Timing Belt Tension

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Toby_HDi
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Timing Belt Tension

Post by Toby_HDi »

Right I'm struggling here a little. I've retimed the engine and put the timing belt back on. However, on turning the engine through 8 revolutions the timing holes no longer line up. I thought this might have to do with the belt being too loose so I tightened it up some more. Now on turning the engine everything lines up - am just a bit paranoid about the tension now

Here's a video then showing the tension atm, let me know what you think. Is it too tight?

Cambelt Tension

Thanks
Toby


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AndersDK
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Post by AndersDK »

Excellent video.

Toby, obviously no one has ever told you, that this test on the timing belt must be done on the longest run of the belt - only.
I.e. on the down run from the diesel pump to the crank.

Another point you should know is, that only on every second revolution of the crank (i.e. engine), you can make the timing holes line up.
Thats because the cam runs at exactly half the revolutions of the crank.

Hope this will help you trough.
Best of luck.
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Post by CitroJim »

Comparing visually the tension applied by the 1.9 and 2.1TD automatic tensioner, I'd have said that looks about right Toby.

Anders, on a diesel, where Toby checked is the longest run. The pump to crank run has a jockey wheel in the way :twisted: Only on 8V petrols is this a nice, long, straight run.

Don't ever try to check the timing against marks between the belt and sprockets. The marks will take hundreds of revolutrions to line up again. The ONLY way to check timing is by using locking pins.

Any more news Toby?
Jim

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Post by citronut »

also you are ment to re/fit all of the locking pins before adjusting the tension,

and as Anders said the timming will/should line up every 2nd full turn of the crank sprocket

regards malcolm
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AndersDK
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Post by AndersDK »

Me and my big ... :oops:
Been a while since I had my hands on a diesel :roll:
My apologies Toby [-o<

Just had another view on that video.
Personally I'd prefer the belt a bit more tight than shown.
Its a fairly short run between the cam and pump as shown, and that should make it a bit more hard to twist the belt :roll:
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Post by CitroJim »

AndersDK wrote: Its a fairly short run between the cam and pump as shown, and that should make it a bit more hard to twist the belt :roll:
Just a little bit tighter Anders, I agree but it'll be critical to check it when the engine is hot and fully expanded and thus tensioning the belt more.

When hot it should be just possible to twist the belt almost 90 degrees between finger and thumb.

After all these years, I'm still surprised at how slack an XUD belt appears to be on a cold engine, being easy to twist it 90 degrees but they do tighten when hot. Although the XUD has a spring tensioner, it is only effective when setting and then it is firmly locked; setting is carried out on a cold engine.

It'll be vital to check the hot tension whilst ensuring there is adequate cold tension. A tight belt when hot will have a shorter life and may damage bearings, especially those in the tensioner rollers.

Problem is, the setting and testing of tension using the finger and thumb method is subjective and depends on how strong your fingers and thumbs are :roll:

It's one of those things that's hard to explain and requires a bit of "feel" and practice. I guess that's why the official procedure involves the use of a tension (SEEM?) gauge to get the tension right and to take the subjectiveness out of it.

It'll be best, if you have any residual doubts Toby, to get someone with a bit of experience to have a check of the tension.
Jim

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