Engine knocking loud when cold??

[built54]

So it's been down in the 40's lately here and when I'm driving my car right after firing it up, around 2-3000rpm the engine just hammers, sounds like rods knocking or really bad piston slap? As soon as it gets up to operating temperature it goes away, it made this same noise during the summer but not nearly as bad. Anyone else hear of this or am I the first to have this type of problem? If its just worn out I want to rebuild it b4 I blow it up so I don't chance tearing the block and heads up...

 

[cobra916]

you might want to try..holding the gas peddle down all the way and turn key..car will not fire up but it will turn over..let it get a few turns (oil pumping) then let go of the gas and car should fire up..hope that helps

 

[04Mach1Blurr]

let it warm up before you drive it. I always waited till after the temp needle was a couple bars over cold heading to normal temp. If it is making the knocking sound still after its warmed up. Start looking for rebuild shops

 

[Semtex]

So it's been down in the 40's lately here and when I'm driving my car right after firing it up, around 2-3000rpm the engine just hammers, sounds like rods knocking or really bad piston slap? As soon as it gets up to operating temperature it goes away, it made this same noise during the summer but not nearly as bad. Anyone else hear of this or am I the first to have this type of problem? If its just worn out I want to rebuild it b4 I blow it up so I don't chance tearing the block and heads up...

I had the same thing, but it was an 06 CLK 55 AMG Mercedes. I swear I thought it would throw a rod on some days. I took it to the dealer and they put "sea foam" thought it swearing it was carbon build up. I thought they were somkin something funny when they said they were going to do that... it was under warrenty so WTF. They did and it stopped for about 15K miles, then slowly came back again.

 

[built54]

you might want to try..holding the gas peddle down all the way and turn key..car will not fire up but it will turn over..let it get a few turns (oil pumping) then let go of the gas and car should fire up..hope that helps

It's not when it first fires up, it's while drivin. Does it even if I let it warm up for about 10 minutes. But once it's up to operating temp it's completely gone

 

[4v_mach1]

meh, i hope my car never goes through this issue, but at certain rpms around 3000 ish my car has this rattling sound...i hope its not detonation or some sort of engine knock.

 

[fast ford brian]

What weight oil are you using ? You might switch to a lighter weight for the winter months , I do with my diesel.

 

[built54]

What weight oil are you using ? You might switch to a lighter weight for the winter months , I do with my diesel.

Always run 5w20....

 

[built54]

meh, i hope my car never goes through this issue, but at certain rpms around 3000 ish my car has this rattling sound...i hope its not detonation or some sort of engine knock.

That's exactly what mine does...

 

[LS2GTO]

Sounds like piston slap, it's about the only 'knocking' noise that completely goes away when warmed up.

Rod knock or a spun rod bering(s) will be there all the time no matter what the engine temperature. If you were knocking real bad from detonation it would always be there and would not be affected by engine temperature. Though to be knocking that bad from purely detonation is kinda rare unless you have very bad gas. But then again, that would all go away with some good gas.

My vote is for piston slap, try some heavier oil especially cold, meaning 10w or something that like.

 

[4v_mach1]

You sure its not the throw out bearing? when the car is cold press the clutch in and see if the sound goes away. My old clutch/tob had this issue.. i could post a video if you want.

 

[built54]

It's gotta be piston slap... It's not the throw out bearing for sure

 

[2007ShelbyCobra]

my car did this as well, went away 95% when its warm. I always let it warm up before i drive it

 

[4.6mustang5.0]

my cobra does the same thing, i usually start it go inside for a few minutes then come back out and leave

you just got to allow some time for the piston to expand so the rings can fully seat against the wall to eliminate the piston slap

 

[Honu's Cobra]

It's gotta be piston slap... It's not the throw out bearing for sure

piston slap due to what? a good friend of mine's Mach is also doing the same thing only his noise never goes away.So what causes the piston slap.:shrug: