This is a story of one thing leads to another, as is often the case.

A couple of weeks ago I started getting a misfire together with a CEL. Went home and checked
for codes and it indicated that cylinder #8 was the culprit. I duly purchased eight new plugs as I
decided it would be best to replace them all. No problems here, until I went to take out the last
plug (#1) and noticed over 1/2 inch of oil in the plug well. Ok, time to change the cam-cover
gaskets as they have been there for 9 years, ever since I changed the secondary chain tensioners
from plastic to metal.

Again, I decided to do a complete job and change gaskets on both left and right covers. Now to my
question regarding the tensioners.
I noticed that on the driver's side, the timing chain was taut and the tensioner was slightly protruding. Pushing
on the tensioner made it retract a little bit and it sprung back when pressure was released. Not so on the
passenger side. The chain was slack by about 1/4 inch and the tensioner was fully retracted i.e. not
providing any tension.

Am I looking at having to replace the tensioners now? Not too sure about that, but I will await input from
those with greater knowledge.

 

First tell us which TENSIONER is installed.

 

The newer metal one.

 

Upon STARTUP, the engine oil pressure will 'extend' the tensioner to take up the slack.

The chain usually gets loose when the cam tries to rotate 'backward' slightly due to valve spring pressure on the back side of the lobe.

A 'stretched-chain' will make it more obvious and may 'slap' if worn too much?

 

On the left bank, the piston part of the guide faces upwards, applying tension to the chain as it travels over the top.

On the right bank, the guide is inverted and applies tension to the chain as it travels underneath. Is this correct?

 

That is correct. The expanding part of the tensioner bears against the 'slack' run of the chain, which is the top on one bank, bottom on the other.

 

Thanks for your reply, which points directly to something I can't quite figure out.

On the left bank tensioner, the piston part of the tensioner is extruded and takes
up the slack on the top section of the chain. A gentle push on the piston causes it
to partially retract and thus allows a bit of slack in the chain. Releasing pressure
on the piston lets it to return to its original position and removes the slack.
The lower section of the chain is tight between the two sprockets. All as expected.

On the right bank, there is about 1/4 inch of slack on the top part of the chain. The
lower section is tight, and the piston completely retracted and seems to be immovable.
To me, it doesn't seem that the tensioner is actually doing anything apart from acting
as a chain guide.

The only thing I can think of, if indeed this is an anomaly of some sort, is that the chain
had slipped a tooth on the socket. I changed the tensioners about 9 years ago and have
had no problems with rattles or timing.

I am thinking of putting everything back together and be done with it, but I hate having
unanswered questions, however trifling they may be.

 

Odd -AFAIK, the metal tensioners have a ratchet arrrangement to prevent their retracting. Can you pull the piston outwards, or is it seized in the tensioner body?

You can confirm timing by rotating the motor by hand to check if the cam flats line up.

You did pull the pin out on that side

 

It might also be just where the engine stopped and cam lobs are pushing the chains differently, especially without oil pressure. If you can roll the engine over, you might find chains behaving the same, .

 

Only the metal lower (primary) tensioners have the 'ratchet' to prevent it from retracting without releasing the lever on the 'teeth'.
The original plastic primaries used a 'ball' to trap oil to prevent collapse.
The secondary tensioners will collapse without oil pressure if enough pressure is applied. (ie valve springs)

 

Bob, thanks for the correction.

 

Taking the advice to rotate the engine by hand I found that yes, the slack is taken up and the right bank tensioner
piston does have some outward movement, so I feel happy to put everything back together again.

This perceived 'problem' has evidently turned out not to be one, but at least I am more knowledgeable now concerning
the operation of tensioners!

Many thanks, as always, for all the suggestions provided.