Name this rattle - 2011 SHO non-PP

[jchaase]

See link:

Symptoms: rattle noise when at idle in park or when in drive and stopped. Anything over about 900 RPM it's gone, but when idling (as is in the garage when I took this video), A/C on, rear defog on, heat seaters on - it makes this noise. It's not necessarily the A/C, as I can get it to reproduce with the climate off - in this video it stops because the compressor cycles and changes engine speed. A little goose of the throttle when it starts the noise will also get it to stop temporarily.

Replaced my belt about 1,000 miles ago... really don't want to dig around in that area any more if I can help it, but I think I may need to. Tensioner? Interested in thoughts!

 

[SHOrod]

Since you live in Minnesota where salt is used on the roads in the winter, the first thing I'd be looking at are the various head shields on the exhaust. Catalytic converter heat shields are pretty well known to rust loose and rattle at idle. Some people rip them off when that happens, but I don't recommend that. A better solution is a really large worm-drive clamp (think REALLY large hose clamp). Many of the hardware and farm supply stores sell them.

If you have a set of ramps or a jack and jackstands, raise the car then use a long screwdriver / stick, etc. to place tension on the various heat shields to determine if that's the case and if so, which one or ones.

-Rod

 

[jchaase]

So the good news is that I've narrowed it down. It's not the heat shields - they actually already each had bands around them that look factory.

New video from underneath:

It occurs when the engine is warm around 800-900 RPM and only when the A/C compressor is running. Idling at a stop light with foot on brake, trans in drive, A/C on is the best way to replicate. The belt tensioner is bouncing around A LOT when the compressor activates, so I'm wondering if the extra strain when that runs is killing the tensioner or the pulley in it has bad bearings or whatever... I can't imagine it'd be the A/C compressor if it only makes noise at a certain speed and works flawlessly for cooling performance otherwise and isn't leaking. But in rewatching this video, the tensioner moves even when the compressor is not engaged. So maybe it is the A/C compressor. That's not good.

Regardless - when I replaced the belt I told myself there's no way in **** I'd be doing that tensioner (I even ordered it and have it in the garage, but not going to do it)... looks like it's time to go to the shop.

Input welcome!

 

[SHOrod]

I installed a new tensioner on my EB MKS when I had the inner fender liner out to replace the PTU and it really wasn't terrible to do. It did require some patience, faith in the jackstands, and small hands though. But if you don't mind spending the money, letting a shop replace it will save you a headache and probably a few sore/stiff muscles.

-Rod

 

[jchaase]

Update... SHO is at the shop. They removed belt and confirmed it's at least something in the belt drive and not the engine. They suspect tensioner. They are replacing it along with the belt and we shall see.

More to come!

 

[jchaase]

It was the tensioner. New belt and tensioner, $260 parts/labor, done.

 

[David Klopper]

@jchaase great that you sorted it out. Do you have the part numbers you used?