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Another S4 chain tensioner pad R&R for posterity

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Another S4 chain tensioner pad R&R for posterity

 
 
Old 04-07-2008, 04:57 AM
  #1  
Rob Edwards
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Default Another S4 chain tensioner pad R&R for posterity

So the GT has 113K miles on it and the chain tensioner pads are original. The right side of the engine compartment is apart, so getting the valve cover off was easy, and so WYAIT.....

Notes for those who haven't done this:

Here's the old pads in situ (I guess the GT cam lobes are ok......)


The tensioner is held to the head with two 5mm hex bolts, and the oil feed tube's banjo bolts are 6 mm.



Each banjo bolt has two washers sandwiching the S-tube, and there is an ominously large oil drain hole right behind the lower mounting hole. I stuffed a piece of paper towel in the drain hole to block any errant washers from going down the drain.

I removed the lower banjo bolt first, the lower washer stayed glued to the S-tube, then I removed the upper bolt, collected its washers, then fished the S-tube out from under the cam while praying the washer would stay stuck. It did.

Schocki has a post that shows the tensioner compressed with a wire holding the pads down. With the tensioner still in place, I couldn't figure out how he got it compressed, but the tensioner can be removed from the head without compressing the pads. And because the piston is so 'incompressible', there's no risk of the thing springing apart during removal. After about 10 minutes of having it sit on the bench, oil slowly leaked out of the piston and it could then be compressed (about 8 mm)






Disassembly is trivial, the piston pulls out, the pad slides off, and the lower pad unscrews. Interestingly, my lower pad was as worn as the upper pad. There are grooves about 1mm deep in each pad:





Another view of the old pads dissassembled:



So after putting the new pads on, I inserted the piston and held it down with a length of wire made from a large binder clip (The Schocki tool) Honestly, this isn't necessary, but it does make putting the tensioner back in a bit easier:



Once in place, I LOOSELY bolted the tensioner down- you want a bit of lateral play so that you can maneuver the S-tube and banjo bolts into place and get them screwed in. Tightening torque is 7 ft lbs for both the banjo bolts and the mounting bolts.

New pads on tensioner in the motor: (Yes, I pulled the paper towel out....) The valve cover is still off if anyone sees any mistakes or wants other pictures.

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Old 04-07-2008, 07:12 AM
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SeanR
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Very nice write up. Adding it to my tech notes.

Thank you.
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Old 04-07-2008, 07:28 AM
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Peter F
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X2

Thanks Rob!

/Peter
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Old 08-18-2009, 02:30 AM
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Hilton
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Just to make sure, there is no spring inside the S4 tensioner piston?

The 86 cam chain tensioner I pulled apart yesterday to remove cams had a spring. I've just spent the last 5 minutes carefully examining my garage for a spring that I may not have noticed coming out of the S4 chain tensioner from my '87, but this thread gives me hope that the S4 design is just different?
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Old 08-18-2009, 12:47 PM
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terry gt
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Nice write up , Colin (lizard) changed the pads in my 91GT . We were not concerned about the amount of wear 65k , but found the pads very brittle , they shattered when we hit them . Terry
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Old 08-18-2009, 12:58 PM
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Tom in Austin
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Noce write-up. Isn't it true that only the 'moving' pad (the one under pressure from the piston) is critical. IIRC, the other pad (the one held in place by screw ... let's call it the 'trailing' pad) isn't under pressure and just takes up any lash in the chain as it goes by.

Doesn't the moving pad face up on the driver's side and down on the pass side?

Mine weren't worn very much and I just replaced the moving pad ...
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Old 08-18-2009, 01:02 PM
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the flyin' scotsman
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I did this same project last winter/spring. Be very carefull with those washers on the oil feed line.........they're aluminium and end up in all sorts of places hidden from view causing much anguish.

Bill Ball asked how to keep the washers in place on assembly; I used a small dab of grease.
What did you use?
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Old 08-18-2009, 01:04 PM
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Rob Edwards
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Off-the-cuff thought- If you only replace the moving pad and there are grooves in the fixed pad, doesn't that provide a shorter path for the chain to move? Therefore, the chain would be getting 'tented' up on the moving pad, likely increasing the rate at which it would wear? I have no idea, having not slept at a Holiday Inn last night. Perhaps the pathlength difference is trivial (?)
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Old 08-18-2009, 01:22 PM
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Tom. M
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Just a note. The oil feed line is only supposed to go on one way. It does fit both ways though and if you get it on backwards then there could be dire consequences.
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Old 08-18-2009, 02:03 PM
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Lizard928
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I use nothing to hold the aluminum crush washers, I am able to get them in and out while keeping them on without trouble.

And it is best to replace both pads, not due to wear, but due to age, they become brittle and as Terry explains can shatter extremely easily.
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Old 08-18-2009, 04:06 PM
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Sailmed
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And we sourced these pads where?
Just askin....
Are they the same for the 86.5's?
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Old 08-18-2009, 04:20 PM
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the flyin' scotsman
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Originally Posted by Firemed View Post
And we sourced these pads where?
Just askin....
Are they the same for the 86.5's?
Roger was my source of supply...............came with a 'kit' he put together for me including all cam cover gaskets, washers, cam chains..........everything from the cyl. heads up.

Pads are a 928 part # for one and a 944 # for the other
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Old 08-18-2009, 04:26 PM
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Rob Edwards
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Mike-

The kit that contains both pads is 944.105.949.00, about $105 the last time I bought a pair. Roger has the upper pad alone (928.105.509.01) for $14.75, last I checked with him. The part #'s I quoted are S4+, dunno if they're the same for 86.5 or not. FWIW, the '87-'91 PET pdf lists them on the bottom of page 25, unreferenced in the diagram, as 'guide piece upper' and 'guide piece repair kit'.
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Old 08-18-2009, 04:55 PM
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86.5 got the same tensioner as the S4s, but the 86 did not.

An easy way to tell which engine you have is to look at the dipstick, if it threads into the block you have the old style.
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Old 08-18-2009, 05:21 PM
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Hilton
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Yep, Colin's exactly right. The M28/44 '86 engine I have in the garage has the threaded dipstick, and a different style of tensioner.

The early 32V tensioner has a very long internal spring, rather than an internal hydraulic damping action, and different shaped pads.

I'll go take pics of it in a few mins and note the part numbers, to add to this thread - I removed it a couple of days ago when taking the S3 cams out of the engine.
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