Scraping/Squeeling Noise in Engine
 

I replaced my resistor plugs with platinums, but it took awhile to get the last one out and replaced. I drove it for a day with 7 new and 1 old plug. Idle was not as smooth but not too rough.

Now with all new plugs, I hear an ugly high pitched scraping noise at start up. I immediately shut the car down and have not touched her since. It's a W126 with 163K and what I suspect to be an original chain. My search of the site seems to indicate timing chain and/or tensioner. I'd appreciate any input.

How long did the noise last? Just curious. You should certainly have the chain checked for stretch before driving it although it could be a failed tensioner too. Try the search engine. There a lot of posts on this subject by pros. I believe that replacing the tensioner can help a little but a badly stretched chain should be replaced immediately.

The noise lasted the full 30 seconds before I shut her down. I'm having her flat bedded to the mechanic in the am to check out tensioner and chain. It's the most unnerving sound I've ever heard from an engine. I don't even want to start it again until I get this fixed.
Thanks Bill.

it could actually be your air pump. there is a plug for it on the right hand side of the front wheel well, disconnect it and try the car again, if there is no noise then your air pump is shot. I would pull your passenger side valve cover forst to check your chain and tensioner. If it is the the air pump just keep it disconnected till you get to your mech then decide if it is worth the fix.

Thanks!
Isn't the air pump connected to the belt system? Could it be seizing and dragging the belt? Also, is there any obvious visual clue that the tensioner is worn?

The air pump has a clutch that engages the air pump when the car is first started up to pump air in to the emmisions system. You are indeed correct it is attached to the belt system. Disconnecting the plug will disengage the air pump clutch and so it will be disengaged and should not engage the pump unless the clutch itself is trashed.
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