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.

http://a64.tinypic.com/kdlkiu.jpg

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
:cheers:

[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!!!! :-D

[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 :thumbsup:

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 :p

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. :-D:cheers:

[Ccmano]

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. :-D:cheers:

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
:cheers:

[XfireZ51]

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
:cheers:

Well Hans, we’ll have a more accurate base tune to work off of for this new motor.

[Paul Workman]

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.


:cheers:

You're not alone! My (Navy electronics instructor) troubleshooting mentor always stressed: "Never assume. You don't know something to be true until you VERIFY it to be true. He also said, one first has to know exactly how (whatever) works...to be able to determine when it isn't working as it should! Makes sense.

I usually feel confident, being a "wrencher" since high school. But, when in doubt or the least bit puzzled, I often will attempt to pick an experts' brains for their experience and clues to further investigate.

But forget just once, and ol' Murphy (Murphy's Law) seems to be just waiting every time I forget and try to assume something! GOTCHA!!! Then, after being fully chagrined, I'm going back to the basics...like I knew I should have in the first place.

Well...no teacher like experience. Serendipity is a good thing! Your among friends, Hans. And, thanks for posting!!

.

[XfireZ51]

Hans,

Remember.

"He who is without sin can cast the first stone"?

Jesus was prescient and was actually prognosticating about working on the LT5 when he uttered these words.

[Wigert]

Thanks for sharing! My Z is using tons of oil so this would be something for me to look into. Is the only way to see the problem by removing the injector housing? Can it be done with the engine still in the car?

Sorry for any stupid questions...

Skickat från min GEM-701L via Tapatalk

[XfireZ51]

Thanks for sharing! My Z is using tons of oil so this would be something for me to look into. Is the only way to see the problem by removing the injector housing? Can it be done with the engine still in the car?

Sorry for any stupid questions...

Skickat från min GEM-701L via Tapatalk

First thing is to look at plugs. There is no need to pull motor for a check of IH gaskets. Just part of doing the top end.

[Ccmano]

Thanks for sharing! My Z is using tons of oil so this would be something for me to look into. Is the only way to see the problem by removing the injector housing? Can it be done with the engine still in the car?

Sorry for any stupid questions...

Skickat från min GEM-701L via Tapatalk

The plugs will give you an indication of where the issue is. (Which cylinders are most affected) Then there is no way around it. The plenum, fuel rail with injectors and injector housings have to come out. This can all be done with the engine in the car. A fairly straight forward process. If you do go in plan on doing both sides.

Good luck, hopefully my error helps you out. How many miles on your car? I suspect this is a high mile thing.
H
:cheers:

[Wigert]

The plugs will give you an indication of where the issue is. (Which cylinders are most affected) Then there is no way around it. The plenum, fuel rail with injectors and injector housings have to come out. This can all be done with the engine in the car. A fairly straight forward process. If you do go in plan on doing both sides.

Good luck, hopefully my error helps you out. How many miles on your car? I suspect this is a high mile thing.
H
:cheers:Thanks for the feedback! My Z is a 1990 with 7700 miles on it, which is not that much. But if I go highway 15 miles it drinks a quart of oil. I have read some of the posts regarding exhaust seal, which I lack and maybe that is a reason. There does not seem to be any blue smoke but if I hold a paper towel behind the exhaust and someone gives is some gas the towel becomes very black...

I have just changed the PVC lines (to Jerry's) in case that is related to the issue. The previous owner had done a strange connection from the top of the PCV valves and the bottom line had been pinched somewhat. Havent driven the Z since the update but it feels like there is a bigger issue.

I have not noticed any noticable oil leak either until just recently. Something I am looking into as well.

Sorry for the long post! Ill need till check the plugs as you suggested.

Skickat från min GEM-701L via Tapatalk

[Ccmano]

With only 7700 miles I seriously doubt you have the same issue. With mileage that low I wonder if the rings have properly seated. I would do a compression and leak down test.
H
:cheers:

[Wigert]

With only 7700 miles I seriously doubt you have the same issue. With mileage that low I wonder if the rings have properly seated. I would do a compression and leak down test.
H
:cheers:Okay good to know. A compression test is a good idea and probably the best way forward. I will do it when spring arrives.

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[5ABI VT]

wow thanks for sharing. Very interesting I wonder if this may have been the issue with many cars I have seen threads about oil consumption etc. What did the plugs look like?

[Wigert]

With only 7700 miles I seriously doubt you have the same issue. With mileage that low I wonder if the rings have properly seated. I would do a compression and leak down test.
H
:cheers:I seem to gave missed a digit, My Z has 77000 miles. What is considered high mile for a Z?

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[Ccmano]

wow thanks for sharing. Very interesting I wonder if this may have been the issue with many cars I have seen threads about oil consumption etc. What did the plugs look like?

The plugs did show signs of oil burning, not wet, but numbers 2, 4 and 7 were discolored. All this came on rather suddenly while I was doing datalogging runs after a header install. Based on what I know of the cars history I suspect it was rather meekly driven most of its life. Me driving it more aggressively likely loosened the now hard gaskets because of the loose IH bolts. At least that’s my theory.
H
:cheers:

[Ccmano]

I seem to gave missed a digit, My Z has 77000 miles. What is considered high mile for a Z?

Skickat från min GEM-701L via Tapatalk

77000 is generally not that high but does make this condition more likely. Rings will definitely be seated with that mileage and more likely not your issue. The higher the miles the more heat and vibration cycles the engine has endured. Add to that age and things like loosening bolts, hardening gaskets and brittle plastic happens.

Pull your plugs and try to identify which cylinders are most affected. A compression and leak down test will tell you if rings or valve guides are a problem. At idle remove the oil fill cap and check for air blowing out of the cam cover, there should be none. Blowing air indicates a ring problem. Check the pcv system for functionality. Run the car with the PCV system open to atmosphere for the same time you have experienced the oil consumption. (Cap the vacuum line to the plenum) If oil consumption stops, this will tell you if oil is being sucked through the PCV system. If all this comes up negative your are left with only three other possibilities. Oil ring collapse, head gasket failure (although that usually manifests in others ways too) and my issue of IH gasket failure. This is where I made my error. I jumped to the oil ring collapse conclusion and never checked IH gaskets first.

Having said all that it is my understanding that some engines simply don’t like to be at full oil level. They consume the first quart and then stabilize at one quart low burning no more oil. Apparently a windage issue but not harmful. Try letting the engine get a quart low and see if it stops there.

There are more exotic possibilities but they generally require a tear down anyway. Follow the basics above and it will take you to the source of the problem.
H
:cheers:

[Wigert]

77000 is generally not that high but does make this condition more likely. Rings will definitely be seated with that mileage and more likely not your issue. The higher the miles the more heat and vibration cycles the engine has endured. Add to that age and things like loosening bolts, hardening gaskets and brittle plastic happens.

Pull your plugs and try to identify which cylinders are most affected. A compression and leak down test will tell you if rings or valve guides are a problem. At idle remove the oil fill cap and check for air blowing out of the cam cover, there should be none. Blowing air indicates a ring problem. Check the pcv system for functionality. Run the car with the PCV system open to atmosphere for the same time you have experienced the oil consumption. (Cap the vacuum line to the plenum) If oil consumption stops, this will tell you if oil is being sucked through the PCV system. If all this comes up negative your are left with only three other possibilities. Oil ring collapse, head gasket failure (although that usually manifests in others ways too) and my issue of IH gasket failure. This is where I made my error. I jumped to the oil ring collapse conclusion and never checked IH gaskets first.

Having said all that it is my understanding that some engines simply don’t like to be at full oil level. They consume the first quart and then stabilize at one quart low burning no more oil. Apparently a windage issue but not harmful. Try letting the engine get a quart low and see if it stops there.

There are more exotic possibilities but they generally require a tear down anyway. Follow the basics above and it will take you to the source of the problem.
H
:cheers:Thanks for the great writeup, I really appreciate it! This forum is a goldmine. I really have a lot to learn here and now several things to investigate. I hope that I am not in for a rebuild...



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[G-Sting]

I also sure appreciate this thread, H. Mistakes, shortcuts - we've all done them. Hopefully, not as a habit, of course. But a job done methodically, correctly and thoroughly the first time... almost always works out best.

But now you have an extra LT5 for your mantel. :mrgreen: ...or install it in an old Porsche 911. :-D

Thanks again for sharing your experiences and expertise.
G

[LGAFF]

Just don’t make a 2nd mistake by telling your wife:)


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[Ccmano]

Just don’t make a 2nd mistake by telling your wife:)


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Learned to not make that one a long time ago....
H
:cheers:

[gtcollins@maxnet.co.nz]

Thanks for your honesty we have all made mistakes hopefully others can learn from your experience last night I was driving my ZR-1 and pulled up at the lights after down changing and was waiting for the lights to change and was looking out my side window and sore a lot of smoke go by I just topped the oil up if you watched the video I did there was on smoke on decel so maybe I need to burn of the top 1 liter there are other vehicle that do the same

Regards Glen

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[A26B]

Thanks for your honesty we have all made mistakes hopefully others can learn from your experience last night I was driving my ZR-1 and pulled up at the lights after down changing and was waiting for the lights to change and was looking out my side window and sore a lot of smoke go by I just topped the oil up if you watched the video I did there was on smoke on decel so maybe I need to burn of the top 1 liter there are other vehicle that do the same

Regards Glen

Glen,
My apology if you already are aware of this;
The LT5 is notorious for slow oil drain-back to the oil pan from the top end after shutdown.

I noticed that you mentioned "just topped the oil up". If you did this based on the dipstick reading after turning the engine off, it is highly probable that you have overfilled. The best time to check oil level in an LT5 is the first cold start of the day.

[gtcollins@maxnet.co.nz]

Thanks Jerry yes I always check in the morning before start up

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[Flyman 27]

Glen,
My apology if you already are aware of this;
The LT5 is notorious for slow oil drain-back to the oil pan from the top end after shutdown.

I noticed that you mentioned "just topped the oil up". If you did this based on the dipstick reading after turning the engine off, it is highly probable that you have overfilled. The best time to check oil level in an LT5 is the first cold start of the day.

Thanks for sharing this Jerry, I had never heard that before.
Good to know.

[ghlkal]

Jesus was prescient and was actually prognosticating about working on the LT5 when he uttered these words.

No doubt!

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.

I would have never suspected this.

Have others heard of this?

[WARP TEN]

Glen,
My apology if you already are aware of this;
The LT5 is notorious for slow oil drain-back to the oil pan from the top end after shutdown.

I noticed that you mentioned "just topped the oil up". If you did this based on the dipstick reading after turning the engine off, it is highly probable that you have overfilled. The best time to check oil level in an LT5 is the first cold start of the day.

Absolutely correct, Jerry. I learned this the hard way when first bought my '93 ZR-1 in 1994 and drove it home to Chicago from the east coast. On my first gas stop I checked the oil and it was more than a quart down! I was really worried so I added a quart and a half. Didn't discover the error of my ways until I was home and read some articles about it in the old Registry newsletters. Fortunately it must have just burned off on the rest of the trip because I never had a problem after that.

And I have had a big adjustment with my 2016 Z06. If one checks the oil in the morning before the first run--my ZR-1 habit of 20 years--it will show empty--no oil on the dipstick. The procedure for the newer dry sump Corvettes is to get the engine to operating temp (at least 175 degrees), turn the engine off, wait for between 5 and 10 minutes, THEN check it. Same old story as with the ZR-1s--few people actually know this, including some GM techs. When I attended the Spring Mountain Ron Fellows Corvette HPDE school, in my group of 12 drivers 10 did not know the procedure on how to check the oil on their cars. Scary.--Bob

[Ccmano]

Old engine is out and now for some cleaning, porting, powder coating and a secondary delete. It’s a shame the old engine didn’t get to run its course. Especially considering the great compression and oil pressure given its mileage. I really wanted to see how many miles it would go.
H
:cheers:

http://a63.tinypic.com/otew5c.jpg
http://a68.tinypic.com/ojf4w3.jpg