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JED
 
ARCSinAK's Avatar
 
Join Date: Jul 2009
Location: Hawaiian Islands/SV Idaho
Posts: 1,509
Garage
Tensioner question

Hi Gentleman-
Any thoughts on my situation would be great.
The Engine History: 120K
Top end rebuild 4 K back, Rebuit valves, rings, all seals.
After about a thousand miles noticed a knocking/tapping noise, which seems to match the revs but is less dramatic the higher the revs. I listened with all of the usually diagnostic tools, hardwood Dowel, Metal Bar ect.
Sounds deep, worse at 950 Idle than a 1100 idle. Hard to tell where it's coming from. I have listened to all the available spots, under the case on the timing chain covers ect. My original thought was that the PO may have re-used the rod bolts and the new top end created more compression and thus leading to a possible rod bearing failure. However, the sounds has remained unchanged after another 3K of spirited driving. The engine runs strong and pulls to 6K. The general opinion I have gathered is that if was a rod bearing it would get dramatically worse in a hurry.

Yesterday, I decided to change the oil and has a look at the magnetic sump and tank plugs. Took a drive got up to 180 degrees, drained the oil, inspected the plugs for pieces of metal and metallic residue. Found no shrapnel and minimal residue.

Here where things get interesting, I added ten quarts of 20/50 and started the engine. The flat six was chattering like mad, scarred me, I thought it was done. Shut her down added another quart and started again, the chattering, gradually, over the course of a minute or so backed off to the sound that has been frustrating me. The same underlining old sowing machine style knock that I have been so frustrated by.

Has anyone else experienced a radical chattering sound after a oil change which then subsides? This 80 SC has had the hydraulic tensioner update. Could a tensioner be loosing part of its tension thus creating the noise and then have lost all or most of its tension after the oil was drained? Only to have re-tensioned itself to a partial state again? Strange how after the oil change the sound was so radical and then returned to the same some what tolerable noise.

I would much appreciate your feedback. I plan to order gaskets for the covers and inspect in the near future but it would be nice to have some opinions first.

Thanks and have a fun weekend.

Old 06-26-2015, 03:22 PM
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Join Date: Oct 2008
Location: Nash County, NC.
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Carrera tensioners aren't fail safe, you'll have to drop the muffler, lower the engine to remove the rear sheet metal so you can get to the chain box.
Bruce
Old 06-26-2015, 04:03 PM
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JED
 
ARCSinAK's Avatar
 
Join Date: Jul 2009
Location: Hawaiian Islands/SV Idaho
Posts: 1,509
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Thanks Bruce
I plan to go that route next, but have you ever experience a radical change in engine noises from a oil change? Then to have the sound return to it's previous state?
Old 06-26-2015, 04:16 PM
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No I don't recall that happening but I have witnessed several defective tensioners over the Carrera years but I've never seen one cause timing to jump like the early style tensioners.
Bruce
Old 06-26-2015, 05:28 PM
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JED
 
ARCSinAK's Avatar
 
Join Date: Jul 2009
Location: Hawaiian Islands/SV Idaho
Posts: 1,509
Garage
It was very dramatic and seemed odd that would return to the previuos sound after a minute or so.
Like the tensioner maybe lost tension then regained some back to where it was. If it was even a tensioner? What other parts/systems could be effected by the recirculation of new oil? I checked the oil pressure immediately and it was solid?????

Old 06-26-2015, 06:14 PM
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