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Is this a failing thermostat? #4560278
10/31/17 01:22 PM
10/31/17 01:22 PM
Joined: Jan 2007
Posts: 806
El Oeste
HawkeyeScott Offline OP
HawkeyeScott  Offline OP
Joined: Jan 2007
Posts: 806
El Oeste
2008 Suburban with 5.3 GM motor in it. Just in the last few days it's been very slow to warm up and doesn't
ever get to the 210-degree mark on the temperature gauge, where it normally runs. It's been running about 195 to 205.

Any experience I've ever had with a car not coming up to temp was fixed by a new thermostat. But before I tear into it, I wanted to check here and see if anyone had any other ideas what is causing these symptoms.

Also, I've used Stant thermostats before with good success. Any other suggestions or brands to stay away from, assuming it is a thermostat issue?

Thanks a lot.

Re: Is this a failing thermostat? [Re: HawkeyeScott] #4560285
10/31/17 01:30 PM
10/31/17 01:30 PM
Joined: Oct 2005
Posts: 7,094
Colorado
Kuato Offline
Kuato  Offline
Joined: Oct 2005
Posts: 7,094
Colorado
If it is running normally during warmup then I agree - thermostat is sticking in the open position.


Thick vs Thin test: 15k / 43k miles complete
Re: Is this a failing thermostat? [Re: HawkeyeScott] #4560301
10/31/17 01:56 PM
10/31/17 01:56 PM
Joined: Jan 2011
Posts: 238
California
DGXR Offline
DGXR  Offline
Joined: Jan 2011
Posts: 238
California
Just curious, how easy can you see the difference between 205F (current normal) and 210F (previous normal) on the temp gauge?


1995 Corvette coupe LT1 6-speed
2006 Tacoma 2.7 2wd access cab
1999 Yamaha YZ400FL
2003 Honda XR400R
Re: Is this a failing thermostat? [Re: HawkeyeScott] #4560304
10/31/17 01:57 PM
10/31/17 01:57 PM
Joined: Aug 2008
Posts: 21,228
ON, Canada eh?
StevieC Offline
StevieC  Offline
Joined: Aug 2008
Posts: 21,228
ON, Canada eh?
Most newer vehicles run around 200 - 212F. Older will run anywhere between 195-200F. (There are exceptions)
It's possible that the thermostat is starting to stick open and about to fail.

I had this problem on my Santa Fe. It would be 195 all the time and then one fall it was 188F and shortly thereafter it failed open and wouldn't go past 100F.


'18 Dodge Grand Caravan GT - AMSOIL SS 5w20
'06 Santa Fe - 535,000km AMSOIL SS 0w30 / ATF
Re: Is this a failing thermostat? [Re: HawkeyeScott] #4560320
10/31/17 02:12 PM
10/31/17 02:12 PM
Joined: Apr 2017
Posts: 465
Utah, USA
28oz Online content
28oz  Online Content
Joined: Apr 2017
Posts: 465
Utah, USA
I've used several brands with success. However, my rule of thumb is the harder a part is to replace, the more likely I will use an OEM part. However, it's a thermostat. OEM ones usually don't cost that much anyways.


-----------------
1990 Nissan 300zx - Castrol Edge Euro 0W-40
2004 Nissan Quest - Pennzoil Platinum Euro 0W-40
2003 Ford Excursion 7.3 PSD - Mobil 1 TDT 5w-40
Re: Is this a failing thermostat? [Re: DGXR] #4560325
10/31/17 02:17 PM
10/31/17 02:17 PM
Joined: Jan 2007
Posts: 806
El Oeste
HawkeyeScott Offline OP
HawkeyeScott  Offline OP
Joined: Jan 2007
Posts: 806
El Oeste
The needle usually sits right on the '210' marking on the gauge. Now it sits to the left hand side of it.

Re: Is this a failing thermostat? [Re: HawkeyeScott] #4560331
10/31/17 02:23 PM
10/31/17 02:23 PM
Joined: Nov 2013
Posts: 1,950
Chicago, IL
EdwardC Offline
EdwardC  Offline
Joined: Nov 2013
Posts: 1,950
Chicago, IL
You might be able to tell if it's getting stuck open by looking down the radiator cap right after you start the car from cold, there shouldn't be any coolant flow since the thermostat should be closed.

Re: Is this a failing thermostat? [Re: HawkeyeScott] #4560346
10/31/17 02:56 PM
10/31/17 02:56 PM
Joined: Dec 2016
Posts: 202
Wisconsin
emmett442 Offline
emmett442  Offline
Joined: Dec 2016
Posts: 202
Wisconsin
The PCM monitors thermostat performance almost every time you start your car cold. It checks to see that the coolant is reaching the target temp within a required amount of time. If not, P0128 sets.

If you aren't getting a CEL, I wouldn't worry about it.


2011 Ford Crown Victoria LX 4.6L V8 auto
2009 Chevrolet Malibu LT 2.4L I4 auto
1974 Dodge D200 360 V8 4 speed manual
Re: Is this a failing thermostat? [Re: HawkeyeScott] #4560376
10/31/17 03:31 PM
10/31/17 03:31 PM
Joined: Sep 2013
Posts: 10,679
Indiana
dlundblad Offline
dlundblad  Offline
Joined: Sep 2013
Posts: 10,679
Indiana
Can you hook a live data reading code reader up?

I bought my truck with what I knew was a stuck open thermostat. No big deal. It went up halfway between the 100*F and the 210*F and stopped. I replaced it with a NAPA (US made part and only t stat locally with a lifetime warranty) and it went up to the 210*F and dropped down to just above the halfway mark.

I was left scratching my head, but the heat felt hotter. Hooked my code reader up and she was at 192*F. The thermostat opens at 195*F.


03 Jeep WJ 4.0 202k Castrol Edge 10w40 HM Fram XG16
02 Volvo S60 2.4T 186k M1 0w40 Mahle OX149D
97 Chevy Blazer 4.3 153k Synpower 5w30 Supertech ST3980 (Ecore)

Re: Is this a failing thermostat? [Re: HawkeyeScott] #4560648
10/31/17 07:39 PM
10/31/17 07:39 PM
Joined: Feb 2013
Posts: 11,081
Phoenix, AZ
Nick1994 Offline
Nick1994  Offline
Joined: Feb 2013
Posts: 11,081
Phoenix, AZ
Yeah I'd replace it.

Just not with a Stant.

My grandparent's Trailblazer had a stuck open thermostat. My mechanic replaced it with a Stant and it began to run hot. Replaced again and it still ran hot. Replaced with an OEM thermostat and it helped a lot. It had a bad fan clutch, but the Stant made it run warmer. This was because the opening of the Stant was smaller than the OEM thermostat, held side by side you could clearly see it, we also used a micrometer, I don't remember the measurements but it was somewhere around 15% smaller.

OEM only for me from here on out.


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: Is this a failing thermostat? [Re: HawkeyeScott] #4560829
11/01/17 02:26 AM
11/01/17 02:26 AM
Joined: Jan 2011
Posts: 2,826
N.Ohio
Lubener Offline
Lubener  Offline
Joined: Jan 2011
Posts: 2,826
N.Ohio
When in question just change it. Less than 10 dollars and 15 minutes to change, it's not worth worrying over.They deteriorate over time. I would go with OEM but if you use a Stant, go with their "superstat" only.

Last edited by Lubener; 11/01/17 02:27 AM.

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