Clicking, ticking, constant with rpms

[Jeremy2994]

Hey guys! I've been chasing this clicking/ ticking noise in my TB for a while now and I've been blaming a small exhaust leak on the manifold or gasket but that doesn't seem to be it anymore.

I've narrowed it down to only happening with the AC on. When I first start the car in the morning and flip on the AC this clicking is very noticeable. But seems to come from the passenger side of the engine (which is why I thought it was an exhaust leak for a long time).

As soon as I turn off the AC the clicking immediately stops! It's not the AC cycling on and off because I know what that sounds like plus I've changed the AC cycling switch the other day just to make sure.

The noise is constant with the rpms and only goes away when the AC is off, bad clutch maybe?

-250k on the odometer
-cleaned throttle body both sides disconnected battery (throtttle body has 100k on it)
-new belt
-new idler pulley
-new tensioner pulley
-new power steering pump
-new water pump
-new fan clutch (AC delco)
All replaced 1k ago

 

[gmcman]

Can you post a vid or soundclip?

 

[Jeremy2994]

I turn the AC off and on a few times in the video and its definitely louder with the AC on, sounds like an exhaust leak but I don't understand why the AC affects it, maybe the extra load?

On the drivers side you can barely hear it. So I didn't film that side.

http://youtu.be/vNWwLyidvjo

 

[coolasice]

Have a helper cover the exhaust pipe when cold, if the sound increases you got a cracked manifold

 

[Sparky]

Just a thought but if it is AC related, it could be noise internal to the AC system caused by the compressor (hence being RPM related) that you're then hearing echo from the dryer (metal can).

Maybe far fetched but I'm trying to think of AC related stuff on that side of the engine bay.

 

[Jeremy2994]

Have a helper cover the exhaust pipe when cold, if the sound increases you got a cracked manifold

Tried that just now no change in noise, still coming from passenger side though.

Just a thought but if it is AC related, it could be noise internal to the AC system caused by the compressor (hence being RPM related) that you're then hearing echo from the dryer (metal can).

Maybe far fetched but I'm trying to think of AC related stuff on that side of the engine bay.

Hmmm the only things around there are the condenser and the line that runs under the radiator I doubt they are causing that noise.

I can't wrap my head around this but it sounds like the exhaust

 

[coolasice]

take the serpentine belt off and start the engine... if the ticking is still there it is not accessory related...

 

[BlazingTrails]

It's an exhaust leak, the reason it is affected by the A/C is because it idles 100 rpm higher. another way to tell is next time you are driving do a WOT pull to get the manifold really hot, then pull over and see if it stopped. When the manifold gets hot it expands and usually temporarily seals the leak until it cool down slightly. It is likely a hairline crack in the manifold. I have had 2 manifolds crack on my truck. Also look for any missing studs on the manifold.

 

[Jeremy2994]

Took the belt off and ran it, difference definitely not accessory related seeing as I replaced most of them.

Exhaust leak it is I believe, I'll pull the exhaust mani off on the weekend and take a look at it. The bolts are all there I can count 11 of them.

 

[Sparky]

It's an exhaust leak, the reason it is affected by the A/C is because it idles 100 rpm higher. another way to tell is next time you are driving do a WOT pull to get the manifold really hot, then pull over and see if it stopped. When the manifold gets hot it expands and usually temporarily seals the leak until it cool down slightly. It is likely a hairline crack in the manifold. I have had 2 manifolds crack on my truck. Also look for any missing studs on the manifold.

I did not realize it idles a bit faster with AC on. Makes sense!

 

[gmcman]

Also when the AC is on, the engine is under a higher load, more pressure in the exhaust manifold.

 

[Jeremy2994]

Alright I'll tackle the manifold for sure and let you guys know! Thank you for the help I'll post back results in a few days!