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Timing issues 1997 a8

  #1  
Old 03-07-2011, 09:38 PM
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Default Timing issues 1997 a8

Ok so i am currently working on my friends 97 audi a8 with a abz engine. That is the 32 valve 4.2 v8. The problem im having is it wont start it seems to be sucking in the exhaust and pushing out the intake. The timing belt is not broken and was recently replaced with the waterpump, i have no idea if the tensioners or rollers were replaced. I did a compression test and got low results but also i was NOT at Wide Open Throttle. I pulled the valve covers to check cam to crank timing and tried mechanically checking TDC but when the mark on the harmonic balancer lines up with the pointer, #1 cylinder is allready on the down stroke. Is that normal? OK but crazy enough the dots on the cam gears are dead on?? The crankshaft bolt was finger tight at best. We do have compression so i figure the valves aernt bent just opening and closing at the wrong times in the cycle to make good compression. If the valves were bent and not closing there would be free play between the lifter and the cam Right? I am aware that this job requires the use of cam lock tools. So TDC on this vehicle refers to what cylinder #?

Any help or direction is greatly appreciated
Thanks
 
  #2  
Old 03-07-2011, 11:08 PM
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On 40V engines, for cam timing and belt change purposes, TDC is cylinder #5.

I've never done the belt on a 32V A8 motor. Bentley only says "TDC" (no cylinder noted) and cam marks facing each other.

Here's a good tutorial on ABZ timing belt change:

http://www.audipages.com/Tech_Articl...breplace0.html
 
  #3  
Old 03-08-2011, 12:58 PM
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Thanks but yeah i allready found that. I usually try to answer my own questions through research but it seems there is a lack of info on this engine. Through my endless hours of research i found that the outter ring on the harmonic balancer/vibration dampner with the "TDC" mark can end up spinning out of its original index point. Due to aging rubber between the ring and the hub. So im trying to mechanically check the timing. This has to be by the biggest PITA that ive ever tried to sort out. {due to lack of information} I also understand that the dots on the cam pulley's where the timing belt rides are useless beacuse of the taper fit between pulleys and shaft. I seen the 40v 4.2 has a crank lock tool but i couldnt find one for the 32v 4.2
 
  #4  
Old 03-08-2011, 05:41 PM
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Yep, I think Audi learned a lot from the 32V. The 40V is much easier to time and do timing belt change. On the 40V, the harmonic balancer bolts to the crank pulley..only goes on one way and easy to remove. The 32V doesn't have the plugged "port" for a crank lock tool, as is the case with 40V...so no tool available that I know of.
 
  #5  
Old 03-08-2011, 07:10 PM
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Ok so i just called my local VW/AUDI dealer and they said "TDC" on the 32 valve v8 refers to cylinder #1. I am gonna call a couple more dealers and just check to make sure. As i have been given misinformation before. (the more information the better) since this is a fine piece of machinery. Im just crossing my fingers and hoping the valves are all good. Any engine ive ever worked on with bent valves had 0 compression. Is there any good place to buy/rent the cam locking tools? Should i trust after market cam lock tools. I do appreciate you taking the time to respond!! Thank you. Hopefully i will be posting a solution soon that will shed some light and help others like me lookin for some answers.
 
  #6  
Old 03-08-2011, 09:17 PM
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One note, that has no doubt occurred to you:

From the 40V procedure view (which I've done), one turn of the crank gear to come back to TDC is only 1/2 turn of the cam belt gears (twice the size and teeth of the crank gear)...so TDC on one turn is the top of the exhaust stroke on #1, then the top of the compression stroke #1 next turn to TDC.

So, with that in mind, this is where Bentley procedure loses me on T-belt timing for 32V engine...don't know if they left out something...crank and cam gear layouts seem to be the same on 40V.

On the 40V, you must turn the engine twice (past TDC once) to get back to TDC #5 each time (top of compression or top of exhaust stroke?) so that cam gear holes are in proper time (correct size holes on outside of gears facing correctly for lock bar to fit). This is the same for lining up inside cam timing marks for chain repair/replacement work. So unless there's something very different about the 32V (and I don't see it), TDC on the crank can NOT line up the cam timing correctly each time...it would change by 180 degrees each time TDC is reached, which would make sense, since one time is for compression and the next is for exhaust. So inside cam timing marks can only line up every second time at TDC...right?

Every piston HAS to hit TDC twice during each 4 stroke cycle, so:

Unless I'm missing something, if crank timing was off one full turn (360 degrees) or cam timing was off exactly 180 degrees (depending on how ya look at it), which it could be, since "correct" TDC isn't specified, then no valves would make piston contact, but during piston stroke, the wrong set of valves would open...intake instead of exhaust & vice verse on each cylinder. Wrong TDC could have been set by hand-turning during belt job, without hurting valves (hand-turn contact would have been absorbed by hydraulic lifters). That would certainly fit with what you described in post #1.

Did this engine EVER run after the timing belt change? My guess is no. If it did, I'm really baffled now.
 

Last edited by silverd2; 03-09-2011 at 07:51 AM. Reason: Correction
  #7  
Old 12-07-2013, 03:26 PM
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Any luck with this??? I'm in the same situation and desperate for help .
 
  #8  
Old 12-08-2013, 07:02 PM
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I would agree it sounds like the cam timing is off.
This may or may not help: It's PDF file and I couldn't figure out how to link to it. Click on the first search result on the page. Also, unsure if this is the correct engine..............
1997 audi 32V 4.2L cam timing procedure - Bing
 

Last edited by aspen79; 12-08-2013 at 07:04 PM.
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