abnormal noise only when hvac is on...

as the title says I am stumped on this one.. When the engine is running, note this sound I hear is only present when hvac is on, and does not exist when hvac is off..recently, I opened the cap on the expansion tank to check the coolant level, could be a bubble in cooling system, do you have to bleed the system each time you take off the cap to check coolant? any help will be appreciated thanks.

Originally Posted by cirez.d 57

as the title says I am stumped on this one.. When the engine is running, note this sound I hear is only present when hvac is on, and does not exist when hvac is off..recently, I opened the cap on the expansion tank to check the coolant level, could be a bubble in cooling system, do you have to bleed the system each time you take off the cap to check coolant? any help will be appreciated thanks.

No, you don't bleed when you're just checking the level...but I always make sure that I lubricate both ET cap and inside ET fitting with coolant...makes cap go on much easier.

On the AC...a few possibilities. One is that the belt is old and dried out and that your car doesn't like it. Another is that either the compressor bearing (and I believe that's replaceable by itself...but not sure) or the AC tensioner pulley is heading south.

Take a hose about 4' long, stick one end in ear and the other around things carefully while car is running with AC on...you might very well be able to isolate the specific source of the sound...even though they're next to one another...just watch out for moving things!

HTH

Doug

Originally Posted by dmax

No, you don't bleed when you're just checking the level...but I always make sure that I lubricate both ET cap and inside ET fitting with coolant...makes cap go on much easier.

On the AC...a few possibilities. One is that the belt is old and dried out and that your car doesn't like it. Another is that either the compressor bearing (and I believe that's replaceable by itself...but not sure) or the AC tensioner pulley is heading south.

Take a hose about 4' long, stick one end in ear and the other around things carefully while car is running with AC on...you might very well be able to isolate the specific source of the sound...even though they're next to one another...just watch out for moving things!

HTH

Doug

Thanks for the quick reply. I know the sound I am hearing is not the bearing or tensioner...in my first post i for to explain exactly where this intermittent thump you can call it is coming from...ive attached an image, and it is the part directly under the MAF, to the Right-center of image. I felt the hose coming out of this unit and sure enough i could feel pressure about every second or so, occasionally i can feel the thump in the break pedal while depressed Again any help would be appreciated, thanks.

anyone?

... the pic doesn't display for me.