pshhhhhhhhhhhhht sound

[snmazer]

I own a 2003 H2, and lately, while driving, I hear a "pshhhhhhht" sound, which I think is coming from under the hood on the passenger side. Ususally it lasts for about 2-3 seconds the first time, right after start up, then it will do it a few more times while driving, decreasing in length each time.
Anyone else here experience that or any ideas what may be the problem?
Thanks
Scott

[Easy Ed]

Just a thought here but have you checked the exhaust manifold bolts on that side ? It is a common problem for either side to have the head of the bolts to "pop" off and while the engine is cold you may hear a exhaust leak till it warms up.

Worth a look.

Ed

[Hellz]

im guessing it is something with the AC unit.

i hear the same thing from time to time. got to figure right behind/below the glove box is some parts of the AC unit.

maybe some others can post exactly whats back there..

[snmazer]

It does only seam to happen when the engine is "cold". It is about 60 degrees here, but I didn't drive my Hummer for about 20 hours. It made the pshhhhhhhhhhhhht sound about 4-5 times. Immediately after start up, then tapered off as I drove. Ther were about 2-5 minute intervals in between the annoying sound. It seems like it quits after the engine is warm.
If it were an exhauste leak would it be a continuous sound though?
As far as the AC, I haven't used it at all since last summer, not sure if that matters or not.
Thank you so far for the replys, and if anyone else has any ideas please post them.
Scott

[Olfart]

Originally Posted by snmazer

It does only seam to happen when the engine is "cold". It is about 60 degrees here, but I didn't drive my Hummer for about 20 hours. It made the pshhhhhhhhhhhhht sound about 4-5 times. Immediately after start up, then tapered off as I drove. Ther were about 2-5 minute intervals in between the annoying sound. It seems like it quits after the engine is warm.
If it were an exhauste leak would it be a continuous sound though?
As far as the AC, I haven't used it at all since last summer, not sure if that matters or not.
Thank you so far for the replys, and if anyone else has any ideas please post them.
Scott

As the engine heats up the exhaust manifold expands and might be sealing the leak if you have broken bolts. I had 2 broken bolts replaced about 6 mo ago. Luckily it was under warranty because they had to pull the heads to get to the bolts to extract them. And yes I did have a hissing sound when engine was cold.
BTW...it's a good idea to run your AC for a few minutes even during the winter so the seals in the compressor don't take a set and possibly start to leak

[snmazer]

Hellz I believe you are correct that it is a ac issue. The other day I turned on my ac and it started making that noise....turned ac off...noise stopped. Any idea why it is doing that, or what needs to be replaced? Also, can I just disconnect or pull a fuse to the ac altogether? I live in wisconsin right on the lake so we usually only have 1 day a year that you would need to use the ac anyway!
Thanks to all that have offered their ideas so far
Scott

[HUMTECH]

#PI01139C: AC Compressor Belt or Tensioner Jumps or Flutters - kw noise rattle information part vibration performance warm cold HVAC - (May 7, 2004)

Subject:AC Compressor Belt or Tensioner Jumps or Flutters

Models:.

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.
Customers may have a concern of hearing a rattle noise under the hood on acceleration. The A/C system might exhibit liquid slugging and deforming the retainer gasket. The retainer gasket deforms, the discharge reed is allowed to flex too far and ultimately the reed fractures. To correct this condition, replace the compressor. For 2002 CK Pickup use P/N 15106396 and Utilities (Dual system) P/N 15169965. For 2003 CK Pickup and H2 (Single system) use P/N15100337, CK Utilities (Dual system) P/N 15100338, CK Pickup (LB7 Diesel) P/N 15100340, CK Pickup (LU3 V6) P/N15100340.
Please Note: The compressor you receive will be pre-filled with oil. It will be necessary to drain the oil from the new compressor, and add the correct amount according to the "Compressor Oil Balancing" procedure in SI, example SI doc id 861833.

[snmazer]

Humtech, if I understand your post, the correct fix would be to replace the ac compressor? Am I able to just remoce or disable the ac without affecting the operation of the vehicle? I never use the ac anyway.
Thanks
Scott

[HUMTECH]

could just take the ac belt off but the hvac system uses the ac compressor in defrost mode as well to help dry the air for better windshield clearing