Cam shaft problem

[arcturus]

Had a look at timing gears. The crankshaft gear has signs of wear in a few teeth I suspect that the cam gear has been replaced at some time as no wear evident.Whilst it's all exposed I will renew with complete set. Don't know if that was the problem . Just have to wiat and see.

[blueosprey90]

Did you try to measure the timing gear "backlash"?

I'm not sure that's the correct term, but by "backlash" I mean the play between the gears. In other words, with one gear held stationary, how much play in the second gear.

And is there a spec for what is considered acceptable?

[arcturus]

I know what you mean but not sure how to go about it A better pic'. The specular reflection from flash smooths out the imperfections. How it should be. (B20)

[Derek UK]

Steel gear doesn't usually wear much. Changing just the fibre gear on the B18/20 used to be done a lot as you used to be able to buy the fibre gear separately. They might be still available but because you get both in the kit they are usually both fitted. Not always though! I think that checking the back lash is in the manual and shows the amount that is acceptable. It has to be quite small, as by the time the gears have moved including the distributer gears, any excess affects the timing.

[blueosprey90]

The B16B Timing gear backlash spec is .0004" to .00016" or .01 to .04 mm.

The crankshaft end play spec is .0004" to .040" or .01 to .10 mm, but I also see a max end play of .0060" or .015 mm. So I'm not sure how to interpret those numbers.


Obviously, you will need a dial indicator to measure both. I'm not sure how you can measure crankshaft end play with the motor in the car. I've only ever done it (non-Volvo) with the motor out where you can push the crank back and forth.

Do you see any evidence of unexpected wear or rubbing on any parts removed to get access to the timing gears?

[arcturus]

Will try to check gear "backlash" with feeler gauge.If I have understood correctly
done it. Can get 0.9mm feeler between teeth! I guess that is worn a bit

[arcturus]

Finding a gear puller for the crank gear is a problem!

[Army]

Originally Posted by arcturus

Will try to check gear "backlash" with feeler gauge.If I have understood correctly
done it. Can get 0.9mm feeler between teeth! I guess that is worn a bit

Although the video in the link below =>

https://www.youtube.com/watch?v=r0NsMzdFcZg

shows a differential gear the method is the same.

A feeler gauge isn't really a great way to check.

An alternative idea of assessing worn helical gears:- You could clean the gears (say brake cleaner) and then smear on a load of engineers blue - rotate the gearing - and have a look at the contact patch.

Ideally this needs to be done with the gearing under load. In your case leaving the spark plugs in and rotating the crankshaft on a compression stroke is going to be about as good as you can get.

The contact between the helical gears should be nicely in the middle of the gear meshing.

I have no idea what so ever how a new set of gears would look. I hope they'd be good but as the system has zero adjustment this way of checking could be a bit of a wild goose chase...

...I've only mentioned it as it sounds like you don't have a DTI (dial gauge).

I feel the urge to point out that this is an ideal time to buy one if you haven't got one!

[blueosprey90]

From Ron's page. There is linked video (from Derek???) of a timing gear failure here.

https://www.sw-em.com/Timing%20Gear%20Notes.htm#Failing Timing Gear noises


https://youtu.be/iXxSRQ0johk

[tdz840]

Is the crank gear round the right way in the pictures of it fitted?
The image of it removed highlights two threaded holes normally used for removal with a dedicated puller
Russ