Question about 1994 Mazda MX-3
Sounds like the excuse is a load of BS to me. If that was the case, the oil would of been burnt off during the normal test drive after they completed the head. I'm assuming you had a blown head gasket?
Blue smoke is indeed oil and if it ONLY occurs at start up then clears itself after some driving, it's the valve stem seals or valve guides (but more likely the stem seals).
They were most likely not replaced during the overhaul.
The stem seals stop oil from the upper lubrication in the head travelling down the valves into the combustion chamber and burning with the fuel.
While the engine is running, there is enough movement in the valvetrain (all the bits that move the valves) so that oil cant make it down into the combustion chamber.
However, when the engine is stopped and left for a period (ie: overnight) oil can trickle down into the combustion chamber through the seals which is why when you first start it up the next day it blows blue smoke. All that gathered oil in the combustion chamber is burning off.
The reason why they probably haven't changed the seals is simple: they make more money.
As a mechanic doing a head you have 2 options: You can either get what's called a 'Headset' which is the head gasket with all the other gaskets involved and stem seals OR you can buy the head gasket by itself and reuse the old gaskets and not replace the stem seals.
The head gasket by itself is half the price of the Headset but you can still charge the customer for the full headset....see where im going? Trust me, this kind of practise is unfortunately very common and one of the reasons I got out of the industry.
Once a car overheats due to a head gasket or any other problem, the stem seals nornally always have to be replaced because they harden due to the heat and lose their sealing power.
The solution? The head has to come off again to replace the seals and these guys probably know it so they are going into BS mode to protect themselves.
You have to insist they fix the problem because it wont go away and don't back down!
Oh, and for future reference there are only 3 kinds of smoke you can get:
Blue = Oil burning
White = Water burning (pretty normal in the morning)
Black = Fuel burning (Mixture running too rich)
Hope this helps :)
Posted on Aug 03, 2008
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Posted on Jan 02, 2017
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