Something under the hood clatters on cold startup

[Howard]

2005 CTS with the 2.8L engine

Could the timing chain be bad? Or is it because I was previously running low on engine oil?

 

[Vette73]

How low was the oil? and for how long?

Does it go away completly when warm?

 

[Howard]

Yes, I'm pretty sure it goes away when warm.

I had to put in about a quart and a half... I must've not checked the oil for 3 weeks? 4 weeks? It was OK back then.

 

[alfa147x]

Does it sound like a stereotypical diesel engine?

 

[Saga]

Huh. Odd. Same thing happened to the truck last week, turned out something in my exhaust was expanding on a cold start and rattling. I could have swore it sounded like an exhaust mount from the front rattling (like a weld had broke) but it always went away as soon as the truck warmed for a minute or less.

Replaced the problem muffler and problem gone.

 

[LTC8K6]

Losing 1.5qts of oil in a month would concern me.

The rattle could be a loose heat shield somewhere that gets tight again when it heats up.

 

[woodie1]

Could be piston slap. How many miles on the clock?

 

[Howard]

Could be piston slap. How many miles on the clock?

Just under 60k

 

[woodie1]

Just under 60k

Don't know much about the 2005 CTS 2.8L engine but if it uses a lot of oil then there must be some abnormal wear. Are you the original owner? If the noise is mild and clears up quickly I'd not be too worried.

 

[Howard]

Does it sound like a stereotypical diesel engine?

You know, it does sound a little bit like a diesel engine, even warm.

 

[SJP0tato]

1.5 quarts is low, but seems unlikely to cause engine damage unless you're doing long sweeping turns that starve the oil pump pickup. Did adding the 1.5 quarts bring it to the "top" mark on the dipstick? Or just somewhere in the middle?
The total fill capacity is 6 quarts right? There's a big difference between 1.5 quarts on a tiny import with total capacity of 3.5 quarts vs yours with 6.

Best thing to do would be to have the hood up, start the car when cold, and see if you can isolate where the noise is coming from. Get one of these:
http://www.harborfreight.com/mechanics-stethoscope-41966.html
or at least a long handled screwdriver if you can't discern where it's coming from in a particular area.

 

[Howard]

1.5 quarts is low, but seems unlikely to cause engine damage unless you're doing long sweeping turns that starve the oil pump pickup. Did adding the 1.5 quarts bring it to the "top" mark on the dipstick? Or just somewhere in the middle?
The total fill capacity is 6 quarts right? There's a big difference between 1.5 quarts on a tiny import with total capacity of 3.5 quarts vs yours with 6.

This engine takes 5 quarts.

 

[angry hampster]

Probably just a little cold start valve tick. Quite a few GM engines from that era show it. The Atlas 4200 in the Trailblazer is notorious for it.

 

[SparkyJJO]

My 98 Camaro V6 has a little clatter when I start it. Has done that since I've had it, mechanic said not to worry, I've put 34k on it since last April alone and have had zero issues, so it doesn't bother me. Car has 154k on it now.

You shouldn't be using that much oil however, heck at 60k you shouldn't be using any. My 12 year old Camaro with 154k on it doesn't use any, it has a small leak around the pan gasket but it doesn't lose even half a quart between oil changes (every 2 months or so). Something's wrong there.

 

[WhoBeDaPlaya]

Mine had some too (06 Lincoln LS) in sub-freezing temps (-30F). Turns out there was a TSB for the accessory belt pulley. Replaced it under the B2B warranty and all's well.

 

[Howard]

Man, my car is burning a liter of oil a month, looks like. This is ridiculous.

 

[LTC8K6]

Are you sure it's burning it?

 

[DonaldC]

Man, my car is burning a liter of oil a month, looks like. This is ridiculous.

How many miles/month is that?

 

[Howard]

Are you sure it's burning it?

Or it could be leaking. I have no idea right now.

 

[Howard]

How many miles/month is that?

About 1100 miles

 

[Rastus]

Check for exhaust leaks.

 

[Painman]

I'm almost strictly a VW/Audi guy, but their engines sometimes employ cam chain tensioners in the rear of the cylinder heads to vary the valve timing. They can pump down while the engine is sitting, causing those rear cam chains to go slack, then whip up and hit the valve covers on a cold start.

If the top of the engine has been starved for oil, and the engine employs devices like this, I could see a similar scenario happening.

 

[Howard]

I'm almost strictly a VW/Audi guy, but their engines

Whose? VW or GM?

 

[Howard]

http://www.cadillacforums.com/forum...489-timing-failure-top-end-rebuild-fully.html

http://www.cadillacforums.com/forum...03/205555-engine-burning-oil.html#post2339308

d'oh