Engine not coming to normal operating temp - Pontiac G8 Forum: G8 Forums - G8Board.com
 
LinkBack Thread Tools
post #1 of 11 (permalink) Old 02-15-2017, 10:00 AM Thread Starter
Senior Member
 
Join Date: Sep 2008
Location: The dirrrrty
Posts: 2,437
Engine not coming to normal operating temp

I've been having an issue for the last couple of YEARS with my cooling system, but have ignored it because whenever I take it in, they say nothing is wrong. Here are the symptoms and what I've done:

- Prior to issue, normal motor operating temp is 91 deg C (A tick below halfway on temp gauge)

- Ever since the issue started, my engine temp likes to stay around 82 deg C (about 1/4 up temp gauge)

- When I put the car in engineering mode, the coolant temp often fluctuates erratically (I've seen it jump from 82 to 90 in a split second)

- Sometimes when the motor is idling, it gets to normal temp (91 C), but when I start driving, it typically goes back down to 82 C

- About two weeks ago, the temp gauge wouldn't move from COLD, I got a "Contact Dealer" code, and the AC turned itself off (I could not turn it back on either). When I got to work, I popped the hood and the motor was barely warm to the touch. On the way home from work, same situation, but halfway home, temp gauge started to go up and code cleared.

- Figured I had a bad tstat, so I had it replaced. Right after that, motor started coming up to normal temp again (91 C) for a day, then returned to 82 C, like previously.

Anybody have any ideas on what could be wrong? I find it hard to believe that the coolant temp can fluctuate so much within seconds as engineering mode is showing me.

2009 G8 GT


35W HID, LED fogs, custom front/rear Pontiac symbol badges, sharkfin, BlueStar Bluetooth, GXP front end, GXP diffuser, x-pipe, straight through mufflers with helmholtz chambers, RotoFab intake , Eibach springs, FE3 shocks/struts, BMR rear subframe inserts
romeyjdogg is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old 02-15-2017, 10:51 AM
Senior Member
 
terryscott621's Avatar
 
Join Date: Sep 2009
Location: San Antonio, TX
Posts: 1,739
Garage
Quote:
Originally Posted by romeyjdogg View Post
About two weeks ago, the temp gauge wouldn't move from COLD, I got a "Contact Dealer" code, and the AC turned itself off (I could not turn it back on either). When I got to work, I popped the hood and the motor was barely warm to the touch. On the way home from work, same situation, but halfway home, temp gauge started to go up and code cleared.
This symptom makes me think it is your coolant temp sensor. I had the same symptoms as above and it turned out to be the sensor. It could also be the sensor wiring. The sensor itself is around $30 from autozone and takes about 5 mins to replace. Might want to do a visual inspection of the wiring first as it can get crimped.

Terry Scott
San Antonio, TX
2009 G8 GXP - Sport Red Metallic (#821 of 1829 / #33 of 74 as Optioned)
Roto-Fab Intake with Amsoil Dry Filter / HSRK / Kooks 1-7/8 Mids / SOLO Mach Shorty (Unbalanced) Catback / Pat G Tune / Norris Motorsports Gen2 Catch Can / BMR Swaybars / BMR Rear Trailing Arms / Tein S-Tech Springs / Koni Shocks & Struts / Whiteline Rear Cradle Bushings / Whiteline Strut Bushings /

400 RWHP / 391 RWTQ

terryscott621 is offline  
post #3 of 11 (permalink) Old 02-15-2017, 10:53 AM Thread Starter
Senior Member
 
Join Date: Sep 2008
Location: The dirrrrty
Posts: 2,437
Appreciate the response, Terry.

I'm guessing the t-stat also went bad recently, judging from the code thrown and cold engine, but I think these are separate issues.

Where can I find the coolant temp sensor?

2009 G8 GT


35W HID, LED fogs, custom front/rear Pontiac symbol badges, sharkfin, BlueStar Bluetooth, GXP front end, GXP diffuser, x-pipe, straight through mufflers with helmholtz chambers, RotoFab intake , Eibach springs, FE3 shocks/struts, BMR rear subframe inserts
romeyjdogg is offline  
 
post #4 of 11 (permalink) Old 02-15-2017, 10:55 AM
Senior Member
 
terryscott621's Avatar
 
Join Date: Sep 2009
Location: San Antonio, TX
Posts: 1,739
Garage
It's on the driver's side of the engine towards the front near the first primary of the exhaust manifold (header). It's a two wire connection sensor.

Terry Scott
San Antonio, TX
2009 G8 GXP - Sport Red Metallic (#821 of 1829 / #33 of 74 as Optioned)
Roto-Fab Intake with Amsoil Dry Filter / HSRK / Kooks 1-7/8 Mids / SOLO Mach Shorty (Unbalanced) Catback / Pat G Tune / Norris Motorsports Gen2 Catch Can / BMR Swaybars / BMR Rear Trailing Arms / Tein S-Tech Springs / Koni Shocks & Struts / Whiteline Rear Cradle Bushings / Whiteline Strut Bushings /

400 RWHP / 391 RWTQ

terryscott621 is offline  
post #5 of 11 (permalink) Old 02-15-2017, 11:07 AM Thread Starter
Senior Member
 
Join Date: Sep 2008
Location: The dirrrrty
Posts: 2,437
Ok, I see it now.

Wiring and harness appear to be fine, but just a bit dirty. I see what you mean about getting crimped as it's a tight bend radius.

Do you know the process for changing the sensor? Will there be coolant leaking out if I do it?

2009 G8 GT


35W HID, LED fogs, custom front/rear Pontiac symbol badges, sharkfin, BlueStar Bluetooth, GXP front end, GXP diffuser, x-pipe, straight through mufflers with helmholtz chambers, RotoFab intake , Eibach springs, FE3 shocks/struts, BMR rear subframe inserts
romeyjdogg is offline  
post #6 of 11 (permalink) Old 02-15-2017, 11:15 AM
Senior Member
 
terryscott621's Avatar
 
Join Date: Sep 2009
Location: San Antonio, TX
Posts: 1,739
Garage
The process is basically just unplug the harness from the sensor then unscrew the old one and replace it with the new one and plug the wire harness back in. Coolant will come out when the old sensor is removed, so have the new one ready to go to limit how much coolant is lost.

Terry Scott
San Antonio, TX
2009 G8 GXP - Sport Red Metallic (#821 of 1829 / #33 of 74 as Optioned)
Roto-Fab Intake with Amsoil Dry Filter / HSRK / Kooks 1-7/8 Mids / SOLO Mach Shorty (Unbalanced) Catback / Pat G Tune / Norris Motorsports Gen2 Catch Can / BMR Swaybars / BMR Rear Trailing Arms / Tein S-Tech Springs / Koni Shocks & Struts / Whiteline Rear Cradle Bushings / Whiteline Strut Bushings /

400 RWHP / 391 RWTQ

terryscott621 is offline  
post #7 of 11 (permalink) Old 02-15-2017, 11:16 AM
Senior Member
 
G8GTLVR's Avatar
 
Join Date: Jul 2012
Location: Kentucky, U.S.
Posts: 245
Garage
Quote:
Originally Posted by romeyjdogg View Post
Ok, I see it now.

Wiring and harness appear to be fine, but just a bit dirty. I see what you mean about getting crimped as it's a tight bend radius.

Do you know the process for changing the sensor? Will there be coolant leaking out if I do it?
It is no more difficult than changing a bolt. The sensor threads into the head. Take the old one out, wrap the threads a couple of times with teflon tape, and screw the new sensor in. Don't over tighten; snug is all you need. I am sure you can look up a proper torque value if you want.

2009 G8 GT
2006 GTO
G8GTLVR is offline  
post #8 of 11 (permalink) Old 02-16-2017, 08:19 AM Thread Starter
Senior Member
 
Join Date: Sep 2008
Location: The dirrrrty
Posts: 2,437
For what it's worth: after I unplugged the connector and plugged it back in, the gauge read correctly. We'll see how it goes.

2009 G8 GT


35W HID, LED fogs, custom front/rear Pontiac symbol badges, sharkfin, BlueStar Bluetooth, GXP front end, GXP diffuser, x-pipe, straight through mufflers with helmholtz chambers, RotoFab intake , Eibach springs, FE3 shocks/struts, BMR rear subframe inserts
romeyjdogg is offline  
post #9 of 11 (permalink) Old 02-16-2017, 09:14 AM
Senior Member
 
terryscott621's Avatar
 
Join Date: Sep 2009
Location: San Antonio, TX
Posts: 1,739
Garage
Quote:
Originally Posted by romeyjdogg View Post
For what it's worth: after I unplugged the connector and plugged it back in, the gauge read correctly. We'll see how it goes.
Awesome! Hope that fixes the issue.

Terry Scott
San Antonio, TX
2009 G8 GXP - Sport Red Metallic (#821 of 1829 / #33 of 74 as Optioned)
Roto-Fab Intake with Amsoil Dry Filter / HSRK / Kooks 1-7/8 Mids / SOLO Mach Shorty (Unbalanced) Catback / Pat G Tune / Norris Motorsports Gen2 Catch Can / BMR Swaybars / BMR Rear Trailing Arms / Tein S-Tech Springs / Koni Shocks & Struts / Whiteline Rear Cradle Bushings / Whiteline Strut Bushings /

400 RWHP / 391 RWTQ

terryscott621 is offline  
post #10 of 11 (permalink) Old 02-16-2017, 11:41 AM
Senior Member
 
BAS G8's Avatar
 
Join Date: Aug 2014
Location: Mississauga, Ontario, Canada
Posts: 1,031
Lets hear it for dirty contacts in plugs.
Wondering if a dab of electrical contact grease they use may help to stop this in future.
BAS G8 is offline  
post #11 of 11 (permalink) Old 02-16-2017, 03:11 PM Thread Starter
Senior Member
 
Join Date: Sep 2008
Location: The dirrrrty
Posts: 2,437
Quote:
Originally Posted by BAS G8 View Post
Lets hear it for dirty contacts in plugs.
Wondering if a dab of electrical contact grease they use may help to stop this in future.
Not a bad idea. I'll give it a try if it starts acting up again, although the OEM connector does have a really beefy rubber grommet/seal protecting the connection.

2009 G8 GT


35W HID, LED fogs, custom front/rear Pontiac symbol badges, sharkfin, BlueStar Bluetooth, GXP front end, GXP diffuser, x-pipe, straight through mufflers with helmholtz chambers, RotoFab intake , Eibach springs, FE3 shocks/struts, BMR rear subframe inserts
romeyjdogg is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac G8 Forum: G8 Forums - G8Board.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome