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  #1  
Old 01-07-2011, 09:17 AM
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m104 timing cover

I have a 1997 e320 HFM-SFI engine
Hate to bring this up again, I have read through most of the posts on the timing cover gasket replacement...I have a question that I cannot find the answer to. I was reading on ALLDATA about the replacement procedure and it said :
  1. Remove guide rail at top (42). NOTE: If the top cued guide rail (42) is taken out of its mounting, the pressure pin in the chain tensioner is moved one detent in the pressure direction. The chain tensioner must be removed to avoid the timing chain being over-tensioned.
So If I remove the top guide rail that is attached to the timing cover, Am I going to have to remove and reset the tensioner?
I have everything disassembled down to removing the bolts on the cover.

Also My son worked for Toyota and he recommended the Toyota black sealant, is this the same as the loctite, since I have a few tubes of it that he gave me. Thanks for any help.
Thanks.

P.S. My Son is in the USAF and just drove his 1979 300sd with aprox. 300k mi. from Atlanta to Phoenix, without any trouble.

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  #2  
Old 01-07-2011, 10:27 AM
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Are you removing the complete cover OR just the upper portion?

Any good grade of RTV sealant will work just fine.

MB's formula is made by Loctite
Attached Files
File Type: pdf M104 remove upper front cover.pdf (174.6 KB, 414 views)
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  #3  
Old 01-07-2011, 11:08 AM
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Once you realize that the tensioner has a one-way ratcheting mechanism inside of it, it will be somewhat obvious when you take it apart on how to put it back in.

One of last things you'll do with this job is to reinstall the tensioner body first, then the internal ratcheting mechanism. Oil pressure will reset the tensioner once the engine is fired up.
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  #4  
Old 01-07-2011, 11:51 AM
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I am just doing the top cover, and the tensioner is in the side of the lower cover, so I was not sure if I should go ahead and remove and reset the tensioner, even though I will be working no where near it..

Thanks for the info!

Last edited by scottessex; 01-07-2011 at 12:08 PM.
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  #5  
Old 01-07-2011, 12:25 PM
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If you're just removing the top cover, I don't see the need to disturb the tensioner.

The only time the tensioner needs to be reset is when the timing chain has gone slack - even momentarily.
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  #6  
Old 01-07-2011, 12:37 PM
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Thanks a bunch, Ill check the tension before I pull off the top slider, when I get it back together I'll recheck, and it it is tighter, I'll pull the tensioner out. Thanks for the info,
this is a great site.
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  #7  
Old 01-07-2011, 09:26 PM
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When you do the top cover it makes life a lot easier when re-installing to have pulled the guide rail retaining pin out that's under the 5mm allen plug.. When you pull that pin it allows some slack in the chain from the guide rail moving so I always remove the tensioner spring first.
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  #8  
Old 01-08-2011, 10:27 AM
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Quote:
Remove guide rail at top (42). NOTE: If the top cued guide rail (42) is taken out of its mounting, the pressure pin in the chain tensioner is moved one detent in the pressure direction. The chain tensioner must be removed to avoid the timing chain being over-tensioned.

So If I remove the top guide rail that is attached to the timing cover, Am I going to have to remove and reset the tensioner?
Yes.

Once the pin is released, the chain guide on the tensioned side relaxes and the chain tensioner will take up the slack.

Kestes is correct in saying that, "the tensioner has a one-way ratcheting mechanism inside of it". (ie it can't slacken if the chain becomes too tight).

Therefore, you MUST remove the tensioner....otherwise the chain will be over-tensioned when you re-insert the pin.

AFTER you have reinstalled the timing cover and pin...you then may reinstall the tensioner...after reinserting the one way element of the tensioner.

(The author has done this specific job three times already!).
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  #9  
Old 01-08-2011, 10:48 AM
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OK will do! I am half way through the job now, just got everything cleaned up and ready to go back together.
Thanks again for the great info. The engine is really clean the cams look like new with 130k miles.
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  #10  
Old 01-08-2011, 11:54 AM
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Tip: the tensioner is hard to screw back in. Removing the air filter box provides room to lever up on the tensioner until the threads are engaged.
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  #11  
Old 01-08-2011, 05:43 PM
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Yes the tensoiner was a little hard to install.
Appears to still have a leak, might be the front corner of the cyl head.
The car runs and drives so well, I hate to have to pull it all the way down and replace the head gasket.
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  #12  
Old 03-10-2011, 01:44 PM
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Quote:
Originally Posted by OzC36 View Post
Yes.

Once the pin is released, the chain guide on the tensioned side relaxes and the chain tensioner will take up the slack.

Kestes is correct in saying that, "the tensioner has a one-way ratcheting mechanism inside of it". (ie it can't slacken if the chain becomes too tight).

Therefore, you MUST remove the tensioner....otherwise the chain will be over-tensioned when you re-insert the pin.

AFTER you have reinstalled the timing cover and pin...you then may reinstall the tensioner...after reinserting the one way element of the tensioner.

(The author has done this specific job three times already!).
I've been researching this job for a while and have the gasket and sealant ready to go, just waiting on time to do the job.

I've read instructions that say to loosen the alternator to get proper access to the tensioner pin. Is this required or can you get to the pin easily enough without messing with the alternator?

thanks
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  #13  
Old 03-10-2011, 10:32 PM
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No, you must loosen the alternator. It would be impossible to apply the required pressure to the chain tensioner to refit it with the alternator in place.

It just requires one very large bolt (14 or 15 mm?) (the top bolt) to be undone and removed and then the alternator pivots and swings down out of the way (be careful that the alternator is not hanging full weight on the electrical harness that is attached to avoid damage to the harness and connections).

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