Technical Can anyone tell me please, what is this Sound?

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Technical Can anyone tell me please, what is this Sound?

borhan0089

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This is a YouTube link for my Fiat Stilo 1.6 16V 2002.


[ame]https://youtu.be/IMEEcAYPtGk[/ame]

The engine has this sound, Is it because of the valves?
Can be fixed easily?
Thanks in advance
 
This is a YouTube link for my Fiat Stilo 1.6 16V 2002.


https://youtu.be/IMEEcAYPtGk

The engine has this sound, Is it because of the valves?
Can be fixed easily?
Thanks in advance

That definitely sounds like the top-end.

I don't know whether the 1.6 engine has hydraulic tappets or a cam variator but I would check those.

Does the sound disappear when you rev it slightly or does it get noisier?


Ralf S.
 
the 1.6 16v has hydraulic bucket tappets between the overhead cam and the valves

1488783690_8b5ebda028b92002e15822cccd7927f7c9c3ae4e.jpg


No cam variator.

It sounds like an unpressurised tappet (failed tappet seals, blocked pinhole oil pathway into the tappet, low oil pressure).

You might be able to hear exactly which pot & whether exhaust/inlet valve by using a stethoscope (or a metal rod against your ear and the other end on the cam covers in various places (obviously...be careful).

If you take the cam housings off to inspect/change tappets, you'll need a cam locking kit, and Ribe sockets/bits (8 and 10 for cam housings? Head bolts are 12? can't remember)
 
It's your timing belt adjuster... it's either the belt that is weak or the adjuster needs to be changed
 
It's your timing belt adjuster... it's either the belt that is weak or the adjuster needs to be changed

so are you saying the sound is a piston hitting a valve, caused by the timing being out because of slack belt?

I don't think the sound can directly be the pre-tensioner, the sound is regular and only on one cylinder. The pre-tensioner is cylinder-agnostic imo.
 
No. Not the timing belt. When the adjuster is weak it gives that sound. That's my personal experience
 
but you can't explain why it makes that sound? Why it only occurs on one stroke of one cylinder, when forces on the pre-tensioner are the same from each cylinder?
 
If the tensioner has partly lost adjustment then that would weaken the spring pressure on the belt.. (you can check by confirming whether the tensioner pointer is still pointing at the reference hole) but you only need the correct spring tension to make sure the belt isn't able to jump off the pulley (which would very likely wreck your valves, not just cause them to "tap" the pistons) so I don't think it's the tensioner in this case.

The car has hydraulic tappets. A hydraulic tappet is a cup with a plate that's fitted into it (and which is able to move in and out), held under a small tension via a spring and a ball bearing. The plate has a pimple on it that sits on the cam lobe. The plate is held in the cup by nothing more than a "pinch" on the open end of the cup.

The tappet fits into an apperture in the head, above the valve, with the plate/pimple resting on the valve and the top/flat face facing the camshaft lobes. The tappet can rotate in the apperture and this allows wear/force to even out.

When the tappet apperture fills with oil, oil enters and fills the tappet cup via a small hole in the side. When the cam lobe acts on the tappet face, it presses the cup downwards. The plate is consequently pressed onto the valve.

This squeezes the spring inside the tappet and the oil in the cup is forced out of the hole... but since the hole is tiny, the oil flow outwards creates a resistance to the force of the cam lobe on the tappet and it doesn't all get squeezed out.

As the tappet face and the plate pimple wear (the tappet becomes microscopically shorter), the spring moves the plate outwards so that the tappet "length" stays constant.

So it's acting like a mini "valve".. keeping a constant length despite wear, or the operating pressure from the cam lobe.

There's a few things that can go wrong. If the oil hole is partially blocked, the oil can't get back into the tappet after it's been squeezed out slightly (under pressure from the cam lobe). Note there is nothing "forcing" the oil back into the tappet.

If the plate becomes jammed inside the cup, then the tappet can't adjust itself to compensate for wear to the pimple or the face. Similarly, if the tappet plate reaches the "pinch" at the end of the cup (e.g. maximum wear) then it can't travel out any more, so the tappet becomes technically too short.

In extreme cases the cup can jam in the cylinder head (so it can no longer rotate) and so the wear is concentrated in one spot.. it's unlikely the plate will also not jam inside the cup and so you again get the symptom of a short tappet.

A short tappet acts like a badly adjusted tappet in the old days of cam-followers (or more analagously) valve shims.. and as my old mechanic used to say "Knock Knock; camshaft, Tap Tap; tappet".



Ralf S.
 
but you can't explain why it makes that sound? Why it only occurs on one stroke of one cylinder, when forces on the pre-tensioner are the same from each cylinder?

Well I'll of this, especially if the noise is worse on start-up and a cold engine and reduces when the engine gets warm and the RPM is increased.

Your timing belt tensioner is most probably a dynamic one. By this I mean it is sprung loaded and when set then it "floats" on it's spring tension. When correctly set the tensioner should be in "the middle of it's permitted float range".

If set incorrectly, or the locking bolt has slipped or the belt has stretch (or shrunk) then the tension static float position will not be central and will be nearer the hard end stops of the float range.

The tensioner works / runs on the slack side of the belt and at lower engine RPM or rough/cold running will move around quite a bit.

The sound you are hearing is the mechanical "clack" noise made when the tension hits the hard end stops.

It would be my advice to get this sorted sooner than later because if the tensioner fails (e.g. some have a composite/plastic toothed wheel as opposed to a metal one) then the cam belt will fall off or slip and you will be in for a big bill.
 
s130, yes I understand how it could make noise, but I don't see why it would only make noise on a a regular frequency at 1/4 of the rev frequency. Would you not expect some irregularity to the noise?

However, checking the tensioner is probably the easiest thing to check, just needs the top half of the cam cover removing iirc
 
Thank you friends..
Two mechanicals said, that this sound is because of the crankshaft and its bearings.
Do you advise me to change the crankshaft with new bearings?
Or a used Motor block?
My fiat has 165000 KM
I found a motor block which has 225000 KM.
What do you think?
I am not sure what to do.
Best regards,
 
i think you need a stethoscope or long metal rod in order to listen at different points on the engine. Crankshaft noise will be at the bottom, tappets near the top, tensioner on the cambelt side. Where is the noise loudest?
 
i think you need a stethoscope or long metal rod in order to listen at different points on the engine. Crankshaft noise will be at the bottom, tappets near the top, tensioner on the cambelt side. Where is the noise loudest?

Hello friend,
Thank you for your replay.
As I saw, the two mechanicals disconnected the water pump and the Generator,
The noise is exactly at the bottom of the engine.
 
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