[Cloud9...68]

Got the balance shaft belt back on, and I seem to have the tension set about right (amazing how much easier this is with the engine on a stand), but I'm a little confused about the wording in the write-up I'm looking at regarding the adjustment of the idler pulley. It says, "You want the top of the idler to just touch the top run of the belt (directly above it) with no more than 1 mm of preload. And the gap to the belt below should be 0.5 mm."



The 0.5 mm gap is obvious, but I don't understand what the author means when he says "no more than 1 mm of preload" in this context. Does it mean that the gap between the top of the idler and the bottom of the belt above should be 1 mm? It doesn't seem like it, otherwise the instruction would have been worded this way.



Here's a picture of my balance shaft belt, centered on the idler:



   



Does it look like my clearances are in the ballpark? Thanks.

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[vliegwielolaf1234]

The workshop manual is straightforward in that , it should be 0 to 1mm .

The idler should just touch the belt with a max displacment of 1mm .

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[Cloud9...68]

OK, thanks. It just seemed like a strange way to word it. Also, I misread the picture in the manual. I thought it said "0.1 mm", when in fact it says "0 - 1 mm", as you say. Good, so I seem to have it pretty close. Just needs a little fine adjustment.



By the way, I'd like to say that it's great to have you on the forum. You've given me (and many other members as well, no doubt) a lot of great tips, suggestions, clarifications, and advice.

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[flash]

correct - there should not be a gap where it indicates the 1mm. look more closely. you should have a DEFLECTION of a maximum of 1mm.

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[Cloud9...68]

Ah, so the idler should actually be deflecting the belt upward to the tune of 0 - 1 mm. So substitute the word "deflection" for "preload" in the quite from the DIY in my first post. Thanks.

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[Cloud9...68]

OK, wait a minute... Armed with my new-found understanding, I went to adjust the BS idler position, and I'm finding that it's physically impossible to simultaneously achieve 0 - 1 mm deflection on the bottom of the belt with the top of the idler, and a 0.5 mm gap between the idler and the part of the belt that's on the lower BS roller. When the top of the idler is just barely touching the bottom of the belt, there's a good 2 -3 mm gap between the idler and the belt on the BS roller. Here's a picture:



   



So, should I leave the gap large like it's pictured, or split the difference between the two?



As an aside, this isn't the first thing I found to be physically impossible. There's absolutely no way to attach the circlip that retains the idler roller assembly on its pin with both of the o-rings in place. I struggled with this for well over an hour, fashioning different types of tools to help press the idler assembly onto farther onto the pin, but no dice. I ended up discarding the inner o-ring, only using the outer one.

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[DaveN]

I have nothing to add that is in any way accurate but when my trusted P-mechanic did mine he ripped a piece of card board from the scrap bin and stuck it between the idler and the belt and said "that's about right" for the gap! The paperboard was about 1mm thick <img src="/forum/images/smilies/968/wink.png" class="smilie" alt="" />

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[Cloud9...68]

Actually, that may help me a little. Do you remember which belt? In other words, did he stick the card board between the top of the idler and the bottom of the belt above, or between the idler and the part of the belt that's wrapping around the lower balance shaft, located at about 8:00 oclock relative to the idler in my picture? I'm guessing it's the latter... If so, that would be a mighty thick piece of cardboard in my case.

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[vliegwielolaf1234]

I have done a few of these belt over the years .

There should be no problem , i use a .5 feeler gauge i bent a bit for this job , it goesbetween lower balanche belt and idler pully .

Then adjust idler so it thouches the belt 0 to 1 mm.

First time keep the nut loose and play around a bit you wil find a way to make it all work .

Keeping it in place while torqing the nut is more of a chalange i think .

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[vliegwielolaf1234]

FOUND YOUR PROBLEM .



When you tension the balance shaft belt , you should rotate the tensioning pully TOWARDS the enigine , and NOT outwards , this brings the belt closer to the idle pully , and is the correct way for this belt .

The tensioning pully/belt wil be very close to the lower balancce shaft pully/belt but this is correct .

You can also see that the belt/tensioner pully is very colse to the plastic cover it should be further away than that , and it wil if you tension the belt rotating the pully inward .





Took me about 15 miles of running this morning and all of a sudden it poped up . then looked at your foto again when i got back and voila there is your problem , solved halfway at the other end of the world by some guy running his ass off for no apperent reason .

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[flash]

yup - i posted about this one quite a while back. it can get pretty darned close to the cover if you go the wrong way too.

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[Cloud9...68]

[color="#7c7c7c"]Vliegwielof1234,[/color]



So, it's the positioning of the tensioner roller that determines the relationship of the belt and the idle roller. That makes sense, as I figured there must be some external factor needed to enable me to achieve both clearances. Once again, thanks a million for your input. I've jokingly told a few people that I should treat this build the way they do with Rolls Royces, and attach a plaque with the names of the people who contributed to the project. Your name would figure very prominently on the plaque!

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[vliegwielolaf1234]

[quote name='Cloud9...68' timestamp='1331480740' post='123124']

[color="#7c7c7c"]Vliegwielof1234,[/color]



So, it's the positioning of the tensioner roller that determines the relationship of the belt and the idle roller. That makes sense, as I figured there must be some external factor needed to enable me to achieve both clearances. Once again, thanks a million for your input. I've jokingly told a few people that I should treat this build the way they do with Rolls Royces, and attach a plaque with the names of the people who contributed to the project. Your name would figure very prominently on the plaque!

[/quote]



If you could take pic after you done so(if put next to eachother you can see the difference ) , and put them on the forum , or get it into the DIY for the belts would be even better .

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[flash]

lol - i pulled up the files for the DIY yesterday. i may have a bit of time to start working on that. i should also be able to add some really good tips from my engine builder, who has found countless issues with the information currently being passed around out there.

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[Cloud9...68]

Yes, I was definitely planning to take a few pictures, and I'll post them here, plus it sounds like Flash is going to explain this part of the procedure in detail in the DIY he's working on.

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[flash]

yup - very critical part of the job, and something that is supposed to be done, according to the book, at least every 15k miles or every year, whichever comes first. most people never go back in, or at most only go back on a short time after doing the belt job, and then fail to re-tension annually.

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[Cloud9...68]

I'm not sure periodic re-tensioning is really needed. Years ago, I replaced my balance shaft belt, and set just a smidge too tight, as it whined pretty noticeably until the car was fully warmed up. Thinking it would loosen up as time went on, I waited several thousand miles, but the whine didn't change one iota. I finally went in and loosened it a bit, and the whine went away. So based on my experience, I don't see any evidence for the belief that the belt loosens over time, requiring re-tensioning. In fact, as touchy as the tensioning procedure is, I'm inclined to think that once you have it set correctly, it's best to leave it alone. Anyone have any alternate experiences?

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[flash]

much of that may be due to the particular belt chosen. conti belts absolutely stretch. my engine guy got REALLY animated about insisting that i not use them. fortunately i was on board with that, and he relaxed. gates don't seem to have as much of a problem.



however, it's even on page 6 of the maintenance schedule, so i think it is prudent to follow that instruction, rather than risk the belt failing and taking out the timing belt, like so many have done already. my balance belt failed, and i got lucky. dan not so much.

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[Cloud9...68]

I definitely think it makes sense to check them at the prescribed interval, but given how tricky it is to get the relationship between the tensioner and idler rollers just right, and then not have it all move away from you when you torque down the nuts, I would only make an adjustment if you're sure the belt has loosened. I've always used Gates, which may explain my experience described above.

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[Cloud9...68]

OK, here are the pictures:



First, with the tensioner set incorrectly, making it impossible to simultaneously achieve 0 - 1 mm deflection of the upped part of the BS belt against the idler below, and a 0.5 mm gap between the idler and the part of the belt going around the lower BL roller:



   

Note the several mm gap between the idler and the BS belt, located at about 8:00 oclock relative to the idler.



Here it is with the tensioner set correctly:



   

Note how the gap has shrunk (down to the specified 0.5 mm, checked with a feeler gauge)



Thanks to vliegwielolaf1234 for pointing out the error of my ways. It's amazing that we live in a time where we can help each other from the other side of the world working on an obscure old German car.



I set the tension of the BS belt using Pete Fitzpartick's method of pushing on the belt toward the gold-colored roller on the water pump, with the goal of feeling the belt start to get tight just as it touches the roller. It feels amazingly loose, but that's the way it's supposed to be - any tighter, and it will whine.

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