Hello all- I have recently got an 02' blazer 4x4 LS. This is my 3rd blazer so I am not all new to blazers. This one has 70k on it and has a strange noise coming from under dash that at first sounds like a vacuum leak. After talking w the previous owner ( of ten yrs ) he informed me that it had a faulty flywheel in 2004 and was replaced under warranty and when they put it back together they left of some insulation on the fuel lines that run from engine along firewall and that is where noise is coming from. There is no way to even see in this location without dropping trans or cutting hole in floor in cab. Can anyone tell me if there is insulation in this location or how to fix this issue without dropping trans. Thank you

 

You can find out very easily if the noise is coming from the fuel lines. On 1998 and newer, there is a vacant terminal in the underhood fuse panel, right next to the fuel pump relay. The circuit goes directly to the fuel pump, and is referred to as the "pump prime" terminal. It's used to activate the fuel pump for testing fuel pressure and leakdown, but it will work fine to determine if it's the fuel you're hearing.



Ignition off. Connect one end of a 14ga wire to battery positive. Connect the other end of the wire to the pump prime terminal. Without the engine running, the fuel pressure regulator will be bypassing fuel, so you will hear fuel rushing through it inside the plenum, and in the fuel lines. If that's the noise you're hearing while driving, that's the problem. Rather doubtful that's what you're hearing, but it's worth a try. It's more common to hear coolant circulating through the heater core if/when the coolant level is low.

 

Thank you for your reply - I have found that the noise is for sure a fuel line noise. The fuel lines were obviously bent up against body during transmission re install. I pushed a piece of rubber between body and lines and it quieted it a lot but can't get to the problem spot w/o removing transmission:-(. Any suggestions would be helpful but if you have ever seen where these lines run you know what I am up against.

 

Know exactly what you're up against. Long pry bar and a block of wood against the body for leverage, or drop the trans.