Link furnished by "Jonas"...
(Dead picture links removed )
As you will have read ,these can fail prematurely, and although the MoCo recommends a check at 40,000 miles, some have failed at 20,000 miles or sooner.
This inspection was done at 27,000 miles.
This is what they look like if they fail...
You can see that the outer (primary) one is OK, and within service limits, and the other (the secondary tensioner) has failed completely, with the shoe totally gone, and shards of metal and plastic lost from the tensioner go into the motor.
First, you need to take off the front exhaust, to get at the cam chest.
Stuff an oily rag in the port, to prevent nesting birds, mice, etc. from taking up home there.
Next, fit a polythene sheet between the lower half of the cam chest and the lower frame rails, and shape it to form a trough that will direct oil to your drain pan. There is always some residual oil left in the cam chest and can make quite a mess.
Loosen the cam chest allen bolts a little at a time, in a diagonal sequence (to prevent distortion) then remove completely. If you leave the top two until last, it stops the cover falling off until you're ready. Also it's wise to notice where the bolts go in relation to the cover as they are different lengths.
This is what the inside of the cam chest looks like. There is a cam plate, which supports the outer shafts of the two cams, and houses the main oil passages to and from the oil pump. The small gear from the crankshaft drives the rear cam, and behind the cam plate, there is a secondary chain, where the front cam is driven by the rear cam.
The primary cam chain is tensioned with a spring-loaded shoe, bearing on the outer faces of the chain.
To inspect the shoe properly, you need to overcome the tension on the spring, and pull the shoe away from the chain. Having done that, you can fit a retention pin to hold it in place.
I bought the special tool from Jims, which comprises a special socket and the two retaining pins.
Having used it, it's an overkill for this job, but as you have to be really careful not to let the tensioner spring back on to the chain (which can take your finger off, or shatter the shoe) and it's needed if you ever do a cam or cam bearing change, I though it was worth buying.
The instructions are not too good, and it's not clear how the unloader is supposed to fit on to the shoe. It will go on two ways.
There's a bit of metal that extends out to the hexagon drive flats, and that's supposed to go below the lower right of the shoe. You need a huge 1 1/4” socket or spanner to rotate the tool. I used a 32mm socket, which is close enough.
Once you have rotated the shoe anti-clockwise, the hole in the tensioner will align with the hole in the cam plate, under the 'H'.
Push one of the pair of retaining pins in the kit through the tensioner, and into the hole in the cam plate.
Now you can inspect your shoe, which needs replaced if more than half the thickness is gone.
As you can see, this one looks pretty much OK.
It would be easy to say, “Well, the outer one's OK, so the inner one will be too.” but if you wind back to the first picture, you can see why that's not a good idea.
At this time, I haven't managed to get a view of the rear tensioner. it would be easy if I took off the cam plate, but that involves removing the push rods, and a whole lot more work, and am off to find a small dental mirror, that hopefully will let me see enough.
The other half of the inspection...
Buy yourself one of these...
I was looking for a simple, cheap mirror, but they were out of stock, and I spotted this illuminated one. Best thing because it gets over the problem that most of us don't have three hands for the light, the tool and the mirror...
The tensioner sits behind the cam plate, and its axle is shown under the yellow ring. The red ring shows the hole where the retaining pin fits.
Using the mirror, you can locate the two hooks on the tensioner. These are what the retaining pin fits through when the tensioner is disengaged, so you slip a sturdy and long flat bladed screwdriver under the rear one, lever it up, and then stick the retaining pin through until it supports the tensioner under the outer hook.
Push the pin in as far as it will go, then remove the screwdriver and push the pin through the rear hook, to secure the tensioner.
This is what it looks like inside:
With the tensioner secured, you are free to use the mirror to inspect the underside of the shoe, which looks pretty good on this one.
When you're finished, get the mirror in there again, and support the tensioner again under the rear hook. Keeping it supported, withdraw the retaining pin, and gently lower the shoe back on to the chain.
Degrease and clean the outer cam cover, remove old gasket, and clean faces. Fit new gasket, replace cam cover, and torque down the allen bolts in the sequence illustrated in your service manual.
(Dead picture links removed )
As you will have read ,these can fail prematurely, and although the MoCo recommends a check at 40,000 miles, some have failed at 20,000 miles or sooner.
This inspection was done at 27,000 miles.
This is what they look like if they fail...
You can see that the outer (primary) one is OK, and within service limits, and the other (the secondary tensioner) has failed completely, with the shoe totally gone, and shards of metal and plastic lost from the tensioner go into the motor.
First, you need to take off the front exhaust, to get at the cam chest.
Stuff an oily rag in the port, to prevent nesting birds, mice, etc. from taking up home there.
Next, fit a polythene sheet between the lower half of the cam chest and the lower frame rails, and shape it to form a trough that will direct oil to your drain pan. There is always some residual oil left in the cam chest and can make quite a mess.
Loosen the cam chest allen bolts a little at a time, in a diagonal sequence (to prevent distortion) then remove completely. If you leave the top two until last, it stops the cover falling off until you're ready. Also it's wise to notice where the bolts go in relation to the cover as they are different lengths.
This is what the inside of the cam chest looks like. There is a cam plate, which supports the outer shafts of the two cams, and houses the main oil passages to and from the oil pump. The small gear from the crankshaft drives the rear cam, and behind the cam plate, there is a secondary chain, where the front cam is driven by the rear cam.
The primary cam chain is tensioned with a spring-loaded shoe, bearing on the outer faces of the chain.
To inspect the shoe properly, you need to overcome the tension on the spring, and pull the shoe away from the chain. Having done that, you can fit a retention pin to hold it in place.
I bought the special tool from Jims, which comprises a special socket and the two retaining pins.
Having used it, it's an overkill for this job, but as you have to be really careful not to let the tensioner spring back on to the chain (which can take your finger off, or shatter the shoe) and it's needed if you ever do a cam or cam bearing change, I though it was worth buying.
The instructions are not too good, and it's not clear how the unloader is supposed to fit on to the shoe. It will go on two ways.
There's a bit of metal that extends out to the hexagon drive flats, and that's supposed to go below the lower right of the shoe. You need a huge 1 1/4” socket or spanner to rotate the tool. I used a 32mm socket, which is close enough.
Once you have rotated the shoe anti-clockwise, the hole in the tensioner will align with the hole in the cam plate, under the 'H'.
Push one of the pair of retaining pins in the kit through the tensioner, and into the hole in the cam plate.
Now you can inspect your shoe, which needs replaced if more than half the thickness is gone.
As you can see, this one looks pretty much OK.
It would be easy to say, “Well, the outer one's OK, so the inner one will be too.” but if you wind back to the first picture, you can see why that's not a good idea.
At this time, I haven't managed to get a view of the rear tensioner. it would be easy if I took off the cam plate, but that involves removing the push rods, and a whole lot more work, and am off to find a small dental mirror, that hopefully will let me see enough.
The other half of the inspection...
Buy yourself one of these...
I was looking for a simple, cheap mirror, but they were out of stock, and I spotted this illuminated one. Best thing because it gets over the problem that most of us don't have three hands for the light, the tool and the mirror...
The tensioner sits behind the cam plate, and its axle is shown under the yellow ring. The red ring shows the hole where the retaining pin fits.
Using the mirror, you can locate the two hooks on the tensioner. These are what the retaining pin fits through when the tensioner is disengaged, so you slip a sturdy and long flat bladed screwdriver under the rear one, lever it up, and then stick the retaining pin through until it supports the tensioner under the outer hook.
Push the pin in as far as it will go, then remove the screwdriver and push the pin through the rear hook, to secure the tensioner.
This is what it looks like inside:
With the tensioner secured, you are free to use the mirror to inspect the underside of the shoe, which looks pretty good on this one.
When you're finished, get the mirror in there again, and support the tensioner again under the rear hook. Keeping it supported, withdraw the retaining pin, and gently lower the shoe back on to the chain.
Degrease and clean the outer cam cover, remove old gasket, and clean faces. Fit new gasket, replace cam cover, and torque down the allen bolts in the sequence illustrated in your service manual.
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