wizzard1222

My 1998 A8 4.2l originally went into emergency shutdown mode while on a highway trip. With emergency dash icon showing, I pulled it off the road.

After tow to closes Audi dealer...they said it was 'probably' a skipped timing belt...damaged valves. Recommended an engine rebuild for about $4k.

Base on that info. & reading a lot of the posts on many Audi forums & audipages.com...I decided to give it a donor engine swap.

The original engine would still start & run for about 2 or 3 minutes before stalling out dead...I believe it was again a emergency shutdown by the computer.

My independent mechanic checked the original engine & found full compression on all pistons !!! No tapping, No raddles, No misfires...even after many months of idle time while I researched for information & assembly of reconditioning parts (timing belt, h2o pump, pulley's, oil coolant seals & pipe, valve cover gaskets, new cam seals...etc.).

Pulled the nose & rad for full open view & access. Found that the oil tooth pulley was very tardy... w/nearly frozen bearings. No broken belt, No missing teeth from the belt, a fatigued dampner/shock. When placing the locking bar on the cams...perfectly in TDC !!!

So w/full compression, cams in TDC & nearly frozen bearings on the oil pulley...we think that the oil pump pully issue caused low oil pressure issue. This could have been the reason for the emergency shutdown mode on the highway !!!

Replacing the oil pulley bearings, new TB, both cam seals pulleys, rollers & new dampner/shock for a trial engine start after slow hand rolling the engine a few cycles. Check the chamber compression again...ok But found two chambers were soaked w/engine oil !!! Probably leaking valve cover gaskets... The plugs has fuel (gas) smell....getting fuel delivered from the gas tank.

Tried to test start the exposed original engine... Slow crank.. no engine start/fire... the battery had a low charge.

Not sure why it wouldn't start...? So we are going to get a full battery charge overnight & give it a whirl again.

Any thoughts, suggestions &/or contributions would be greatly appreciated & helpful.

joshe8695@yahoo.com

Oil pulley??

silverd2

Yep, ABZ engine has oil pump run off the timing belt. Newer 40V engines have internal chain drive to run pump directly off the crank.
Bad bearings alone should not have had much effect on oil pressure, as long as the gear was turning...which it HAD to be, running off the timing belt.With bearings replaced, the pump should turn easliy by hand without much resistance..otherwise there could be a pump problem.

Valve cover gaskets wouldn't allow oil into the combustion chambers...only outside onto engine and exhaust manifold OR into top of spark plugs, which would be readily apparent as soon as you pull off plug wires. Oil in the chambers could only come from bad rings, head gasket or badly leaking valve stem seals (stem seal leaks usually burn off at start up, with a brief puff of blue smoke and undetectably while running).

Wet plugs (with gas) will prevent the motor from starting and/or indicate a probable spark problem.

With low battery, as soon as get the engine running, put a voltmeter directly onto battery poles...should read between 13.5 and 14 Volts...if not, the alternator is not putting out enough to keep battery up or there's a bad connection between there and the battery, possibly in the junction in front right fender well.

wizzard1222

Hey Silverd2: Thanks for the comments & suggestions.

The replace bearings from the donor engine did/does work freely...what a difference. The old frozen bearing looked like it had rust build up on the outer housing area. My guess is that water/mosture was the cause. They were not broken out of the housing like some wheel bearing I have had on other vehicles....just frozen (rusted) in the housing.

On the value cover issue, I may not have describe the 'found' oil properly from the spark plugs. Yes, the oil was on top of the spark plugs as you would either be removing the spark plug or installing an iginition coil rubber boot. No oil in the chamber or on the piston head...no puffs of oil from start up(s)...or oil burning smell. No oil leaks around the head gasket or oil cooler...yes, I think that the oil is coming thru the valve cover gaskets onto the top of the spark plugs. Thanks again for your thoughts & confirmation.

With the Audi being idle for many months & w/the suspected engine valve damage (from the Audi dealer...skipped timing belt?)...I constantly charged the battery w/handy charger & a solar trickler. That would keep the alarm system active.
So when the time finally came to begin the scheduled donor engine swap...I had the battery fully charged...not sure about the alternator since I did not have a problem before the emergency computer shutdown on the highway. I do not think the alternator is/will be an issue....but we will follow your suggestion to check the voltage....wonderful next step.

We are planning to also get a vag-com (ross-tech) readings to scope the entire electronic...modules. I know that will all of the sensors planted everywhere...it would be a guessing game w/o a electronic readout...we'll keep you posted.

Wow...thanks for the many suggestions.
I'll probably be ordering a Bentley's repair dvd manual as well. Probably should have gotten that when I was rounding up all of the 'reconditioning parts' for the donor engine.

If we can get the original engine working...I'll either recondition the donor engine as a spare or possibly sell the donor engine 'as is' to anyone else needing a transplant !!1

silverd2

Glad I could be of assistance. I was going to suggest checking out the old engine before assuming it was unusable. It's easy to check for jumped cam timing. There are marks that can be lined up at TDC on both cam gears and the crank gear. If they all line up, the belt has not jumped time...which it really can't do, unless it was incredibly loose or actually broke teeth. I can tell by eye, when it's right...but critical checking would be done with a camgear locking tool that only fits alignment holes on the gears when timing is correct.

I do highly recommend the Bentley CD...it can be vague at times and occasionally incorrect, but 99% a good thing to have. There's always someone here on the forum to help explain the vague portions and the typos.

silverd2

P.S. If I haven't mentioned it, the most obvious thing to do on all these cars is to have the codes read...at least on a handheld code scanner (free scan at lots of auto parts stores like AutoZone, Advance, etc) or better yet a more thorough advanced VagCom (or similar) diagnostic.

wizzard1222

My AZO store doesn't have the vag-com for Audi/vw...but I have sent other friends that direction w/their vehicles.

As well, I can not get the 'opened front end' Audi to any shop w/o an additional tow bill.

My older cars don't have OBDI (1991 Lincoln
Town Car...1989 Buick LaSabre...they don't have that old scanner anymore). Basically: they just have scanners for the newer vehicles...say back 10 years or so.

Yes, I have one of the inexpensive vag-com's but as you mentioned...it's very limited on the info. & data that are reported on the avaliable "modules". We are awaiting arrival of a new vag-com (Ross-Tech) to elimate chasing loose ends.

Thanks again for the positive suggestions.

wizzard1222

Forgot to mention that one of the 1st things is to re-check the cam position sensor(s)...just have a feeling from reading & research.

Tracking the electrical 'spark' is our 1st target...rechecking the compression values & of course the fuel delivery system. With the better Ross-Tech vag-com, that should save a lot of tail chasing !!!