Anyone has done timing belt change yourself?

[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.

Actually, the block comes to TDC and the mark on the flywheel lines up both times (2 revs crank to each rev of cam and pump) so just looking at the flywheel mark, it is impossible to tell which is firing.  You need to look at the cam or pump to know.

I would agree with the previous post that there can be slight differences in timing belts.  Those differences are so slight that the injection pump timing is not affected enough to cause the engine to run differently, in my experience, but doublechecking the cam timing (a critical aspect to engine life) is certainly very, very wise whenever a new belt is used.  

As Jake mentioned, I would certainly recheck the cam timing after torqueing the bolt.  I have firsthand broken a cam using the locking tool and only going to 33lbs, and have seen two others cams that were broken by other people and so just don't do it that way.  I know of one fellow who had the cam gear slip on a car he bought new that had never had the cam bolt undone prior to the valve mashing.  I do not trust 33 myself.  The difference between 33 and 45 is not a lot as far as torque.  I can easily hold the cam with my hand at the start of a compression stroke and go from 33 to 45.  

It is interesting to see the different experiences and how they shape each individual's process regarding this fairly critical yet simple procedure.  Anyone know how to skin a cat?

Andrew

would like to point out one thing regarding the flywheel marking.  The TDC notch has a little "0" beside it.  This other notch 180 degrees away from this doesn't have the "0".  It's kind of small but you can find it if you look

[Steve Landeau]

I guess I'm looking at it from the other side of the street. I understand and agreee with all you've mentioned regarding the very close tolerances with valve timing on the diesel engine. That is all the more reason to expect that the distance between 20 teeth on one belt must be the same as 20 teeth on another belt.
If there's something I'm missing here, I'd be happy to be proven wrong before I break an engine.

[tylernt]

... expect that the distance between 20 teeth on one belt must be the same as 20 teeth on another belt.

Sounds logical to me too. But I'm happy to be corrected...

[chrissev]

I guess I'm looking at it from the other side of the street. I understand and agreee with all you've mentioned regarding the very close tolerances with valve timing on the diesel engine. That is all the more reason to expect that the distance between 20 teeth on one belt must be the same as 20 teeth on another belt.
If there's something I'm missing here, I'd be happy to be proven wrong before I break an engine.

like I said before, timing belts aren't all exactly the same size.  They're made by many different companies at different times on different machines and there is no way to ensure that they are all exactly the same.  The belts will all fit on any vw diesel, this is true, and the teeth will fit in the gears and the new belt will look the same as the old belt you took off, but it might be slighly bigger or smaller.  That is why Bentley's guide says you need to loosen the cam gear and re-align the cam with the crank each time you replace the timing belt.  (this procedure is only found in the portion of the bentley guide that deals with diesel engines, for gas engines no looseing of the cam gear is needed).  I just follow the procedures in the service manual to the letter and I know a bit about why some of the procedures are there.  People who don't have the manual might not know about certain procedures and might unknowingly take shortcuts.

[dieselweasel]

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.

Actually, the block comes to TDC and the mark on the flywheel lines up both times (2 revs crank to each rev of cam and pump) so just looking at the flywheel mark, it is impossible to tell which is firing.  You need to look at the cam or pump to know.

I would agree with the previous post that there can be slight differences in timing belts.  Those differences are so slight that the injection pump timing is not affected enough to cause the engine to run differently, in my experience, but doublechecking the cam timing (a critical aspect to engine life) is certainly very, very wise whenever a new belt is used.  

As Jake mentioned, I would certainly recheck the cam timing after torqueing the bolt.  I have firsthand broken a cam using the locking tool and only going to 33lbs, and have seen two others cams that were broken by other people and so just don't do it that way.  I know of one fellow who had the cam gear slip on a car he bought new that had never had the cam bolt undone prior to the valve mashing.  I do not trust 33 myself.  The difference between 33 and 45 is not a lot as far as torque.  I can easily hold the cam with my hand at the start of a compression stroke and go from 33 to 45.  

It is interesting to see the different experiences and how they shape each individual's process regarding this fairly critical yet simple procedure.  Anyone know how to skin a cat?

Andrew

would like to point out one thing regarding the flywheel marking.  The TDC notch has a little "0" beside it.  This other notch 180 degrees away from this doesn't have the "0".  It's kind of small but you can find it if you look

As stated before, with the "0" mark on the flywheel aligned with the pointer, the engine is at either #1 or #4 TDC compression.  180 degrees from this mark will be #1 and #4 bottom dead centre.  Since the camshaft and injection pump turn only once for every two revolutions of the crank, you need to have a look at the cam lobes or the injection pump sprocket to determine which stroke the engine is on.  

It is interesting how everyone has different methods.  I have noticed this being a mechanic.  As a young apprentice, I would ask three different mechanics how to do something and each would give a different method.  Over time, I have developed my own methods that I trust and work well for me.

[dieseldan]

Cars with AC are a bit harder to install.  The idea of rotating the engine by hand before starting up is an excelent way to insure that things won't bump into each other where they shouldn't.  Just make sure you turn it using the crank bolt and not the camshaft bolt like I did when I broke the end right off.  Also, avoid belts that look like they have been sitting on the shelf for years.  If it says "made in WEST Germany", it is OLD.  Most important, do not guess if you are unsure.  Stop and get help.
Daniel

[g-spec]

with the crank at TDC the number one cylinder is firing!!!!
quick question.....how tight should the timing belt be???
i dont have the tensioner with the indicator like it says in the bentley!!!!

[tylernt]

quick question.....how tight should the timing belt be???
i dont have the tensioner with the indicator like it says in the bentley!!!!

Try to twist it 90 degrees between the cam and IP. If you can't quite get it to go 90 degrees, it's tight enough.

I don't know how tight is too tight, though. Too tight will wipe out your IP bearings and maybe the other bearings too.

[vwmike]

The tensioner will begin to whine if it's too tight.  :wink: