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stuzbot
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Joined: March 30, 2018
Posts: 377
Location: Pining for the Puddles of Yesterday
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 Posted: Sat Mar 31, 2018 7:29 am Post subject: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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Hi all. First post here, but I've been lurking for a long time. So here goes:
I'm doing a cambelt replacement on a 1,6TD T3 Syncro I bought recently and I've run up against a bit of a puzzler.
I've turned the engine over so it's at TDC. The pump has lined up nicely, so the pump-locking tool fits neatly in its hole and the camshaft is also properly aligned...
...or so I thought, until I tried to fit the camshaft locking tool into the slot in the back of the camshaft and found it wouldn't fit.
Sorry. The image is a bit crap, but the slot in the camshaft is below the level of the casing, so the tool won't fit...
So, I rotated the engine again, until the camshaft rotated 180 degrees and now the lobes are in the expected positions and the camshaft locking tool fits perfectly...
Lobes at 'ten to two'...
Locking tool fits...
Only trouble now is that the engine is no longer at TDC. Or is it...? Because with this as well, there is confusion.
While turning the engine over and looking through the wee peep-hole in the flywheel cover, I didn't see any marks which looked like an etched number zero or a line, or anything I've seen on other vehicles. the nearest thing I found to a TDC type mark was this notch, which is what I'd used when positioning everything the first time [when the camshaft turned out to be 180 degrees out]...
This is what I'd assumed was the TDC mark on the flywheel
With the engine rotated so the camshaft turns over 180 degrees and the camshaft locking tool fits, there's nothing in sight through the flywheel peep-hole, except this metal lobe, which looks far too imprecise to be a TDC marker...
Can this be the TDC marker?
So, now I'm at a bit of a loss what to do next. It seems possible the camshaft might be 180 degrees out. But I don't know enough about these engines to know if that's even possible. Would the thing even have run if the camshaft was 180 degrees out?
I've not driven the van much. Only about 80 odd miles home from where I bought it and a couple of brief spins round the block to keep things ticking over. I thought it sounded a bit noisy, but put this down to either tappet clearances needing adjusting or the fact the bottom engine covers are missing.
It starts OK, doesn't put out any smoke when running and pulls OK too. But, like any van this age, it's been through a few pairs of hands before it got to me and has had various bits of work done on it and, according to the seller did have the cylinder head replaced a few years back, which leaves me wondering if the camshaft was put back in the wrong way up.
So
* Is my camshaft 180 out?
or
* Am I just being an idiot and looking at the wrong TDC mark on the flywheel? |
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?Waldo?
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Joined: February 22, 2006
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| Posted: Sat Mar 31, 2018 8:20 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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The crank rotates twice for every rotation of the camshaft and pump. Because of that, with a properly timed engine, the crank will be at TDC when the cam is aligned for TDC for #1 cylinder and then if you rotate the crank a full rotation, it will again be back at crank TDC but the cam will be set for TDC for #4.
The cam sets the stroke so it cannot be 180° out because that just means the crank needs to be rotated a full rotation. The pump needs to be set to match the cam, though, so it CAN be 180° out and it sounds like yours is. Yes, it will run that way, but be a little down on power and will smoke a little more than normal. The difference is surprisingly little.
Here's a pic of the stock vanagon diesel pressure plate and the TDC mark. The TDC mark is the angled notch between the two humps that poke out.
It is CRITICAL that cam timing be set precisely. This is a huge threads but starts right off with precise information on timing a 1.6TD: https://www.thesamba.com/vw/forum/viewtopic.php?t=640611 |
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stuzbot
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Location: Pining for the Puddles of Yesterday
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| Posted: Sat Mar 31, 2018 8:47 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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| ?Waldo? wrote: |
| The crank rotates twice for every rotation of the camshaft and pump... |
I'm trying to work this out in my head [as it's too dark to get back out to the van now]....
So, if I rotate the engine so the camshaft rotates 360˚ [so it's properly aligned for the camshaft locking tool to fit] then the crank will only rotate half a turn... which might bring the other timing mark I was originally looking at back into view? That sounds like it might solve the mystery!
| ?Waldo? wrote: |
| The pump needs to be set to match the cam, though, so it CAN be 180° out and it sounds like yours is... |
Hmmm... How would I tell if the pump was 180˚out?
| ?Waldo? wrote: |
Here's a pic of the stock vanagon diesel pressure plate and the TDC mark. The TDC mark is the angled notch between the two humps that poke out...
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Great! –that's exactly what I was looking for. That looks like the notch I was using as the mark, before I got confused. I don't remember noticing the lobes either side, but they may well have been there. I'll have to have another look tomorrow when it's light again.
Yep. I read through that thread the other day and made some notes. One thing that did puzzle me was several people recommending to loosen off the cam sprocket when fitting the new belt. If the engine timing is already correct, why would you need to allow the cam sprocket to rotate? Is it just so you can be very precise when placing the new belt?
I've only done one cambelt change before and it was several years ago and on a different type van. So I'm having to refresh my memory on a lot of this stuff.
Thanks for your help, BTW.
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?Waldo?
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| Posted: Sat Mar 31, 2018 9:10 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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| stuzbot wrote: |
| ?Waldo? wrote: |
| The crank rotates twice for every rotation of the camshaft and pump... |
I'm trying to work this out in my head [as it's too dark to get back out to the van now]....
So, if I rotate the engine so the camshaft rotates 360˚ [so it's properly aligned for the camshaft locking tool to fit] then the crank will only rotate half a turn... which might bring the other timing mark I was originally looking at back into view? That sounds like it might solve the mystery! |
360° is a full rotation. If the cam lock doesn't fit and then you rotate the cam 360°, it will be right where it was before rotating it and the camlock still will not fit. If you rotate the camshaft 360°, then the crankshaft will rotate 2 complete rotations (720°) and the crank will right back where it was. If you rotate the camshaft 180°, then the crankshaft will rotate 1 complete rotation (360°) and be right back where it was.
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| ?Waldo? wrote: |
| The pump needs to be set to match the cam, though, so it CAN be 180° out and it sounds like yours is... |
Hmmm... How would I tell if the pump was 180˚out? |
Rotate crank to its TDC mark on pressure plate. Look at cam. Is it on the #1 or #4 position? If it is on #4, then rotate the crank another full turn back to TDC and it will be at #1. With crank at TDC and cam in position for #1 cyl, look at the pump sprocket. Is it correctly aligned for the pump lock or is it 180° out? If it is 180° out, then you will need to remove the timing belt, rotate the pump sprocket 180° and reinstall belt.
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| Great! –that's exactly what I was looking for. That looks like the notch I was using as the mark, before I got confused. I don't remember noticing the lobes either side, but they may well have been there. |
This pic of yours appears to be pointing at the lobe to the right side in the pic I posted:
Your other pic does not appear to be pointing at the TDC mark either. It might be correct, but the shadow looks wrong and makes it look like it isn't a V-notch.
| Quote: |
| One thing that did puzzle me was several people recommending to loosen off the cam sprocket when fitting the new belt. If the engine timing is already correct, why would you need to allow the cam sprocket to rotate? Is it just so you can be very precise when placing the new belt? |
If you rotate the crank to TDC going only clockwise and stop exactly at the crank TDC mark and the camlock fits exactly into the slot in the end of the cam then the cam is correctly timed. If it is off at all, then the sprocket needs to be adjusted. There are a couple reasons to simply go through the full routine and loosen the cam sprocket off the cam. One reason is that it is much easier to install the belt that way - put the belt on all the other components, place the cam sprocket into the remaining loop of the belt, lift it onto the end of the cam. With the correct tools it is very easy to remove and properly install the cam sprocket. There are definite time savings with doing that as opposed to wrestling the belt on over the installed sprocket, but the end result of precisely correct cam timing is what really matters. The next reason is that there might be a manufacturing difference between the old belt and the new belt. Any difference will result in the cam being improperly timed. Again, though, as long as the end result is being able to rotate to TDC exactly and have the camlock fit precisely is what matters.
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| I've only done one cambelt change before and it was several years ago and on a different type van. So I'm having to refresh my memory on a lot of this stuff. |
If it wasn't a VW diesel then it only loosely applies. These are extreme interference engines and any mishap in cam timing can be very expensive. |
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Zeitgeist 13
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| Posted: Sat Mar 31, 2018 10:48 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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I have a bottle of Montana Red touch up paint left over from my old '70 Bay that I use to highlight TDC marks. This removes ambiguity, especially if you're unsure or inexperienced with the timing procedures.
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'89 Bluestar ALH w/12mm Waldo pump, PP764 and GT2052
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MarkWard
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| Posted: Sat Mar 31, 2018 10:56 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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The pump sprocket has a reference notch on the backside that matches a notch in the pump bracket when the pump is at TDC for cylinder 1 on the firing stroke.
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stuzbot
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| Posted: Sun Apr 01, 2018 3:39 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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| ?Waldo? wrote: |
360° is a full rotation. If the cam lock doesn't fit and then you rotate the cam 360°, it will be right where it was before rotating it and the camlock still will not fit... |
I think we're on the same page here. Just a misunderstanding. I meant if I turn the camshaft another full rotation from where I left it yesterday [cam lock tool fitting properly - crankshaft not on mark] then the camshaft will come back round to the right position but the crank will only do a half turn, thus [hopefully!] coming back on mark.
| ?Waldo? wrote: |
| Rotate crank to its TDC mark on pressure plate. Look at cam. Is it on the #1 or #4 position? If it is on #4, then rotate the crank another full turn back to TDC and it will be at #1. With crank at TDC and cam in position for #1 cyl, look at the pump sprocket. Is it correctly aligned for the pump lock or is it 180° out? If it is 180° out, then you will need to remove the timing belt, rotate the pump sprocket 180° and reinstall belt. |
Cheers!
| ?Waldo? wrote: |
| Your other pic does not appear to be pointing at the TDC mark either. It might be correct, but the shadow looks wrong and makes it look like it isn't a V-notch. |
I think it's just the pic. It's a bit hard to get some light down that wee peep-hole and then get a camera in there without blocking the light. The pic you posted...
looks like what I'm seeing with the crank in this position...
even down to the rivet[?] just to the right [your pic] / just above [my pic], the timing mark. I'm pretty sure that's it. It is a V-shaped notch, just like your pic shows.
| ?Waldo? wrote: |
| There are a couple reasons to simply go through the full routine and loosen the cam sprocket off the cam. One reason is that it is much easier to install the belt that way - put the belt on all the other components, place the cam sprocket into the remaining loop of the belt, lift it onto the end of the cam... |
Gotcha! –I'll do it that way then. I'll have to knock up some kind of cam-sprocket holding tool then. I've got the other two tools for pump and cam, but not that one.
| ?Waldo? wrote: |
| If it wasn't a VW diesel then it only loosely applies. These are extreme interference engines and any mishap in cam timing can be very expensive. |
The previous one I did was a VW; an old LT35. That one was fairly straightforward as regards actually fitting the new belt, but was a complete pig of a job to do as, in finest VW fashion; to get to the bit you wanted to change you had to dismantle half the van to reach it. In that case radiator, fan cowling, fan, power steering pump, water pump and the crank-bolt itself.
I suppose I should be thankful that, in this case I've only had to remove the air filter housing, a couple of pulleys, rocker cover and the exhaust silencer [so far!]
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stuzbot
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| Posted: Sun Apr 01, 2018 3:44 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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| Zeitgeist 13 wrote: |
| I have a bottle of Montana Red touch up paint left over from my old '70 Bay that I use to highlight TDC marks. This removes ambiguity, especially if you're unsure or inexperienced with the timing procedures. |
I did think of putting a dob of paint on it to make it easier to find, but I think I'll be OK with locating it now. It's just when you're not quite sure what you're looking for the first time.
As I said in previous post, other ones I've seen have had a V or a zero or line of some kind actually engraved in the metal. With this one I thought the V-shaped notch was a likely candidate, but without being able to see the whole flywheel you're never sure if it's just a coincidental variation in the shape at that point.
| MarkWard wrote: |
| The pump sprocket has a reference notch on the backside that matches a notch in the pump bracket when the pump is at TDC for cylinder 1 on the firing stroke. |
Ta! –I'll have a look for that.
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?Waldo?
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| Posted: Sun Apr 01, 2018 8:18 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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| stuzbot wrote: |
| ?Waldo? wrote: |
360° is a full rotation. If the cam lock doesn't fit and then you rotate the cam 360°, it will be right where it was before rotating it and the camlock still will not fit... |
I think we're on the same page here. Just a misunderstanding. I meant if I turn the camshaft another full rotation from where I left it yesterday [cam lock tool fitting properly - crankshaft not on mark] then the camshaft will come back round to the right position but the crank will only do a half turn, thus [hopefully!] coming back on mark. |
Definitely not the same page. If you rotate the engine so the cam rotates 1 full turn, the crankshaft will rotate 2 full turns, not a 1/2 turn. Every 180° of camshaft rotation the crank rotates a turn. If you rotate the engine so the cam rotates a precise 360° the crankshaft will be in the exact same position afterward. If the crank is not at TDC when the camlock fits, then no amount of rotating the engine will get them to align. |
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stuzbot
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| Posted: Mon Apr 02, 2018 4:25 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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| ?Waldo? wrote: |
| Definitely not the same page. If you rotate the engine so the cam rotates 1 full turn, the crankshaft will rotate 2 full turns, not a 1/2 turn... |
Duh! –Yes. Of course. You'll have to forgive my inane drivel. I seem to have left my brain outside under the van. :?
Whatever the jumbled nonsense I spouted earlier, I was able to turn the crank over, so that everything came nicely into alignment and get the belt swapped.
I couldn't get the cam sprocket knocked off the taper at all. It just wouldn't budge –even when I gradually increased the force with which I was 'tapping' it to a level where I started feeling uncomfortable hitting it that hard, so decided to bail out, for fear of damaging the crank bearings.
I managed to get the new belt on by feeding it round the crank sprocket, and cam sprocket and then, while holding it tight on the cam sprocket so it couldn't slip, pulling it taut across to the pump sprocket and very slowly feeding it onto the pump sprocket while turning the engine over by hand and allowing the rotation of the pump sprocket to draw the belt into place.
Nerve-racking stuff and; given I was very slowly turning the engine over with a socket, holding the belt on the cam sprocket and feeding it onto the pump sprocket, all at the same time, I appear to have temporarily evolved three hands at some stage during the procedure.
Much to my amazement, after managing to get the belt on in this unorthodox way, and fully expecting to find everything had gone way out of whack, I found that everything looks like it has stayed lined up perfectly. Maybe the god of cack-handed mechanics was smiling on me, for once?
New belt in place. Fingers still firmly crossed
I've tensioned up the belt and obsessively turned the engine over with a socket half a dozen times or more, checking and double-checking that flywheel mark, crank tool and pump locking tool confirm that everything has stayed perfectly aligned each time and [fingers crossed!] it's looking good.
Of course the real test will come when I put all the pulleys and exhaust silencer back on and fire the engine up properly. But that will have to wait til tomorrow, as it's lashing down with rain here today.
Incidentally. Although, in the end, I didn't manage to budge the cam sprocket off its taper, I did have a flash of inspiration with regard to a sprocket holding tool which I used when loosening its bolt. Something lots of us will have lying around and which saves making or buying special tools:
The good ol' common or garden Pipe Spanner. Fitted a treat through the holes in the sprocket and had the extra advantage that I could tighten the jaws together to hold it in place. I hereby re-christen it "VW Tool X34712"
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stuzbot
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| Posted: Mon Apr 02, 2018 4:47 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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BTW. Whatever the outcome of this job and –even though i regularly curse Volkswagen's design team and the dead generations from which they spring, when I come across a bolt which seems especially designed to be inaccessible without dismantling half the van– I really appreciated the layout in the back of the van, when working on the engine:
It's just so convenient being able to set all your tools out round the top of engine bay, so you've got everything to hand. It's almost as good as having a workshop.
My other and previous VW vans are LTs which trick you into thinking the engine will be convenient to work on by having it under a hatch in the front cab. But you end up having to contort your body round the hinged up passenger seats to reach anything and VW have strategically placed various hard angled pieces of metal around the working area in all the places your kneecaps are going to want to touch down.
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?Waldo?
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| Posted: Mon Apr 02, 2018 8:02 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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| Be sure to rotate by hand 2 full rotations of the crank back to TDC for #1 before using the starter. Feel for any possible valve/piston contact in the process. When returning to TDC, go only clockwise and do not pass TDC. Make sure when you arrive at TDC the camlock will slide in perfectly. |
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stuzbot
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| Posted: Tue Apr 03, 2018 1:11 pm Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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It's Alive!
Got a break in the rain today so I went out and, in a fit of paranoia, took the rocker cover off again, did another half dozen turns of the crank by hand and triple- [or is it quadruple- by now?] checked all my alignments again.
Then back on with covers, pulleys, silencer etc. and it was time to cross fingers and toes and hit the starter...
Hermanito [as my Syncro is called] fired up first turn of the key and without a load of shrapnel flying into the air. So I'm pleased to report that Operation Cambelt seems to have been a success.
Still sounds a bit 'tappety' to me –as it did before I changed the cambelt. So I think next on the agenda will be to check the pump timing and/or valve clearances. Mind you, as I said previously, I'm missing my underneath engine covers, so it's hard to judge if the engine is sounding a bit noisy simply because of lack of sound insulation, or because of valve clearances or pump timing being slightly off.
But that will be another thread for another day. :)
Cheers for the bits'n'bobs of advice folks!
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MarkWard
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| Posted: Tue Apr 03, 2018 1:25 pm Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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You probably lucked out. I don't think you caught what I was saying about the pump sprocket and pump lock tool. The sprocket has 2 identical holes opposite each other for the pin. One way times the pump 180 degrees out. That is why you need to pay attention to the notch on the backside of the pump sprocket and the notch on the pump support bracket. So yes, sounds like the gods were shinning on you.
Not sure about your timing belt installation comment. I don't recall ever having a VW diesel or gas timing belt fight me to the point where I needed to "walk" a belt into position. Oh well, its running. I'd call that a result. The 1.6 should have mechanical valve followers that require adjustment. Did you check the valve clearance while you had the valve cover off?
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?Waldo?
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| Posted: Tue Apr 03, 2018 1:50 pm Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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| MarkWard wrote: |
| You probably lucked out. I don't think you caught what I was saying about the pump sprocket and pump lock tool. The sprocket has 2 identical holes opposite each other for the pin. One way times the pump 180 degrees out. That is why you need to pay attention to the notch on the backside of the pump sprocket and the notch on the pump support bracket. So yes, sounds like the gods were shinning on you. |
Only the 1.5 and very early 1.6 pump sprockets had two symmetrical lock pin holes. After the first couple years of the 1.6, they switched to a pump sprocket that only has one pump lock pin hole and has a hole that is a little larger and offset outward opposite the pump lock pin hole. With that change they also added the mark to the outside of the sprocket rather than only on the pump side of the sprocket. In the pic he posted, you can see the pump sprocket only has the single lock pin hole and has the timing mark on the outside of the sprocket correctly aligned with the mark in the timing cover backing plate.
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?Waldo?
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| Posted: Tue Apr 03, 2018 1:57 pm Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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Stuzbot, in looking at that pic, it looks like you tensioned the belt by rotating the tensioner the wrong way. You are supposed to rotate the body of the tensioner Clockwise to tension the belt. Be sure not to over-tighten it as it will ruin your intermediate shaft bearings and pump shaft bearings very quickly if over-tightened.
...and congrats on getting it running. |
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stuzbot
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| Posted: Wed Apr 04, 2018 10:59 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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| MarkWard wrote: |
| ...I don't think you caught what I was saying about the pump sprocket and pump lock tool. The sprocket has 2 identical holes opposite each other for the pin.... |
| ?Waldo? wrote: |
| ...After the first couple years of the 1.6, they switched to a pump sprocket that only has one pump lock pin hole and has a hole that is a little larger and offset outward opposite the pump lock pin hole... |
What he said ^^ My pump only has one hole in the sprocket that the tool will fit.
| MarkWard wrote: |
| Not sure about your timing belt installation comment. I don't recall ever having a VW diesel or gas timing belt fight me to the point where I needed to "walk" a belt into position. |
It was because I couldn't get the cam sprocket to tap off the camshaft, so had no way to rotate that sprocket to tension the belt between cam and pump. So I had to pull it tight between cam and pump sprockets by hand and "walk it on", to use your phrase.
| MarkWard wrote: |
| ...The 1.6 should have mechanical valve followers that require adjustment. Did you check the valve clearance while you had the valve cover off?... |
No. The clearance figures I've seen for the tappets say they should be measured with the engine warm. So, obviously that would have to wait til I got everything back together again.
| ?Waldo? wrote: |
| ...it looks like you tensioned the belt by rotating the tensioner the wrong way. You are supposed to rotate the body of the tensioner Clockwise to tension the belt... |
I'm not sure whether that pic was before or after I adjusted the tensioner. I can't remember whether, in the end, I turned it clockwise or anticlockwise. In fact, I think I may just have pushed it up by hand as it was a bit awkward trying to tighten it with one hand while holding the tensioning tool with the other.
Does it really make any difference whether you go clockwise or anticlockwise? The tensioning movement is just caused by an offset axis in the centre of the pulley. So turning it either way will have essentially the same effect.
| ?Waldo? wrote: |
| Be sure not to over-tighten it as it will ruin your intermediate shaft bearings and pump shaft bearings very quickly if over-tightened. |
I think it's just a wee bit tighter than I'd like. It's not alarmingly taut –with a firm push of my thumb, I can depress or raise it about 1cm up or down, midway between cam sprocket and pump sprocket– but I'd prefer a wee bit more slack. Given the fact my cam sprocket is immovable though, I think that's as good as I'm going to get. Besides the belt will stretch a wee bit as it beds in, so I'm hoping it'll be OK.
| ?Waldo? wrote: |
| ...and congrats on getting it running. |
Cheers! –now I need to psyche myself up for the ordeal of doing the cambelt on my LT, sometime this summer. As I said earlier, I've done one of them before and it's a pig of a job, mainly because of the amount of 'stuff' you have to remove to get near the damned thing.
I must be a glutton for punishment!
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1992 VW LT35 2,4D [SOLD]
1993 VW LT35 2,4D [SOLD]
1992 VW T3 1,6TD Syncro [SOLD]
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?Waldo?
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| Posted: Wed Apr 04, 2018 11:35 am Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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| stuzbot wrote: |
| Does it really make any difference whether you go clockwise or anticlockwise? The tensioning movement is just caused by an offset axis in the centre of the pulley. So turning it either way will have essentially the same effect. |
Rotating clockwise gives more 'wrap' to the cam sprocket reducing the likelihood that it will jump time. Not a huge difference but enough of one that every VW manual says to rotate the tensioner body clockwise.
| Quote: |
| ?Waldo? wrote: |
| Be sure not to over-tighten it as it will ruin your intermediate shaft bearings and pump shaft bearings very quickly if over-tightened. |
I think it's just a wee bit tighter than I'd like. It's not alarmingly taut –with a firm push of my thumb, I can depress or raise it about 1cm up or down, midway between cam sprocket and pump sprocket– but I'd prefer a wee bit more slack. Given the fact my cam sprocket is immovable though, I think that's as good as I'm going to get. Besides the belt will stretch a wee bit as it beds in, so I'm hoping it'll be OK. |
The cam sprocket being bolted to the cam does not alter the tension of the belt. Also, the timing belts do not stretch unless they are defective. If they did, then the pump and cam timing would become progressively retarded as the belt wore in. That isn't the case. I have personally measured the timing of pump and cam, run a vehicle through the entire timing belt interval, and then measured the cam and pump timing just before changing the belt for the sake of science - to see whether or not it moved. It didn't. It was exactly the same after 60,000 miles. The belt will actually tighten slightly as the engine gets to normal operating temperature due to the block expanding. If it's too tight, the belt might loosen a bit as your intermediate shaft bearings and pump bushings wear out though.  |
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stuzbot
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| Posted: Wed Apr 04, 2018 12:22 pm Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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| ?Waldo? wrote: |
| ..Rotating clockwise gives more 'wrap' to the cam sprocket reducing the likelihood that it will jump time... |
That makes sense. I'll give it a swivel the other way then
| ?Waldo? wrote: |
| ...The cam sprocket being bolted to the cam does not alter the tension of the belt.. |
This is the bit I don't understand.
If we're talking about how tight the belt is between the cam sprocket and pump sprocket [which is where the manuals show to measure it with the special tool] then, given that the belt & sprockets are toothed, it seems to me there are only three ways to reduce the tension in that area:
1: Increase the amount of belt between those two sprockets [ie. move the belt one tooth towards the centre area between the two sprockets] –but would that mess up the timing?
2: Move the sprockets themselves closer together –which could only be done at the pump side and would affect pump timing
3: Rotate the cam sprocket slightly clockwise on its shaft, while keeping the cam stationary, so that the belt loosened very slightly –but not so far that the belt effectively moved one tooth towards the pump sprocket.
Option 3 seems to be the only one that would allow for a slight lessening of tension, without altering any of the other parts of the equation.
Hmmm....
...but now I think about it a bit more, lessening the tension at the tensioner would theoretically allow the belt to loosen very slightly between cam sprocket and pump sprocket by allowing the teeth on the belt to move to the right within the teeth on the cam sprocket and to the left within the teeth of the pump sprocket. It seems like such movement would be so tiny as hardly to make any difference, but maybe it's enough?
Anyway, I'll give it a go when I go out and swivel the tensioner the other way and see what happens.
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1992 VW LT35 2,4D [SOLD]
1993 VW LT35 2,4D [SOLD]
1992 VW T3 1,6TD Syncro [SOLD]
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?Waldo?
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| Posted: Wed Apr 04, 2018 1:25 pm Post subject: Re: Would 1,6TD JX Engine Run if Camshaft was 180 Degrees Out? |
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| Between the cam and pump is where you measure the tension, but because all of the sprockets can turn, the tension is normalized across the entire belt give or take the pulse of pressure from a valve spring being compressed/released or the pump plunger being pushed/returning. First consider that the crank drives the entire belt system. Because the pump and cam are driven by the crank, even if the tensioner is loose, the belt will be taut between crank and pump and between pump and cam with the slack always being in the tensioner area. 'Tensioner' is a bit of a misnomer. It really shouldn't add tension to the belt. It's purpose is to remove the slack from the belt so the belt cannot jump teeth during operation. If you are tensioning it to the point that you are stretching/relaxing the belt between the cam and pump and actually changing the timing then the belt is too tight. |
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