M103 rattle when warm

[pull3rb0y]

Hello again,

i have a second problem with my M103......

The car is completly quiet when cold. No knock / clicking or rattle.

But once it gets hot. the car starts the rattle when i put my foot of the gas. it does it while driving as well as in neutral....

Here a Video

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My workshop says it could be a piston slap.... i hope it´s not

Does anybody had such noises or a piston slap in a M103? It seems to come from the manifold / catalytic converter area and goes away as soon as i let the car cool down.

 

[Bellow]

I doubt that it's piston slap as piston slap is worse when an engine is cold and tends to reduce/disappear with increased temperature.

When was the oil last changed? Was it run low? Is it contaminated/diluted with any other fluid eg, coolant or fuel?

It might be valve gear related but to my ears sounds like a big-end problem.

If there's no obvious fuel contamination by visual/smell, analysis of the oil will show its condition and any wear metals which would confirm/refute big end bearing failure and possibly highlight a valve gear problem (if it other than just excessive valve clearance).

 

[optimusprime]

Never known a bad M103 engine .Might be that the heat shield ls loose, or silencer bracket , sound to far back to the rear to be the engine sound . There is a double U shaped bracket on the silencer to gear box they do come loose . What are the exhaust manifold gaskets like ..can you see ant black soot in the area .

 

[pull3rb0y]

Thanks for your answer…
My car gets oil change every year (so far it is around 6000km old)

Never ran low on oil and there is no oil in water. Oil pressure is perfect (cold and hot)

I really hoped there is only a problem with the exhaust or cat.

 

[pull3rb0y]

I will do another video of the cold / warm start and those noises from the engine bay

 

[Bellow]

It might be external eg, heatshield, exhaust etc. If it is generated internally, it should be audible through the oil filler cap when removed.

 

[Bellow]

Is the cat mounted low down? Has it been through deep water recently?

 

[pull3rb0y]

Is the cat mounted low down? Has it been through deep water recently?

what do you mean?
My cat is right after the manifold downwards. you only see a bit of it. between manifold and o2 sensor...

no, the car has not been through deep water....

 

[Bellow]

what do you mean?
My cat is right after the manifold downwards. you only see a bit of it. between manifold and o2 sensor...

no, the car has not been through deep water....

Some cats are under the floor. If submerged in deep water they can contract and crush the internals which then causes a rattle when warm again as the honeycomb internal cannot regain its original dimensions but the outer shell will.

 

[pull3rb0y]

sorry i think i´m little bit dumb...

which of these is the cat? 1 or 2?

this is exactly the exhaust i have.

 

[Bellow]

1. Well above ground level.
Homing in on whether the noise is emanating from within or outwith the engine is the first step here.

 

[Bellow]

Never ran low on oil and there is no oil in water.

Water in the oil is the question. It is possible for water to get to the oil and still have on oil in the water.

 

[pull3rb0y]

Okay.. i should be able to disassemble the cat from the manifold and bend it a little bit away...

 

[Bellow]

Okay.. i should be able to disassemble the cat from the manifold and bend it a little bit away...

Why would you want to do that? Anyway, any attempts at realignment will compromise the seal.
Ascertain what is causing the noise and go from there - unless you've identified the cat as the source?

 

[pull3rb0y]

If I disassemble the cat from the manifold it shouldnt make that noise anymore if it’s from the cat?

Or is there a easier way?

 

[Will]

Doesn’t sound like an engine or cat noise to me.

It sounds like a loose external rattle. I’d remove the poly V-belt and run the engine for a few seconds to see how it sounds. Also check the exhaust brackets, but it doesn’t quite sound like metal on metal to me.

Belt tensioner?

 

[Bellow]

If I disassemble the cat from the manifold it shouldnt make that noise anymore if it’s from the cat?

Or is there a easier way?

All you'll hear is exhaust noise.

 

[pull3rb0y]

i thought ii would be still able to hear the rattle.....

But i will search for loose external things first...

 

[Bellow]

i thought ii would be still able to hear the rattle.....

Not a chance.

But i will search for loose external things first...

Why? An external rattle is an inconvenience. An internal problem could finish off the engine.

If it is generated internally, it should be audible through the oil filler cap when removed.

Or, with the dipstick removed, slip a hose over its tube and hold to your ear (you can operate the throttle directly in the engine bay). If the noise is audible through the hose it's internally generated. If not it's external. Correct diagnosis always trumps wishful thinking.