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Join Date: Aug 2005
Location: NYC
Posts: 2
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3.2 smoke on gear change
I have an 1985 3.2 911, the engine runs fine and oil consumption seems normal however I am beginning to notice a small puff of smoke behind me on gear changes but it dosent seem to be there on acceleration just changing gear. What is the likely cause of this problem the vave stem seals or could it be the rings?
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08-14-2005, 01:11 PM
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Join Date: Feb 2000
Location: Los Angeles
Posts: 13,333
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Have someone drive behind you, and find a road with a long downhill section that you can maintain a constant speed on. If they see smoke when you lift off the accelerator, you probably have a problem with valve guide wear.
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Jack Olsen 1972 911 My new video about my garage. • A video from German TV about my 911 |
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08-14-2005, 01:38 PM
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Ok thanks for that jack ill give that a try!
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08-14-2005, 01:52 PM
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Location: Yorkshire UK
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Is valve guide wear the most common cause of smoking on the 3.2 and if you have smoking due to valve guide wear are you risking further damage to the engine if you continue to run it other than obviously causing more wear to the guides?
Steve |
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08-14-2005, 01:58 PM
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Location: Greater Metropolitan Nimrod, Oregun
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it depends on the clearance -- the valves transfer heat to the guide and thence into the head, etc.
if the valve stem does get too hot....
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"A man with his priorities so far out of whack doesn't deserve such a fine automobile." - Ferris Bueller's Day Off |
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08-14-2005, 02:08 PM
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So what your saying is if the clearence is too much the valve may overheat and possibly stick which could result in piston contact?
By the time the guides are this worn would you expect lots of smoke from the exhurst or could the guides be quite worn but still have intact stem seals and be giving off very little smoke? Steve |
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08-14-2005, 02:16 PM
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Location: Greater Metropolitan Nimrod, Oregun
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Yes, or... the valve could break at the stem, destroy the entire combustion chamber and perhaps the crank as well.
I can't answer the 2nd question - but I do know that you want to be very very sure that there will be no harm before driving it.... Also, a little smoke to 1 person might be a dangerous telltale to another.
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"A man with his priorities so far out of whack doesn't deserve such a fine automobile." - Ferris Bueller's Day Off |
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08-14-2005, 02:54 PM
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Adding to what Jack said - "Have someone drive behind you, and find a road with a long downhill section that you can maintain a constant speed on. If they see smoke when you lift off the accelerator, you probably have a problem with valve guide wear."
A good pcar wrench told me to do the same but to leave the car in gear with throttle closed so you will be at high revs (4k or so) then after a few seconds of throttle closed, floor it. If you see a big belch then intake guides are probably worn. What's happening is that while throttle is closed, the cylinder vacuum can suck oil past the intake valve guides, then when you punch it, it burns off big time. That said, I don't see how this can help you if you have bad exhaust guides tho. I figure there's no cylinder vacuum against the exhaust guides since the exhaust valve is never open during the intake stroke.
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08-14-2005, 04:03 PM
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