Cold engine knock revisited

[Dj Blag]

Has anyone found any new info regarding the cold engine knock on newer
Foresters?
I have been to the dealer twice, left it overnite, and it didn't make the
noise. The dealer told me to come in whenever it makes the noise so they can
check it. It's usually on my way to work-not very convenient, especially
since the school year just started.
I don't blame the dealer. Has anyone contacted Subaru direct about this?
Thanks Group,
Chas Gaffen

 

[Edward Hayes]

Much has been said about cold noise as being the timing belt tensioner.
eddie

 

[Edward Hayes]

It may be a problem "normal" but get it fixed. It's not doing the belt any
good. eddie

 

[Dj Blag]

Eddie, is there a manual or graphic where I can see what is going wrong?
What is it doing to the belt?
Chas

It may be a problem "normal" but get it fixed. It's not doing the belt any
good. eddie

 

[Todd H.]

It may be a problem "normal" but get it fixed. It's not doing the belt any
good. eddie

What I'm saying is that when you have it "fixed" 3 times and the new
tensioner is sometimes noisier than the last, one starts to conclude
that all the tensioners are noisy on startup by design, and no amount
of replacement will improve it.

Do you have a datapoint to contradict this? I.e. does anyone actually
have this engine and not get this ticking during cold start? If so,
then it's worth my time to try to get it replaced a 4th time.

Best Regards,

 

[Bill Putney]

What I'm saying is that when you have it "fixed" 3 times and the new
tensioner is sometimes noisier than the last, one starts to conclude
that all the tensioners are noisy on startup by design, and no amount
of replacement will improve it.

Do you have a datapoint to contradict this? I.e. does anyone actually
have this engine and not get this ticking during cold start? If so,
then it's worth my time to try to get it replaced a 4th time.

Todd - You sure this isn't the piston slap problem?

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

[Todd H.]

Todd - You sure this isn't the piston slap problem?

I guess I'm not.

Does piston slap go away when the vehicle warms?

Piston slap wouldn't explain how this noise semeed to get louder the
last time I complained about it and they replaced the timing belt
tensioner with a new one that was apparently noisier than the previous
one.

But I guess I'm curious about the sound and temperature dependence of
piston slap.

 

[Carl 1 Lucky Texan]

Is the tensioner pumped up like a hydraulic lifter? maybe there is an
oil sludge or other type problem getting the thing to tighten up?

Carl
1 Lucky Texan

 

[Bill Putney]

I guess I'm not.

Does piston slap go away when the vehicle warms?

Piston slap wouldn't explain how this noise semeed to get louder the
last time I complained about it and they replaced the timing belt
tensioner with a new one that was apparently noisier than the previous
one.

But I guess I'm curious about the sound and temperature dependence of
piston slap.

Piston slap does go away as the engine warms.

Do a google search on this newsgroup - there have been a lot of threads
on the piston slap issue.

I was ignoring that you said it seemed louder with one tensioner than
with another one because sometimes we *think* we notice changes like
that when there really was no change - not that *you* would ever do
something like that. 8^)

I just thought I'd mention the piston slap thing because it apparently
is a problem on certain late model engines so that if you weren't aware
of that before now that at least you could either rule it in or out.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

[Dj Blag]

Can someone please describe how the tensioner is laid out, that it would
make noise when cold, AND how is it hydraulic?
Chas

 

[Todd H.]

Can someone please describe how the tensioner is laid out, that it would
make noise when cold, AND how is it hydraulic?

As it was explained to me, the tensioner is hydraulic--oil pressure
evidently provides the pressure on a rock-like arm to tension the
belt. As the pressure spikes with the revolutions of the engine, the
tension spikes a little too, causing the audible ticking until the
tension/pressure is stabilized as the engine warms and the oil becomes
less viscous.

What two metal surfaces are banging together to cause the tick I'm not
certain.

 

[Todd H.]

The tensioner is a self contained unit filled with oil and is spring loaded.
It is completely separate from the engine oil supply. To replace the
tensioner the book says to SLOWLY push the plunger back into the main body.
It appears to be somewhat like a liftgate hydraulic arm. eddie

Good info...

Curious now, what provides the energy to pressurize the oil in the
tensioner? That is, why does this tick noise from the tensioner go
away as things heat up? Is it related to the viscocity of the oil in
the tensioner?

 

[Dj Blag]

Good question Todd, I was going to ask the same thing. In addition, what in
there is causing the sound, and why couldn't Subaru design that flaw out??
chas

 

[Edward Hayes]

The spring supplies the energy just like in a tailgate lift.

 

[Edward Hayes]

Think of a spring loaded shock absorber with oil as the damping medium.
eddie

The spring supplies the energy just like in a tailgate lift.

 

[Dj Blag]

Gotcha, so how does that produce noise? If it is a belt, it sounds like its
rubbing somewhere.
Chas

 

[Edward Hayes]

If air get into the oil then the air takes up oil space and when cold the
air mass gets smaller and the spring can't overcome the extra range needed
to keep the belt tight. As the tensioner/air warms up the air expands and
the belt tightens. eddie

 

[Damon S]

Has anyone found any new info regarding the cold engine knock on newer
Foresters?
I have been to the dealer twice, left it overnite, and it didn't make the
noise. The dealer told me to come in whenever it makes the noise so they can
check it. It's usually on my way to work-not very convenient, especially
since the school year just started.
I don't blame the dealer. Has anyone contacted Subaru direct about this?
Thanks Group,
Chas Gaffen

Mine knocks like a diesel in the morning. I have just over 50,000
miles on it. I took it to the dealer to have a look at it and the
first thing that they wanted to do was change the cam belt tensioner.
I agreed but the noise was just as bad and I came back a week later to
discuss this further with the dealer. As luck would have it, the
representative from Subaru was there and he listened to it and said
that it was, in fact, the worst that he has ever heard. He explained
to me that the problem was that they used slightly undersized pistons
and the knock that you hear is the fact that they are rattling around
in there until the engine is good and warm and things have expanded a
bit.
The solution for subaru is to replace the Piston's with slightly
oversized ones. the solution for my baby is to replace the motor
since the motor is still relatively new. If this is a problem and
I assume it is, then tell them you would like to have this fixed ASAP.
The rep told me that this is not what the motor is supposed to sound
like cold or hot.
Good Luck.

 

[Mike B.]

Just came back from the dealer (11-7). Changed the TB tensioner.. NOPE... still
ticks. Says he fixed one noise, still has the tap. The dealer highly suggests I
come back and have all 4 pistons replaced under warranty! But before I hit 60K.
Currently at 51600. Says it will take 2 days. Looking over Christmas
holidays. They changed all belts (timing, air and PS) for $86 out of pocket.
They replaced the TB tensioner.
Also fixed my BLINKING AT HOT TEMP light. Was the trans locking switch. Again
under warranty.