r/Cadillac • u/PuroLavadichi • 1d ago

My car makes this rattling noise whenever it starts up but after like 15 to 20 seconds, it goes away other then that It doesn't have any issues.

8 Upvotes

91% Upvoted

14 comments sorted by

7

u/gargen_state 1d ago

That's an XTS?

I have a 2016 XTS, I had a similar sound on cold starts. The front catalytic convertor where the pipe was welded into the flange that boltsto the cylinder head cracked. When it got warm it would expand and seal.

I put on a new catalytic converter, could.have it welded too.
*

I don't think it will let me attach a pic. Dm me if you are interested.

3

u/Glittering_Clue9920 1d ago

Wouldn’t a cracked bracket not stop rattling no matter now long the car is running though?

3

u/gargen_state 1d ago

Not a small crack, essentially when things get hot they expand and seal the cracks. And then when it cools it contracts enough for the gap to present again.

It doesn't take much to get the exhaust leak sound.

What you can do, start the car with the hood open and place a piece of paper near the flange to pipe joint, just upstream of the oxygen sensor, and watch it flutter. Or use your hand and feel the moving gas. Do not touch the pipe.

4

u/cmcnei24 1d ago

Common issue on XTS. I never fixed mine because i could never find the micro-cuts in the exhaust and the dealership wouldn’t fix it without replacing the catalytic converter which I wasn’t about to do for a bit of noise for 15 seconds.

3

u/IAmLusion 1d ago

That exhaust leak farting its way through a crack?

3

u/dchauss 1d ago

Use smoke w/ a puffer bulb …the cracked area will blow the smoke away- that will get you to general area- then use soapy water or something to narrow down where the crack is and mark it for welding. If not comfortable- find an independent muffler shop to fix it.👍

2

u/Overall_Difference84 1d ago

Mines done the same thing for years.

1

u/Luckyjz711 1d ago

Sounds like lifers to me personally but it could be a number of things.

1

u/Advanced_Alarm_7353 1d ago

Why the hell are you showing us your finger? Smh.

1

u/Impressive_Task_2138 19h ago

Bank 2(front converter when you look down at it) has weld crack/broken at the flange. Replacement or find an exhaust shop to weld it. It can fully fracture causing the converter and that oxygen sensor to hit your cooling fans

1

u/NothingRemote9619 16h ago

I call it the “microwave” sound. Had a 13 XTS that did it for years. Made the car sound like a heap of shit on startup

1

u/hogancheveippoff 14h ago

loose heat shield. as it warms slightly it expands so rattle stops.

get under car, find loose shield (connector prob. rotted).

take a can of pop/beer, cut can so you just have the bottom of can. drill hole in centre of base large enough for volt to go through. reattach heat shield with base of can, it will deform to shape of shield and will remain secure.

spray paint can base black and you won't even see it ;)

1

u/Puzzleheaded-Tea5641 5h ago

The cat at the front of the car cracks at the flange that bolts to the engine. It’s just an exhaust leak

-1

u/tw4200 1d ago

This is more than likely timing chain rattle.

How many kms? When was your last oil change?