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Thread: Timing belt idler question

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    Timing belt idler question

    Hi Guys,

    there been a strange noise coming from what I think is the timing belt idler (the small pulley at the top between the banks. I took the front cover of today to have a look the noise seemed to be in time with some white markings on the belt and went away when I sprayed a little wd on. However after i stopped the engine I noticed that the belt was slack on this pulley and it was able to move freely, despite the belt being seemingly tight on the cam pulleys. Worried I sent a text asking my local mechanic to come have a look this week. As I finished my text and turned around I heard a click I had heard before and saw the rear cam pulley on the front bank rotate a few degrees. The belt was now tight on the idler pulley. Is this normal or have I got issues with my tensioner or something else? From looking at the receipts the timing belt etc were done only a couple of years ago.

    Thanks in advance for any help.
    Steve

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    I read through the "timing belt how to guide" a couple of other people asked about their slack belts but got no answers.

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    If the engine moves back slightly then you can get some slack there. To check everything is okay, I would remove the covers for the whole cam belt and then rotate the crank by hand until the timing marks on the ca sprockets and rocker covers line up. I'd use a small square off the rocker cover as optical illusion can make it look a tooth out when it is way less. Once you have achieved this by only rotating clockwise, then have a look a the hydraulic tensioner. It should have a couple of mm of the piston showing. Less than 1mm and I'd worry - more than 4 or 5mm and I'd worry.

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    Quote Originally Posted by Nick Mann View Post
    If the engine moves back slightly then you can get some slack there. To check everything is okay, I would remove the covers for the whole cam belt and then rotate the crank by hand until the timing marks on the ca sprockets and rocker covers line up. I'd use a small square off the rocker cover as optical illusion can make it look a tooth out when it is way less. Once you have achieved this by only rotating clockwise, then have a look a the hydraulic tensioner. It should have a couple of mm of the piston showing. Less than 1mm and I'd worry - more than 4 or 5mm and I'd worry.
    Whats the significance of the piston? What do I need to be worried about?

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    The cambelts are very similar as the 6A12 in FTO and I have done several...out of them about half where fitted wrongly because non specialists DON'T READ THE MANUAL and think they know it all lol.

    Sounds to me (and I stand to be corrected) that whoever fitted the belt didn't RESET the hydraulic tensioner and it has reached it's full extent and you have slack. I would sort it as soon as possible.

    It tends to happen when mechanics try to short cut doing the old 'slit old belt down the middle and slide on a new belt' trick. The tensioner is already half way extended to after old belt stretched and then new belt stretches a little over time and there you go!

    You are supposed to reset the hydraulic tensioner and take up slack with the OFFSET pulley before releasing it.

    While on the subject NEVER fit timing belt with all marks lined up...teh crank needs to go BACK about 1 tooth. Otherwise when tensioner does its job it will pull all the slack from the very long 'front' run of belt around water pump and you will end up a tooth out. Engine will run as ECU compensates but you will loose about 15-20% power at higher revs.

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    Quote Originally Posted by andyp_fto View Post
    The cambelts are very similar as the 6A12 in FTO and I have done several...out of them about half where fitted wrongly because non specialists DON'T READ THE MANUAL and think they know it all lol.

    Sounds to me (and I stand to be corrected) that whoever fitted the belt didn't RESET the hydraulic tensioner and it has reached it's full extent and you have slack. I would sort it as soon as possible.

    It tends to happen when mechanics try to short cut doing the old 'slit old belt down the middle and slide on a new belt' trick. The tensioner is already half way extended to after old belt stretched and then new belt stretches a little over time and there you go!

    You are supposed to reset the hydraulic tensioner and take up slack with the OFFSET pulley before releasing it.

    While on the subject NEVER fit timing belt with all marks lined up...teh crank needs to go BACK about 1 tooth. Otherwise when tensioner does its job it will pull all the slack from the very long 'front' run of belt around water pump and you will end up a tooth out. Engine will run as ECU compensates but you will loose about 15-20% power at higher revs.
    Thanks Andy,

    I really appreciate the reply. It makes sense as the belts were only done about 5000 miles ago. Just trying to find someone to come and sort it now as I am too worried to drive it, and not feeling confident enough to check the timing and reset the tensioner myself. I don't suppose you fancy the job, I'm happy to pay, or know someone who can help.

    Thanks
    Steve

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    Quote Originally Posted by CHESHIRECAT View Post
    Thanks Andy,

    I really appreciate the reply. It makes sense as the belts were only done about 5000 miles ago. Just trying to find someone to come and sort it now as I am too worried to drive it, and not feeling confident enough to check the timing and reset the tensioner myself. I don't suppose you fancy the job, I'm happy to pay, or know someone who can help.

    Thanks
    Steve


    I would be happy to help but I'm up to my eyes in it with the 'proper job' / my own cars / house renovation and family crap for next month or so...

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    This post shows the cambelt with the engine out and the covers off.
    https://www.clubvr4.com/forum/showth...l=1#post701713
    The tensioner pully is on the left as you look at the picture, between the crank pulley and the rear cam. That pully is attached to a pivot arm - the pivot point is the bolt just below the pulley, with the pivot arm going down and to the left. The hydraulic tensioner is perpendicular to the end of the pivot arm and you can see there is a small ~2mm gap between the tensioner pivot arm and the body of the hydraulic tensioner. What you can't see is the piston of the hydraulic tensioner pushing on the underside of that pivot arm. Assuming all is okay then when you wind the crank forwards (clockwise) the gap should remain at about 2mm. If there is no gap then it is likely the hydraulic tensioner has failed. If the gap gets bigger, over about 5 or 6mm then it is likely that the tensioner pulley is badly adjusted, as per Andys post above.
    The photo on this link shows the hydraulic tensioner and the "grenade pin" that holds the piston at the right depth for correct operation. If your tensioner pulley is set perfectly and your hydraulic tensioner is in good condition, you can reinsert the grenade pin.
    https://www.viamoto.co.uk/proddetail...+VR4+EC5W+EC5A
    I hope all that makes sense.

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    Quote Originally Posted by andyp_fto View Post
    I would be happy to help but I'm up to my eyes in it with the 'proper job' / my own cars / house renovation and family crap for next month or so...
    Ok, no worries.

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    Quote Originally Posted by Nick Mann View Post
    This post shows the cambelt with the engine out and the covers off.
    https://www.clubvr4.com/forum/showth...l=1#post701713
    The tensioner pully is on the left as you look at the picture, between the crank pulley and the rear cam. That pully is attached to a pivot arm - the pivot point is the bolt just below the pulley, with the pivot arm going down and to the left. The hydraulic tensioner is perpendicular to the end of the pivot arm and you can see there is a small ~2mm gap between the tensioner pivot arm and the body of the hydraulic tensioner. What you can't see is the piston of the hydraulic tensioner pushing on the underside of that pivot arm. Assuming all is okay then when you wind the crank forwards (clockwise) the gap should remain at about 2mm. If there is no gap then it is likely the hydraulic tensioner has failed. If the gap gets bigger, over about 5 or 6mm then it is likely that the tensioner pulley is badly adjusted, as per Andys post above.
    The photo on this link shows the hydraulic tensioner and the "grenade pin" that holds the piston at the right depth for correct operation. If your tensioner pulley is set perfectly and your hydraulic tensioner is in good condition, you can reinsert the grenade pin.
    https://www.viamoto.co.uk/proddetail...+VR4+EC5W+EC5A
    I hope all that makes sense.
    Thanks Nick, so if the tensioner has not failed and it is just a case of it being badly adjusted how do I correct it?

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    And to access this is it through the wheel arch?

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    It's mostly through the wheel arch, yes. The tensioner pulley has an offset mounting point, so you loosen the bolt, rotate the pulley and retorque the bolt. Obviously, loosening the bolt can leave significant slack on the belt, so I'd be doing something to hold the belt to the cams during the process.

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    Pics make it easier to explain..The tensioner pushes in to reset slowly, don't rush it. I use a G clamp held in a vice as my vice doesn't open wide enough....I usually use a snap rivet fattest that will fit to lock it 'retracted. Gives something to grip with pliers too when ready to pull it out.

    tens.pdf

    The pulley is 'lightly' tensioned against the belt to take up the slack to ensure the hydraulic tensioners range is big enough....

    pulley.pdf

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    When I did the tensioner setup I used a 1/4” torque wrench set to 3Nm plus the little pulley pin tool to apply the correct belt tension, while the other hand had a 3/8” torque wrench set to 48Nm, poised to tighten the pulley bolt. Once the smaller wrench clicked, I held it in place and quickly nipped up the pulley bolt to 48Nm.

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    Quote Originally Posted by andyp_fto View Post
    Pics make it easier to explain..The tensioner pushes in to reset slowly, don't rush it. I use a G clamp held in a vice as my vice doesn't open wide enough....I usually use a snap rivet fattest that will fit to lock it 'retracted. Gives something to grip with pliers too when ready to pull it out.

    tens.pdf

    The pulley is 'lightly' tensioned against the belt to take up the slack to ensure the hydraulic tensioners range is big enough....

    pulley.pdf
    Thanks, that helped massively.

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