Dumb mistake -- timing belt

OK, the car is a 1998 Audi A4 Quattro, one of the first with the 30v 2.8 motor.

I was taking things apart to replace the fan belt (it was disintegrating) and discovered that the timing belt tensioner had siezed. It ended up pushing the bearing out of line, which pushed the timing belt forward, but not off the gears.

On the drivers' side, it was fine; on the passengers side cam, it was about 1/4 of the width of the belt off the front of the cam gear. This is the side with the tensioner.

Anyway, I was careless in poking around the broken/seized pieces, and accidentally released the tension on the timing belt entirely. I think that the cams each moved. The crank stayed put.

So now I have timing parts and tools on order. The basic plan would be to line everything back up on tdc, then install the locking bar etc. and proceed with the new timing belt.

Anyone BTDT, or have a helpful hint or two to share?

Interference engine, by the way. Wouldn't be much of a question otherwise.

Thanks, all. Matt

Once you think its all lined up and have pulled the tensioner pin(or however its tensioned), pull the spark plugs out and roll it over at least 4 complete turns carefully with a ratchet on the crank pulley bolt. If it doensn't bind up from piston/valve interference, check your alignment again and put it back together.

Kenny_McCormic wrote: Once you think its all lined up and have pulled the pensioner pin(or however its tensioned), pull the spark plugs out and roll it over at least 4 complete turns carefully with a ratchet on the crank pulley bolt. If it doensn't bind up from piston/valve interference, check your alignment again and put it back together.

Definitely do this, and definitely stop and recheck your work if you feel ANYTHING!

Timing belts don't need to be tight like a V belt. If you over tension them, the tensioner will fail in short order, and you'll be in trouble. Two revolutions of the crank will put you through a complete cycle.

93gsxturbo wrote:

Kenny_McCormic wrote: Once you think its all lined up and have pulled the pensioner pin(or however its tensioned), pull the spark plugs out and roll it over at least 4 complete turns carefully with a ratchet on the crank pulley bolt. If it doensn't bind up from piston/valve interference, check your alignment again and put it back together.

Definitely do this, and definitely stop and recheck your work if you feel ANYTHING!

I'm assuming the timing marks were not aligned when the belt came off. Be VERY careful! It's amazing how much arm power multiplied by a crank throw is. Valves bend EASY. You don't want a long lever when doing this and definitely do NOT spin it with the starter. I recently saw a Hemi hydrolocked due to a bad (leaking) injector that bent a rod from spinning it with the starter.

You might do good to borrow a borescope (or even buy a HF setup, they are getting down there now), stick it through the plug holes and see just what's happening. Use a short ratchet on the crank pulley and if you feel ANYTHING unusual, STOP! Then borescope each hole before doing anything else.

Yeah, no breaker bars here, just a normal 3/8" ratchet. With the plugs out you should be able to turn it without much resistance.

There are no timing marks on a V6.

The way you are supposed to do it is get it to TDC #1, install a locking pin that goes through the block into a notch in the crank, and then hang one of these babies:

across the funny looking ears in front of the cam pullies. (Locking tool also shown, not to scale!) It only goes on one way.

THEN, you loosen the cam pulley bolts and smack the pullies with a rubber mallet. The ears that the locking plate tie into are keyed to the camshaft but the pulleys are not, they just sit on a taper.

Put the belt on... tension the belt... then tighten the cam pullies back down and remove all of the locking devices.

The 3 liter is even more fun than this.

In practice, what is usually done is you make your own timing marks. Since you're too far gone for that, if you carefully roll the crank and cams over to proper TDC (there should be a TDC mark on the crank damper), you can approximate the timing belt tool and just put the belt on like a normal engine, without loosening the cam pulleys.

A lot of engines are done this way now.

Knurled wrote: Put the belt on... tension the belt... then tighten the cam pullies back down and remove all of the locking devices.

That's pretty much how a ALH TDi is done: Lock the crank, lock the injection pump, lock the cam, pop off the cam pulley, loosen 3 injector pump pulley bolts, install belt, tension, torque cam pulley, torque injection pump pulley, remove locking devices, manually rotate 4x to test. So simple to write... 4-6 hours to do...

Marking TDC on the pulleys is known as the "mark and pray" method. Sometimes it works... sometimes it doesn't. When it does, you get to brag about how you did the timing belt on a TDI without the expensive tools. When it doesn't, you're buying a new head and maybe a short block as well.

Ian F wrote: Marking TDC on the pulleys is known as the "mark and pray" method. Sometimes it works... sometimes it doesn't. When it does, you get to brag about how you did the timing belt on a TDI without the expensive tools. When it doesn't, you're buying a new head and maybe a short block as well.

That's why you mark the pulleys to the belt and make identical marks on the new belt before you try to put it on.

Heck, I do that on ALL timing belt jobs. 15 seconds to save acres of hassle, you know it's lined up or not at every point in the process.

In reply to Knurled:

+1 i did that on my 1st timing belt job and dont understand why you wouldn't do it every time. its a pretty damn good check to make sure you arent off a tooth here or there.

Some of the longer belts, Subaru comes to mind, have marks on them to make things easier.

I did this one the last time around, so I know the basic drill. Will definitely make sure I do a couple of very, very easy rotations of the motor by hand before I call it good. Crank nut is like 24mm or something so I only have the 1/2 inch ratchet to fit.

Locking pin and bar are on their way.

Based on looking at the motor last night, it looks like things didn't move very much when the belt came off. Maybe like 1/4 turn of one cam? I will be really, really careful about turning things to line them back up.

Matt

Knurled wrote: There are no timing marks on a V6. The way you are supposed to do it is get it to TDC #1, install a locking pin that goes through the block into a notch in the crank, and then hang one of these babies: across the funny looking ears in front of the cam pullies. (Locking tool also shown, not to scale!) It only goes on one way. THEN, you loosen the cam pulley bolts and smack the pullies with a rubber mallet. The ears that the locking plate tie into are keyed to the camshaft but the pulleys are not, they just sit on a taper. Put the belt on... tension the belt... then tighten the cam pullies back down and remove all of the locking devices. The 3 liter is even more fun than this. In practice, what is usually done is you make your own timing marks. Since you're too far gone for that, if you carefully roll the crank and cams over to proper TDC (there should be a TDC mark on the crank damper), you can approximate the timing belt tool and just put the belt on like a normal engine, without loosening the cam pulleys. A lot of engines are done this way now.

I got nauseous just reading that. No timing marks. If I tore into an engine that complicated and didn't see timing marks I'd just back away and call a wrecker. My tiny brain couldn't handle not being able to see the exact location of rotation for the cams and the engine.

In reply to slefain:

Even fords and other more basic cars are like that now. I just tore into a blown 2.3 shortblock I got for free to make a table out of. Drive sprocket just spins on the crank, clamped down by the crank pulley bolt.

I would guess its because that's the only way to keep the timing consistent enough engine to engine to meet today's ridiculous emissions standards.

Knurled wrote: That's why you mark the pulleys to the belt and make identical marks on the new belt before you try to put it on. Heck, I do that on ALL timing belt jobs. 15 seconds to save acres of hassle, you know it's lined up or not at every point in the process.

Please don't ever touch a TDi...

Treb wrote: I did this one the last time around, so I know the basic drill.

Yep. And re-iterating the drill should be reassurance enough that yes, it really is that easy.

You may wish to have an extra set of hands available to rotate the cams and the crank.

Knurled wrote:

Treb wrote: I did this one the last time around, so I know the basic drill.

Yep. And re-iterating the drill should be reassurance enough that yes, it really is that easy. You may wish to have an extra set of hands available to rotate the cams and the crank.

Thanks, Knurled. I definitely appreciate it. Now, wanna come over tomorrow night and rotate the cams for me?

Good point about the extra hands. Will see what I can do.

Cam bar and crank locking pin arrived today, so will start on the serious bits tomorrow. Installed the new tensioner pieces and water pump yesterday.

I hate to ask, but how bad is the 3.0? Matt

Treb wrote: I hate to ask, but how bad *is* the 3.0? Matt

Four cam pullies, variable cam timing is built into the pullies so expensive solenoid valves and such are right behind them. Cam location is done by funky devices that locate in the middle of the cams themselves, and no way to approximate it due to the design so you have to suck it up and buy the toolset. Same for the cam pullies, which must be reset to a zero point before tightening them down.

The fun is that the bolts that hold the multipiece pullies together can and will back out, destroying the solenoids ($600 ea) if you're lucky. Usually they just jump time. The last one I did was $8k to put back together with incidentals. Cross fingers, but every one I've touched got the cam pullies removed, the bolts replaced with new, and said bolts Loctited. And none have failed yet.

Find a 3-liter on car-part. Go on, find one that doesn't say "PARTS ONLY". Kind of a shame, really. If they didn't fail so much, they'd be cheaper and more plentiful, and they are aluminum-block engines. Only aluminum V6 that they made, and I'm fairly sure that normal 30v heads will go on there.

I just did my first timing belt job, and I slit the old belt with a boxcutter lengthwise while it was still installed. It only took a few minutes, and left me with two skinny belts on the sprockets. I took off one, left the other, and then slid on the new belt. After checking that all the teeth lined up, I cut off the remaining half belt.

It worked really well. I made all sorts of marks to make sure nothing slipped (I was a little paranoid).

So the engine is all put back together; spun it a few times with the front all opened up and the plugs out and no worries.

Started it up briefly; ran fine.

Will finish putting it back together tomorrow night (mostly just putting the bumper back on.)

Thanks for the advice, everyone. Matt