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Possible Bent valves

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Old 05-12-2010, 11:54 AM   #1
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Default Possible Bent valves

99 a6 with 2.8 30v

something went wrong mechanically with my timing belt system.

i wasnt driving the car when it happened but the person driving it described it as a clicking started coming from one side of the engine then the rpms started to drop then it stalled.

i now know that one of the timing belt rollers locked up.

i am going to replace it, and if it turns out that some of the valves got bent what kind of repairs am i looking at?



is it even feasible that i could replace the cylinder heads myself if say, i got rebuilt headers?
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Old 05-12-2010, 12:09 PM   #2
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Apologies in advance for this, but:

http://forums.audiworld.com/showthread.php?p=23920578

I have a head if you need it.
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Old 05-12-2010, 12:19 PM   #3
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Quote:
Originally Posted by 4Driver4 View Post
Apologies in advance for this, but:

http://forums.audiworld.com/showthread.php?p=23920578

I have a head if you need it.
haha you A hole- gimme a break im a teenager and that was back when i first got this A6.
ill admit i knew practically nothing but that was a couple months ago. hence the "audi world junior member" right below my name on the forums.

i do have to say thanks though 4driver4. you definatly deserve the "Tech Guru" under your name.
basically everything i know i learned on this site.
give me some credit though- i went from barely even knowing what a water pump was to doing my timing belt job in like 4 months.


so can you enlighten me yet again on this issue.




and btw i knew you would be the first one to respond on this thread :-p
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Old 05-12-2010, 12:23 PM   #4
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LOL - sorry.

I'd start by getting the belt back on right and checking the compression or doing a leak down test. It is entirely possible to have the timing out far enough to lose compression and run crappy without damaging valves. If you do have bent valves because the belt jumped, you are probably looking at half a dozen exhaust valves, and it will make more sense to repair the head you have. But I'm getting ahead of myself. Get a belt on right and see if it runs.
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Old 05-12-2010, 12:27 PM   #5
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ok- i plan on doing it this weekend

will be back on the form the instant i get it done haha
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Old 05-13-2010, 07:21 AM   #6
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I bought a 98 A6 last Dec with a similiar issue, the bolt sheared off on one of the pulley's the timing skipped about 30 degrees on one cam, and it quit running. I planned on rebuilding it but got lucky, it didn't bend anything. I had another car a few years ago that wasn't so lucky, bent most of the exhaust valves. but personally I love the 2.8 engine, it is really a easy engine to do a topend rebuild. so as said, get a belt and time it, chances are you could be fine. if not it isn't to badly priced to rebuild yourself, I think I had about $600 in Parts when I redid my valves (don't recall if that included the water pump though) but valves gaskets belt etc..
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Old 05-13-2010, 07:52 AM   #7
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On the 2.8l 30V AHA and ATQ V6 engines do only the exhaust valves hit the pistons with a jumped or broken cam belt? That seems to be implied in your posting? On the 99 A6 V6 30V AHA that I took a part last month the exhaust valves on bank 1 actually had the valve heads broken off their stems, but the intake valves looked OK.
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Old 05-13-2010, 04:29 PM   #8
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yes that is what i am hoping for jschick- maybe i will get lucky.

i was wondering (this could be a stupid question)

when i put the belt back on and everything, how do i time the cams if they are severely off.

like say i put my tools down and went and did something and someone came over and started spinning the cam sprockets (without the timing belt on) and then i had no way of knowing where they should be, how do i line them up correctly.

the tech article i followed last time said to just lock the cams and leave them where they were, along with the crank, it dosent explain what to do if the cams are already off time when you do the job

hopefully you know what i mean- tell me if i am not getting my point across
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Old 05-13-2010, 09:15 PM   #9
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Quote:
Originally Posted by Peter Badore View Post
On the 2.8l 30V AHA and ATQ V6 engines do only the exhaust valves hit the pistons with a jumped or broken cam belt? That seems to be implied in your posting? On the 99 A6 V6 30V AHA that I took a part last month the exhaust valves on bank 1 actually had the valve heads broken off their stems, but the intake valves looked OK.
If the belt jumps a few teeth, the exhaust valves will be the first damaged. The belt has to jump really far for the intake valves to get damaged. Think about what happens when valve action is later than crank action.
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Old 05-13-2010, 09:38 PM   #10
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Quote:
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y
when i put the belt back on and everything, how do i time the cams if they are severely off.
Lock the crank, use the locking bar to turn the cams back into position, install the locking bar and belt, then tighten the sprockets back down.
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1983 Mazda RX-7 (revolutionary sports car)
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Old 05-14-2010, 04:12 AM   #11
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yes use the lock bar, you can really only turn the cam so far with no belt (valves hit pistons) so if someone turns a cam while you are not looking!!! it will only go so far, just spin it back and use the lock bar. Be careful not to let the cams "sping" back. at some point in their revolution the cams will spin on their own because of the springs/valves on the cam lobes if this happens it is possible to bend a valve, not real likely but possible. so use a wrench to spin the cams!! it is very important to then loosen the cam sprockets, you will need a puller to pop them free from the cam, (just loosen the cam bolt about 1 turn then use, just enough to use a puller to get them loose) if you don't do this you will not get the slack out of the belt with the tensioner. You will see many posts on T-belt jobs throwing codes, generally this is why!
it can be done without the cam bar and tools but it is hard to get the slack out of the belt it could take several revolutions of the crank and a few adjustments of the belt (moving one tooth here or their on the pullies) i used to do this with just a yard stick instead of the lock bar, but the bar is well worth the $$ if you plan on keeping the car or plan on getting another!
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Old 05-14-2010, 12:29 PM   #12
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i lol'ed at this and the other thread..... to many "budding" mechanics out there.... this isnt your budies honda.
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Old 05-16-2010, 07:28 AM   #13
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well what happened was the the timing belt tensioner roller basically sheared off. the bolt holding it on to the engine block broke in half.

no i have to get the screw out that is in the hole.

any good ways of doing this?
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Old 05-16-2010, 08:55 AM   #14
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Bolt was over torqued.

Use an EZ out or some other extractor.
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Old 05-17-2010, 07:23 AM   #15
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Quote:
Originally Posted by 4Driver4 View Post
If the belt jumps a few teeth, the exhaust valves will be the first damaged. The belt has to jump really far for the intake valves to get damaged. Think about what happens when valve action is later than crank action.
Yes, but all six of the exhaust valves on bank 1 broke their heads off and the intakes were apparently untouched? I would have thought that with enough rotation of the crankshaft, the bank 1 pistons would have had a chance to hit
the intake valves on bank 1.
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Old 05-24-2010, 11:29 AM   #16
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Ok well got another chance to work on the car. got the broken tensioner screw out of the hole.

now i am trying to time the cams.

i basically turned the crank and it turns indefinitely without hitting any valves, or without any resistance, i should say. no matter where i turn the CS to, the cam sprockets on botch sides will only turn about 30 degrees untill they feel like they hit something.

if you want me to i will make a youtube video of what i mean.
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Old 05-24-2010, 11:29 AM
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