Timing belt tensioner

Jon_O · **Joined:** Sun Jun 30, 2013 12:22 pm **Posts:** 27

Hi,

I have encountered a problem while replacing the rocker arms on my engine.

I am having difficulty in re-installing the timing belt tensioner. I should make clear here that I did not remove the tensioner as the engine was partly dismantled when I got it home. Where the tensioner seems to locate on the rear timing cover is directly in front of a recess but no threaded bolt hole. To the right is a threaded hole with two dimples that locate the lugs of the ribbed (alternator belt) tensioner.

I am perplexed.

Can anybody please help me out? It would be much appreciated.

DOC4444 · **Posted:** Sun Jun 30, 2013 1:01 pm

I wonder if you have the TB and SB tensioners mixed up. There are a lot of photos that can be accessed through the NOOB guide that will hopefully help you to clarify.

DOC

Jon_O · **Joined:** Sun Jun 30, 2013 12:22 pm **Posts:** 27

Thanks for your response DOC but they are not mixed up. There is no way to mistake them but even if I did, the problem would be that there is no threaded hole behind where it seems to locate in order to fasten (either one) to the cylinder block.

It's a mystery.

Hexus · **Posted:** Sun Jun 30, 2013 2:03 pm

http://www.youtube.com/watch?v=mbi3rRSEdA4&feature=c4-overview&list=UUtRd0ADTAvGGaPDYU6MrGIQ

Start at the 3:00 Minute mark.

papaindigo · **Posted:** Sun Jun 30, 2013 2:19 pm

Go to http://www.greendieselengineering.com/f ... st/72.page and download a copy of the PDF.
1. pictures 2 and 3 show the serp belt tensioner on the passenger side of the engine just above the power steering pulley.
2. pictures 6 and 7 show removal of the serp belt tensioner and the hole its bolt screws into with what appear to be 2 flanking dimples.
3. pictures 8 and 12 show the location of the timing belt tensioner.

For what it's worth be careful threading the TB tensioner back in place. Based on working on 2 different CRDs it appears that they came from the factory with a Helicoil thread installed in the bolt hole.

arengant · **Posted:** Sun Jun 30, 2013 2:34 pm

Which can strip out easily... happened to me!

geordi · **Posted:** Sun Jun 30, 2013 2:36 pm

What Papaindigo said. Watch out for that helicoil, it is in there. This also cannot be stated enough: DO NOT OVERTORQUE THAT BOLT!!!!!

The proper torque for the timing tensioner is 28 lb-ft, maybe just a shade more. THAT IS IT. I have heard (but have not seen) where some books apparently state that the torque is like 80 lb-ft... This is DISASTER.

If you are having difficulty installing the timing belt, do NOT use the tensioner as the 'loose pulley' to get the room to work. Remove the idler pulley above the tensioner, and install that one last as you are working the belt in. That way, you don't stress that helicoil.

Jon_O · **Joined:** Sun Jun 30, 2013 12:22 pm **Posts:** 27

Thanks geordi & arengant about the added warning of a stripped thread and helicoil. My engine seems to have no hole and thread, stripped or intact; nothing.

I'm baffled. A pint of Marston's Old Empire may help.

geordi · **Posted:** Sun Jun 30, 2013 3:03 pm

Jon_O wrote:

Thanks geordi & arengant about the added warning of a stripped thread and helicoil. My engine seems to have no hole and thread, stripped or intact; nothing.

I'm baffled. A pint of Marston's Old Empire may help.

After you have had a chance to lubricate things... Could you maybe grab a picture of what you are looking at, and upload it? I can edit the image and give you a pointer to exactly where the tensioner SHOULD bolt in, and perhaps I can identify why you don't seem to have the hole for it. I suppose it is possible that the person that disassembled it somehow plugged the hole, but that seems unlikely.

You can send the file (or post it easily in the public folder and then link it here) using Dropbox. If you don't have it, here is a link to use to sign up, and we both get extra free space for it! http://db.tt/EAx8lor

Jon_O · **Joined:** Sun Jun 30, 2013 12:22 pm **Posts:** 27

Thanks once more geordi.

I have dropbox so I have uploaded a few photographs. The link is below (I hope it works).

https://www.dropbox.com/sh/1g2lfj2y6llxjzp/lV0pYPwfDG

One of the photos shows the timing cover in place and where the tensioner should locate. Behind this position there is no threaded hole. The location would be on the left and has the largest non-corroded/rust free circular area in the middle of the picture (maybe I should've pointed at it but hopefully all will be clear).

The hole to the right is threaded and is a potential serpentine belt tensioner position I believe. The left section where the tensioner seems to locate looks as it would look from casting. It looks black just as some un-machined areas above. The surface is flush and flat and doesn't look like it has ever been drilled & filled.

What do you reckon?

geordi · **Posted:** Sun Jun 30, 2013 4:52 pm

I see where the confusion is coming from. The tensioner doesn't bolt into the block itself. It ONLY holds onto the aluminum inner timing cover, and then is itself covered by the stamped steel outer (front) timing cover. The serpentine belt tensioner doesn't go anywhere in this area, it sits over on the left hand side behind the power steering pump. I usually don't remove the serpentine tensioner to remove the front cover, but I'm a lazy mechanic.

Here is your image edited, the arrows indicate the single point of attachment for the tensioner, and there had better be a helicoil within this hole. If that bolt doesn't fit properly OR the hole is smooth... You can't reassemble the engine properly or the timing WILL be flawed and the rockers will all break. It just is not worth the risk. If the hole is smooth, that means that the mechanic already overtorqued that bolt and ripped out the threads and the helicoil.

Jon_O · **Joined:** Sun Jun 30, 2013 12:22 pm **Posts:** 27

Thanks once more geordi.

Just to clarify; does the tensioner bolt onto the aluminium timing cover alone with a short bolt?

If so, this would explain why there is no hole behind. However, the hole on my timing cover is completely smooth. In fact, it doesn't even look like it was threaded and damaged, it simply looks drilled and smooth.

Should this be tapped and if so is this where a helicoil is placed?

I wonder what on earth happened to mine.

On a side note; thanks for the advice on the serpentine tensioner; I was pretty sure it goes exactly where you stated but considering the dimples/recesses in the other location too I wondered if other layouts existed.

arengant · **Posted:** Sun Jun 30, 2013 6:07 pm

One bolt for tb tensioner, three for serp tensioner

I have the heli coil kit I can mail you to redo it. It was easier than I thought.
IF you are not on a time crunch of course

geordi · **Posted:** Sun Jun 30, 2013 6:46 pm

If it is completely smooth... Hoo boy, someone screwed that thing up pretty good. To answer your question, the bolt is about 2.25 inches long, obviously because it has to clear the tensioner, but it doesn't thread that deep into the cover. So yes, it is somewhat of a short bolt.

The thing with doing another helicoil in there that would worry me - You have to make the hole smaller so that the bolt actually still fits the tensioner. Lets assume for a moment that the hole was already threaded - Those threads will be cut into the walls of the hole, making the hole a half-size larger, while inserting the helicoil will make the hole a half-size narrower.

For this example, I am referring to half-sizes, based on the thickness of the helicoil wire itself. If that could be split in half and threaded in, you theoretically would result in a perfectly smooth hole. Make sense? The 'other half' of that helicoil wire then narrows the bore of the hole, hence my 'half-size' concept.

To my way of thinking, since the factory chose to insert a helicoil, that means they over-bored the hole or drilled it perfectly sized (before cutting the threads) for the bolt to smoothly slide right through. Once they tapped it, they realized that the bolt would not thread in, because the hole was now that thread-depth wider. Unfortunately, when the threads are ripped out, you now have a newly-smooth hole... And are back to the same problem they had at the factory.

Cut the threads, insert the helicoil... And it should end up being exactly sized to let the bolt slide right through the threads, tips-to-tips. Insert another coil inside the first (if that even would work) and the bolt won't fit. Too narrow.

Or... I could be completely off my nut, and Arengant will tell me to STFU because his method worked. I'll be OK with that option! :5SHOTS:

arengant · **Posted:** Sun Jun 30, 2013 7:09 pm

If the hole is indeed smooth then I feel your pain. Could you do double helicoils?

My helicoil pulled out, it unwound, but did NOT strip the aluminum threads. I did re tap it with the heli coil kit but it was not a traditional retap where I went up in size. If you stick the bolt in the hole with no heli coil it should enter realtively freely but you should be able to tell if there are still threads in the aluminum.

Jon_O · **Joined:** Sun Jun 30, 2013 12:22 pm **Posts:** 27

Thanks arengant for the kind offer. I will consider that but as you state, the time factor may be considerable.

I can't believe what an awful design this is and that they leave the factory like that. The TB idler pulleys thread into the block as do the idlers for the serpentine belt yet the critical TB tensioner threads only a few turns through a fairly thin piece of aluminium. Not only that but through an insert. I'm shocked.

Nevertheless, that seems to be the case and as such I have a problem. I think you can get twinserts to reduce the diameter by having one insert inside another and that may work. Another option is a new timing cover from a salvage place I know to reduce the cost of dealer prices but as that would have been removed from an existing engine it could have a similar problem.

Nothing seems to be straightforward with this thing.

I've just noticed your latest post arengant. The hole is smooth with no trace of ever being tapped at all.

Once I eventually overcome this problem I fully anticipate having a problem with the injectors. They were unmarked in a box so I don't know what cylinders they correspond to and I believe this may cause me a problem but I'll cross that bridge when I come to it.

Thanks for the helpful input so far.

geordi · **Posted:** Sun Jun 30, 2013 8:02 pm

If the injectors are the ones that originally came with the car and the front timing cover is too - then you won't have problems with the injectors.

There are (ok, SHOULD BE) two big barcode stickers on the timing cover. Each will have 12 digits on it, and those correspond to the 6 digit code on the injectors: XXXXXXYYYYYY would be the six-digit codes for injectors 1 and 2, then AAAAAABBBBBB are for injectors 3 and 4.

If those barcodes aren't intact... Then you have one option: GDE.

I agree with you about the timing cover and that bolt hole - That hole cost me an extra $1200 when the idiot mechanic ruined the cover by WAY overtorquing it, not telling anyone that he didn't bother to read the book I GAVE HIM, and actually finishing the reassembly. Thankfully, it fell apart on the dumbarse on the test drive. Unfortunately, the $1200 was for a set of rockers I shouldn't have needed to buy, and didn't know enough at the time to notice that I got back FORTY broken rockers in the box of parts! Something decidedly rotten in denmark with that math...

Maybe you can use a metal socket, like is used in wood furniture? Think about a threaded socket with a flanged end - inserted into the BACK of the timing cover, so it actually pulls against the flange and the aluminum for strength. You'd need to get it secured somehow, but that is the best (and strongest) option I can think of for that hole.

DOC4444 · **Posted:** Sun Jun 30, 2013 8:31 pm

What Geordi is referring to is GDE can reprogram the ECU to match your injector codes. HOWEVER, this will only make a very small difference in ultimate performance. In view of your other issues, I would wait until you are sure you have a fully functioning motor, then send your ECU off to GDE for all the tweaks in one trip.

Regarding your missing helicoil, a threaded insert that is flanged on one end and is staked in the hole would be a good choice and no tapping would be required.

DOC

Jon_O · **Joined:** Sun Jun 30, 2013 12:22 pm **Posts:** 27

Hello once again to all those taking an interest in this and especially those who have contributed. Thanks a lot.

Well, it was getting late yesterday (I am on GMT Time) so I had a couple of pints and have approached it again today and discovered something that should have seemed rather obvious but once more I shall emphasise that I didn't take this apart but just have a box of parts and nuts & bolts to figure out what goes where.

Here is a link to help illustrate what I shall endeavour to explain:

https://www.dropbox.com/sh/1g2lfj2y6llxjzp/lV0pYPwfDG

The rear of the rear timing cover (the face that meets the block) has a hex machined behind the bolt hole. I looked at this because the hole intrigued me as it was totally smooth as I've previously written it looked as though it had never been tapped and damaged.

I then looked more closely at the tensioner and saw it had a copper, circular mark from a washer, or flanged nut or bolt (which can be seen in the photograph by my thumb). It was then that I saw a lone copper-plated lock washer in the box with several other unknown fasteners and I put two & two together.

Maybe a bolt could be held captive in the hex and the nut secure the tensioner so I rummaged around and found a suitable bolt with a head that fits the hex and protrudes enough to engage the nut and hey presto.

It is interesting to note that the nut has a green paint mark on it as do many other bolts on the engine which must be from the factory (probably denoting that it has been torqued or such like). Therefore, if this is correct it is the original factory fit solution.

It also differs from the threaded insert within other rear covers that some of you guys have mentioned. The nut & bolt seems substantially superior to a threaded insert in the cover (which I have never seen). It really threw me off track because all of the helpful articles and videos show the tensioner being bolted from the front into what I assumed was the block; later thought into a missing insert but now seems to be with a nut & bolt.

From memory, do your covers have the hex as mine does or are they different (which would be unusual)?

I shall try to continue now.

Sorry if this was a bit convoluted but things like this are interesting and it seems people encounter similar problems.

Thanks ever so much so far and I'll update my progress.

geordi · **Posted:** Mon Jul 01, 2013 12:11 pm

Well now, THAT would be the first thing designed on this engine that has me saying "now that is a smart design"!

I can't remember from the one that I pulled apart, but perhaps someone else can chime in. I don't think the USA spec units have that, I think they are just smooth at the back. Very interesting!

This design (amounting to a stud to attach the tensioner to) must be what the VW TDI does, because that also has a stud for the tensioner, although I also have no idea where or how the back of that stud looks.

Great work, I'd say you figured it out! See, proof: a pint -or several- are useful to lubricate the thinking pistons. :5SHOTS:

Timing belt tensioner

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