Timing marks

hranko · Post by **hranko** » Sat May 12, 2007 12:54 pm

After driving VW diesels for about 12 yrs, I'm attempting a DIY timing belt change for the first time and something just isn't looking right.

I've got the flywheel mark lined up with the indicator in the bellhousing, and the notch in the cam isn't anywhere close to where it needs to be for the lock tool to slide into place. By that, i mean it's maybe five degrees off. Such that the back(intake/exhaust) side of the notch is up higher than the front (injection pump) side of the notch.

Is this right, or am I a tooth out of time? I've always assumed that all of the marks should line up just right, but I don't know for certain. If you line it all up so the cam and pump pins engage, the flywheel mark can't even be seen through the inspection hole.

The car in question is a project '91 Jetta non-turbo that I've had for about a year but haven't driven since November. I've put about 2000 miles on it and it always seemed like it had good power and economy, though I did think it was a bit hard to start in cool weather, even after new glow plugs. I've found some evidence of questionable work practices by the PO's while going through it, so I'm not ruiing anything out.

Thanks for any tips.

-Jeremy

tawney · Post by **tawney** » Sat May 12, 2007 1:32 pm

You're getting ready to remove the old belt? or are you starting to put the new one on? I guess in either case, the only problem is that it's not properly timed right now. Temporarily ignore the flywheel mark, lock the pump, loosen, (but don't remove,) the bolt on the cam, and bump the cam sprocket loose. Remove the belt. Snug the cam sprocket just enough to rotate the cam, and lock the cam in place. Loosen the cam sprocket bolt just enough so you can turn the sprocket without putting much force on the camshaft. (Too much force on the camshaft and it will snap in two.) Rotate the flywheel to TDC. Install your new belt, (you'll have to rotate the cam sprocket a little to get it to line up,) tension the belt properly, tighten the cam sprocket bolt, remove the pump lock and the cam lock. Manually rotate the crankshaft through a few rotations to make sure it rotates smoothly. You should be ready for the smoke and fire test.

Vincent Waldon · Post by **Vincent Waldon** » Sat May 12, 2007 2:56 pm

Yup, just to be super-clear... there is *no* keyway on the camshaft of the diesel.... it's just a tapered shaft that can be in any position.

So, nothing says the cam and the flywheel have to line up initially... the point is to use the flywheel as the absolute reference. As the previous poster correctly points out: with the engine at exactly TDC you loosen the cam sprocket enough so that it is free to rotate. Now you can manually set the cam slot exactly parallel using the tool of your choice (flat file, door hinge, official wedge), tension the belt, tighten the cam sprocket nut, and there: the cam is perfectly aligned to the TDC mark on the flywheel.

One hint: as you do this keep checking the TDC mark to ensure the crank hasn't moved a bit in the meantime.... nothing is locking it in place and it tends to wander a little as you move everything else around.

Congrats on your first right-of-passage for a VW diesel guy.... next up, setting the pump timing... and later, resealing the injection pump !!!

Vince

audiesel · Post by **audiesel** » Sat May 12, 2007 9:27 pm

Correct me if I'm wrong, but I think there is also a slight chance that the TDC mark on the flywheel could be off if the engine has ever been removed in the life of the car. When I first did the belt on mine, my TDC mark was no where near where it should have been. I found TDC by removing the #1 injector and using a stiff wire as a feeler gage. When I found TDC that way, I looked at the bell housing and there was a faintly painted mark on the flywheel. Aparently it had gotten put back together wrong and somebody made a new TDC mark.

Anyway, that's probably not the case for you, but I thought I'd mention the posibility in case it might be useful.

calebc3 · Post by **calebc3** » Sat May 12, 2007 9:37 pm

Did the PO with questionable work habits ever change the clutch?
I had a 91 jetta for a while where the pressure plate had been put on wrong. Yes it is possible: the alignment pins can be smashed when tightening. This will put the timing mark in the wrong place. I think there are 6 bolts so it would be off by an interval of 60 degrees? The car drove fine. I was working on it and could not find the TDC mark on the flywheel when everythng else was in position. Took the valve cover off and when #1 piston was at its highest no flywheel mark. Had to drop the tranny to verify.
Maybe consider it as a last option.
If you are a tooth off you should be able to tell something is wrong.

Post by **Fatmobile** » Sun May 13, 2007 3:05 am

I've got the flywheel mark lined up with the indicator in the bellhousing, and the notch in the cam isn't anywhere close to where it needs to be for the lock tool to slide into place. By that, i mean it's maybe five degrees off.

I wonder what degree the flywheel timing mark is off, when the cam slot is lined up properly with the head.
Like mentioned if it's off by multiples of 60 degrees your flywheel plate might be bolted up wrong.
Otherwise I'm curious how far it's off,... and still running

.

hranko · Post by **hranko** » Sun May 13, 2007 7:10 am

Yes, the PO (actually, from the receipt it was the Firestone dealer, egad!!) did change the clutch. But the mark isn't anywhere close to 60 degrees off. My guesstimate would be maybe five degrees; just far enough that you lose sight of the flywheel notch through the little inspection hole.

tawney · Post by **tawney** » Sun May 13, 2007 3:20 pm

If it's only off by five degrees then it's not the flywheel thats 'off', it's the cam; use the flywheel tdc mark, and adjust the cam and pump accordingly.

There are six bolts holding the pressure plate to the crank shaft, but one bolt is not equally spaced, so if someone does put it back on incorrectly, it would be a multiple of 60 degrees 'off', and they would also have to leave out that one bolt. The bolts holding the flywheel to the pressure plate are all equally spaced but there are two alignment pins which should insure correct alignment. Evidently the pins can be smashed, (it would almost have to be intentional,) and if so the misalignment would again be a multiple of 60 degrees off.

libbybapa · Post by **libbybapa** » Sun May 13, 2007 5:30 pm

FWIW, a gasser flywheel would bolt right up and might have a timing mark 5Â° off... Perhaps someone installed a gasser FW and compensated for the timing mark?

Andrew

hranko · Post by **hranko** » Sun May 13, 2007 6:50 pm

Sounds like I know what I need to do anyway. Turns out that I'm now going to be away from the car for a week, but it will still be there when I get back. Thanks to all for the advice.

tawney · Post by **tawney** » Sun May 13, 2007 8:02 pm

libbybapa wrote:FWIW, a gasser flywheel would bolt right up and might have a timing mark 5Â° off... Perhaps someone installed a gasser FW and compensated for the timing mark?

Andrew

I have a flywheel from a gasser in my miscellaneous parts collection, and after a bit of comparing, the one I have has an 'O' right where the notch is on the diesel flywheel, (at least by measuring with a caliper to the two nearest bolt holes,) and then there is the familiar looking notch, which if used would position the crank about 2.5 or 3 degrees past tdc. So, if Andrew's suggestion is correct, it would result in the cam being positioned "Such that the back(intake/exhaust) side of the notch is up higher than the front (injection pump) side of the notch"

Hranko, don't you just love the endless possibilities!

However, if there's only one notch, I'm guessing its the real thing. The wire-down-the-injector-hole is one way to find out for sure.

dexev · Post by **dexev** » Mon May 14, 2007 10:09 am

This looks like as good a thread to be chided as any other...

I was timing my pickup this weekend and needed to adjust the cam a few degrees (after loosening the sprocket) to get the locking tool in. I picked a convenient cam lobe and whacked it with a rubber mallet. It worked, but I figure I probably shouldn't have done that...

3Bunnys · Post by **3Bunnys** » Tue May 15, 2007 7:59 am

I've found that a big pair of channel locks or a small pipe wrench will rotate the cam shaft nicely. Just grab hold of one of the rough areas between lobes. This is also a good way to hold the shaft if you want to remove the bolt clamping the pulley in place.
Hammers and impact wrenches have their uses, but one must be judicious in their use. They are not for everything.
regards R