280z smoking after new valve seals - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 14 (permalink) Old 04-03-2017, 11:24 AM Thread Starter
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280z smoking after new valve seals

Hey everyone,
I will just start from the beginning. In august of last year I turned on the car and backed out, nothing weird, but then all of a sudden the car started to smoke really bad and misfire so I let it just run and then i just drove and problem solved. Over the winter I started the car and it ran for 15 seconds and then started missing and started to smoke(blue). And I wasnt going to drive it so I just let it run, the problem did not solve itself like the previous time. So I did some research and decided it was the valve stem seals.

I ordered the parts and began working, the job was my first serious job working on the car besides the simple oil change, etc.. The job took me several weekends but I got it done and I turned on the car this past weekend. It started strong and it ran really good for 10-15 seconds and then the same thing happened, It started to misfore and smoke(blue). So I went to a local nissian mechanic that works on z cars and he said to change the plugs and pcv valve. So I got a new pcv and plugs. I am having trouble removing the pcv hose so i have to cut it, but before I do that I will get a new hose. I changed the plugs and it ran longer for around 30 seconds and the same thing, all the plugs had oil on them. Is it possible that the problem is the pcv valve or something else. I serously doubt its the rings because the car only has 77k miles. It is a 1977 280z.

Thanks
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post #2 of 14 (permalink) Old 04-03-2017, 11:48 AM
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Just a thought:

When you had the engine apart did you replace the valve cover gasket? I believe a leaking valve cover gasket can oil the plugs.
There is also something called a spark plug tube seal. I'm not sure if the 280z has one as I haven't taken that much of my motor apart.

But yes, usually if your car has oil on the plugs itll be leaking rings.

Run a compression test. If your car is getting oil regularly in the combustion chamber it will not run correctly as it will lower the octane rating in the gas, and cause misfires.

If they had oil on the hex portion, add some antiseize to keep the oil out. If it was on the electrode portion, it is likely leaking valve rings or the tube seals.

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1984 AE 300zx Turbo

Last edited by Echutton; 04-03-2017 at 11:50 AM.
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post #3 of 14 (permalink) Old 04-03-2017, 12:34 PM
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I think that "tube seals" are unicorns and found in BMW's and Hemi's.
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post #4 of 14 (permalink) Old 04-03-2017, 02:09 PM Thread Starter
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Originally Posted by Echutton View Post
Just a thought:

When you had the engine apart did you replace the valve cover gasket? I believe a leaking valve cover gasket can oil the plugs.
There is also something called a spark plug tube seal. I'm not sure if the 280z has one as I haven't taken that much of my motor apart.

But yes, usually if your car has oil on the plugs itll be leaking rings.

Run a compression test. If your car is getting oil regularly in the combustion chamber it will not run correctly as it will lower the octane rating in the gas, and cause misfires.

If they had oil on the hex portion, add some antiseize to keep the oil out. If it was on the electrode portion, it is likely leaking valve rings or the tube seals.

Yes the Valve cover gasket was replace at the time, I have not heard of a spark plug tube seal and nor did I see one but I am fairly new with working on cars, I used to hire someone but most of the time they wouldnt do good work for the money.
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post #5 of 14 (permalink) Old 04-03-2017, 04:11 PM
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what kind of plugs did you get? they must be NGK type. 2nd the compression test, both dry and wet. that will tell you a bit about what is going on.


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post #6 of 14 (permalink) Old 04-03-2017, 05:19 PM Thread Starter
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what kind of plugs did you get? they must be NGK type. 2nd the compression test, both dry and wet. that will tell you a bit about what is going on.


Bon
Yes, they were NGK plugs, its just hard to imagine the rings would be significantly worn to let oil burn on all cyclinders and only after 15 seconds and it only has 77k miles, I will try to a compression gauge so I can test it.

Thanks
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post #7 of 14 (permalink) Old 04-03-2017, 07:02 PM
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The Z and ZX series have no tube seals. That is quite incompatible with their head design.

The compression test will tell you a lot. If you're seeing blue smoke, oil is getting into the combustion chambers. There aren't many ways that can happen: rings or valve stems.

If oil consumption isn't excessive (no more than a quart per 1000 miles) oil usage isn't a critical problem.

Last edited by pilgrim; 04-03-2017 at 07:04 PM.
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post #8 of 14 (permalink) Old 04-03-2017, 07:12 PM Thread Starter
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The Z and ZX series have no tube seals. That is quite incompatible with their head design.

The compression test will tell you a lot. If you're seeing blue smoke, oil is getting into the combustion chambers. There aren't many ways that can happen: rings or valve stems.

If oil consumption isn't excessive (no more than a quart per 1000 miles) oil usage isn't a critical problem.
Someone told me that if the PCV was stuck it would cause a constant vaccum in the crankcase and bring oil right into the intake and therefore explaining why oil is on each spark plug. Is this possible?
And the car misfiring and burning oil will stall the engine out after 45sec-1min after starting it and therefore prevents me from driving it.
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post #9 of 14 (permalink) Old 04-03-2017, 08:06 PM
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Rings valve stems or bad head gasket are your possibilities. Valve stem seals and guide failures are characterized by a big puff of oily smoke as you start up. After a few seconds it burns off. Your valve cover gasket isn't possibly the problem and whoever told you it could be should never be consulted for advice again, because that's just tragically stupid. You need to run a compression check to see if the problem is rings, and check your coolant for oil and your oil for coolant to see if your head gasket is bad although it's possible to have a bad head gasket without that cross-contamination.

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post #10 of 14 (permalink) Old 04-03-2017, 08:41 PM
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Rings valve stems or bad head gasket are your possibilities. Valve stem seals and guide failures are characterized by a big puff of oily smoke as you start up. After a few seconds it burns off. Your valve cover gasket isn't possibly the problem and whoever told you it could be should never be consulted for advice again, because that's just tragically stupid. You need to run a compression check to see if the problem is rings, and check your coolant for oil and your oil for coolant to see if your head gasket is bad although it's possible to have a bad head gasket without that cross-contamination.
OP didn't specify where the oil was at on the plugs. It is entirely possible a leaking valve cover gasket can leak oil down the side and into the holes of the plugs. Without anything on the threads of the plugs it can also seep through the cracks and get into the combustion chamber. It is entirely possible, although not likely. I added this in case the OP had oil on the OUTSIDE of the plugs as well as inside.

Also; I was the one that recommended the compression check. I guess OP shouldn't trust that advice either considering my advice is "tragically stupid".

However, yes, a head gasket could be the problem, although its probably less likely than the idea of a bad valve cover gasket. As I stated before the only way to find out is to run a compression check. Although the head gasket is not likely. If it is leaking internally from all 6 cylinders it is most likely a leaking valve seal. Plus OP stated blue smoke, which usually means oil burning, white smoke for head gasket. Also, he'd likely find a milky mix of oil and antifreeze on the plugs. I assume if he replaced the valve cover gasket he also replaced the head gasket when he replaced everything else; which means if one of these is bad its likely the PCV valve...

OP, also check the PCV valve, as you're right, it can cause problems similar to what you're experiencing. It will blow seals and gaskets and cause oil leaks. Check to see if its stuck closed or needs cleaned out.

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1996 Z32 300zx Twin Turbo - SOLD!
1977 280z
1984 AE 300zx Turbo

Last edited by Echutton; 04-03-2017 at 08:46 PM.
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