Truck is making vibration noise help please

[dominopizza]

symptom: truck is making loud vibrating noise from the engine side i think. (can't pin point it)

truck doesn't make noise from cold start. when i start driving for 2~3 min and stop on red light, it makes vibrates. but it doesn't vibrate as soon as I put the truck in park.

Also, it vibrates when I use my window buttons. Also, vibration significantly decreases when I turn my A/C on.

I can't really confirm where the noise is coming from since it happens when the car is in drive and i don't have anyone around to step on the brake pedal for now.

What could be the problem?

 

[raKnizek]

Maybe take a look at your engine mounts. It sounds like various load conditions and RPM levels are inducing the vibration. For example the higher rpm and low load on a cold start (not in drive) is a very different condition than low rpm w a relatively higher load (in park w brakes applied). Are the rpms at a normal and steady level when the engine is warmed up and you're sitting at a stop light?

Give your belts a check too. Turning on/off AC will engage/disengage the belt and compressor. Using more or less electrical equipment can change the load on the alternator and belt as well.

Could also be something transmission related but that seems less likely based on what you described.

 

[dominopizza]

belt is ok. i have belt wear tester and it's in very much in good condition and rpm is normal when engine is warmed up. You made me realized that it might be the alternator. because even though battery is only 2 years old, sometimes truck is having hard time starting up like it's low on battery. Also, truck makes squeaking noise when cold start, and the sound go away after it warms up. (this sound problem persisted for a year, and i guess i got too used to the noise).

I'll try to test my alternator....

I

 

[gamefreakgc]

belt is ok. i have belt wear tester and it's in very much in good condition and rpm is normal when engine is warmed up. You made me realized that it might be the alternator. because even though battery is only 2 years old, sometimes truck is having hard time starting up like it's low on battery. Also, truck makes squeaking noise when cold start, and the sound go away after it warms up. (this sound problem persisted for a year, and i guess i got too used to the noise).

I'll try to test my alternator....

I

Squeaking noise at startup on a cold start is a belt. Try using a belt conditioner spray, it softens the rubber a little so when cold it doesn't squeal.

Have you had your battery checked? If the battery is not holding a charge or working properly (dead cells) it will cause a lot of stress on the alternator. I had a battery go bad on my on an older Toyota and my engine idled rougher and made all sorts of odd noises. Replaced battery and was good again. Would fit with the window symptom, since there's nothing else possible that would cause rolling up the window to affect the engine idle.

Turning on the A/C increases the idle, which hides a bad idle nicely. Also increases the output of the alternator slightly...

 

[dominopizza]

thanks for the input guys.. i found the problem... it was my muffler rusted in half. lol

i guess after 240k , muffler connection gave out. time to go to salvage yard and get one.