Why is my MX5 Blowing smoke?????????`

alexpav · Postby **alexpav** » Wed Aug 10, 2011 10:27 pm

Hey Guys and Gals,

Ive got an NA8 which blows quite a bit of blue-ish smoke on startup for about 5 minutes then clears up completely and seems to drive and perform as normal.
(it does ping a bit also)

Anyone know what this may be? Valve stem seals?

Cheers

Alex

project.r.racing · Postby **project.r.racing** » Wed Aug 10, 2011 10:35 pm

sounds like valve stem seals with that description.

manga_blue · Postby **manga_blue** » Wed Aug 10, 2011 10:45 pm

Can be valve stem seals. Also a slight chance that it's a faulty PCV valve (top centre on driver's side of cam cover). Gently pull it out and check that you can blow softly back up through it but shuts if you blow hard. $10 replacement from Repco, etc - no real difference between that and a $35 Mazda one.

alexpav · Postby **alexpav** » Wed Aug 10, 2011 11:01 pm

Hey
Thanks for that, have checked the PCV valve and seems to be fine...il change it anyway for the sake of $10.

Any other suggestions anyone?

Cheers

geofiz · Postby **geofiz** » Wed Aug 10, 2011 11:17 pm

A little hard to check by yourself, but if it puffs a little smoke on gear changes, pretty good bet it is valve stem seals.

alexpav · Postby **alexpav** » Wed Aug 10, 2011 11:21 pm

its a small car il stick my head out the window and check

haha

Does anyone know if valve stem seals can be changed without ripping apart half of the engine bay?

I ask as a 200sx can be done fairly easily with most of the engine still in tact...

Hjt · Postby **Hjt** » Wed Aug 10, 2011 11:23 pm

throw a can of suburu throttle cleaner thru your engine manifold, i have heard it can help with the pinging. can is about $19 from any dealership

Postby **Okibi** » Thu Aug 11, 2011 12:46 am

Valve stem seals can be done with the engine still in the car, its a slow an tedious process.

I helped a mechanic mate do the seals in my NB, it was awhile ago but the rough technique was (don't quote me on this!) : we removed the exhaust cam carefully then pressurised the cylinder with compressed air and used a special punch tool that pushes down the valve spring and catches the collet then swapped over the valve stem seal and put it back together then moved to the next valve then started the next cylinder etc then did the intake side.

It's a PITA so easier to pay a mechanic to do it for you, I think I got the seals from Bill at MiataRoadster.

Postby **NitroDann** » Thu Aug 11, 2011 12:51 am

As dave said, like most jap twin cams, air compressor method is doable.

Dann

Benny · Postby **Benny** » Thu Aug 11, 2011 4:30 pm

Generally, if you valve stems or the seats are worn, they will blow smoke when the engine is under vacuum.
So, get to the top of long hill and when going down hill, check your mirrors for smoke when you lift off the throttle.
If you lift off and the smoke starts, it's your valves.
If it blows smoke when accelerating, then it's your rings.

Rings do expand and contract and if you have a cracked ring, or the ring is stuffed and isn't exapnding and contracting as it should, then they need to be replaced, which is an engine out job.

If you need to replace the valves etc., it's a lot better to do this with the head removed from the engine, and then you can also clean up the ports etc and change over the head gasket.

alexpav · Postby **alexpav** » Tue Aug 16, 2011 8:01 pm

Thanks everyone
wynns stop smoke has worked an absolute treat for now

Mr Morlock · Postby **Mr Morlock** » Tue Aug 16, 2011 8:46 pm

the immediate reaction is that it is probably knackered. You did not give much information such as KM's, how much oil is used between scheduled changes, and whether a simple check from a local mechanic has been done ie a compression check. Wynns' is just a band aid.

timk · Postby **timk** » Tue Aug 16, 2011 10:47 pm

I had the same symptoms as bad valve stem seals, but it turned out to be a toasted #4 bore. So it's not always an easy fix! :oops:

Benny · Postby **Benny** » Wed Aug 17, 2011 6:35 pm

When I was about 17, I had a Holden HD panel van that had done about 250,000 MILES and was blowing smoke continuously.
I didn't want to fix it, as I knew I was trading it, and the smoke got so bad that I had to carry a 5 gallon (about 20L) can of oil so I could keep re-filling it.

A friend of mine suggested I try this stuff could Nu-Metal, which came ina tube and you took out the spark plugs and wejt through a routine of warming the engine, squirting some of this stuff down the plug hole a few times in each cylinder, etc etc.

It actually worked!
The smoke almost dissapeared and it stopped using oil!

I traded it a few weeks later, but in that time, it performed quite well and the dealer didn't even know the engine was shot.

I wonder if that stuff is still available.