at the temperature gauge, and it was at 230... and rising quickly. I pulled into a parking lot, nosed it into the wind (it was a very windy out), shut it down, and put the hood up. There was nothing leaking, and it was full of coolant.

Once it had cooled down, I drove it the 6 blocks to a friend's house and left it in his driveway. Barely made it there, before it the temperature gauge was heading past 210, yet again.

Assumed one of three things.... thermostat, water pump, or a fan clutch. When it was hot, the top radiator hose was tight... and had noted that the fan appeared to be working properly. Start easy first, as always... so that meant the thermostat. I found that the thermostat had failed shut.

Factory thermostat, 18 years old with 130,000 miles. Came close to costing me an engine.

I'm going to place an order with RockAuto, and make plans to slap a new water pump, belts, hoses, plugs, wires, coolant, oil and filter on it as well, sometime in the next few weeks. Seems like it would be an excellent Memorial Day weekend project.

Re: Thermostat failed closed, happy I avoided disaster [Re: mrsilv04] #4759723
05/17/18 09:39 AM
05/17/18 09:39 AM
Joined: Jan 2017
Posts: 2,022
VW Fanboy Island
maxdustington Online content
maxdustington  Online Content
Joined: Jan 2017
Posts: 2,022
VW Fanboy Island
I thought they were supposed to fail in the open position? Or is that just aftermarket tstats?

Planned obsolescence.

EDIT: A belated birthday gift! HBD!

Last edited by maxdustington; 05/17/18 09:39 AM.

03 Jetta AWP/09A 205k kms
Edge 0W40 + Mann 719/30
Re: Thermostat failed closed, happy I avoided disaster [Re: mrsilv04] #4759774
05/17/18 10:27 AM
05/17/18 10:27 AM
Joined: Dec 2013
Posts: 3,989
Manchester, England
Olas Offline
Olas  Offline
Joined: Dec 2013
Posts: 3,989
Manchester, England
230f is only 110c and the pressurised system doesn't boil until 120c so it's more than likely going to be fine.
Good job you let it cool down when you did : thumbsup


Cable ties should hold it
Re: Thermostat failed closed, happy I avoided disaster [Re: mrsilv04] #4759787
05/17/18 10:43 AM
05/17/18 10:43 AM
Joined: Nov 2013
Posts: 1,950
Chicago, IL
EdwardC Offline
EdwardC  Offline
Joined: Nov 2013
Posts: 1,950
Chicago, IL
Nice work! I had two overheating issues in the past, one due to a connector coming loose for the radiator fan and another where there was a leak in the cooling system. I caught both in time that both vehicles have kept going for many thousands of miles since.

Another trick that you probably already know, is to turn the air to full heat. It should help cool the coolant since I believe it's plumb in a loop before the thermostat.

Re: Thermostat failed closed, happy I avoided disaster [Re: maxdustington] #4759908
05/17/18 12:33 PM
05/17/18 12:33 PM
Joined: Jun 2003
Posts: 17,834
Deplorable in apple valley, ca
Chris142 Offline
Chris142  Offline
Joined: Jun 2003
Posts: 17,834
Deplorable in apple valley, ca
Originally Posted By: maxdustington
I thought they were supposed to fail in the open position? Or is that just aftermarket tstats?

Planned obsolescence.

EDIT: A belated birthday gift! HBD!
it's a myth. A stat can stick in any position. There are some garbage aftermarket ones that will latch open around 220f.


02 Wrangler carlube 5w30
87 F250 traveler 15w40
07 fjcruiser Chevron 10w30
Z400 castrol T 10w40
Can am maveric edge 5w40
57 case tractor 15w40
Re: Thermostat failed closed, happy I avoided disaster [Re: Chris142] #4759955
05/17/18 01:17 PM
05/17/18 01:17 PM
Joined: Dec 2006
Posts: 8,451
Illinois
mrsilv04 Offline OP
mrsilv04  Offline OP
Joined: Dec 2006
Posts: 8,451
Illinois
Originally Posted By: Chris142
it's a myth. A stat can stick in any position. There are some garbage aftermarket ones that will latch open around 220f.


I would have *much* rather had a garbage one that stuck open. One that sticks open doesn't try to ruin your engine and leave you stranded.


2004 Silverado - on its 3rd Jasper engine in less than one year.
Re: Thermostat failed closed, happy I avoided disaster [Re: mrsilv04] #4759958
05/17/18 01:18 PM
05/17/18 01:18 PM
Joined: Jun 2005
Posts: 5,278
North Texas
ARB1977 Offline
ARB1977  Offline
Joined: Jun 2005
Posts: 5,278
North Texas
If the factory one lasted that long. I would buy another. Good job on shutting it down in time.


2015 Tacoma 4.0L 60K (as of 02/23/18)
AMSOIL SS 0W30 / Toyota filter

2018 CRV 1.5L (as of 05/11/18)
Factory fill / Honda filter
Re: Thermostat failed closed, happy I avoided disaster [Re: mrsilv04] #4759962
05/17/18 01:24 PM
05/17/18 01:24 PM
Joined: Feb 2014
Posts: 595
Margate England
Claud Offline
Claud  Offline
Joined: Feb 2014
Posts: 595
Margate England
Why do you feel you need to replace the water pump?. Any signs of it leaking?.
I guess the other items are planned maintenance, I hope it's not because you had a wake up call on Monday night.

Claud.

Re: Thermostat failed closed, happy I avoided disaster [Re: Claud] #4759981
05/17/18 01:38 PM
05/17/18 01:38 PM
Joined: Dec 2006
Posts: 8,451
Illinois
mrsilv04 Offline OP
mrsilv04  Offline OP
Joined: Dec 2006
Posts: 8,451
Illinois
Originally Posted By: Claud
Why do you feel you need to replace the water pump?. Any signs of it leaking?.
I guess the other items are planned maintenance, I hope it's not because you had a wake up call on Monday night.

Claud.


Just because it upset me badly enough. They're not that expensive, and I'm simply in the mood at this point. I can get a lifetime warranty unit for less than $60. I was assuming that I might need to replace it, and am still considering it.

This truck is used like a truck should be used (towing and hauling), and the peace of mind is simply worth it.


2004 Silverado - on its 3rd Jasper engine in less than one year.
Re: Thermostat failed closed, happy I avoided disaster [Re: mrsilv04] #4760021
05/17/18 02:01 PM
05/17/18 02:01 PM
Joined: Feb 2013
Posts: 11,098
Phoenix, AZ
Nick1994 Online content
Nick1994  Online Content
Joined: Feb 2013
Posts: 11,098
Phoenix, AZ
My mom had an 03' Buick Rendezvous that the factory thermostat stuck closed while she was in traffic. It overheated and blew the head gasket. No coolant in the oil, but exhaust gases in the coolant. It would overheat if she wasn't moving so she was careful. She drove it for another year.


2015 Hyundai Sonata 2.4L 88k Motorcraft Synthetic Blend 5w30 & OEM
2000 Toyota Camry 2.2L 231k Valvoline 5w30 & Fram Ultra
1996 Jeep Cherokee 4.0L 147k Mobil 1 HM 10w40 & Fram Ultra
Re: Thermostat failed closed, happy I avoided disaster [Re: mrsilv04] #4760037
05/17/18 02:09 PM
05/17/18 02:09 PM
Joined: Nov 2008
Posts: 12,761
NH
supton Offline
supton  Offline
Joined: Nov 2008
Posts: 12,761
NH
I don't like doing timing belts but there is something to being said about replacing WP, tstat and coolant all at the same time.

Glad you made out ok.


2011 Toyota Camry, base, 2.5L/6MT, 170k, hers
2010 Toyota Tundra DC, 4.6L/6AT, 144k, ours
1999 Toyota Camry LE, 2.2L/4AT, 195k, his
Re: Thermostat failed closed, happy I avoided disaster [Re: mrsilv04] #4760050
05/17/18 02:17 PM
05/17/18 02:17 PM
Joined: Jun 2003
Posts: 17,834
Deplorable in apple valley, ca
Chris142 Offline
Chris142  Offline
Joined: Jun 2003
Posts: 17,834
Deplorable in apple valley, ca
Originally Posted By: mrsilv04
Originally Posted By: Chris142
it's a myth. A stat can stick in any position. There are some garbage aftermarket ones that will latch open around 220f.


I would have *much* rather had a garbage one that stuck open. One that sticks open doesn't try to ruin your engine and leave you stranded.
you didn't understand. they stick open and latch @ normal temps. The latch has no effect on it sticking closed anywhere in it's travel. They can still stick closed. The 1st time the engine gets warmed up they latch and stick open. Usually the day after it was installed.


02 Wrangler carlube 5w30
87 F250 traveler 15w40
07 fjcruiser Chevron 10w30
Z400 castrol T 10w40
Can am maveric edge 5w40
57 case tractor 15w40
Re: Thermostat failed closed, happy I avoided disaster [Re: mrsilv04] #4760189
05/17/18 04:50 PM
05/17/18 04:50 PM
Joined: Jul 2013
Posts: 1,811
Ottumwa, Iowa
jhellwig Offline
jhellwig  Offline
Joined: Jul 2013
Posts: 1,811
Ottumwa, Iowa
Am I the only one that remembers when this used to occur regularly? It has been 15 years since I had one stick closed but it used to happen more often. It was great when they came out with these fail safe ones but everyone I have had has stuck open. Now I just get the regular ones.


Sparks fly from my fingers.

1995 Chevy K2500 Suburban lt 5.7
2014 Toyota Sienna
1983 Chevy K5 350

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