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Pontiac Montana-Vibration heard only inside car when stopped


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JonL
New User

Nov 10, 2011, 5:32 PM

Post #1 of 4 (4372 views)
post icon Pontiac Montana-Vibration heard only inside car when stopped Sign In

2003 Pontiac Montana;3.4 liter;160,000 miles> low pitch vibration/humming noise heard in car cabin while in park or stopped at intersection. Cannot hear sound outside of car. Sound dissipates as car speed is increased. Sound is not related to increase in engine RPM. Engine does not miss or hesitate, engine smooth through increase in RPM.
engine does not appear to be running rough at idle. Checked exhaust system for source of vibration, nothing found.
Cannot really feel vibration, but you hear that type of sound.
Intermitant smell of coolant inside car started about the same time.
Some dash lights are out> Left side of speedometer and the stereo lights went out after start of humming sound.
Timing of problem-The car had sat idling for 20 minutes in heat of day to keep AC running about a week prior to problem start, but engine temperature gauge never showed elevated temp.
Transmission has started to slip on lower gear shifts when cold, about 2 months prior to this vibration issue.
Does this sound like some type of failure in engine or transmission dampening; or a vibration translated through HVAC system/firewall into cabin/dash? Can't a find a prior history of this system for Pontiac Montana's online.
Would like suggestions for trouble shooting to find source? Sound is getting on my my wife's nerves, need to solve.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 10, 2011, 7:39 PM

Post #2 of 4 (4349 views)
Re: Pontiac Montana-Vibration heard only inside car when stopped Sign In

My WAG (wild arse guess) is if this doesn't change with RPM with the smell of coolant I think it MIGHT (long shot) be in the HVAC system like perhaps the blower motor/squirrel cage. Odor of coolant? Hope you don't need a core as most are no freaking fun. Any change with blower speed?

Back: 20 min with A/C on shouldn't be a problem. Think of the cabs, limos, livery cars, and tons more that wait that long or longer.

That's about all I can think of not RPM related or affected much by engine speed,

T



JonL
New User

Nov 10, 2011, 10:38 PM

Post #3 of 4 (4334 views)
Re: Pontiac Montana-Vibration heard only inside car when stopped Sign In

Thanks, I'll look at HVAC first.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 11, 2011, 3:50 AM

Post #4 of 4 (4330 views)
Re: Pontiac Montana-Vibration heard only inside car when stopped Sign In

Blower and cage first. Perhaps rodent issues and off balance? Might feel it by hand on body of blower motor if so?

T







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