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MG MGB Technical - After Oil Change a Puff of Blue Smoke

Hi all,

After a nice 75 mile drive this morning in my 72B I decided to change the oil. After draining the oil and removing the filter I put the new filter on after filling it as best I could with 10W40. I then cranked the engine with the coil wire removed until I got pressure on the gauge, then started the engine. I immediately got a fairly large cloud of blue smoke from the tail pipe which immediately dissipated.

The engine continued running just fine - no funny noises or smells and no more blue smoke. Pressure was about 40lbs at idle (exactly what it was prior to the change and the same for the past few months since I got the car) and about 75lbs at speed. I then went for a drive around town and out on the highway - speeds of anywhere from 25 in stop and go traffic up to 55-60 on the open road and everything *seems* just fine after another 75 miles.

Went for a short spin after the engine cooled down a little bit ago and again, everything seems fine.

My question: *Is* everything fine? Given the blue smoke and the obvious oil burning smell I was/am terrified I blew something and would need a ring or valve job. I'm new to this and trying to be as careful as I can. Any thoughts would be appreciated, thanks!

Greg
Greg Smela

Greg. An oil burning smell is not all that uncommon after an oil change. You always seem to get a little spilled oil. You should have an 18V engine with the inverted oil filter. I can never remove these without considerable oil spill, some of which I always seem to miss when I clean up. If the oil burning smell goes away, I would not worry about it. I am sure you checked for leaks around the oil filter and the adapter where the adapter goes into the engine after the engine came up to full oil pressure. If you see no leaks, there is no external source of oil to cause a problem. As to the puff of blue smoke. Are you sure that this is new? A little oil can drain down into the combustion chambers when the engine is turned off and sits. There is a greater chance of this if the valve guides are slightly worn and the valves seals getting a little old. (And they were not the best design in the first place.) I rarely see this in my own cars when driving them, but have often seen a puff of smoke when someone else is driving one of my cars. This even happens on cars with rebuilt engines in good condition. The fact that you are not seeing blue smoke as a regular part of the exhaust (as when it is idling) makes me think you do not have a problem. I would keep a close eye on the oil consumption for a while to make sure you are not burning oil. Also check the spark plugs for signs of oil fouling. Most MGs leak or use a small amount of oil and this is nothing to be concerned about. If oil usage becomes excessive, you have a problem. Do you have the "mushroom" type PCV valve going to the intake manifold? I had the same symptoms as you describe along with increased oil usage and traced it to a bad diaphram in the PCV valve. Replace the diaphram and have had no further problems. Les
Les Bengtson

Thanks for the response Les,

This was a very noticeable cloud of blue where there hadn't been one before. Also, the burning smell was from the blue exhaust not from a spill - I had checked that having spilled enough in my day! That's what scared me but I think I'm feeling somewhat reassured now! I'll watch it for a while and check the plugs.

Could I show pressure even if the oil hadn't properly circulated completely through the engine when I first started it?
Greg Smela

No need to crank over engine after an oil & filter change.

Cranking it with the ignition wire off probably loaded oil and fuel into the cyls and when it fired up it burnt this off.

Nothing to worry about - I would worry if these engines don't use oil - they are designed to, so some oil gets by the rings to lubricate the upper cylinder.
chris

Thanks Chris -

It's funny how these machines have their little quirks and it does take some time to get to know them. Having said that I do appreciate all the experience available on this board from the "regulars".
Greg Smela

This thread was discussed between 01/12/2001 and 02/12/2001

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