Cold engine knock revisited

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,

-- Todd H.

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")

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.

-- Todd H.

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

Todd H. wrote:

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")

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

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.

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?

-- Todd H.

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

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

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.

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.