Editing Forums/Z31P/z31-repairs-forums engine-mechanical/Question

{{ForumImport
|op_user=1986zxt
|op_date=2016-04-23 13:43:48
|post_count=9
|archive_url=/Z31performance_archive/forum/z31-repairs-forums/engine-mechanical/25688-question.html
}}

'''1986zxt:''' <small>(2016-04-23 13:43:48)</small>

My car is losing one qt of oil every 400-500 miles. No leaks or drips. Car emits a puff of smoke out of the exhaust on start-up and anytime turbo is in boost. The exhaust tips are black. Obviously the oil is being blown out the exhaust.

My mechanic seems to think valve stem seals. Does this sound reasonable? Any other possible culprit?

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'''mtherkamp:''' <small>(2016-04-25 16:09:25)</small>

Could be either that or turbo seals. I guess it could also be a pcv problem if the valve is stuck open under boost it could draw oil into intake that way

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'''1986zxt:''' <small>(2016-04-26 01:45:22)</small>

Turbo was just replaced, rebuilt by Joel. Was wondering about PVC. It's getting worse pretty quickly. Will be getting into it this weekend.

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'''nismo kid:''' <small>(2016-04-26 03:28:09)</small>

What do the back side of your valves look like? If the valve stem seals are indeed bad the valves will have build up on the backside & stem of the valves. Remove your exhaust manifolds & intake manifolds so you can peak inside the ports. You could also snake a bore scope through the lower intake manifold. Is turbos compressor wheel still clean or covered in oil? Personally I'd do a Fuel injection service (BG or equivalent), replace all the valve stem seals then continue to monitor it. This would probably be the most cost efficient solution.

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'''1986zxt:''' <small>(2016-04-26 13:10:53)</small>

{{Quote|user=nismo kid|What do the back side of your valves look like? If the valve stem seals are indeed bad the valves will have build up on the backside & stem of the valves. Remove your exhaust manifolds & intake manifolds so you can peak inside the ports. You could also snake a bore scope through the lower intake manifold. Is turbos compressor wheel still clean or covered in oil? Personally I'd do a Fuel injection service (BG or equivalent), replace all the valve stem seals then continue to monitor it. This would probably be the most cost efficient solution.}}

Will be getting into it this weekend. Will start on the passenger side and see what it looks like. Thanks for the tips

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'''1986zxt:''' <small>(2016-09-01 13:19:59)</small>

Forgot about this post. Two of the valve stem seals on the driver's side were shot.

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'''1986zxt:''' <small>(2017-01-04 20:50:06)</small>

… and it is still using mucho oil. Methinks I had a detonation issue that I was not detecting and over time, POOF. Anybody know of a reputable shop in or around the Nashville, TN area for a rebuild ? The guy that has been working on my car, I believe, has surpassed the limit of his abilities.

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'''Augustus Maximus:''' <small>(2017-01-05 14:37:25)</small>

Get a VG30e from a Maxima or Pathfinder and have that swapped in.

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'''Ski300zx:''' <small>(2017-01-26 10:12:31)</small>

you can pull off the pcv hose while the engine is running to check it… should have vacuum where the hose goes. or take it off and shake it, see if its gummed up. take off the intake tube where the breather goes in and see if you see oil residue on the intake, thats a sign of a bad pcv. if you aren't sure, i think they cost 4 dollars, i would just change it.

as far as valve stem seals, you dont need to take the head off to change them, just remove the valve covers, then remove the rocker arms. use a leak down tester to put compressed air into the cylinder. this will hold the valve up. I use about 60psi, that should be fine. as a cheap insurance policy, rotate the engine so that piston is at least near top dead center. that way in the valve accidently falls down, it will just lay on top of the piston rather than falling in and now you have to pull the head.

use an overhead valve spring compressor to compress the valve and remove the keepers, retainer and spring. remove the old seal and install the new one. repeat for each cylinder, rotating the engine to tdc before u take out the keepers.