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Old 04-26-2021, 05:13 PM   #1
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Default Replacing the valve stem seals could cause 2.4 94

Wondering about replacing my valve stem seals could cause a major failure to the guides or valves because Ive had blue smoke for 14 years.


Its 94 212,000 2.4 - needs a quart once a month. Lots of city driving



Runs smooth no noise... new injectors....plugs look oil coated quickly.


Idling for 30 seconds then revving causes a big blue cloud.


Wondering if the only safe thing to do is the replace the whole head at once.
Maybe carbon- maybe new valve seals would starve oil to the guides?
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Old 04-26-2021, 05:25 PM   #2
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Guides don't need oil. That's why they are sealed.
You may want to run a bore scope (endoscope camera) through your spark plug holes to see how your cylinder walls and rings are. If, for instance, you have no cross-hatching left, and there is a groove at the top of the stroke, you might be wasting your time to do stem seals only.


A compression test would be a good idea, also.


Those cameras are cheap on eBay, by the way.
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Old 04-26-2021, 06:34 PM   #3
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At this age and mileage those seals could be rotten.
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Old 04-26-2021, 08:55 PM   #4
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Quote:
Originally Posted by Reserector View Post
Guides don't need oil. That's why they are sealed.
You may want to run a bore scope (endoscope camera) through your spark plug holes to see how your cylinder walls and rings are. If, for instance, you have no cross-hatching left, and there is a groove at the top of the stroke, you might be wasting your time to do stem seals only.


A compression test would be a good idea, also.


Those cameras are cheap on eBay, by the way.



more accurately a WET compression test would be better. valve stem seals show their wear/tear at high vacuum, like coasting down a hill off throttle in 4th at 2500rpm. theyll suck oil through the stem seals and burn it.
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Old 04-26-2021, 09:23 PM   #5
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I replaced the seals in my former 93, it had the smoke also, mostly at startup, the seals were shot, I used OEM seals and replaced them using the rope in the cylinder method. Hardest part was compressing the valve springs, ended up buying two different spring compressors.


Replaced the seals at 276K miles, two comparison pics,



old vs new seal:





old vs new seal on 1/4" extension, I had to hold the old one or it would slide right down the extension, new seal fit snug:


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Old 04-27-2021, 02:57 PM   #6
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Quote:
Originally Posted by street_rulerr View Post
.... valve stem seals show their wear/tear at high vacuum, like coasting down a hill off throttle in 4th at 2500rpm. theyll suck oil through the stem seals and burn it.
I never thought about it before, but worn valve stem seals could cause an engine to loose some of its vacuum.
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Old 04-27-2021, 04:37 PM   #7
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yah. theres a huge hill by where i grew up. i used to test cars valve stem seals there. doing exactly what i said. it was like a 3/8-5/8mile long hill so it was good to use as a test road.
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Old 04-27-2021, 04:40 PM   #8
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To add to that, one thing I like to do when looking at a used car is to have someone else start the engine (cold) and look for smoke out the tailpipe.
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Old 04-29-2021, 01:45 AM   #9
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Im looking for extra valve keepers in case I drop one.


Also have high crank case pressure when removing oil cap

Last edited by nissanhbuser3227; 04-29-2021 at 02:39 AM.
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