Smoking on Hot Start

gottadiesel

Flyin Low
Feb 16, 2009
459
0
0
Vancouver, Washington
I think I know what the issue is, but would like some verification... The car lets off a good puff of blue smoke when I start it up while still hot, do not notice any on a cold start. Also do not notice any oil burning any other time or driving condition, I am sure there is a little, as it seems that all 7Ms use some oil - hearsay only...

Anyway I am thinking that I have a valve stem seal leaking and I am pretty sure it is on #1, though the last leak down I did, came out at 9% on #1, but does not mean it did not get worse since then. I say #1 only because I have now gone through 3 sets of plugs during initial start-up and #1 is always in the worst condition, while the other 5 look all about the same... (my fuel injectors are all stable, so assuming and it looks like it is from oil)

The motor has about 4k miles on it since complete re-build. Because of a lack of time, I had a shop do a complete long block re-build. They were familiar with the 7M and seemed to be knowledgeable about the tight tolerances etc... that it requires to be reliable.

My next step was going to be to take it back to them, as they have been very willing to assist if there are any warranty issues with the motor and demonstrate the blowing of blue smoke on hot startup and see what they are willing to do. The only other issue I had with them was my main rear seal, they paid me for my time to replace it, so thought they may offer to do the same.

Unless someone sees a better route to go, I figured I would also setup to do another leak-down to see if something has changed since my last test.
 

hvyman

Dang Dude! No Way Man.
Staff member
Apr 17, 2007
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Fullerton,CA
Valve stem seals would not be part of a leak down test. Only whats in the combustion chamber so either a valve hg or ring.

Have you dont a compression test?
 

mkiiichip

New Member
Sep 10, 2007
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^ That, and valve stem seals tend to make the motor smoke, on cold start.

gottadiesel;1635094 said:
(my fuel injectors are all stable, so assuming and it looks like it is from oil)

Stable fuel injectors? What do you mean by that?
 

gottadiesel

Flyin Low
Feb 16, 2009
459
0
0
Vancouver, Washington
hvyman;1635097 said:
Valve stem seals would not be part of a leak down test. Only whats in the combustion chamber so either a valve hg or ring.

Have you dont a compression test?

Um Yeah, you are right, it would test the valve seat, but oil should stop before then, so no applicable... Am I thinking right on this? Leakdown done at TDC, so all valves should be closed anyway so would not matter... not sure what I was thinking there...

Yes did compression test, but again about 3k ago - all within 5 psi ranging from 165-170

---------- Post added at 04:11 PM ---------- Previous post was at 04:05 PM ----------

mkiiichip;1635114 said:
^ That, and valve stem seals tend to make the motor smoke, on cold start.

HHmm, I guess I was thinking that the oil would be freshly settling back down to oil pan after shutdown and if there was a seal leaking, it would either settle in the guide area until valve opened, then down to cylinder or if that valve was open, it would settle all the way to the top of the piston, then smoke when you restarted... then I guess with that thinking, what would happen to it if you didn't restart, I guess it should still smoke when it is cold start also...

mkiiichip;1635114 said:
Stable fuel injectors? What do you mean by that?

Sorry for the vagueness, I meant that I had them all flow tested throughout 3 levels of DC along with 100% and a leak test... They were all within 1 or 2% of each other so no chance of #1 running richer than the others and causing the #1 plug to blacken... It does not ever foul, I am just saying it looks darker and not as clean as the others...
 

hvyman

Dang Dude! No Way Man.
Staff member
Apr 17, 2007
12,568
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Fullerton,CA
Only on no1?

Either a ring or valve stem seal. Odd that it would only do it on hot start tho.
 

gottadiesel

Flyin Low
Feb 16, 2009
459
0
0
Vancouver, Washington
hvyman;1635454 said:
Only on no1?

Either a ring or valve stem seal. Odd that it would only do it on hot start tho.

Yep only on #1... Well my thought is that with my oil consumption, it may well be burning on a cold start, but it would take it longer to burn off, as cylinder temps are low, therefore may not really show up with the moisture that usually comes with the cooler temps outside and the motor being cold... I have begun to start to smell it when idling as a stop light at times also... so it may be burning other times, but that is the only time it is real noticeable... Based on my compression readings from just after break-in and that I am pretty confident that it has been leaking some since startup only getting worse now... that it is a valve seal versus a ring...

Thank you for your insight, if you think of any other information that can be gleaned from your experience, please feel free to throw it at me... Thanks!