Newbie timing belt job. Advice needed - have i accidentally streeeeetched the T-belt?

hi guys

sorry for all the newb questions, but being cautious as i'm learning about this car and motor doing things for the first time, etc. i did a search and didn't really find this asked before. i'm wondering if i may have stretched my timing belt, and if so, should i be worried?

finished my first TB install, followed the bentley and the drive-by wire write-up and using the factory tools and OEM parts from idparts

when i first got all the timing components apart i could see the crank seal was leaking. received some sound advise on how to replace the seal, and also to remove the crank sprocket WITH the motor timed/TB installed.

so did the TB job and waited for the crank seal to arrive. replaced it all- belt, all rollers, roller studs tensioner, timing belt, waterpump, etc. all and all seemed pretty strait forward. but when i installed the TB on to the cam sprocket it was REALLY tight getting it ON the cam shaft itself. it look a lot of pulling and effort. when i adjusted the tensioner (the IP bolts were loosened. the cam gear was on the cam shaft, i only hand tightened the bolt as far as i could, but NO wrench) and tightening the belt i did NOT really notice the cam gear or IP gear "turn", as it was described in the bently and writeup. unless it was really subtle amount. i do most of the work at night and sometimes the lighting is not ideal. then turned the motor over by hand a few times, all timing marks still perfectly aligned.

silicone crank seal and crank yank showed up. swapped the new one in. let it sit overnight. next day re-installed the TB belt and it was MUCH easier getting the cam gear on the cam shaft. like the belt had maybe stretched?? with IP bolts loose and cam gear finger tight, again didn't notice the sprockets slip as i adjusted the tensioner. alignment marks are dead center on the tensioner, locked it down. turned the motor over by hand and all aligns as it should. just a little nervous about the belt. that it might have been stretched or looser than it should be? the belt felt SUPER tight before, but maybe it's just as tight now, just no real experience to compare what it should "feel" like.

should i be worried or does this sound normal?

and when pushing on the belt between the cam and IP is there a distance you can measure etc (is the term "deflection"?)?

thanks for any feedback!
Mike

Was the cam sprocket loose when you put the belt on? I mean, more loose the second time than the first. Since the cam end is tapered it really makes a big difference. Can't really think of anything else if all the idlers are in situ

You haven't stretched the belt.

Recheck that everything is mounted the right way, tensioner, rollers etc, then take a step back and relax, go for a ride....

yes, both times cam sprocket was loose/off the cam shaft. wrapped the belt around the cam gear and then slipped them together onto the cam shaft. first time really hard. second time was sooo much easier. both times tightened the cam gear nut by hand as far as i could but used no wrench, etc.
adjusted tensioner to the "mark"
checked belt routing - good

ok, thank you for the reassurance! : )

hoping to get it back on the road saturday!

I had the same experience...first, belt was impossibly tight, so much so that I was tired from trying to jam it on the cam snout repeatedly. Then, I took a little break and gave it another go & it just slipped right on?? I think maybe some of the teeth weren't fully engaged on the belt/sprockets the first time.

I'm not sure about this, but I think the tensioner actually applies a specific tension when adjusted correctly. That way if the belt is slightly longer or shorter it still applies the same tension.

proffjl said:

I'm not sure about this, but I think the tensioner actually applies a specific tension when adjusted correctly. That way if the belt is slightly longer or shorter it still applies the same tension.

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That is exactly right.
If you disect or just look over a tensioner - it has an internal spring which wraps around the center a number of times. They serve as a dynamic and not static (read constant) adjustment mechanism which is always on the job providing constant tension through cold and heat, wear and tear on the belt. The "tensioning" of the tensioner is an adjustment to "set' the tension of the spring (or pulley) against the belt at the proper force. The tensioner is composed of an eccentric block that rotates around the block stud until the tensioner spring reaches the specified tension or location on the tensioner setting.

See this link for further info....
http://www.litens.com/belttension1.cfm

thanks to all of you for the feedback.
with this and also my new timing belt tracking off-center on the IP (read on here over and over it's "normal") it is a leap of faith for a newb to just "go for it"
i followed the bentley and write-up to a T, so should be a-ok
i got the car 99% back together last night. just have vacuum hoses and fuel lines and then fire it up tonight : )

It is a challenging job - and gives you quite a sense of accomplishment... not to mention a few hundred in your wallet for your effort.

I'm sure you rotated the engine a few times to check things for interference. And yeah... the belt seems to want to ride on the engine side of the IP sprocket. The only help in tracking the belt gets is the tensioner with the pulley shoulders. I think as long as there is a bit of sprocket showing on the inside of the IP sprocket you are OK.

Let us know how you make out.

Cam sprocket slip?

Hi, my name is Shaun and I ran my car low on oil. Now that I got that off my shoulder: I have a severe knock. So I replaced lower bearings first because easy. Still have knock. Now replacing cam cuz second easiest place to look for a knock. All lifters are good, cam looks good. Will put the new one in anyway since I am there. In reading install instructions I see #1 cylinder cam lobe should point straight up (#1 TDC). I did locate crank to TDC before starting this process. After reading this I noted my original cam (still sitting in the car at this point) does not sit as described; rather it is about 45 degrees advanced. Upon taking cam sprocket off, noted evidence it could have slipped on tapered mounting surface as there are score marks signifying it slipped and the degree of rotation of these marks match how far out the cam is from sitting at TDC. I can see this happening since there is no key to positively position the cam sprocket. Yes? NO? Maybe so? As a result of this "discovery" I'm thinking it was not my cam/lifters, but maybe my timing is off enough to knock bad, but not enough to bend a valve. lucky me perhaps...

Would live some insight from you Pro's. Thanks folks.

hey man, my car has been running great since asking this question a while back, lots of solid advice on here!

when i had my cam sprocket off i didn't notice any scoring on the tapered shaft, at all. it's good to follow the write-up and bently for torque specs but i remember someone (frank possibly??) told me to crank that nut down a bit more than spec, to help avoid slipping... which does happen... since yours does have the scoring and is 45 degrees off of where it should be, it sure sounds like it has slipped. hopefully no valves where bent etc. however i am no tdi expert, so if i were you, i would try starting a new thread asking your question with the new subject header AND post some pictures if possible- i'm sure you'll get some more feedback quickly! good luck!
MB

schoolbuilder said:

Hi, my name is Shaun and I ran my car low on oil. Now that I got that off my shoulder: I have a severe knock. So I replaced lower bearings first because easy. Still have knock. Now replacing cam cuz second easiest place to look for a knock. All lifters are good, cam looks good. Will put the new one in anyway since I am there. In reading install instructions I see #1 cylinder cam lobe should point straight up (#1 TDC). I did locate crank to TDC before starting this process. After reading this I noted my original cam (still sitting in the car at this point) does not sit as described; rather it is about 45 degrees advanced. Upon taking cam sprocket off, noted evidence it could have slipped on tapered mounting surface as there are score marks signifying it slipped and the degree of rotation of these marks match how far out the cam is from sitting at TDC. I can see this happening since there is no key to positively position the cam sprocket. Yes? NO? Maybe so? As a result of this "discovery" I'm thinking it was not my cam/lifters, but maybe my timing is off enough to knock bad, but not enough to bend a valve. lucky me perhaps...

Would live some insight from you Pro's. Thanks folks.

Click to expand...