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  #1  
Old 05-26-2003, 01:11 PM
aly
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Unhappy chain slack

hey it's me again...i finally finished installing the chain on my 4.5 V8, and i installed the rails and tensioner and all, i crancked the engine by hand CW and everythng seems ok, but when i cranck it CCw the chain slcks to the extent that i can pull it off the distributer gear...is this normal?
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  #2  
Old 05-26-2003, 01:32 PM
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Why would you turn the engine counter clockwise? If you were able to turn it clockwise through at least two complete revolutions you should be good to go.

If you haven't fired up the engine since the chain and tensioner replacement, the tensioner hasn't pumped up and only the spring tension of the tensioner is supporting the chain.

Roll it over clockwise through two complete revolutions yet again, to be sure you haven't messed with the cam timing. If all goes well, put it back together and fire it up.
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  #3  
Old 05-26-2003, 01:44 PM
aly
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thanks i did crank over two revs, and it looks ok, the timing took me a while to get right but it's good now. how does the tensioner work exactley?
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Old 05-26-2003, 01:55 PM
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I can't tell you how it works "exactly", but I'll give you a general how it does.

The push rod on the tensioner contacts the tensioning rail, pushing the chain toward center, in effect removing any slack. When the engine is run, the oil, which is now under pressure, enters the tensioner at pressure, further tightening the chain. There should be a check valve inside the tensioner which will keep the push rod extended even when the engine isn't being run, so the chain is properly tensioned at the next start-up. As the tensioner gets old, the check valve leaks down, and that main spring you had to work so hard to compress (to install the new tensioner) gets weak. Lack of retained oil pressure and that weak spring cause chain rattle at start-up, continued chain rattle can cause a chain failure resulting in several thousand dollars of damage.

Again, roll it over through two complete revolutions before you do anything (I'm a little OCD when it comes to hand cranking, I'll go four complete revs - on the 560 I did six, only to learn it takes six and half to make the chain complete one revolution). If the timing has somehow gotten off, you will eat valves on your first attempt to start.
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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.
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  #5  
Old 05-26-2003, 02:22 PM
aly
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will do ! thanks a lot for your help
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