2005 Tahoe 5.3 Intake Question

[blk00ss]

Can someone tell me what the line is at the front of the intake manifold that has what appears to be a green cap on it? Almost looks like some sort of bleed off area. I noticed last night on my wife's Tahoe that we're getting a noise (sounds kind of like a miss), tick noise and it seems to be coming from that green cap area. The noise changes if you place pressure around it.

 

[Jeff M]

The line that I think you are referring to is part of the EVAP system, that line is attached to a solenoid valve located on top of the intake which opens and closes to allow fuel vapors to be pulled into the intake and mixed with the fresh air for combustion. Are you getting a check engine light? If no lights are on then I suspect everything with that system is fine, it runs a leak diagnostic every time you start the car. I would be looking at the exhaust manifold and bolts, they commonly crack or break causing exhaust leaks, that might be what you are hearing.

 

[blk00ss]

The line that I think you are referring to is part of the EVAP system, that line is attached to a solenoid valve located on top of the intake which opens and closes to allow fuel vapors to be pulled into the intake and mixed with the fresh air for combustion. Are you getting a check engine light? If no lights are on then I suspect everything with that system is fine, it runs a leak diagnostic every time you start the car. I would be looking at the exhaust manifold and bolts, they commonly crack or break causing exhaust leaks, that might be what you are hearing.

The truck makes the noise after idling for a bit. I assumed a bad seal to the intake at that location since it sounded much like when my EGR on my LS1 Camaro wasn't seated well, plus its also located at the front of the intake. I noticed it after fixing the tranny cooling line last night (BTW Thanks for the help). Truck was already warm but once at idle for a few minutes I heard tap tap tap noise and it got better or worse when placing pressure on that green cap thing.

 

[Jeff M]

The valve with the green cap is the EVAP solenoid valve which I believe is normally closed and opens when the solenoid is energized. Maybe the valve is failing and the solenoid cannot hold it open, does it feel like the valve is chattering? That part along with the canister vent are common failure items, I have replaced them both but I have always had the check engine light come on. The valve is only held in place by a single 10mm bolt so it is easy to change...I think I would keep looking before buying the part thought.

 

[blk00ss]

The valve with the green cap is the EVAP solenoid valve which I believe is normally closed and opens when the solenoid is energized. Maybe the valve is failing and the solenoid cannot hold it open, does it feel like the valve is chattering? That part along with the canister vent are common failure items, I have replaced them both but I have always had the check engine light come on. The valve is only held in place by a single 10mm bolt so it is easy to change...I think I would keep looking before buying the part thought.

Funny, the LS1 EGR was held by only 1 10mm bolt also and it seemed to always move around causing a similar suction/ intake tick. I will indeed continue to explore the issue before ordering the part. Thanks for the help on this issue as well.