Cold engine rattle

[Pardue]

I have noticed my car sounds horrible until it warms up. When I start the car and the idle drops the engine sounds like it is rattling/knocking until it warms up. When the engine warms up it sounds fine. Any idea what might be causing this? The noise is only present WHEN THE CAR IS WARMING UP. Thanks in advance for any help.

 

[Tbone]

We have a noisy valvetrain as it is. Cold seems to amplify that problem. Try a thicker oil. If youre running 20w try 30w.

 

[Pardue]

I am currently running 5w30 but it's probably dino oil from the dealership I bought the car at. Could this be the problem since it's not synthetic or synthetic blend? Could it be a pulley or tensioner bearing causing the noise since it only does it when the engine is cold?

 

[19COBRA93]

Since you just bought the car and don't know its history, I'd change the oil. You don't know what (or if) they put in it, so you should change it out with some good stuff.

 

[Pardue]

Since you just bought the car and don't know its history, I'd change the oil. You don't know what (or if) they put in it, so you should change it out with some good stuff.

I am doing that this weekend for sure. Thinking about Castrol Full Syn 5w20 with Mobil 1 filter.

 

[SeVeReDiStOrTiOn]

Mine does it also so did my LS1...probably just a little piston slap. I wouldn't worry about it.

 

[Fullboogie]

If you've got enough piston to wall clearance to cause "rattling/knocking" for several minutes until it's warmed up, you've got a problem that ain't going to be cured by different weight oil. You may want to do a leakdown test.

 

[Marc s]

If you've got enough piston to wall clearance to cause "rattling/knocking" for several minutes until it's warmed up, you've got a problem that ain't going to be cured by different weight oil. You may want to do a leakdown test.

Very true. My car has .0045 piston to wall clearance and has zero piston noise when cold.

 

[Pardue]

If you've got enough piston to wall clearance to cause "rattling/knocking" for several minutes until it's warmed up, you've got a problem that ain't going to be cured by different weight oil. You may want to do a leakdown test.

I don't think it's on the botom end, it sounds more like valvetrain noise.

 

[08stang]

i have always noticed more valvetrain noise when starting up on cold days when the motor warms up it subsides, cars done it since it left the show room floor so never worried about it try a 5 w 30 oil seems to help a little with my car.

 

[Pardue]

i have always noticed more valvetrain noise when starting up on cold days when the motor warms up it subsides, cars done it since it left the show room floor so never worried about it try a 5 w 30 oil seems to help a little with my car.

That sucks but maybe I will just live with it for now. I did notice the noise is louder around the tensioner and the pulley above the tensioner. Maybe those are causing the noise.

 

[frank s]

Old-fashioned mechanics used stethoscopes to locate automotive noises. If you don't have a stethoscope, just about any hollow tube and some solid rods work pretty well. Stick one end right at the entrance to your auditory canal and the other against hard, stationary parts of your car. Be careful of rotating parts. You'll be delighted at how well these things channel sound into your hearing apparatus.

I have used lengths of rubber tubing for this purpose, but my favorite is the tubular steel handle for a bottle jack I bought in about 1961.

Once you've found the origin of your noise you'll be better able to deal with it. Then you can loan your stethoscope to your friend so he can discover a cure for the squeak in his rear end (let him get in the trunk while you drive).

 

[BAKnBLK2010]

If you've got enough piston to wall clearance to cause "rattling/knocking" for several minutes until it's warmed up, you've got a problem that ain't going to be cured by different weight oil. You may want to do a leakdown test.

I must be in trouble then because my 5.0 has had piston slap since day one when cold. 17,000 miles on the clock now and still running strong. Every LS1 I ever owned had cold weather piston slap also and they all had over 100,000 miles when I sold them.

 

[Fullboogie]

Then we have very different definitions of "piston slap". Because I don't know of any healthy engine that rattles pistons when cold.

 

[SeVeReDiStOrTiOn]

Then we have very different definitions of "piston slap". Because I don't know of any healthy engine that rattles pistons when cold.

The LSx and LS based engines are very healthy and most of them do it...some worse than others.

 

[Pardue]

My problem is definitely not piston slap. I am about convinced my problem is related to a bad pulley or tensioner.

 

[Vapour Trails]

There is a known issue with the separator plate contacting the flywheel when the engine isn't up to temperature. It usually occurs from 2-3k rpm. It sounds like a empty tin can rattling. I have the same issue, but it is not a serious problem.

 

[07VistaChicago]

I also had a weird rattle when cold. It was my o2 sensor rattling. It had loosened up after a dyno session.

 

[pos 88 gt]

Have you checked the stick to see how much oil is in it?

Does it make the noise cold at idle or when you are driving?

Are there check engine lights?

If you just purchased the car, take it back and have it inspected. Take a video of it, drop it off in the over night so when they start it, it will be cold.

 

[Sprayin Blue 3V]

My problem is definitely not piston slap. I am about convinced my problem is related to a bad pulley or tensioner.

I don't see how a pulley or tensioner would change sound with temperature? I might be an idiot though lol.

How are you sure its not piston slap? A lot of engines have this problem when cold because the parts haven't expanded like they are when at operating temperature. You see it more with older engines, but if the car was routinely beat before the engine reached operating temperature, this can become more of a permanent thing.