Grinding or crunching or grinding sound immediately after startup

[gdgiordano]

The noise doesn't seem to be super temperature sensitive. It only happens immediately after cold cranking the engine and during the normal rpm spike to 1800. The belt looks fine and the tensioners have been checked and are super firm.
any ideas? this sound is terrifying. It sounds like a heavy metal object being drug across concrete.

 

[rb142]

My first reaction to that description is that the starter Bendix is hanging up ... which would mean a starter replacement. Try to narrow down the location of the noise.

 

[gdgiordano]

My first reaction to that description is that the starter Bendix is hanging up ... which would mean a starter replacement. Try to narrow down the location of the noise.

Would this happen if the engine had already been running for 1.5-2 seconds?

 

[rb142]

No, it happens right as the engine starts.

There are too may things it could be. You need to isolate where the noise is coming from.

 

[gdgiordano]

No, it happens right as the engine starts.

There are too may things it could be. You need to isolate where the noise is coming from.

How should I do that?

 

[gdgiordano]

I do know it isn't the power steering pump. It was doing it before it was replaced.

 

[2000StreetRod]

camshaft timing chains?

Since you have the SOHC V6 it could be the camshaft timing chains: Timing chain rattle resolution process - SOHC V6

 

[gdgiordano]

Since you have the SOHC V6 it could be the camshaft timing chains: Timing chain rattle resolution process - SOHC V6

I know it's not that. I ran it without the belt on it. All the sound is from the valves.

 

[2000StreetRod]

internal to engine

I know it's not that. I ran it without the belt on it. All the sound is from the valves.

If the sound still happens when the serpentine belt is removed then it is possibly internal to the engine. If it sounds like marbles rattling around inside the engine it is probably the timing chain striking something metal inside the engine.

 

[gdgiordano]

Since you have the SOHC V6 it could be the camshaft timing chains: Timing chain rattle resolution process - SOHC V6

Plus the noise is not sustained. How many camshaft tensioners are there? Is it a noise that would only sometimes occur and immediately go away?

 

[gdgiordano]

If the sound still happens when the serpentine belt is removed then it is possibly internal to the engine. If it sounds like marbles rattling around inside the engine it is probably the timing chain striking something metal inside the engine.

Nah it's the clicking that I think is normal from the valves. Using the stethoscope down low and the midsection of the motor is silent.

 

[gdgiordano]

Are those two camshaft tensioners replaceable while the motor is in?

 

[2000StreetRod]

thread answers many questions

The thread I posted a link to will answer many of your questions.

 

[gdgiordano]

The thread I posted a link to will answer many of your questions.

I looked at those. I feel like it is a VERY heavy sound. definitely a LOT bigger than marbles. maybe a marble being crushed by a 2 ton led brick. I definitely wouldn't call it a rattle. It is a very rough but steady sound that can be felt in the floor boards. My mechanic was able to remove the tensioners at the shop with the help of a lift. They are very solid. It takes a LOT of effort to get them to budge.

Know of any pre oiler kits that a good and easy?

 

[2000StreetRod]

flexplate?

It could be a broken flexplate, a bad rod or main bearing, a broken motor mount, or something in the torque converter or transmission.

 

[2000StreetRod]

pre-oilers

I installed an Accusump but I've decided to install a motorized pre-oiler on my 2003 Centennial. It's still in the planning phase.

 

[gdgiordano]

It could be a broken flexplate, a bad rod or main bearing, a broken motor mount, or something in the torque converter or transmission.

Forgive my ignorance but what main bearing(s), flexplate or rod are you referring to?

I know that the tranny, TC is good.

Wouldn't a motor mount be obvious?

 

[2000StreetRod]

crankshaft bearings

Forgive my ignorance but what main bearing(s), flexplate or rod are you referring to?

The crankshaft main and rod bearings. The flexplate bolts to the crankshaft flange and the torque converter. The harmonic balancer can also make noise when the outer section begins to separate from the inner section.

Wouldn't a motor mount be obvious?

The flexible part can break and not be noticed because the weight of the engine keeps the two parts in contact unless there is enough torque to separate the two.

 

[gdgiordano]

The crankshaft main and rod bearings. The flexplate bolts to the crankshaft flange and the torque converter. The harmonic balancer can also make noise when the outer section begins to separate from the inner section.

The flexible part can break and not be noticed because the weight of the engine keeps the two parts in contact unless there is enough torque to separate the two.

Are those things an issue? Or just a noise?

As for the motor mount, Would that be temperature sensitive?

 

[2000StreetRod]

significant issues

Are those things an issue? Or just a noise?

The least significant to repair would be the harmonic balancer.

As for the motor mount, Would that be temperature sensitive?

Probably not. Although the engine has a tendency to shake more on a cold start than a warm start.