Cam chain noise

greg bradbury · 08-21-2006, 12:58 PM

Hi,

I have just completed a rebuild and have installed the "Carerra pressure fed cam chain tensioners" in my 1983 SC. What I now hear is a pretty loud cam chain whurring noise. It's builds up with rpm to be loudest at about 2500 rpm. By about 3200 rpm it quietens down again as other noises take over I suspect. Has anyone else experienced this?

By the way I didn't fit the oil flow reducing valves to the cam oil feed lines as recommended in Waynes' rebuild book. My reasoning was that I had pitted cams that had to be reground so I thought that more oil in this area would be a good thing. Could fitting the oil reduction valves lower the pressure to the tensioners and therefore lower the annoying whurring sound?

Thanks,
Greg

garibaldi · 08-21-2006, 03:45 PM

Hi, yes, I had a similar problem on my 77 911 turbo, and had it once or twice again after that on some cars that had some in for work. If you are getting a noise that sounds like a chain is getting dragged out over the side of a metal garbage can that is faint, and may come and go, then it may likely be the chain tensioner. Some pressure feds can and do go bad, most of the time, as I have seen , it is the check valve on them. Pull the covers off, and pull the tensioner, there is a small tin cap that holds the ball bearing for the check valve in, if that is loose, then its bad. Dont know if that is tried and true, but the bad ones I have pulled out had that tin peice loose. Seems that it can either be faulty manufacture, or when you compress the tensioner to install it, if done too fast it can mess it up. Now would you like the good news???? Take off your oil filter, carefully cut it open to get the filter element out and hack both metal ends off of the cartridge so you can unfold the paper element like a scroll. See how much metal shavings are down in the pleats. If there are any, then I would advise you tear the motor down, pull everything out since all of that debris has passed through the engine, and oiling system, including the pump, coolers crank etc. Its a mess but its best not to leave debris in the engine.

greg bradbury · 08-21-2006, 04:28 PM

The sound is not as harsh as what you describe. It is the sound of the chain going over the ramps. I'm pretty sure about that as it's the same sound that my Moto Guzzi motorcycle did when I put an automatic chain tensioner into it some years back. Because the chain is being held tight against the ramp you get a whurring noise that wasn't there before.

When I pulled out the old tensioners they were pretty stiff and the idler arm was very tight on the bushed shaft. The shaft came good after it was cleaned but I didnt want to put the old tensioners back in as they looked shot.

Also another factor is that I renewed the engine sound pad. I didn't shell out for an original and put in one cut from some pretty light weight material from Clarke rubber. I think I'll try replacing this first.

When I did my oil change at 1000km there was very little swarf on the magnetic sump plugs, so I think the motor is OK, just a bit on the noisey side (annoying but it has never been a quite ride)

garibaldi · 08-21-2006, 04:47 PM

You should not hear any noise of the chain against the ramp, the ramps are plastic, and the normal sound is far overpowered by the rest of the motor. The idler and tensioner will feel stiff and fine by hand, but that doesnt mean squat if the check valve is shot, the tensioner has a very stiff spring in it, so just feeling it by hand wont do. You really should pull the cover and be sure, if it were me. The shavings on the drain plug is common, but that again will tell you nothing, the metal that gets ground away with the bad tensioner being a culprit will yeild aluminum particles, since the chain is rubbing the case. I would at the very least cut the filter open, what is it $12 and a more definitive answer?

greg bradbury · 08-21-2006, 07:45 PM

Unfortunately I threw the filter out in the garbage. I will check further. I thought that Carerra tensioners were supposed to cure all my tensioner ills not cause problems.

garibaldi · 08-22-2006, 06:57 AM

You should take the filter off the car you have on now if it is still making the noise. When mine did the similar thing, it had remnants of aluminum chips in the filter. The carrera tensioners do help, but nothing is totally foolproof, it is a mechanical part, and it can fail, just that its likelyhood is not as high as the original tensioners. It may not be the culprit, I am just saying that I have seen them fail here and there, and when they do, the chain will make a noise in the case as you described.

greg bradbury · 08-22-2006, 12:57 PM

thanks Christian.

hcoles · 08-26-2006, 08:35 AM

my experience on this.
tensioners can have infant mortality or DOA
I like the idea of checking the oil pleats
another thing to do is pull the tensioners, and try slowly compressing the piston with large channel locks...don't push too hard... but you should feel a definate hydraulic lock with a small amount of oil coming out of the "vent".. if you press down and the piston just goes down will little resistance...that may indicate a bad tensioner.
I put the new restrictors in... my 2 cents is that the oil flow rate to the tensioners is very small and supplied upstream of the restrictor...I'm thinking this is not an issue either way... or the change would not have been a phase in.
also you might want to check that all the ramps are the correct ones for the location and are properly installed on the detents/etc.

Also look for wear on the sprockets to see that the chain is running free on the sprockets and not being pushed to one side or the other

others please help if I put incorrect info. here