ophelious

Good afternoon, gents!

85RX7 12A

I have noticed (more and more, recently,) that I am getting what I think is smoke from burnt oil coming out of the air intake on the air cleaner when the car is turned off (which means it's probably burning while running and just blowing away.) I took the top off the air cleaner and can see that the smoke is coming up from the carb pre-heater pipe (if that's what it's called...the flexible aluminum one.) Wherever it's burning (it sure smells like oil) it seems to be down that hose. Any ideas what's down there that oil could be leaking into/from?

I know that the hose is supposed to supply warm air to the carb on cold days, but I don't have a great idea of where it's going or what might be leaking. The smoke is not coming from the carb itself, but right up that hose and then out the front of the air intake.

Thanks for any ideas.

ray green

iTrader: (14)

Could it be that oil from a leak in the OMP or it's lines is finding it's way to the pre-heater pipe, then getting burned by the exhaust heat?

ophelious

It's interesting that you say that, because while I was looking at it a minute ago I noticed that one of the plastic tubes for the oil meter pump was broken. (Assuming it didn't work in the first place, I've been premixing oil in my gas.)

My question would be this...I thought the OMP only injected oil, and then a tiny bit, when the car was first started. Would it still be leaking after 1/2 hour of driving? Of course, when I get home I'll take a closer look to figure out where the other end of the plastic tube is (though it's snapped off up by the carb...I don't think it's long enough to reach down to the other side of the engine where smoke is, would it?

If it helps, I'm not POSITIVE that it's oill....it's possible that it's coolant.

I'm not sure what the warm air flexible pipe hooks into (looks like some kind of heat shield over an emissions thing.) It's in that area that I can see some of the smoke originating. It's as if coolant or oil were dripping on that little box when it's hot and some is burning off and blowing out the sides and some is burning off and going up the pipe.

I can't see as much as I'd like because the burning seems to be happening under that heat shield...

ray green

iTrader: (14)

An uncapped OMP is like an uncapped oil well, it will just keep squirting and squirting every time you press the accelerator peddle. To see how this work, forget to hook up your lines at the carb and drive 50 miles and your whole engine will be covered with oil. Ask me how I know.

So yes, you need to make sure the OMP isn't the source of the "oil" and fix that, if necessary. Options would be to replace the broken OMP line(s), then you wouldn't need to premix. Or you could removed the OMP and add a block plate.

Of course if the OMP isn't pumping at all, and there's no oil leaking from it or the tubes, I guess that's a solution, but not one I'd be happy with.

The flexible air pipe hooks up to a shield over the exhaust manifold. When the engine is cold, a bimetallic coil opens a flap in the air box to draw hot air directly off the exhaust manifold and into the carb so that it warms up faster and functions more efficiently. Once the carb warms up, the flap closes (if it's working properly) and cooler air is drawn through the air horn.

So the smoke could be oil boiling off the exhaust manifold and being sucked up the hose into the air box.

If it's not oil, another possibility is a coolant leak at the intake manifold. There are two O rings in the manifold that seal the coolant ports into the manifold which can start leaking. Look for coolant pooling on top of the engine, down under the carb. If there's fluid in there, draw a few drops into a tube or straw and mix it with water. If it mixes, it's coolant, if it doesn't it's likely to be oil.

You might want to do a good degreasing of the the area, that should help pinpoint the source of the leak, whatever it is.

74RX4

iTrader: (10)

These symptoms often mean the metering pump gasket or o-rings are leaking. The oil is blown back onto the exhaust manifold and the inside of the heat shield surrounding it. The heat riser pipe attaches to this heat shield. Oil soaks the insulation material lining the heat shield and the oil smokes as it slowly burns off. If your pump is working your broken line is leaking, but it may be a bad gasket or o-rings that is causing the smoke.

mazdaverx713b

iTrader: (91)

it could also be the front cover gasket leaking. often times guys replace the OMP seal thinking that is leaking, only to find out that the front cover gasket is at fault. I would clean the area thoroughly and drive the car for a few miles. stop and see if you can pin point the leak.

if the oil is leaking onto the exhaust manifold, it may be caused by air turbulence in the engine bay, causing the leaking oil to blow rearward as you are driving. this oil will collect onto the exhaust manifold as you drive and if the heat shield is still in place, along with the pre heater tube, you will get smoke into your air cleaner.. providing the flapper in the air cleaner housing is open.

wankel=awesome

^this

ophelious

Thanks for all the great ideas. I know a guy who has an OMP and lines, so I'll start there. The OMP I've got is covered in cruddy looking oil, so that's probably the culprit.

mazdaverx713b

iTrader: (91)

it is most likely not the entire cause of the leak. the front cover gasket is prone to failure and should not be ruled out. its easy to start with the OMP of course, but if the leak persists, its time to look at that front cover gasket. the OMP can also fail to seal internally. there are o-rings inside of it that go bad and cause it to leak. be cautious in that you could also be trading one leaking OMP for another. they are easy to rebuild, so also consider that as an option.