Pressure fed chain tensioner question

[maurice povey]

Hi
Recently fitted new t/chains and upgrade tensioners.(2.4T in a 914-6). Can pressure fed chain tensioners cause an increase in engine noise?

[boyt911sc]

A failed or collapsed hydraulic tensioners would make a loud rattling noise. Even a new one that was not properly primed would result to abnormally noisy engine. Check the tensioner/s for firmness by compressing it. A good tensioner would require a lot of force to compress the piston. A long rod or screw driver is a good tool to test it in situ.

Tony

[maurice povey]

Hi Tony, thanks for your reply, i had the rattling noise you refer to which led me to replace the old hydraulic tensioners with the later oil pressure fed tensioners, the noise i am now referring to is more of a whining noise (apart from the one coming from the passenger seat!) which seems louder than previously. I know i'm sitting closer to the cam timing chains etc. in a 914-6 than the 911 but the characteristic whine of the 6cyl motor seems louder than normal. I have very good oil pressure and am wondering if this is causing the chains to be running too tight?
Maurice

[Walt Fricke]

Maurice
It is a common misconception that the pressure feeding these tensioners causes the tensioner pressure. It does not. The pressure the tensioner imparts to the idler comes from the stiff spring inside the tensioner.

The oil in the tensioner just serves as a shock absorber, damping what otherwise would be nasty vibrations in the system. The funny little formed metal cap you see sticking out the top of the tensioner body is a pressure relief valve. If the tensioner is full of oil, the rest squirts out the relief. As the tensioner piston moves upward, the pressure on the oil in the main body forces oil into the area under the piston though a one way valve. This stiffens the tensioner in the new piston position. When the idler presses harder down, a little oil squirts out under the top of the piston, and the cycle repeats.

Your noise is coming from somewhere else, or it is normal chain noise (though if you didn't get the chain wheel parallelism right with the shims, that can cause more noise than usual.)

[maurice povey]

Hi Walt
Thanks for your reply and info re-tensioners, very interesting, going on from your explanation it would seem unlikely the tensioners are causing the noise and more like the chain sprocket alignment as you suggest which means engine out in a 914-6 to check, i will take it back to the garage that did the work to see what they say.

Maurice

[Walt Fricke]

Maurice - parallelism was just a guess.

The 911 engine makes all sorts of valve train noises, and they can be hard to pin down. To diagnose by using engineering a guy could use an audio spectrum analyzer, but to my knowledge no one has done this while simulating various causes of noise - combustion knock, too much or too little valve lash (or what it sounds like when just right), and parallelism - including if it is right side or left side which is out of spec, and what the combination of both out sounds like. And rod knock. So we tend to stooge along. Busy shops tend to have a mechanic or two whose ear is well trained, and a stethoscope can help some in isolating the location of a noise.

So your noise might just be normal. Or not.