Timing belt broke

[Aydenmtb]

I have a 2005 Audi a4 2.0t. Was driving the other day going about 35mph at around 1100 rpms and my belt snapped, my water pump had been leaking and washed away the timing marks on my camshaft gear. I’m trying to retime the motor and throw a new belt on and do a compression test to see if any valves are bent before i go ahead and pull the head off. I have the cams in time but I’m not sure about how I should go about timing the crank gear to top dead center, any help? I noticed that the crank gear has a certain circular bulge on it, I suspect that has something to do with timing but I’m still not sure. Any help would be much appreciated, thank you.

[a4lownslow]

Rotate the crankshaft until the timing mark lines up it’s that simple. FYI no chance you don’t have bent valves


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[Jayz691]

There is a mark on the crank(balancer), its a little "nick" so can't wash away. Line it up with the arrow on the cover, and check the cam gear. And yes, very slim chance theyre not bent. Have seen it a few times, so not a "no chance", but highly unlikely.

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[Theiceman]

I have a 2005 Audi a4 2.0t. Was driving the other day going about 35mph at around 1100 rpms and my belt snapped, my water pump had been leaking and washed away the timing marks on my camshaft gear. I’m trying to retime the motor and throw a new belt on and do a compression test to see if any valves are bent before i go ahead and pull the head off. I have the cams in time but I’m not sure about how I should go about timing the crank gear to top dead center, any help? I noticed that the crank gear has a certain circular bulge on it, I suspect that has something to do with timing but I’m still not sure. Any help would be much appreciated, thank you.

take plug number one out .. drop a dowel in it . turn crank until dowel is at very top. or use a dial indicator with an extension if you have one.

[Aydenmtb]

Got it timed, did a compression test and reading
Cyl. 1, 145psi
Cly. 2, 148psi
Cyl. 3, 0psi
Cyl. 4, 58psi
By this test I’m assuming I have 4 or more bent valves. If anyone could direct me to a thread about pulling the head of the motor and replacing broken valves that would be much appreciated.

[80sGuy]

First timing-belt change? How many miles on the car? Like everyone says, very little chance of not resulting in bent-valves

[Cyrik]

Got it timed, did a compression test and reading
Cyl. 1, 145psi
Cly. 2, 148psi
Cyl. 3, 0psi
Cyl. 4, 58psi
By this test I’m assuming I have 4 or more bent valves. If anyone could direct me to a thread about pulling the head of the motor and replacing broken valves that would be much appreciated.

The amount of time you're going to have to spend removing JUST the cylinder head AND the amount of money you'll have to spend on seals/gaskets/fluids (and other parts like head bolts or the coolant flange that you're probably going to HAVE to replace anyway) doesn't make it worth it in my opinion. Also please consider you'll have impact points where the valves hit the pistons (which creates hot-spots, no bueno). You're probably better off buying a whole new long block rather than replacing a few valves.


Edit: If you're really keen on doing this, check out these links:

Turbo DIY (Video features a B8 A4 but is more or less the same vs the B7): https://www.youtube.com/watch?v=gn2H4mrk5qM
Intake DIY (listed for carbon cleaning the intake valves but it's the same procedure to remove the manifold): https://www.audizine.com/forum/showt...eaning-The-DIY

Quote from Aluthman:

Remove the turbo and intake manifold using existing DIYs. Remove the timing belt. Remove the valve cover. Disconnect all wiring to the head and the hoses to the flange. Unbolt the head bolts and lift off the head. Clean head and block. Check head for flatness with a straight edge and feeler gauges, deck head if necessary. Reinstall in reverse order using new gaskets and head bolts.

Other info from Aluthman: https://www.audizine.com/forum/showt...ht=smoking+gun

Valve replacement should be just like any other cylinder head. I don't know specs but with a little bit of search you can find torque specs and clearances for everything you need 👍

[Aydenmtb]

So I’ve spent the last week pulling the head and rebuilding it replacing the bent valves. I had 3 intake and 3 exhaust valves that were bent. I reused all of the other valves that were not bent, cleaning them up and making them look new again. I then lapped all the valves before reinstalling them back into the cylinder head. I’ve completely put the head back together and fitted it to the block today. Before I decided to just put everything back together I did a compression test on each cylinder. I plugged the compression tester into each spark plug hole and cranked the motor by hand via the crank gear. I’m reading low compression on all cylinders especially 1 and 3. I’m wondering if this is due to not oiling the motor first and also not cranking it with the starter to do a compression test? All the head bolts are torqued to spec and a brand new head gasket as well. I’m also wondering if my crank timing could be off by 180°? But that doesn’t really make sense because when piston 1 is at the top of the stroke it should be at TDC right? Any help on figuring this low compression bullshit out would be extremely helpful, thanks!

[Aydenmtb]

The amount of time you're going to have to spend removing JUST the cylinder head AND the amount of money you'll have to spend on seals/gaskets/fluids (and other parts like head bolts or the coolant flange that you're probably going to HAVE to replace anyway) doesn't make it worth it in my opinion. Also please consider you'll have impact points where the valves hit the pistons (which creates hot-spots, no bueno). You're probably better off buying a whole new long block rather than replacing a few valves.


Edit: If you're really keen on doing this, check out these links:

Turbo DIY (Video features a B8 A4 but is more or less the same vs the B7): https://www.youtube.com/watch?v=gn2H4mrk5qM
Intake DIY (listed for carbon cleaning the intake valves but it's the same procedure to remove the manifold): https://www.audizine.com/forum/showt...eaning-The-DIY

Quote from Aluthman:



Other info from Aluthman: https://www.audizine.com/forum/showt...ht=smoking+gun

Valve replacement should be just like any other cylinder head. I don't know specs but with a little bit of search you can find torque specs and clearances for everything you need 👍

I should also mention that there were no visa or impact points on the pistons or and scoring around the piston walls

[Aydenmtb]

I should also mention that there were no visa or impact points on the pistons or and scoring around the piston walls

Visible**

[Brenton159]

you need to be using starter motor to do a compression test as will leak past rings faster than you can turn by hand, dont need to put oil in unless you are troubleshooting

[Theiceman]

agreed with above .. and no one can really evaluate the quality of your valve rebuild.. if its still low compresion it really cant be anything else..

i might have contacted a machine shop to check it over before putting it back on . Im sure they would have a jig that checks leak down with no cams in, that truely checks your vales as they all would be closed.

removing the cams and checking of course removes any timing issues . never done it but it would seem to me to be the ideal leak down test

[Aydenmtb]

Okay well then I’ll hook up the batter and give the motor a spin and hope for the best. Really don’t want to pull this fuckin head off again lol.

[Aydenmtb]

you need to be using starter motor to do a compression test as will leak past rings faster than you can turn by hand, dont need to put oil in unless you are troubleshooting

Okay so I took your advice and hooked up the battery and cranked the motor over with the starter to do the compression test and you were definitely right, the starter had to be used. Here are my test results
Cyl. 1, 180psi
Cyl. 2, 180psi
Cyl. 3, 115psi
Cyl. 4, 150psi
As you can see cylinders 1,2, and 4 have good compression. To my annoyance, cyl. 3 is still reading lower than the other ones. My question is, is the compression in cyl. 3 enough for the motor to run right? Or should I take the head back off the block and re lap the valves on that cylinder. I should also mention that that’s the cylinder with all new valves, maybe I just didn’t lap them enough? Any help would be appreciated, thank you guys!

[Jayz691]

Did you do it dry, then wet? Just to rule out any pre-existing ring/cyl issues? If its still low with some oil in the cylinder, then I would be looking at the head, in that cyl. If compression goes up in 3, then I'd double check for any damage below the head. Seems like that cyl took the most damage. Did you replace guides and seals, or just the valves themselves?

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[Aydenmtb]

I decided that once the car gets warm and oil gets in everything the compression numbers would probably even out so I decided to just throw the motor back together and hope for the best. And to my surprise it runs! And it runs really well, this job has been a massive pain in the ass but I appreciate everyone on this page helping me out! If anyone reading this is doing the same job as I am feel free to reach out and ask questions as I know there aren’t really any forums talking in depth about how to do this job properly

[Jayz691]

Well, good luck with it. I would have tried to find out why 1 cyl was so low. When doing a comp test, its not so much about the #'s, but all them being pretty even. Think ya want writhing like 8-10%. 1 being so low, idk, hope it works out for ya. Maybe do another test, with the engine hot, after ya drive it for a little.

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[Nirvana09]

Not an exact comparison but when my 1.8t had a warped head had 'low' compression in two of the cylinders and 'low' was 125. Something is definitely going on if you are seeing numbers like 115.

[Theiceman]

get engine warm.....not hot repeat test

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[Jayz691]

Get engine hot, not warm..repeat test, lol.

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