Smoke from Engine - Help me diagnose please!

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Hi all, I have an old Maserati Biturbo that I bought in a non-running condition. It had a bad engine so I sourced a replacement used engine.

I got everything back together and have been seeing a lot of smoke from the tailpipe.

I initially did a compression test:
cylinder 1 - 120
cylinder 2 - 115
cylinder 3 - 130
cylinder 4 - 123
cylinder 5 - 118
cylinder 6 - 118

not super high but all within 10% of each other.

No real smoke until it heated up a little bit and then really heavy at high revs - then when warm pretty much all the time.



At that point I thought maybe the turbo was blown or perhaps there were valve stem seals blown. After reading more about it, I figured it was the turbo on one side or another.

I pulled the exhaust Y pipe and:

Passenger's side:


Driver's side:


So clearly an issue on just that side. I figured the turbo on just that side blew so I pulled the engine to get at it and upon pulling the exhaust manifold off the head it was clear that the oil was coming into the system ahead of the turbo:


So then I figured that a valve stem seal had blown on that cylinder. I pulled both heads and cleaned up the valves from a LOT of oily soot and replaced all seals.
It was the top left cylinder in the below picture - cleaner than the rest due to burning oil right?

I did find a bad seal on this intake valve - note the soot:




Here's the cylinder in question:

a few scratches but nothing with any depth to it at all.
All the valves fit in the guides properly and the cylinder sleeve diameters all check out per specs

So I buttoned it all back up
All fixed right? - no

I got it back together and still smoking like crazy. Here's the view right out of the exhaust manifold.

[video:youtube]https://www.youtube.com/edit?o=U&video_id=WYnkPgDsHFI[/video]

I pulled the turbo on that side again and same source of oil.

So, is this a simple case of stuck or broken rings? Could anything else have caused this problem? The good compression in cylinder #4 (the fouled cylinder) has me confused

I also had a bit of gas in my oil early on but I have chalked that up to excessive cranking with the distributor cap 180 degrees off (whoops!)

Thanks for your comments
 
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This seems to be an awful lot of work to dance around the fact that the rings in the "new" engine are worn. Did you do a "wet" compression test?

What is the spec for compression? Turbo engines are often set up for lower compression in the first place. Those numbers on an NA engine combined with smoke from the tailpipe would make the obvious conclusion that the rings are shot.
 
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Any way to run it without the turbos, just to be sure?

If you have a way to take the inlet air from the turbo out of the picture and run it N/A to eliminate the turbo as a source of the oil.

Did I understand that you replaced all seals on ONE cylinder, or replaced all valve seals?
 
Originally Posted By: Chris142
How long did you run it? Often an engine thats been sitting will smoke a while till it clears up. My old scout fumigated the neighborhood for 45 minutes.

I ran it for a while in the garage and driveway and then took it for a short drive. It wasn't letting up. I thought maybe oil in the exhaust was the problem which is why I pulled the exhaust completely and was able to see smoke from the exhaust manifold itself
 
Originally Posted By: mk378
This seems to be an awful lot of work to dance around the fact that the rings in the "new" engine are worn. Did you do a "wet" compression test?

What is the spec for compression? Turbo engines are often set up for lower compression in the first place. Those numbers on an NA engine combined with smoke from the tailpipe would make the obvious conclusion that the rings are shot.


I did not do a wet compression test and I can't find a compression spec in the manual. I would think so too. just trying to make sure before I dive in
 
Originally Posted By: javacontour
Any way to run it without the turbos, just to be sure?

If you have a way to take the inlet air from the turbo out of the picture and run it N/A to eliminate the turbo as a source of the oil.

Did I understand that you replaced all seals on ONE cylinder, or replaced all valve seals?


I thought about this too and I could probably do this but the oil is very clearly coming in from cylinder #4's exhaust port into the manifold and then hitting the turbo. I briefly considered the thought that the turbo could be spitting oil up but there just isn't any way.

I replaced all the valve stem seals on both heads and replaced head gaskets too.
 
Originally Posted By: castle
Originally Posted By: mk378
This seems to be an awful lot of work to dance around the fact that the rings in the "new" engine are worn. Did you do a "wet" compression test?

What is the spec for compression? Turbo engines are often set up for lower compression in the first place. Those numbers on an NA engine combined with smoke from the tailpipe would make the obvious conclusion that the rings are shot.


I did not do a wet compression test and I can't find a compression spec in the manual. I would think so too. just trying to make sure before I dive in
give it a couple squirts of oil. then check the compression. if it goes up a few psi they are ok. if it goes up say 25 psi or more they are bad.
 
If the car blows blue smoke during acceleration, it's the rings, if you are coasting down hill in gear and the car starts smoking, then its the valve guides... The vacuum in the cylinders will pull the oil through the guides when you are coasting down hill with the throttle off and it's in gear if they are worn out...
 
Originally Posted By: castle


84E75D5F-9D0D-48C9-AD70-0EB8CD4E8C27_zpsd1rpejfy.jpg
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a few scratches but nothing with any depth to it at all.

"the cylinder sleeve diameters all check out per specs"


I disagree COMPLETELY

Those "piston ring marks" are NOT normal.

Water got into that cylinder at one time to make those.
 
Originally Posted By: Linctex

I disagree COMPLETELY

Those "piston ring marks" are NOT normal.

Water got into that cylinder at one time to make those.


Will new rings solve this or are you saying I need a new sleeve there?
 
Not a motor head at the least but did the head gasket go & was it replaced? Had same issues with an old Nissan 200SX with turbo. Had new head gasket & new seals put in & the smoking completely went away. Please dont burn me for this question fellow BITOGers.
 
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Originally Posted By: thorromig
Not a motor head at the least but did the head gasket go & was it replaced? Had same issues with an old Nissan 200SX with turbo. Had new head gasket & new seals put in & the smoking completely went away. Please dont burn me for this question fellow BITOGers.


It didn't fail while I've had the car but I don't know the history of the motor.

I did just replace the seals and head gaskets but the smoke persists
 
You doan need no stinkin' specs. Do a wet compression test. Misery loves company, there must be a board for Maserati enthusiasts somewhere on the interwebz. My WAG is that the rings are shot.

PS, when you find a board,ask them what the deal is with the Buick portholes?
grin2.gif
 
Originally Posted By: Merkava_4
What is the year of this Maserati Biturbo ?


The car is an 86 but the engine is from an 85 - a couple slight differences between the two. The carburetor setup is different on the two with the 85 having a manual choke and the 86 a coolant choke. Also the turbos from the 85 are just oil cooled while the 86 added coolant to the turbos. I'm using the water cooled turbos.
 
Originally Posted By: andyd
You doan need no stinkin' specs. Do a wet compression test. Misery loves company, there must be a board for Maserati enthusiasts somewhere on the interwebz. My WAG is that the rings are shot.


There is but it's a narrow group. Not too many people. I have posted this there but as this is more generally mechanical in nature vs Maserati specific I figured I'd open it up to the collective here
 
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