alambert

Hi all. Just getting through a head gasket replacement on my 944s2. I did all new rollers, new timing belt, front main seal, and water pump when getting through it all, but when starting it up for test runs, I’m getting a strange rattle/whir/rub from the belt area. You can hear it from the front of the engine, but when searching around with a hose in my ear, it’s most prominent around the spring tensioner idle pulley (the smooth one, not the toothed). It’s possible it could be sourced from lower but I don’t know what it would be.

See attached video for the noise. Could this be caused by a over-tight cam belt? I have removed the balance shaft idler and and still getting the noise, so I know it’s not that slapping. Any help or ideas would be appreciated.

931guru

Sounds like a bearing going bad. Remove the tensioner and spin the sprocket bearing out of the car. It is probably noisy.

Of course, it could be the water pump bearing or one of the balance shaft idler bearings.

alambert

That’s what I initially thought— so I did pull it all off and replace all the idlers and pulleys. They’re all new, as well as the water pump. But the noise remains. I suppose I could’ve gotten a bad roller? But what’s the likelihood of that

931guru

Just because it is new doesn't mean it is good.

alambert

This is true. I suppose I’ll pull it off and double check. I’d be annoyed if I have to send it off for a warranty replacement but I guess not the end of the world

walfreyydo

Did you replace all the rollers for the balance shaft as well? You can try removing the balance shaft belt and running the car briefly to see if the sound remains. I would also do the same with the accessory belt(s).

Like 931guru said, also check the bearings on the tensioner toothed sprocket pulley as well. Good bearings will spin freely and smoothly without any roughness or "stickyness"

alambert

Yes, I did replace the balance shaft ones too. The new toothed gear and roller seemed to be good when I tested them but could have been bad and just not showing until they warmed up… I’ll try running with the B/S taken off but I dont think the sound is coming from there. My hose in the ear stereoscope got the most pronounced noise from the secondary idler on the tensioner / the block right behind it

alambert

I haven’t had a chance to pull the roller out yet but a hose in the ear makes me 95% confident it’s the tensioner idle roller being bad out of the box. I ordered a new one and will update if that was the culprit once installed

michaelmount123

You asked if a too-tight cam belt will create a noise. The answer is YES.
MM