I have a 2000 A4 1.8T Q Tiptronic that had a highway speed timing belt failure. (I think) The motor just shut off. Now the starter spins, but the engine does not turn over.

How deep do I need to go to confirm this and determine what is toast and what is still usable?

I have a 1999.5 AEB engine that I could use as a donor to fix it. But from what I've read the 2000s have the ATW code engine. Looks like I would have to remove the intake manifold to be able to see that, any better way to verify the engine code?

From what I've read the heads are different, and the AEB uses cable throttle control, while the ATW uses wire.

What could I use from the AEB, and what other parts would I need to complete the repair. For example could I use the AEB head and use the ATW intake and throttle assembly?

Thanks

 

First of all, if you think you have a timing problem, don't keep turning the motor over, you could be causing more damage.

When the motor shut down was it accompanied by any horrendous noises? There are many reasons the motor could shut off and not start up again other than a timing belt failure (lack of fuel, lack of spark.)

Start by pulling the upper timing belt cover off and visually inspect for damage or a loose timing belt. If everything looks fine and dandy, you can double check that the timing is correct by removing spark plug #1 and resting a dowel on the piston face. Put the car into a high gear and push the car forward to confirm that the cam pulley mark matches the mark on the valve cover when the dowel is at its highest position (top dead center.) A compression check would not be a bad idea either.

If the timing is correct and the car still has good compression then the problem is with fueling or ignition (or an electrical gremlin.)

The engine code is stamped onto the right front corner of the head and should be visible without removing anything other than the top engine cover, no need to remove the intake manifold.

A 2000 A4 will have an ATW motor. The ATW is the bastard child 1.8T motor. It uses an 058 block (same as the AEB, so the timing components are identical) while being DBW with a small port head and secondary air injection.

You could use the AEB head and intake manifold, but to use the ATW intake manifold you would need to get a transition spacer (034 Motorsports makes them) and you would need to delete the SAI as there would be no provision for it on the back of the head. The DBW throttle body will bolt up to either intake manifold.

That's getting ahead of yourself though, figure out what broke (if anything) and take it from there.

 

First, thanks for taking the time to make such a thorough response!

Well... Finally had some time to take a quick look at this again, its my son's car.
He did not hear any horrendous sounds, it just shut off, and he coasted to the side.

I just unsnapped the TB cover and took a peek. The belt is intact. So I hope that is a good thing.

I have not tried to turn it over again, but when I did previously it sounded like the starter was spinning but the engine was not turning over. What would that suggest? I know a starter solenoid could cause that, but given the other circumstances, I doubt that here.

I'll have more time Monday to dive in to it.

Thanks again. one of the best things about these cars is the user/enthusiast support!

 

The belt being intact is a good thing, did you happen to give it a press to check for tension? It should only deflect 1/8" or so. It would also be a good idea to take a rod or ratchet extension and press down on top of the metal plate on the pulley. It should not move at all if the tensioner is working properly. If that checks out you can be fairly certain nothing went wrong with the timing system.

The next thing I would do is scan for codes (really should have been the first step.) That may help point us in the right direction and will save time over guessing and checking things.

One of the most basic things should be to ensure that the car didn't simply run out of gas, has the gas gauge been working properly and what does it read?

 

The belt is definitely taught and I could not see any deflection pushing on the tensioner with a ratchet extension. Its hard to see much, I don't have it in service mode with the front pulled out yet.

It has fuel in the tank.

I'm alone right now so don't have anyone to watch while I turn the key, but I'm pretty sure the starter turns, but it does not seem to be turning over the engine.

Saw this thread. What do you think the chances are that the crank pulley locating lug / key is sheared? How would I verify that?

https://www.audiforums.com/forum/b5-...topped-140063/

I have a Vagcom, but I don have a laptop handy to use with it right now. I may have to drag the desktop out to the garage.

 

I think it's rather unlikely that you sheared the crank key off. This can be easily tested by cranking the motor with the upper timing belt cover off and seeing if the timing belt rotates or not. You could also verify that the crank and cams are timed properly by the method I mentioned earlier. Pull the #1 spark plug and stick a dowel down to rest on top of the piston. Then watch for the dowel to be at its highest point as the cam pulley lines up with the mark on the valve cover.

Drag that desktop out, you need to scan for codes to point us in the right direction. It could be a bad fuel pump relay, it could be a faulty crank or camshaft position sensor, the codes will tell us more (if any exist.)

 

Ok heres the vagcom results...

16795 Secondary Air Injection System
P0411-35-00 incorrect flow detected

16726 Cam Shaft Position Sensor (P40)
P0342-35-00 signal too low

 

The Timing belt does not move when engaging the starter, but the accessory / alternator belt does move.

 

How old is the belt? Sounds like a classic case of the timing belt losing teeth because it's way past its service interval. I predict a valve job is in your future.

 

The timing belt was done in the 80+K mileage range, its in the 130's now. So its not really out of spec. Fluids were maintained, oil changed, etc.

Yea, I expect major work, if it even makes sense cost wise to fix it. Just trying to get a solid diagnosis, and figure out if my 1999.5 1.8t with AEB engine could be a donor. It runs great, but has some other wear and tear.