Always stick to the basics, no short cuts....!!!!!

[Ccmano]

I was somewhat hesitant to post this, because, as you will see, it is really embarrassing for me. My hope is that by posting this it will save someone else from making the same mistake I have recently made.

Many years ago when I was a trainee at Mercedes-Benz I worked with a crusty old German master technician named Herrman. Herrman would always drill into us that when diagnosing a technical issue to always stick to the prescribed basic diagnostic procedures. Never ever take a short cut even if you think you know what the problem is. I saw this play out countless times when Herrman was called in to fix a problem that no one else could. He would always quiz the technicians to find out if they went through all the diagnostic steps to find the issue. Invariably short cuts were taken which resulted faulty diagnosis and unresolved problems. He would cuss them out from top to bottom. He was the best technician I ever worked with.

Well... now it is me that is guilty taking the short cut. You may remember my recent thread on my high mile Z that suddenly started burning significant oil. I ran several tests and checked “all” the systems. I came to the conclusion that at least one of the oil rings had given up and that was the cause. I decided to replace the engine with low mile 91 engine that I recently purchased. Given the 180k miles on the current motor I thought this was reasonable.

I am now in the process of tearing down the old engine in preparation for pulling it out of the car. Today I pulled everything off the top of the motor including of course the plenum and injector housings. To my uncomfortable surprise I found that the injector housing to head gaskets were stone hard and the IH bolts were loose. Upon closer examination there were significant signs that oil was being sucked from the breather passages directly into the cylinder heads. The gaskets were literally soaked with oil. It was obvious where the oil was coming from.



I even recall thinking that the IH gaskets could be a possibility. I dismissed the thought because I saw no sepage into the valley and frankly I had never heard of such a thing on our engines. And of course I had convinced myself that the oil rings were the issue. Had I followed through to properly diagnose the issue I could have saved myself an engine replacement, at least for the time being. Taking a short cut bit me in the a$$.

All is not lost, my high mile Z will now have a virtually new drive train (trans is brand new and the diff has been rebuilt) with some additional goodies like top end porting, headers and a fresh finish on everything. The old engine which was surprisingly strong with great compression (and apparently no oil ring issues) and oil pressure will be parted out to recover some of the costs.

Herrman was always right. Stick to the basics and never ever take short cuts when dealing with technical issues. I hope this will help someone else from going down the same rabbit hole.
H

[32valvZ]

I never met a man who hasnt ever made a mistake or taken a short cut in his life. But I have met a few who didnt admit when they did...

You are man enough to admit when you make an error.... that speaks volumes about your character.... Live and learn.... we all do it that way!

Hey, it never hurts to have an EXTRA LT-5 in the garage!!!!

[tccrab]

Don't beat yourself up over this.
Yes, it's a lesson, but the good news is that your Z will be better than new when you're all done.
I personally chased an electrical gremlin for longer than I'd care to admit, that I actually caused.
Long ago, my injectors began failing because of Ethanol, part of my diagnosis was to back probe the ECM connector to see if the injectors had high Ohm's.
I just jammed my DVM's probe into the female connectors never once realizing that I was stretching the inner diameter of the female connectors.
When the engine was cold it ran just fine.
When it got to heat soak, the connectors would expand just a little and the misfiring would begin.
Drove me nuts.
I spent hundreds of $$$ on parts that I didn't need trying to nail that gremlin to the wall. Coil packs, wires, plugs, had the plenum off 3 different times, new secondary vacuum hoses, solenoids, etc, etc.
Thanks to a post just like yours, someone else had made the same mistake and admitted it, hoping we'd all learn from it.
I sure did.
I re-pinned my ECM plug with new female connectors (cost me maybe $20.00) and the stumble magically went away.

Hopefully the next guy with high oil consumption will read your post and thank you for your experience and your honesty.
You may feel humbled now, but thanks to you, you've saved the next guy from making the same mistake.
My hat is off to you, and thank you for helping us all out.

'Crabs

[RussMcB]

Thanks for sharing.

[Dynomite]

Yes .......been there and done that on a 95' which I still do not know what caused Inj1 fuse to keep blowing for sure but somehow fixed the issue.

On your 180K miles engine take some photos of the timing chain guide facings wear (When you get it apart). Especially interested in the condition of the two guides pushed by tensioners.

and thank you

And yes....I remove wiper motor when pulling engine.

Oh.......If you are parting out the 180K engine I am collecting Fuel pressure regulators......and you know why

It is the unique failures (often on high mileage engines) that are very interesting to diagnose and very surprising often the causes of some failures.

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[conesare2seconds]

Thanks for the heads up.

[HAWAIIZR-1]

Thanks for sharing and greatly appreciate it.


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[XfireZ51]

I can imagine what Rene said when u informed her of the reason why you just bought a new motor.
I think Herman’s rule of thumb is known as Occam’s Razor.

[XfireZ51]

Also Hans, do use new O2sensors on the new motor. The oil seepage would explain at least a part of the discrepancy we were seeing between right and left banks in terms of the BLMs and the stalling as we were tuning the motor. A reason why the IAC counts were dropping to 0 too. An oil soaked vacuum leak.
Hell we had it running pretty good in spite of this.

[Ccmano]

Originally Posted by XfireZ51

Also Hans, do use new O2sensors on the new motor. The oil seepage would explain at least a part of the discrepancy we were seeing between right and left banks in terms of the BLMs and the stalling as we were tuning the motor. A reason why the IAC counts were dropping to 0 too. An oil soaked vacuum leak.
Hell we had it running pretty good in spite of this.

Yes had the same thought, that this was the cause of some if not all of the tuning peculiarities we were seeing. But boy it ran really well. Too bad we can’t see it run with the issues fixed.
H