How to change thermostat on 2007 pontiac montana

Question edited for clarity.
Question moved to model category.

Pontiac Montana Thermostat Replacement Cost Estimate

https://repairpal.com > estimator > thermostat-replaceme...
The average cost for a Pontiac Montana Thermostat Replacement is between $570 and $623. ... Labor costs are estimated between $204 and $257 while parts are priced ...
Or DIY.

about replacing a transmission with one from a Junkyard or cross referencing them. and to show you that not all 4T65E transmissions are interchangeable, although they look alike. Guys with the comp g package or the Impala police option often find this out the hard way.
Your car and the potential donor car will have a tag in the trunk (usually under the spare tire cover) that lists the RPO codes for your car, along with your VIN. RPO=Regular Production Order. Several of these codes relate to the transmission, and you will need them to begin to find a proper match. If you can't find the RPO tags, you can look up the RPOs for a nominal fee ($5) according to the VIN number at the following website: www . compnine . com .
I know these transmissions are different in at least 5 areas, and you have to match each area for a proper swap.
FIRST is the transmission type, which relates to torque converter size, the strength of the internal gears, and the strength of the differential. Here are the basic types along with their RPO codes:
M15 - 245 mm (9.6 in) torque converter
MN3 - 258 mm (10.2 in) torque converter
MN7 - 258 mm (10.2 in) torque converter and heavy-duty gearbox and differential (see 4T65E-HD)
MD7 - 245 mm (9.6 in) torque converter (Chinese version)
M76 - 245 mm (9.6 in) torque converter (with all-wheel drive capability)
You will want a match these RPO codes.
SECOND is the final drive ratio. The PCM can detect the difference, and in some cars may not engage if the correct final drive is not present. Here are the RPO codes for the four different final drives used in the transmission.
FQ3 - RATIO TRANSAXLE FINAL DRIVE 2.86;
FR2 - RATIO TRANSAXLE FINAL DRIVE 2.93;
F83 - RATIO TRANSAXLE FINAL DRIVE 3.05;
FR9 - RATIO TRANSAXLE FINAL DRIVE 3.29;
To narrow year search for potential cars, the following site have pretty good info on the final drives used on various cars. Click on the years of the cars in question.http://www.gmtuners.com/transmission/index.htm
THIRD is the converter stall speed. There will be small differences for most cars as it is based on car weight as well as final drive value and engine ratings. Reusing the cars original torque converter will address that area. Some indication of stall speed value is given in the K-factor information in the above gmtuners page. This bottom of this page from the gmtuners website will show you how to decipher the four digit code on the torque converter. http://www.gmtuners.com/gmtransinfo.htm
FOURTH, the torque converter needs to have the correct lockup clutch friction material for the PCM that controls it (regardless of HD nor not). This changed over the years. The newer ones can be used on older transmissions with calibration changes, but older type in newer transmissions will fail. Reusing the cars original torque converter will address that area.
FIFTH is area is electrical compatibility, and this is what trips up a lot of guys. 3 different electrical interfaces to the transmissions were used from 97-08. Some of these differences had to do with how the PCM determined what gear the transmission was in, or was commanded to be in. If you look on a GM parts web site, you will see that three different internal harnesses are available for the 4T65E. Each of the three harnesses is listed below along with the cars that use the harness. Your car and the donor car will have to match. If you have any additional insight, please leave me a comment and I can correct this post.
CARS USING HARNESS 24241204
Buick Century 4DR Custom2000, 2001, 2002
Buick Century 4DR LIMITED2000, 2001, 2002
Buick Lesabre 4DR CUSTOM1998, 1999
Buick Lesabre 4DR LIMITED1998, 1999
Buick Park Avenue 4DR Base1997, 1998
Buick Park Avenue 4DR ULTRA1997, 1998
Buick Regal 4DR GS1998, 1999, 2000, 2001, 2002
Buick Regal 4DR LS1998, 1999, 2000, 2001, 2002
Buick RENDEVOUS 4DR2002
Buick Riviera 2DR Base1997, 1998, 1999
Chevrolet Lumina 4DR Base w/ 3.1L (LG8) eng2000, 2001
Chevrolet Lumina 4DR LTZ1997, 1998, 1999
Chevrolet Monte Carlo Z341997, 1998, 1999
Chevrolet Venture2001, 2002
Oldsmobile 88 4DR Base1997, 1998, 1999
Oldsmobile 88 4DR Regency1997, 1998
Oldsmobile 88 4DR Royale, Base and LS1997, 1998, 1999
Oldsmobile 88 4DR ROYALE LSS1997, 1998, 1999
Oldsmobile Intrigue 4DR Base1998
Oldsmobile Intrigue 4DR GL1998, 1999, 2000, 2001, 2002
Oldsmobile Intrigue 4DR GLS1998, 1999, 2000, 2001, 2002
Oldsmobile Intrigue 4DR GX1999, 2000, 2001, 2002
Oldsmobile Silhouette1999, 2000, 2001, 2002
Pontiac Aztek Hatchback Base and GT2001, 2002
Pontiac Bonneville 4DR SE1998, 1999
Pontiac Bonneville 4DR SSE1997, 1998, 1999
Pontiac Grand Prix 2DR GT1998, 1999, 2000, 2001, 2002
Pontiac Grand Prix 2DR GTP1999, 2000, 2001, 2002
Pontiac Grand Prix 4DR GT1998, 1999, 2000, 2001, 2002
Pontiac Grand Prix 4DR GTP1999, 2000, 2001, 2002
Pontiac Grand Prix 4DR SE2000, 2001, 2002
Pontiac MONTANA Base1999, 2000, 2001
Pontiac MONTANA EXT MOBILITY SPECIAL2002, 2003
Pontiac MONTANA MPV1999, 2000, 2001
Pontiac MONTANA MPV BASE2002, 2003
Pontiac MONTANA MPV EXT1999, 2000, 2001, 2002
Pontiac MONTANA MPV EXT BASE2002, 2003
Pontiac MONTANA MPV EXT UPLEVEL2002, 2003
Pontiac MONTANA MPV SPECIAL2000, 2001, 2002, 2003

CARS USING HARNESS 24241205
Buick Lesabre 4DR CUSTOM2000, 2001, 2002
Buick Lesabre 4DR LIMITED2000, 2001, 2002
Buick Park Avenue 4DR Base1999, 2000, 2001, 2002
Buick Park Avenue 4DR ULTRA1999, 2000, 2001, 2002
Chevrolet Impala 4DR Base2000, 2001, 2002
Chevrolet Impala 4DR LS2000, 2001, 2002
Chevrolet Monte Carlo LS2000, 2001, 2002
Chevrolet Monte Carlo SS2000, 2001, 2002
Oldsmobile Aurora 4DR 3.5L2001, 2002
Oldsmobile Aurora 4DR Base2001, 2002
Pontiac Bonneville 4DR SE2000, 2001, 2002
Pontiac Bonneville 4DR SLE SSEI2000, 2001, 2002
Pontiac Bonneville 4DR SSEI2000, 2001, 2002

CARS USING HARNESS 24237264
Buick Century 4DR Custom2003, 2004, 2005
Buick Century 4DR LIMITED2003
Buick LaCrosse 4DR Base2005, 2006, 2007, 2008, 2009
Buick LaCrosse 4DR CX2005, 2006, 2007, 2008, 2009
Buick LaCrosse 4DR CXL2005, 2006, 2007, 2008, 2009
Buick LaCrosse 4DR CXS2005, 2006, 2007, 2008, 2009
Buick LaCrosse 4DR SS2008, 2009
Buick Lesabre 4DR CUSTOM2003, 2004, 2005
Buick Lesabre 4DR LIMITED2003, 2004, 2005
Buick Lucerne 4DR CX2006, 2007, 2008, 2009, 2010, 2011
Buick Lucerne 4DR CX CLOTH2009, 2010, 2011
Buick Lucerne 4DR CX CLOTH PLUS2009, 2010, 2011
Buick Lucerne 4DR CXL2006, 2007, 2008, 2009, 2010, 2011
Buick Lucerne 4DR CXL LEATHER2009, 2010, 2011
Buick Lucerne 4DR CXL LUX & CONFIDENCE2009, 2010, 2011
Buick Lucerne 4DR CXL LUXURY2009, 2010, 2011
Buick Lucerne 4DR CXL SPECIAL EDITION2006, 2007, 2008, 2009, 2010, 2011
Buick Lucerne 4DR CXL ULTRA2009, 2010, 2011
Buick Park Avenue 4DR Base2003, 2004, 2005
Buick Park Avenue 4DR ULTRA2003, 2004, 2005
Buick Regal 4DR GS2003, 2004
Buick Regal 4DR LS2003, 2004
Buick RENDEVOUS 4DR2003, 2004, 2005, 2006, 2007
Buick Rendezvous2003, 2004, 2005, 2006, 2007
Buick TERRAZA2005, 2006, 2007
Chevrolet Impala 4DR 50TH ANN SPL2008
Chevrolet Impala 4DR Base2003, 2004, 2005
Chevrolet Impala 4DR FLEET 1FL2011
Chevrolet Impala 4DR FLEET 2FL2011
Chevrolet Impala 4DR LS2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
Chevrolet Impala 4DR LT2006, 2007, 2008, 2009, 2010
Chevrolet Impala 4DR LT 3.52006, 2007, 2008, 2009, 2010, 2011
Chevrolet Impala 4DR LTZ2006, 2007, 2008, 2009, 2010, 2011
Chevrolet Impala 4DR POLICE2004, 2006, 2007, 2008, 2009, 2010, 2011
Chevrolet Impala 4DR SS2004, 2005, 2006, 2007, 2008, 2009
Chevrolet Impala 4DR TAXI2011
Chevrolet Malibu 4DR SS2006, 2007
Chevrolet Malibu Hatchback MAXX SS2006, 2007
Chevrolet Monte Carlo Base2003, 2004, 2005
Chevrolet Monte Carlo LS2003, 2004, 2005, 2006, 2007
Chevrolet Monte Carlo LS LS2003, 2004, 2005
Chevrolet Monte Carlo LT2005, 2006, 2007
Chevrolet Monte Carlo LT 3.52006
Chevrolet Monte Carlo LTZ2006
Chevrolet Monte Carlo SS2003, 2004, 2006, 2007
Chevrolet Monte Carlo SS HI Sport2004, 2005
Chevrolet UPLANDER2005, 2006, 2007, 2008, 2009
Chevrolet Venture2003, 2004, 2005
Oldsmobile Silhouette2003, 2004
Pontiac Aztek Hatchback Base2003, 2004, 2005
Pontiac Aztek Hatchback GT2003, 2004, 2005
Pontiac Bonneville 4DR SE2003, 2004, 2005
Pontiac Bonneville 4DR SLE2005
Pontiac Bonneville 4DR SLE GXP2004, 2005
Pontiac Bonneville 4DR SLE SSEI2003
Pontiac Bonneville 4DR SSEI2003
Pontiac G6 Base2006, 2009
Pontiac G6 GT2007, 2008, 2009f
Pontiac G6 GT UPLEVEL2009
Pontiac G6 GXP2006
Pontiac Grand Prix 4DR Base2006, 2007, 2008
Pontiac Grand Prix 4DR GT2003, 2004, 2005, 2006, 2007
Pontiac Grand Prix 4DR GT22004, 2005
Pontiac Grand Prix 4DR GTP2003, 2004, 2005, 2006
Pontiac Grand Prix 4DR GXP2005, 2006, 2007, 2008
Pontiac Grand Prix 4DR SE2003
Pontiac Grand Prix 4DR SE12003
Pontiac MONTANA EXT MOBILITY SPECIAL2003, 2004, 2005
Pontiac MONTANA MPV BASE2003, 2004, 2005
Pontiac MONTANA MPV EXT2003, 2004, 2005
Pontiac MONTANA MPV EXT BASE2003, 2004, 2005
Pontiac MONTANA MPV EXT UPLEVEL2003, 2004, 2005
Pontiac MONTANA MPV SPECIAL2003, 2004, 2005
Pontiac SV-62005, 2006, 2007, 2008, 2009
Saturn Relay2005, 2006, 2007
GM FWD Transmission ID chart

Follow the radiator hose back to the engine. Where the hose meets the engine is where the thermostat is. Should be two or three bolts holding the fixture on. Inside of that fixture is the thermostat. Make sure the engine is cooled down and make sure to replace the coolant that you will lose changing this. Easy fix.

put in a radiator flush ,run it for 20 miles it can be a blocked core in both the radiator and the heater.that should clean it. then refill with a 50/50 mix anti freeze then bleed it of air. put your heater on full .run the engine on tick over.then push in the radiator hose to push the air out of the expansion bottle cap .it is off . then refit your cap.

you have a GM common problem and that is a bad intake manifold gasket. GM change the gaskets to plastic and they crank and leak causing over heating. here is a picture of one i took from a 2005 pon. bonneville with 74,000 miles on it

Sounds like your head /intake gaskets are leaking better get system ckecked and compression test done soon .....It may cost more later

I believe the Montana has a 3.4 Liter V6 Engine.
This thermostat is located under the exhaust "crossover" pipe that runs between both the front and rear cylinder heads. Divers side.
Remove the heat shields (10mm bolts) and then the nuts on the exhaust studs. (6 total)
Two bolts hold the T stat housing to the intake.

Yes, it can be removed and run without the thermostat. However, your gas mileage will suffer and the heater may not work very well.

public library...Chilton or Haynes auto repair manuals or collisionrepairadvice.com     make sure you bleed the system

check the coolant level fiirst...if that is low it wont give you any heat.....to change the thermostat you have to follow the top radiator hose to the engine.at the send of it you will see a clamp take it loose...then you will see the thermostat housing its held in place by 2 bolts . once you remove them you have the thermostat....make sure you clean all the old gasket material off both the housing and mount.also make sure you get a new gasket.