Anyone has done timing belt change yourself?

[ancient]

HI, I am thinking about doing a timing belt change myself on my 91 ecodiesel jetta.  Has anyone done it before?   Possiblly a complete step by step instruction?  Any special tools needed?  Any input will help.  Thank you.

[vwmike]

I think a good majority of the common posters here have changed a timing belt. First I should start by saying there is very little margin for error so you must be fairly confident in your skills as a mechanic before you take this on. I don't know of any step by step instructions online, but there is a write-up in the manual. I strongly suggest you pick up a Robert Bentley manual for your car. You will need a few special tools to do the job. They are lock tools for the camshaft and the injection pump that hold them in place while you put the new belt in place and tighten everything down and the pin wrench for the timing tensioner (you can do without the pin wrench but it makes life much easier if you have it). You will also want to replace the timing tensioner and the valve cover gasket while it's all apart. If the cam seal is leaking this is also a good time to replace it.

Basically you'll have to start by removing the V-belts that drive the alternator and the power steering pump as well as the A/C compressor if your car is so equipped. From there you must remove the crankshaft pulley that the V-belts ride on. Then both upper and lower timing covers must be removed. The valve cover must also be removed.

Rotate the engine by hand using a rachet on the crankshaft bolt until the notch in the end of the camshaft is aligned with and parallel to the gasket surface on the cylinder head. This is when you slide the camshaft lock plate in. The pump lock pin should also be able to slide through the sprocket and into the corresponding hole in the pump bracket.

Using a 19mm socket or wrench you can now loosen the bolt holding the camshaft sprocket onto the end of the camshaft. There is no key indexing this sprocket onto the cam. It is just an interference fit. I find that tapping a couple of chisels between the sprocket and the cylinder head on either side is enough force to pop the sprocket off of the end of the cam. I always leave the bolt threaded in a bit so that the sprocket doesn't go flying off.

You can loosen the timing tensioner and remove the old belt pretty much any time after you've lined things up and installed the lock tools. Be sure the crankshaft stays properly aligned. There will be a mark on the flywheel that is visible under the plastic plug on top of the transmission. Be sure this stays centered. Remove the old timing tensioner from the side of the head and slide the new one on. Start the nut on the stud after it to keep it in place but do not tighten it down yet. Install the new timing belt over the crankshaft sprocket and injection pump sprocket being sure that the belt is tight across the front side where it rides on the intermediate pulley. Slide the belt over the camshaft sprocket and make sure it rests properly on the tensioner.Tighten the cam sprocket bolt down a bit so that the sprocket is close to where it needs to be.

You should now double check the mark on the flywheel to ensure that it is in fact still in the right place. If it is way off then take the belt off and put it back on more carefully. If it is close then try rotating the tensioner with your pin wrench to snug up the belt. If it still isn't perfect then try rotating the crankshaft back and north a bit with the rachet. See if it passes over the mark more or less in the center of it's sweep as there will be a small amount of play in the locks. If so then try tightening up the belt and camshaft sprocket fully. Check again to be sure that everything looks to be lined up properly. The question I always ask myself is if it would be any better if the belt were moved one tooth in either direction. If the answer is yes then you have a problem and need to pull it back apart again. If the answer is no then it's probably as good as it's going to get.

Obviously you'll have to put everything back together now. It would be the ideal time to put new V-belts on it as they are already off.

I realize I left some things out, but that's just to give you an idea of what is involved.

[Steve Landeau]

The first one I did, I marked the belt teeth and pulleys with a sharpie before pulling the old belt off, and transferred the marks on the old belt to the new belt just to be sure the new one went on exactly like the old one. I did  have the cam and injector pump locking tools, but it seemed to me that if you were careful, you could get away with the change without the tools.

[vwmike]

The biggest problem would be getting the cam bolt loose. You might be able to do it with the impact if you could get it on there. I know my impact wouldn't fit in there though.

[ancient]

Since with the use of special tools would be a safer way to go with.  where can I buy the special tools from for a reasonable price?  And thank you for all your help.  Now I have something to follow.  And I do have a bently manual, but I still want to double check with the experts.  thanks.

[chrissev]

Since with the use of special tools would be a safer way to go with.  where can I buy the special tools from for a reasonable price?  And thank you for all your help.  Now I have something to follow.  And I do have a bently manual, but I still want to double check with the experts.  thanks.

special tools are not required.  You can use a bolt of the right size to lock the injection pump pulley, and several pieces of steel can be wedged into the slot in the cam to lock it in place.  The only tool you might need is a puller to get the cam gear off.  The person who suggested marking everything and then putting the new belt on in the same place as the old one should not be listened to.  Timing belts aren't all a uniform size.  It depends on the manufacturer of the belt.  The idea with loosening the cam pulley is that you line up the crank exactly with the cam, and you avoid any possibility of contact between the pistons and the valves.  Another thing you need to watch for is that the injection pump is hard to lock at TDC with a locking pin and will slip off TDC a bit, so you need to hold it right at TDC when you put the belt on.  It is easy to tell where TDC is on the pump as you will feel pressure when you turn the pump pulley which will release when the pump pulley passes TDC on the pump.  The idea with the pump locking pin is to prevent the pump from moving PAST TDC, but you still have to hold it there with your hand because the pin allows the pump pulley to move back away from TDC.  If you have good compression it should be easy to get the belt on the pump and crank pulleys and then you just slip it over the cam pulley anywhere and let the cam pulley move freely.  That way the cam and crank are perfectly aligned.

[tylernt]

I have done two timing belts now without the locking tools. It's a little fiddly but can be done.

I have never removed the camshaft sprocket, either. Just left it alone.

To make sure I don't really screw up, I turn the engine over a few times by hand to make sure the valves aren't hitting the pistons, and that everything (cam, crank, pump) still lines up to TDC after the belt has gone around a few times.

[NOTORIOUS VR]

Same here... I've done the timing belt recently w/o any of the tools... It's not a problem at all.

You'll be able to do it w/o a problem if u get a buddy to help u.

[VW Smokr]

IIRC most of the dealership techs held the cam in place for tightening or un-tightening with a pair of Vise-Grips on the cam and wedged against a shop rag on the head. Oh yeah, grasp the cam between the lobes, not on the lobes! It takes quite a good grip, and I prefer to wrap a piece of leather around the cam where it will be gripped, to try to avoid any chipping (of the tool or the cam) that might drop junk down into my engine.

Works for me.

J.R.

[vwmike]

A large crescent wrench on one of the cam lobes is also a widely used method if the lock concerns you.

[Steve Landeau]

With all due respect, I understand that this may not be the "preferred" method, but timing belts have to be the same, or at least close enough for this method to be accurate. If it takes 20 teeth to make a revolution with your old belt, it will take 20 teeth with the new belt. If they were not the same, they would not mate up to the pulleys. Your pulleys dont change, the belt has to fit them regardless of the manufacturer.

FWIW, I am a newbie in the forum, and am relatively new to diesels, but I have extensive professional mechanic training, and was in the belting industry for nearly 10 years (I'm not trying to "toot" my own horn, just trying to support my reply to the original post).

[fspGTD]

The method I use to loosen the cam pulley bolt is to wrap a boxed-end 19mm wrench around the bolt head leaving the handle sticking up.  Then I take a decent sized hammer, and give the end of the wrench a good whack to loosen the bolt.  That usually breaks the cam pulley bolt free pretty quickly and easily.  Locking the injection pump pulley is optional.  The friction and inertia of the rotating assembly is an adequate counter hold for this method.

When torqueing the pulley bolt, I've not had any problems with the stock torque specs holding the pulley to the cam, but cleaning up the conical pulley to cam mating surfaces is a good idea.  There should be no nicks or burrs.  Cleaning the cam pulley bolt threads and using some anti-seize on them to lubricate and protect them is also a good idea.

I do tighten the cam pulley bolt with the cam locking tool installed.  I've tried without it and had problems with the cam timing moving by about 1.5 degrees without it.  If you try without it yourself, be sure to re-check your cam timing afterwards to see if it is off.  I've found torqueing by hand to the low 30's ft-lbs factory specs with the cam locking tool counter holding seems to be safe, at least I haven't broken any of cams yet doing it at least.  Just make sure when removing the bolt not to counter hold with the cam locking tool.  Corrosion in the bolt threads can freeze things together and make a lot more torque required to break a bolt free than it took to bring it up to torque.  This thread contains a graphic example of why you should be sensitive not to put too much torquing stress through your cam locking plate:
http://www.vwdiesel.net/phpBB/viewtopic.php?t=1156

[towns]

quick question; with the block at TDC (according to flywheel) which cylinder is firing, #1 or #4?

[chrissev]

With all due respect, I understand that this may not be the "preferred" method, but timing belts have to be the same, or at least close enough for this method to be accurate. If it takes 20 teeth to make a revolution with your old belt, it will take 20 teeth with the new belt. If they were not the same, they would not mate up to the pulleys. Your pulleys dont change, the belt has to fit them regardless of the manufacturer.

FWIW, I am a newbie in the forum, and am relatively new to diesels, but I have extensive professional mechanic training, and was in the belting industry for nearly 10 years (I'm not trying to "toot" my own horn, just trying to support my reply to the original post).

hmmm, well the bentley guide specifically says to loosen the cam sprocket:  page 16 diesel fuel system, "2. Loosen the camshaft drive belt sprocket bolt 1/2 turn.  Loosen the sprocket from the camshaft end by tapping the back side of the sprocket with a soft-faced hammer."

From what I've seen of these engines, the valves and the pistons come very close to each other when the engine is running.  They come so close actually that if your belt jumps a tooth, they will come in contact with each other.  On the 1.9 engines which develop a problem with the crankshaft pulley key, the small amount of movement that results from the loose key causes slight contact between valves and pistons resulting in slightly bent valves.  So you are not dealing with a lot of room between the pistons and valves in this extreme interference engine.   They come quite close to each other.  

I'm not dissing your "extensive professional mechanic training" and I understand that you probably have much more mechanical experience than me, but you have to understand that vw diesels are unique beasts and they have certain quirks to them that people (like me) who have owned a lot of them have come to know very well.  These things are often overlooked by mechanics with years of experience who are not familiar with the peculiarities of the VW diesel engine.  The one rather interesting thing about these engines that most people who have owned a few cars with these engines installed in them know is that there is an extremely small amount of room between pistons and valves when these things are running.  They are not like your average interference engine where you basically need a catastrophic timing belt failure to get the pistons to hit the  valves.  With these little diesels, even a small amount of inconsistency between the crank and camshaft positioning will result in the pistons lightly banging the valves, which over time will bend the valve stems and cause damage to the cylinder head components.  You don't notice it right away, you just gradually notice a decrease in performance, perhaps some smoking, and when you take the engine apart to find out what is wrong you see that the valves are slightly bent and the pistons have little marks on the tops of them.  

So this is why I cringe when people suggest just marking the position of the old belt and putting the new belt in the same place, without bothering to re-align the crank and the camshaft by looseing the cam sprocket.  This method might work on the majority of interference engines out there, but with a vw diesel, it is a crap shoot that can backfire on you over time as your valves are slowly bent by slight imperceptible contact with the pistons.  

I'm just trying to save a few old vw diesel engines from people who don't understand them and through lack of knowledge end up damaging them unintentionally.  It takes very little time to loosen the cam pulley bolt and knock the pulley off the taper lock.  But it can save your engine.  

Chris

[chrissev]

quick question; with the block at TDC (according to flywheel) which cylinder is firing, #1 or #4?

firing order is 1,3,4,2.  so 1.