timing chain noise
 

Hi I am new to a 82 911SC . I have had a 68 912 for a couple of years. The 82 911 had been running great with no problems. I changed the oil on Friday evening and on Saturday after 50 miles from the oil change, a clattering noise developed from the engine. The noise is only at lower rpms. The clanking noise suddenly cuts out and the engine runs quiet at higher rpms. The cars runs as normal with no hesitation anywhere. I have check fan and fan belt and the noise seems to be from the left timing chain area. The car has tensioner and pop off valve upgrades. Driving last evening the noise would quit at oil pressure between 2500-3000 Just like a switch being turned off. At lowering rps and oil pressure the noise would reappear. Any suggestions on what to do nest? Need reference to good 911 mechanic in Boston area. Love the 911 and can"t wait to get back on the road

Bill:
First: Do not run the engine!
The tensioner most likely collapsed which shows up during low RPM's with the noise you describe.
To fix you have to open the chain cover, inspect the tensioner and the small oil line feeding it.
Take a picture and post it here.

Second:
Get the Bentley SC Repair Manual to learn more about your SC.

Thanks for the reply Gunter. I will work at removing the tin and getting the cover off. I will not start the engine. The PO kept the Bentley Manual that was in the car when I looked at it. I have called and left a message to see if he still has it other wise I will order it on line. Again thanks for the help.

I have to ask a question of the board at this point. He changed the oil. OK, so for a moment there was no pressure on start up with the new oil (maybe). Or maybe a bit of air got into the oil line going to the tensioner. Would it be possible to bleed that line to see if the tensioner will pump up? does the tensioner bleed itself? I know you have to pre-fill them when installing new. Also, a ramp may have failed.

I'd like to believe there was a reason this occurred when the oil was changed and not a random event.

Milt I tried cracking the oil line open. Thinking on the same lines as you. I made a big mess real fast. Might cracking it ever so slightly have a chance of working. I do think is is somehow related to the oil change. It was the first oil change of the car for me. I use 20-50. Don't know what was in it when I bought it. Just went to the parts house to buy a floor jack and jack stands. I have a bi coastal life at the moment and all tools are with the 912 in California. I need to start learning about the 911 real quick Diving in.

I'm assuming you have the correct amount of oil in there and that you have checked it via the dipstick on level ground at operating temp's?

yes correct amount of oil check running at temp with the dipstick. removing non functioning AC unit to make getting tin off easier. any trick to disabling that

Well, if it's not working, there is probably not much refrigerant in the system. You could do the correct thing and have it vacuumed out or just assume there is so little left that opening the lines won't release much into the atmosphere. When I opened mine nothing came out.

Remember that the oil pressure on the tensioner is a back-up. The spring would have to fail for you to even need the pressure on the tensioner.

Could it be that this is simply a spring that is no longer working and the pressure is only enough to provide tension at hi RPM?

i recall about 1 week ago, maybe 2 weeks, someone posted the exact same problem. Oil change, went for a ride, chain noise on/off at various RPMs.... Im not sure what became of the thread but anyway...seems you are not alone. Maybe search the threads going back a few weeks and speak to the poster about what he found out. good luck

here is the earlier thread... its a 3.2, but anyway - similar scenario
http://forums.pelicanparts.com/showthread.php?t=416411&highlight=timing+chain+noi se