MNRS6

2005 Audi A6, 4.2L, 80,000 miles.

I was driving my wife's car a month ago and the engine stopped while going 65 mph. I was coming down an on ramp and was definitely WOT. I slowed down and coasted to the next exit. I tried to restart the engine and nothing. I have free roadside so I had the car flat-bedded home 5 miles away.

When cold I did notice the car did 'clang' during start-up. After the failure I suspected a cam/timing belt issue. Did a compression check and verified 0 compression on 2 passenger side cylinders and 1 on the drivers side.

Long story short, I pulled the engine and found the passenger side intake cam bolt was loose?? When I manually turn the engine over I can see the cam does not move.

My big question, do I have bent intake valves for sure? Or do I just have to align the cam with the proper tools and wrap it up? I would like to double check the compression on the drivers side but how do I crank the engine over by hand easily? I cannot find anything to crank on.

Thanks ahead of time!!! It's been quite the job so far but great experience overall.

ProtoFly

I think that you would want at a minimum to pull the plugs and get a borescope in there to check for bent valves. I suppose it's -possible- that there's no damage, but I'm going to say very unlikely.

Even if you have no damage, I'd still change out the tensioners and guides while the engine is out.

My 4.2 decided to shed a plastic guide on the upper right, and that caused the exhaust cam to skip a tooth. Piston to valve contact occurred.

MNRS6

Should have the rest of the timing covers off later tonight. Did you just have new exhaust valves put in or did you swap in new heads? When putting in new valves do the seats away have to be ground?

Prospeeder

Valve are bent for sure. Especially since you were on it hard higher rpms its absolutely got bent valves.

MNRS6

Pulled the intake and yep they are for sure bent. Found one of the chain guides off the crank chain was broken. I assume this caused a tooth to get skipped and resulted in the valve contact.


Nice S-shape you can see on this one.


Whats the best next step??
1. Bring heads to rebuilder?
2. Buy used heads?
3. Try to tackle valve job myself?

We are in deep!!

Prospeeder

I would just do a valve job. Alls you need is to replace the bent valves and lap them in. Replace all chains and guides and roll another 100k

MNRS6

Why don't the seats need to be ground? You really made my day with this info btw.

I have seems valve prices at about $50 each, anyone know of the best deal around?

Prospeeder

Grinding the heads is way more than nessesary. If The seat it in good shape, which on german stuff always is unless it has 300k miles. Just lap the valve in and your good. The new valves come cut at the correct angle, just needs lapped in. Done it lots of times no problem. If just lapping wont make a good seal, which is obvious if you have done valves before, I use a seat cutting tool and by hand cut it some until the valve laps in nicely.

50$ a valve is insane

http://www.fcpeuro.com/products/audi...lve-077109601q

MNRS6

Just giving everyone a update on my timing belt issue. I pulled the engine and tore it down all the way down to a block, pistons and crank.

So here are the damages. All 40 valves bent! Turns out the main timing chain guide broke and a piece of it was sucked in between the crank sprocket and chain. This is what put all the valves out of timing and put a nice 's' shape is all of them. I bought used heads online which only had 8 bad valves which I lapped in and installed. Long story but it's all back together and running great. Just in time for snow here in MN. I think I spent $1700 in parts and maybe $500 in tools, not bad for me head and a full engine pull.

Hate to say this but the car is now getting traded in. It's the wifes car and she doesn't like all the power, boo. Hello Ford escape! Anyways, I can now look for the next project, either S4 wagon or 2nd Gen A8.

Thanks to everyone for all the help on this project, by far the biggest auto project I've done yet!

ProtoFly

I'd love to see pictures of the back of your engine with the damage. Did you take any?