Timing Belt Sprocket Removal

[MarkC]

Help please!

My timing belt failed yesterday after 19K miles of use. Root cause appears to be a small bolt that came loose from somewhere, jamming between the timing belt sprocket (on the crankshaft) and case causing the sprocket and belt to both fail.

For starters, I need guidance on removing/replacing the sprocket.

Secondly, is there anything I can do short of pulling the head to assess what damage may have occurred to the valves?

Thirdly, and recommended course of action in fixing the valves? Any rebuilt heads out there? I,m justnot sure how quickly I can have mine repaired.

2001 NB, 2.0L, AVH code engine.

Thanks,

Mark

[AndyBees]

Originally Posted by MarkC

Help please!

My timing belt failed yesterday after 19K miles of use. Root cause appears to be a small bolt that came loose from somewhere, jamming between the timing belt sprocket (on the crankshaft) and case causing the sprocket and belt to both fail.

For starters, I need guidance on removing/replacing the sprocket.

Secondly, is there anything I can do short of pulling the head to assess what damage may have occurred to the valves?

Thirdly, and recommended course of action in fixing the valves? Any rebuilt heads out there? I,m justnot sure how quickly I can have mine repaired.

2001 NB, 2.0L, AVH code engine.

Thanks,

Mark

2.0L 4-Cylinder - AEG, AVH, AZG, BDC & BEV Engines

CAUTION: These are all interference engines. Do not rotate camshaft or crankshaft when timing belt is removed, or engine damage may occur.

Simply put, your engine is considered "interference" meaning that when the Camshaft Timing is not in sink with the Crankshaft Timing, pistons will contact valves.

Based on what you have stated, there is no doubt that damage has occurred.....valves (mostly exhaust) and piston(s).....maybe even a bent rod!

So, with that in mind, you will need to remove the head for inspection, repair and/or replacement. Also, since the bolt went to the bottom, the Crankshaft Sprocket may be damaged too!

In my humble opinion, you don't need to be tackling the problem/issue using a DIY guide typed up by a member! You really need a Bentley Manual or VW Service Manual to work your way thru this job.

Sure, I can sit here and write-up a rather detailed step-by-step set of procedures that gets the head off the engine block. Then what's next........? Putting it back together has numerous important tasks that require the use of appropriate torque values, etc., which are listed in the manual. Sure, someone may scan, cut-paste, and/or copy-paste some general guidelines, but I still say the best way to approach your problem is to be armed with a manual, proper tools and place to do the work~!

There is another Thread in this forum relating to a DIY involving the head. In my humble opinion, the same advice applies there as well!

EDIT: Here is a link to a PDF file for doing scheduled maintenance that includes Timing Belt replacement: http://www.justanswer.com/uploads/eb..._180339_tb.pdf ........... Taking off the Intake Manifold and associated things as well as Exhaust Manifold gets you down to the basics! Remove the Valve Cover and there will be the head bolts, Camshaft, etc.

I hope the link works!

[D2Beetle]

Take the head off and have a machine shop look at it, 2.0's are not that expensive to rebuild. You really cannot make an informed decision without at least having the machine shop look it over. If the head can be rebuilt the shop will replace belt sprocket for you.

[MyOtherRidesAVette]

No way to tell what damage has been done till you get the head off. Bent valves minimum to holes in the pistons.

Here's a link to the head R&R by The Book.

2.0L Head R&R
head removal diy

Anything from rebuilt heads to complete rebuilt or new long blocks are available. Few hundred to a few thousand. Just start Googling.

And ditto what AndyBees said above. Buy a Bentley, DVD-ROM Repair Manual is going to be way better than the paper Maintenance Manual (I have an extra, current version, new, unopened, yet to be registered, $65 shipped to Lower 48). You need tightening torques, sequences, etc, etc. DIYs are nice for tips and tricks, but you'll need a little more to do the complete job.

MORAV

[MarkC]

revised below

[MarkC]

Originally Posted by AndyBees

2.0L 4-Cylinder - AEG, AVH, AZG, BDC & BEV Engines

In my humble opinion, you don't need to be tackling the problem/issue using a DIY guide typed up by a member! You really need a Bentley Manual or VW Service Manual to work your way thru this job.

Sure, I can sit here and write-up a rather detailed step-by-step set of procedures that gets the head off the engine block. Then what's next........? Putting it back together has numerous important tasks that require the use of appropriate torque values, etc., which are listed in the manual. Sure, someone may scan, cut-paste, and/or copy-paste some general guidelines, but I still say the best way to approach your problem is to be armed with a manual, proper tools and place to do the work~!

There is another Thread in this forum relating to a DIY involving the head. In my humble opinion, the same advice applies there as well!

EDIT: Here is a link to a PDF file for doing scheduled maintenance that includes Timing Belt replacement: http://www.justanswer.com/uploads/eb..._180339_tb.pdf ........... Taking off the Intake Manifold and associated things as well as Exhaust Manifold gets you down to the basics! Remove the Valve Cover and there will be the head bolts, Camshaft, etc.

I hope the link works!

Thanks, Andy. The pdf you provided does identify the torque value for the crankshaft sprocket bolt. I'll pull it off tomorrow.

Thanks, Morav. The "by the book" head R&R procedure identifies the sequence, torque, and tension information I was looking for.

Thanks, D2Beetle. I was planning to take the head to a local shop for inspection, but for yucks,
i was thinking of retiming it, putting on a new timing belt, and checking compression before going thru the effort of pulling the head.

[VDubYah]

As tempting as that sounds I don't think you will get it to run. It has bent valves and low compression in those cylinders and will most likely not fire. In addition each rotation knocks the bent valves against the top of the pistons.

[D2Beetle]

Actually, attempting to start it will damage it more, don't ... been there done that ...

[simonsi]

Originally Posted by MarkC

checking compression before going thru the effort of pulling the head.

Good, sensible test if you have the time and energy. Turn the engine over by hand to see if she will, that will give you a feel for if there is any compression, turning over 2 crank rotations will give compression on each cylinder in turn. Only if she turns over without binding and appears to have compression on each stroke is it worth pulling the plugs and turning her on the starter with a compression gauge.

Don't try a start - pointless risk, you test compression at starter speed - remember to open the throttle wide when testing.

I'd be amazed if you haven't got at least some valve damage though TBH

[MarkC]

Today I pulled the cam cover off. Nothing unusual from topside. The camshaft was left in a position such that no valves were fully lifted. In this position, I can rotate the crank fully without feeling any pistons/valve touching. I rotated the camshaft to fully lift one valve (maybe 100 or 150 mils higher) and I could feel the valve touch its piston.

I going to hold off on pulling the head until I can throw on a new TB and check to see if I get compression in all four cylinders by hand-turning the crankshaft and using the "finger over the sparkplug hole" technique. If I've been a good boy and the camshaft stopped where I found it, maybe just maybe pistons and valves didn't collide. What a Christmas present that would be!

Bad news is I'm having no luck finding a crankshaft sprocket locally. NAPA lists one for about $40 but can't get it until late next week. Even called two VW dealers who offered to get me one in 3 to 5 days (for up to twice the NAPA price). I'll keep looking.

[BeetleMyHeart]

I thought I had read somewhere that 2.0 NA's weren't interference engines then on this thread someone quotes as they are. This has to be one of the toughest mysteries of the world; what engines in different brands and applications are actually interference.

If the 2.0 is an interference engine I don't see how the same could be in a dead spot where all of the valves are retracted away from the pistons through a full revolution. The cam didn't just instantaneously stop after the belt broke. The cam probably turned a couple more times as the crank was still spinning like crazy as it has more inertia. I would be extremely surprised if you didn't touch a single valve on a single piston.

[AndyBees]

Originally Posted by BeetleMyHeart

I thought I had read somewhere that 2.0 NA's weren't interference engines then on this thread someone quotes as they are. This has to be one of the toughest mysteries of the world; what engines in different brands and applications are actually interference.

If the 2.0 is an interference engine I don't see how the same could be in a dead spot where all of the valves are retracted away from the pistons through a full revolution. The cam didn't just instantaneously stop after the belt broke. The cam probably turned a couple more times as the crank was still spinning like crazy as it has more inertia. I would be extremely surprised if you didn't touch a single valve on a single piston.

The info I posted about the list of engines being Interference is correct ........research it if in doubt.

Edit: http://www.justanswer.com/uploads/eb..._180339_tb.pdf

Something to think about: The pistons are always "chasing" the Exhaust Valves as they close during the exhaust cycle. So, when a TB snaps, shears off teeth, jumps teeth, etc., there is a 100% assurance that at least one Exhaust Valve is going to be hit by a piston! On an Intake Stroke, the piston is always pulling away from the Intake Valve and less likely to come in contact with a piston under the same circumstances.

So, based on the above, Exhaust Valves are more likely to get trashed. If the driver tries to re-start the engine or doesn't push in the clutch/kick in neutral on an automatic, depending on where the Cam stopped, at least one Intake Valve will get trashed!

CAUTION to the Original Poster: Even if you put a NEW TB on and the engine starts and runs fine..........do not trust it! The lifter(s) on the cylinders that had piston to valve contact will last about 1200 to 1500 miles and then destroy your head............ask me in a PM how I know!

[MarkC]

no doubt about it, the 2.0 IS an interference engine. That said, the interference only occurs when valves are at or about full lift.

In slowly rotating the camshaft using a wrench on the cam gear nut (with crankshaft off of TDC), there are four "stable" positions that the camshaft wants to be in. This stability is produced by two valves that are near full open (lots of spring force) with one of those valves approaching full open and the other beginning to close. This is where I found my camshaft. In this cam position there appears to be no piston/valve interference. However, if the cam is rotated such that a valve is fully open, there can be piston-valve contact.

Andy, your point about the piston chasing the exhaust valve is well taken. That is why I want to do the compression test. If I'm lucky and all four cylinders make compression, then valves were not bent. Correct?

[AndyBees]

Mark,

Although a recent experience involved a TDI 1.9 Diesel engine, the basics of the results are "about" the same.

The dude was driving (his words) along at about 45 mph up hill when his engine went kaput (TB stripped teeth off). He said that he immediately shifted to neutral and coasted onto the shoulder of the road. This was a dealer purchase used 99 NB that was supposed to have had a TB job done at 60k miles which stripped teeth at 105k miles.

Anyway, I helped him and another dude replace the TB with a "used" TB. With the engine supported (above and below)and the TB set, we started the engine it sounded great...... nothing unusual. So, based on that, and the owner's decision, we ordered and installed a "complete" new TB kit.

Well, about 1100 miles later, he called me saying the engine had died again............two of the lifters had collapsed and thoroughly damaged the head. When we removed the head, those lifters involved the Valves that had made contact with pistons (evidenced by an imprint on each piston)......one Exhaust and one Intake in different cylinders.

Results: The Hydraulic Cam Followers (lifters) have very thin tops that cannot withstand such an impact!

At a minimum, I'd replace the lifters! You cannot see the "spiderweb" type cracks that result when such and event takes place.

The "valve overlap" in relation to Crankshaft rotation on a gasser engine is more than it is on a diesel engine. But, the gasser engine's combustion chamber is in the head as opposed to being inside of the Piston as with a TDI diesel. Thus, there is some additional room for error in the larger combustion chamber of a gasser engine and the recessed valve arrangement.......but, you and I know that contact did take place with one or more valves!....Which one(s) is the big question!

[MarkC]

Installed the new crankshaft sprocket and TB, timed it up, and spun the engine with a wrench on the crankshaft. Results: no compression in 3 cylinders. Pulled the head and found no visible damage to valves or pistons, but the valves are obviously bent.

I purchased a rebuilt head and am now getting the block cleaned up. Hopefully in a few days,we'll be back to normal.

[MarkC]

Just to wrap up this thread, I thought I'd list the total cost of repair.

Rebuilt cylinder head (J&C Enterprises, Fairmont, WV) - $207
crank sprocket & bolt, timing belt, tensioner
NGK plugs, thermostat cover, o-rings, G12 - $200
Gaskets and head bolts - $90
Head bolt tool - $22
water pump and serpentine belt - replaced at no charge
my labor - free

Lesson learned is to use blue locktite on all small bolts inside the timing belt cover.