Oil leaks can be a difficult problem at the best of times, especially with a mid-engined car like the Toyota mr2 were access and visibility is restricted. Even harder can be when the oil is leaking inside the engine in to one of the combustion chambers, figuring that out cant be an exact science but there are certain ways to give you an idea of what is going on ranging from when the exhaust is smoking to what Colour the exhaust smoke is.
Colour of the exhaust smoke
This is more to tell you if it is actually oil that is leaking and being burned. When oil has entered the combustion chamber and been burned and sent back through the exhaust pipe it comes out as a blue-ish Colour. If the smoke is black this means the mixture is too rich, do not instantly presume that it means the car is adding extra fuel as it’s only relative to the oxygen content, so too little air would also cause smoke this Colour. That could be as simple as an old, blocked air filter. Another is thick white smoke that does not disperse as quickly as steam would, this could indicate coolant being leaked in the cylinders, on rare occasions heavy white smoke can mean improper burning of fuel sometimes caused by the wrong fuel or extremely low compression (mainly diesels) and comes out the exhaust looking similar to steam but very thick and heavy. Steam itself is normal to come out the exhaust, especially after just running it on a cold morning and looks like, well steam!
When does it smoke?
If it smokes bad after the engine has been sitting for a while then slowly gets better, that would point to oil being able to leak downwards in to the cylinder or intake while it’s not running. This allows it to collect in or around a cylinder and ready to be burned once the engine is started, giving off the blue smoke. This dies down afterwords as the leak could be small and only enough to give off enough smoke if it’s been allowed to sit for a while. Make sense?
Another similar time it could be leaking from the same areas would cause it to smoke when slowing down and low throttle or off throttle. The main areas for oil to leak from the top is valve seals and valve guides, so when there is low throttle there is a higher vacuum to suck the oil through faster than when on throttle or could then allow oil to be burned next time throttle is applied.
Omitting blue smoke when under high load is more likely to be as a result of worn piston rings or to be more exact, the oil control ring which usually sits the lowest on the piston. Sometimes, and in most cases, this means taking the engine a part so new ones can be fitted which can be a long or expensive job if you are paying for someone to do the job for you. On the better side of things, the oil control rings can some times be gummed up with carbon and oil deposits, this can be removed without stripping any parts. Some methods of this can be done with pouring a little diesel down the spark plug holes or using specific fluids for the job which also claim to free up the gunk, to a point this works but not always 100% effective.
Some of these special formulas can be purchased here! Go have a look and give them a try!
Remember to read for specific instructions for each product on the bottle, also when adding fluids down the spark plug holes make sure the plugs are removed, allowed to sit for a good 48 hours with turning over the engine by hand ideally every so often, once fluid has gone from top of pistons crank the engine over without allowing it to start to be safe (disconnect injectors etc), then let the engine start up and clear itself up. A good idea would be to change the oil after this as well!
PCV Valve Stuck Open
This is were the PCV is not operating properly and out of all these problems, probably the one you would want as it’s a much cheaper, easier and quicker fix. If it is burning oil and the PCV valve is the problem, it will most likely be stuck open, allowing oil vapor to be constantly sucked through in to the inlet and burned by the engine in the normal combustion process. To fix this you should only need to replace the PCV valve and all should be fine!
Tips for Stopping Oil Leaks?
Any other tips or advice you have for this, please let me know in the comment section! Always helps to know what other people are doing with these problems and how they have got on. As well as any interesting stories you have of these kinds of problems I would love to hear! I like a good read on these things 🙂