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Engine Running Too Cool ? #4520815
09/19/17 11:58 PM
09/19/17 11:58 PM
Joined: Jan 2007
Posts: 17,501
Clovis, CA
Merkava_4 Offline OP
Merkava_4  Offline OP
Joined: Jan 2007
Posts: 17,501
Clovis, CA
2000 Buick LeSabre

When I got back to the car from the grocery store, I decided to take the car for a little test trip and watch the water temperature. A/C was off for the whole trip. At the start of the trip, water temperature was 167F and ambient temperature was 70F. Took the car on the freeway for 21.5 miles. As soon as I got on the freeway, the engine starts cooling off. Stayed between 155F and 156F for the whole trip. Exited the freeway and drove about two blocks to the house.

During the time the car was sitting in the driveway at idle waiting for me to open the garage door, the temperature spiked to 182F. The same exact trip the day before with the A/C on, the engine reached a maximum temperature of 176F. Thermostat is not supposed to open until 192F.

What you guys say ?

Re: Engine Running Too Cool ? [Re: Merkava_4] #4520816
09/20/17 12:00 AM
09/20/17 12:00 AM
Joined: Jun 2003
Posts: 17,365
Deplorable in apple valley, ca
Chris142 Online content
Chris142  Online Content
Joined: Jun 2003
Posts: 17,365
Deplorable in apple valley, ca
Thermostat stuck open


02 Wrangler durablend 10w40
87 F250 traveler 15w40
04 Tahoe super-s 10w30
Z400 castrol T 10w40
Can am maveric edge 5w40
57 case tractor 15w40
Re: Engine Running Too Cool ? [Re: Merkava_4] #4520819
09/20/17 12:02 AM
09/20/17 12:02 AM
Joined: Aug 2014
Posts: 1,453
Gulf Coast, MS
3800Series Offline
3800Series  Offline
Joined: Aug 2014
Posts: 1,453
Gulf Coast, MS
Same exact thing with my Regal. Car hit a equilibrium on the highway and once you got off the balance shifted.

Re: Engine Running Too Cool ? [Re: Chris142] #4520821
09/20/17 12:06 AM
09/20/17 12:06 AM
Joined: Sep 2015
Posts: 2,260
Malaysia
zeng Offline
zeng  Offline
Joined: Sep 2015
Posts: 2,260
Malaysia
Originally Posted By: Chris142
Thermostat stuck open

+1

Re: Engine Running Too Cool ? [Re: Merkava_4] #4520824
09/20/17 12:18 AM
09/20/17 12:18 AM
Joined: Feb 2013
Posts: 10,712
Phoenix, AZ
Nick1994 Offline
Nick1994  Offline
Joined: Feb 2013
Posts: 10,712
Phoenix, AZ
OEM thermostat replacement only Merk. My grandparent's Trailblazer had the thermostat replaced and it ran warmer, turns out the Stant opening was a lot smaller than the OEM one.


2015 Hyundai Sonata 2.4L 84k Mobil 1 AFE 0w30 & OEM
2000 Toyota Camry 2.2L 230k Valvoline 5w30 & Fram Ultra
1996 Jeep Cherokee 4.0L 147k Mobil 1 HM 10w40 & Fram Ultra
Re: Engine Running Too Cool ? [Re: zeng] #4520830
09/20/17 12:24 AM
09/20/17 12:24 AM
Joined: Aug 2006
Posts: 9,808
Central Washington
Colt45ws Offline
Colt45ws  Offline
Joined: Aug 2006
Posts: 9,808
Central Washington
Originally Posted By: zeng
Originally Posted By: Chris142
Thermostat stuck open

+1

Ive replaced probably half a dozen thermos in just mine and a couple of friends cars for this same behavior.

Replace the stat.


-Colton
2002 Ford Crown Vic PI 207k, Ex-Kootenai County, ID Unit #42
Down for engine swap
2003 Ford Crown Vic PI 75k
Castrol EDGE HM 5W30, Fram XG2
Re: Engine Running Too Cool ? [Re: Merkava_4] #4520882
09/20/17 02:39 AM
09/20/17 02:39 AM
Joined: Aug 2017
Posts: 211
Cincinnati, USA
Dave9 Offline
Dave9  Offline
Joined: Aug 2017
Posts: 211
Cincinnati, USA
Maybe T-stat but maybe not. The way those are geared, along with the 3800 torque (if/when in good shape) they're barely loafing along at a steady (speed limit) on the highway.

Owners of others cars will not understand that my same generation with a 3800, could run at 40MPH IDLING. Bad side, shifting was anything but performance oriented, and the gearing and high torque wears down brakes faster, like a train pulling when you brake to slow down.

Up to you, you can pull the t-stat and test it in a pot of boiling water if you like, but at that point I'd throw a new one in just because it makes sense to do so while it's so accessible.

However if it were me, I'd warm it up first then drive it like I stole it to get the temperature up, blow a little carbon off the valves, and see if you get that typical temperature plummet that happens when coolant gets around the t-stat rating then suddenly cools down the engine a few degrees because it opened.

Re: Engine Running Too Cool ? [Re: Merkava_4] #4520931
09/20/17 05:59 AM
09/20/17 05:59 AM
Joined: Sep 2016
Posts: 156
MN
Tman220 Offline
Tman220  Offline
Joined: Sep 2016
Posts: 156
MN
No need to over-analyze, no need for a pot of boiling water. It runs too cool and its the thermostat's fault. With the correct thermostat that engine will run pretty steady 194-197F on the highway.

Last edited by Tman220; 09/20/17 06:10 AM.

2012 Regal GS Turbo PP 5w30
1994 Camaro Z28 LT1 355 CI, 430 RWHP PP 5W30
Re: Engine Running Too Cool ? [Re: Merkava_4] #4520941
09/20/17 06:38 AM
09/20/17 06:38 AM
Joined: Jan 2003
Posts: 3,081
Coastal South Carolina
edwardh1 Offline
edwardh1  Offline
Joined: Jan 2003
Posts: 3,081
Coastal South Carolina
if the oem has a hole in the stat (to allow bipass water circulation), get a stat that has that too.


These products are all new every year?? They are a revolution!!! Razor blades, mens shirts, TVs, wiper blades, gutter guards, hearing aids... according to the ads. But also all new last year
Re: Engine Running Too Cool ? [Re: Merkava_4] #4521004
09/20/17 08:21 AM
09/20/17 08:21 AM
Joined: Dec 2006
Posts: 7,658
Toronto, Canada
KrisZ Online happy
KrisZ  Online Happy
Joined: Dec 2006
Posts: 7,658
Toronto, Canada
A stuck open thermostat is much harder to spot in warm climates. In Canada it's quite easy but you have to wait for the late fall/early winter to see the temp. gauge not reaching the normal position.

I also vote for a new, OEM thermostat.


2015 Dodge Grand Caravan-27k miles.
2006 Mazda 3-163k miles
Re: Engine Running Too Cool ? [Re: Merkava_4] #4521097
09/20/17 10:15 AM
09/20/17 10:15 AM
Joined: Feb 2008
Posts: 683
Atlanta, GA
RoGuE Offline
RoGuE  Offline
Joined: Feb 2008
Posts: 683
Atlanta, GA
I just had this issue on my Malibu where the temp gauge didn't move at all from cold. Replaced the thermostat and all is well. I was getting a P0128 code. Do you have access to a scan tool?


2007 Chevrolet Malibu
2.2L Ecotec
Re: Engine Running Too Cool ? [Re: Merkava_4] #4521391
09/20/17 02:44 PM
09/20/17 02:44 PM
Joined: Jun 2003
Posts: 5,921
Illinois
SHOZ Offline
SHOZ  Offline
Joined: Jun 2003
Posts: 5,921
Illinois
I changed t-stats on both my Hyundais this summer. Both OE and both were 'lazy'. they would run about 180-183F n the highway. But in the winter when coasting and slowing down the temp would dip below the 180F marks. Since changing them the run 185F-190F.


2008 Hyundai Accent 1.6L 5 sp manual hatchback
2010 Hyundai Genesis Coupe Track 2L Turbo 6sp manual
Re: Engine Running Too Cool ? [Re: Merkava_4] #4521473
09/20/17 04:59 PM
09/20/17 04:59 PM
Joined: Sep 2007
Posts: 968
TX, USA
JMJNet Offline
JMJNet  Offline
Joined: Sep 2007
Posts: 968
TX, USA
Since it is a Buick, get ACDelco T-stat only not aftermarket.


  • 2017 Toyota Sienna
  • 1995 GMC Suburban 6.5L Turbo Diesel


Re: Engine Running Too Cool ? [Re: JMJNet] #4521833
09/21/17 02:35 AM
09/21/17 02:35 AM
Joined: Jan 2007
Posts: 17,501
Clovis, CA
Merkava_4 Offline OP
Merkava_4  Offline OP
Joined: Jan 2007
Posts: 17,501
Clovis, CA
I've already had the new ACDelco thermostat sitting in the box for about 12 years. I even have a couple of extra seals that go around the "saturn" perimeter. What I don't have is the thermostat housing gasket. I got two on special order. Nobody stocks them anymore. Thanks for the replies guys. smile

Re: Engine Running Too Cool ? [Re: Merkava_4] #4521880
09/21/17 06:15 AM
09/21/17 06:15 AM
Joined: Sep 2015
Posts: 1,529
USA
mk378 Online content
mk378  Online Content
Joined: Sep 2015
Posts: 1,529
USA
Thermostats with a rubber seal that wraps around the edge of the flange don't need any other gasket.

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