General: Haynes manual seems have some unnecessary steps

[shiningliao]

I been reading my Haynes V70 & S80 manual as science fiction...

I found the engine repair instructions seems having unnecessary step... or something I don't understand. Maybe some engine guru could enlight me at here.

The short story is:
When refit the camshaft sprocket(s), Haynes manual says you have to insert a cranshaft stop tool and turn the cranshft!!!!

What for? Why?

Here is the further explanation and you should see where I am comming from clearer:

1). When remove the timing belt, position the cramshaft to the right place (so that piston 1 at the TDC). Then refit the new timing belt without moving the cranshaft. This make sense and clear.

2). When remove and refit the camshaft sprocket(s) which is one extra step beyond remove the timing belt, you will have to turn the crankshaft to stop at the stop tool. Why???

Compare these 2, it just doesn't make sense.

Interesting enough. This extra step is not required for Petrol engine without VVT. But for Diesel and Petrol engine with VVT, you need such extra step!!

Anyone could explain this?


By the way, the petrol engine is much more complicated than diesel !!!

If you haynes manual, check page 2A.8 step 18 onward for petrol engine. page 2B.6 step 11 and 13.

[Paul Clifton]

The vvt (vernier) pulleys are not keyed and when removed/replaced have to be set-up in a certain way therefore the cams have to be locked (from the rear) with special tools at TDC no1, in this position minute adjustment of the crank can be undertaken (belt on) during set-up.
This is over simplified as the actual instructions/method is more involved and I would not recommend DIY for this.

Paul.

[shiningliao]

Originally Posted by Paul Clifton

The vvt (vernier) pulleys are not keyed and when removed/replaced have to be set-up in a certain way therefore the cams have to be locked (from the rear) with special tools at TDC no1, in this position minute adjustment of the crank can be undertaken (belt on) during set-up.
This is over simplified as the actual instructions/method is more involved and I would not recommend DIY for this.

Paul.

Thanks for the reply, Paul. I understand what you said at here. It make sense to me.

The trouble is manual says "turn the cranshaft" before timing belt is on!!! This is completely wrong to me... unless my knowledge is wrong. That's why I want to find out.

I understand the VVT could make things even more complicated when refit and setup. However, the diesel engine doesn't have VVT. The manual also says "turn the crashshaft..." before the timing belt is on!!!

[Clan]

well it's not very clear from the lines from the Haynes manual although the crankshaft and camshaft have to be in the correct position before you take the belt off thats what they are trying to say , there is a mark on the cambelt lower crankshaft cam belt pulley which lines up with a line on the block at about 11 o-clock position , and marks scribed on the top pulleys which line up with marks on the top plastic cover ,this is good enough when just changing the belt but is not an absolute correct position as there can be a few degrees of inaccuracy but not so bad that a whole tooth will be in the wrong place so good enough for changing the belt . These Marks are not TDC it is a safe position with all pistons halfway down so it is possible to rotate camshafts to the correct position safely without valves hitting pistons .

It's when you have the top pulleys off you need these tools to precisely locate the crank shaft and camshafts ..and to do that properly there is a tool to locate the crankshaft in the "safe" position to allow the camshafts to be independantly rotated to set in the correct position. To fit the crankshaft locking pin you have to take the starter motor off and remove a blanking plug behind and insert a tool with a pin which locates the crankshaft in an exact position . Then the cam position sensor and distrubutor ( if 850 ) have to be removed to allow the special cam locking tool to be fitted to the back of both camshafts which will locate the camshafts in their exact location relative to the cranklshaft . so now all you have to do is fit the pulleys with the bolts loose so they can rotate in their slotted groove but set them in the middle of the groove so you can move them clockwise or anticlockwise . Then the belt can go on and be tensioned properly , lastly tighten the pulley retaining bolts and remove locking tools . you may have to mark the top pulleys again with a timing mark relative to the cut-outs on the plastic cover .

Removing the pulleys isnt needed except for major engine work and getting the correct cam timing back is not quick and easy !

[shiningliao]

Okay,

Now I got it. (Correct me if I am wrong)

* changing timing belt doesn't require such precision.

* After such major job (remove camshaft sprocket), it is possible the camshaft sprocket mark need to be remarked.

Wonding how does "professional" correct cam timing back apart from this technique? Do they use some extra electronical equipment?

[Clan]

yes the best presicion for belt changing is to the the nearest tooth of course ,
but to do correct cam timing is to the nearest 1/2 degree or better .

And the above IS the professional way!