Your chain tensioner.

[Carolyn]

This little article is intended to provide some guidance to members who aren't fully equipped mechanics, but would like to take on some jobs on their Roadster:

The chain tensioner is to be found at the right-hand end of the cylinder head (hiding somewhat under the spring cylinder for the belt tensioner). If you take a peek, you'll spot it as a small lozenge-shaped flat plate, secured by two 10 mm nuts.  It can be removed without disturbing the belt tensioner.

It is the source of almost all of the oil and muck on your engine. It is sealed by a Viton 'O' ring, which you can see below on the right-hand tensioner.  This 'O' ring flattens over time and starts to leak oil.  So, if there's a load of oily muck on your engine, you might wish to change the 'O' ring.  To do this, remove the tensioner from the car.

It is an oil-pressure operated device that keeps the timing chain at the correct tension when the engine is running.  Below is a picture of two tensioners,side by side:


You can see that the left one is compressed and the right one isn't.  They have a spring inside the cylinder, which pushes out the piston.  When the tensioner is unlatched (right hand one), the spring pushes the piston out to apply sufficient tension for starting the engine.  Once out, the piston is held in place by the ratchet mechanism. (You can see the teeth on the right hand one).  The spring is not that powerful and can easily be compressed by hand when the ratchet is released.  The ratchet is there to ensure that enough tension is on the chain at start-up.

Once you have the tensioner out, you can replace the 'O' ring.  These are quite specific to this device.  Normal generic 'O' rings will not do the job.  They can be found for sale on the internet.  Use a small screwdriver to prize it out of its groove and take it off.  Replace it with your shiny new one.  While the tensioner is out, take some 400 grit wet&dry and clean around inside the hole it came out of.  This helps the new O ring to seal.

A word of caution here:  Don't be tempted to cure the oil leak by moving the tensioner out a few mm and squeezing some sealant behind the plate, and then tightening it back up.  If you do this, the spring will push out the piston, and the ratchet will hold it there.  This would put too much tension of the chain, causing fairly short-term destruction of the timing gear and then the engine!!!

Now it's time to replace the tensioner.  You will need a rag in your hands for this job, as it's full of oil.  Using your thumb, disengage the ratchet by pushing down on the outer lip until you can push the spring in.  This is fiddly,and you might need to take a few goes to get the hang of it.  Push the piston all the way in (oil will come out at this point- hence the rag!) and swing the little hook over the pin that sticks out from the top of the piston. (You can see all these bits in the photograph).  This, too is fiddly and, if it's your first time, you might want to get a mate to do the hooking, while you hold the piston down.  That little hook is very clever.  If you now push down on the piston, you will see that the hook is pushed out of the way.  The hook must be in position for re-installation of the tensioner.

It will only go into the engine one way round,so you really can't get this wrong.  Gently push the tensioner back into the engine.  If you're too rough, you might release the hook and you'll have to take it out and try again.

Put the nuts back on and tighten.  Some people also put some sealant of the face of the plate to aid the 'O'ring.  Your preference!

Now you need to release the hook by a small,sharp turn of the engine. (Do this by hand with a spanner or ratchet on the nut at the end of the crankshaft.)  You will hear a distinct 'click' as the piston releases.  You must be sure you've heard it 'click', before you start the engine.

That's it.. and now you can clean all the muck of your engine.... or not....

[Jrichards20]

 s:bowdown: :bowdown: s:bowdown:  Thank you! Deserves a sticky. Great write up.

[shnazzle]

THanks Carolyn.

We've been cheating all these years and using this how-to from across the pond:  m http://spyderchat.com/forums/showthread ... ioner-Seal m

Now we have our own  s:) s:)  And with more detail with regards to the do's and dont's!

[Ardent]

Nice one.

Whats next?  :-) :-) :-)

[Carolyn]

Nice one.

Whats next?  :-) :-) :-)

 dunno... What's needed (for the non-mechanic)?

[Tomo70]

Nice little write up. thanks Carolyn.

Just a little question. Which way does the crank bolt need to be turned.

Another job off my list.   s:crazyeyes: :crazyeyes: s:crazyeyes:

[Carolyn]

Nice little write up. thanks Carolyn.

Just a little question. Which way does the crank bolt need to be turned.

Another job off my list.   s:crazyeyes: :crazyeyes: s:crazyeyes:

Clockwise - give it a quick slap - makes the chain knock the piston back and the hook off.  You can also do it by moving the car forward in gear - but the crankshaft method is better.

[krazysteve]

Nice little write up. thanks Carolyn.

Just a little question. Which way does the crank bolt need to be turned.

Another job off my list.   s:crazyeyes: :crazyeyes: s:crazyeyes:

good write up.  s:) s:)  
 You can put the car in 4th gear and rock it back and forth, you will hear the tensioner click one or two times.

[Carolyn]

:bowdown: Thank you! Deserves a sticky. Great write up.

Thanks for pointing that out.  It's a pretty good guide.  However, if you hear a 'click' at any time during the installation process, that is a BAD THING!  That means the piston has released too early.  Time to take it out and try again.

[loadswine]

The crankshaft bolt is 19mm if that is of use.

[jinxedkitten]

If you are just replacing the ORING, a good fit tensioner o-ring size is :21.82 x 3.53 mm, oil the o-ring very slightly.

If you are replacing the TENSIONER, there is no need to prime it with oil, but again, oil thenew  o-ring very slightly.