ALH timing belt

Why do you need to loosen the cam pulley when replacing the timing belt on the tdi? Just did mine without loosening it, and didnt have to get the fuel pump timed. Do flat rate VW techs just follow the manual because every video/document/walkthrough i have looked at says loosen the cam pulley.

To corectly tension the belt the cam pulley and in your case the pump pulley need to be floating so the tensioner can properly take up the slack. On the AHU the pump shaft has to float.

You can do it however you want and not have a problem but there is one correct way.

Your belt is probably looser than it should be.

If anything it would be too tight, I loaded the belt very slightly on the cam fuel pump side with the crank before i set the tensioner

And as part of the procedure i spun it around twice and rechecked the tension marks on the tensioner and it was still in spec.

BigCVids, the first TB change I did on my 2000 Jetta was done like you did it ....... by me. As at the time, I did not have the "proper tools" nor a Bentley Manual. And, down through the years with all my MK2 VW Rabbits, Jettas, etc., with the 1.5 and 1.6 diesel engines, that's pretty much how I changed the TB ....... never an issue!

Having said that, the correct way, is to pop loose the Cam Pulley and the three Injection Pump bolts (obviously TDC and locked in place) ... it makes the process so much easier to do.

Lastly, it is a very potential "knuckle skinning" procedure trying to "stretch" and work the TB onto the Cam and IP pulleys simultaneously........ and, if you miss it, well, you got to re-group and do it again!

bigCVids said:

Why do you need to loosen the cam pulley when replacing the timing belt on the tdi? Just did mine without loosening it, and didnt have to get the fuel pump timed. Do flat rate VW techs just follow the manual because every video/document/walkthrough i have looked at says loosen the cam pulley.

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You can easily get the cam 1 or 2 teeth out with this method.. As mentioned the proper method is to loosen cam, have it spin freely and finish up the job. The way you did it is typically referred to as 'mark and pray'. I have done a couple jobs like this just for myself, I have even counted the teeth between marks that I've made to make sure it went back exact.. It works fine if you do it right, if you do it wrong it can be disastrous.

If it's tensioned properly (notch aligns), rotated several times (maybe even run it and rev it) and the cam,crank and IP align, don't see what could be wrong. Just dial it in with VCDS or equal.
The tension can get unevenly applied doing it that way, but whatever works.
So why loosen the cam? To ensure that the tension is evenly applied.
And the dealer techs occasionally do this incorrect anyway.

If I didn't have access to the proper tools I'd have no qualms doing what you did if you took the slack out of the belt. I believe I've said as much here in the past.

I wouldn't count teeth or mark the belt. I'd line the cam up by eye and pin the pump since it has springs that resist its being in the correct position and a 6mm bolt or drill bit is easy to find.

A tooth off on either of these is easy to see.

It's more hassle to get the belt on your way than it is to pop the sprocket off the cam so I don't see the point of not doing it correctly.

^agreed^
It can be tough to line up those cam lobes by eye, I would at least pull the vacuum pump and eyeball the slot, better yet, insert a cam locking tool.

NO NO AND NO!

Here's why.

The belt has some manufacturing tolerance in it. So does everything else. When you tension the belt there must be EXACTLY ONE fixed reference. Since the CRANK must be at TDC that HAS TO BE the fixed reference.

If you lock TWO pulleys (or on an ALH, THREE since the IP can be pinned with the bolts locked down) then you WILL load the side of the teeth of the belt to some degree. That's BEGGING for a premature, no-notice failure somewhere down the road -- maybe 30,000 miles later, maybe 40,000, who knows.

It almost-certainly will not fail on very short time and miles, but you're asking for trouble in the long run. I'm willing to bet that a very large percentage of belts that DO fail prematurely without apparent cause were changed previously exactly this way, and that's why they failed.

steve6 said:

I have even counted the teeth between marks that I've made to make sure it went back exact.. It works fine if you do it right, if you do it wrong it can be disastrous.

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I painted timing marks on all 3 gears then transferred them to the new belt. Worked awesome. Im thinking there is big engineering paranoya on these cars. It seems to me like this procedure makes more sense if you need to physically change or remove a hard part to perform a repair, like the camshaft or the injection pump.

What exactly did you hope to gain by starting this thread, since your mind is clearly made up and you are clearly not interested any other perspective????

There is solid, time-proven, scientific rationale for the timing belt procedure... starting with how in any physical system something's gotta give... and in the case of TDI timing belt installation it's the cam sprocket, on purpose.

Guessing he was just curious, thought he'd built a better mouse trap.
If the 3 magic points align and the tension is even around the belt, what can go wrong?
I would never recommend any other that the tried and true method.
If everything is bolted up when you tension, good chance it will fail.

bigCVids, get back to us 10k miles from now.
Just rotating the engine by hand a few times won't reveal slight piston/valve contact.
You are already overcoming compression and friction and won't feel it.
Time will tell.

Vince Waldon said:

What exactly did you hope to gain by starting this thread, since your mind is clearly made up and you are clearly not interested any other perspective????

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I am interested in other perspectives, but i would like to know the ACTUAL reasoning for this, other than taking your car back to the dealer to get the injection pump timed. I see lots of fear mongering with the "oh my god you didn't do what the shop manual said" type of crowd. I see and understand the "correct tension" argument, however the manual clearly states "Rotate crankshaft 2 complete revolutions. Place crankshaft at TDC and ensure belt timing is correct. Ensure timing belt tensioner pulley marks are still aligned." which is just good juju anyways to make sure you didn't screw something up. I'm just arguing for the "if its in time before, why would i take it out of time" camp. There is a cost savings and time savings with this as well. My nearest VW dealer is 150km away, charges 160$ an hour, and I don't have access to a scan tool that will let me access the tables to time the pump. The injection pump bolts are TTY as well, which means they need to be replaced which is another trip to the dealer before the repair.

flee said:

bigCVids, get back to us 10k miles from now.

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Already got 20000kms on the belt. I'll get back to you at 20k miles

Again, the risk isn't in 10 or 20k miles, probably. It's in the ~50-60k+ range where the side-loading of the teeth, if it occurred (and it probably did) has materially increased the risk of a premature belt failure.

bigCVids said:

Already got 20000kms on the belt. I'll get back to you at 20k miles

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It's called 'mark and pray' because sometimes, maybe more than half of the time,
engine destruction doesn't occur. With the factory method it never occurs.

flee said:

It's called 'mark and pray' because sometimes, maybe more than half of the time,
engine destruction doesn't occur. With the factory method it never occurs.

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That is a point i cant disagree with.

Now that i am done sticking my hand in the beehive, and i have riled all you fine folks up, i feel like an official member of the forum.

No need to visit the dealer for pump timing, that is what vcds is for. If you own one of these cars and perform your own work there really is no reason to not own the proper software. If you keep an eye out you can get a preowned cable here in the for sale section. When you do that then you can loosen the IP pulley and the cam and make for certain the procedure is done right. You mentioned tty bolts... Does that mean you didnt replace any of those as well in your timing belt change? Just asking for lots of trouble here IMO for no reason.

Didn't bother changing them, since I didn't loosen them. I would never re-use anything tty.. thats just asking for tons of trouble.

Uh, the engine mount bolts are all TTY. It is impossible to get the belt off or on without removing them.

Well now we're curious.

Aren't the motor mount fasteners all TTY? Did you change any bits other than the belt?

The bolts for the mount bracket to the block are not TTY. The bolts for the engine mount to that bracket are TTY - you don't want to reuse those.

For mark and pray, you marked the sprockets and the new belt.

Since the cam to cam-sprocket is not a keyed relationship, you are relying on the previous mechanic having done that part properly...

Given your disdain for correct procedure, guess the previous wrench had the same feelings?

Odds are you'll be fine... but on the off chance that a previous mech got the cam-to-cam-sprocket wrong, you are taking a $2k gamble. (cost of re-doing the head should valves hit pistons).

Not worth it IMHO.

Nah. It's as "good" as the previous job. If it didn't hit before it won't hit now.

Previous comments on side loading the teeth don't make sense. The factory instructions don't have any method to account for any minute amount of backlash between belt and sprockets. Also both sides of the teeth are loaded. One side of the teeth see a load from the crank the other from the driven components.

As I stated previously in this Thread, the first TDI TB job on my 2000 Jetta was done exactly as BigCVids did his and by me (I never used paint though...LOL). If I remember correctly, I only changed the TB and Tensioner, nothing else. That was at 67k miles and about 100k miles later, I changed everything per proper procedures using all those goodies that come in a complete TB Job kit (including that Liter of Coolant) from one of the Vendors on here. I also purchased VCDS shortly after that first TB job which showed the timing was slightly above the center line in the graph. According to my Excel Spreadsheet, the engine averaged over 50 mpg during those 100k miles.....

Now, on the flip side, I did a complete TB job (same kit) on my ALH in the Vanagon a couple of years ago. Last May, 2017, at about 50k miles into the new kit, the Water Pump locked ... The TB withstood the carnage and I got it shut down before it jumped time.

So, as everyone has stated, 100k miles, proper kit and tools, including VCDS.. that buys you the best insurance you can get with a TB job.

Below, is a pic of the TB after the Water Pump failure...

Windex said:

For mark and pray, you marked the sprockets and the new belt.

Since the cam to cam-sprocket is not a keyed relationship, you are relying on the previous mechanic having done that part properly...

Given your disdain for correct procedure, guess the previous wrench had the same feelings?

Odds are you'll be fine... but on the off chance that a previous mech got the cam-to-cam-sprocket wrong, you are taking a $2k gamble. (cost of re-doing the head should valves hit pistons).

Not worth it IMHO.

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Engine has 370000+kms on it now, and the kid i bought it from said the timing belt had not been done as long as he has owned it since around 200000kms, so first thing i did was very anxiously drove it home and parked it until the parts came in. I replaced everything under the cover: water pump, all the idlers, tensioner, belt. Its not so much of a disdain, it is a lack of trust of automotive engineers, and german engineers are well known to make things 10x more complicated than they have to be.

AndyBees said:

As I stated previously in this Thread, the first TDI TB job on my 2000 Jetta was done exactly as BigCVids did his and by me (I never used paint though...LOL). If I remember correctly, I only changed the TB and Tensioner, nothing else. That was at 67k miles and about 100k miles later, I changed everything per proper procedures using all those goodies that come in a complete TB Job kit (including that Liter of Coolant) from one of the Vendors on here. I also purchased VCDS shortly after that first TB job which showed the timing was slightly above the center line in the graph. According to my Excel Spreadsheet, the engine averaged over 50 mpg during those 100k miles.....

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Set it TDC, locked the cam, and injection pump. Painted my lines with whiteout(whiteout makes a great cheap marking compound. It is suprisingly durable) across the gear and tooth on one tooth on the IP and Cam, and 2 on the crank. Transferred the marks over to the new belt, double checked and reinstalled. It's very similar to timing a 3.5 Ecoboost except on a older one you need to count teeth and mark it. The only benefit i could see to taking that cam gear off is to slide the belt off nice and easy. If you take the tensioner off before sliding the belt off, the belt comes off without any forcing or abnormal tension. The only problem is putting the tensioner back on is a bit of a bastard with the belt already there.

And as for post repair mileage, it is around 58ish MPG. Getting the VCDS eventually, hoping for the Canadian dollar to start doing better. I have also ordered the 2 tty bolts for the engine mount, didn't even realise they were.

BigCVids, you're going to find that the "Mark and Pray" method of changing a TB is looked upon as something "shade tree" mechanics do and is not recommended by any of the regulars that hang out on this forum, especially the Gurus. It is not the accepted way to do it.

No one with limited or no experience wrenching should attempt to change the TB using the M&P method, especially if their best piece in the tool box is White-out. Anyone planning to own a TDI beyond 100k miles, should invest in the proper tools, VCDS and a Bentley manual.

As for MPGs, all things being equal, they'll all do about the same, with speed being the adjusting factor! (comparing apples to apples and oranges to oranges).

Funny part is easier to do it the correct way and the timing is bang on when your done. Mark and pray can be all over the place and especially if the belts are slightly different. Also belts stretch and you do not know where the timing was before you started.

OP came asking for advice and did not like the advice given. Mark and pray is not the correct way to do a TB job. Can you make it work? Probably. Is it correct? No.

Changing a camshaft seal reducing the chances of an oil leak is a good thing. Hard to do that without removing the camshaft gear.