Blue smoke from exhaust

Hi and thanks for using 2CarPros.com.

Anytime there is blue smoke, oil is being burned. However, why only when warm? There are several things that can cause this. First, I would check engine compression. If there is a weak cylinder, do the test "Wet".

https://www.2carpros.com/articles/how-to-test-engine-compression

See picture 3 for the manufacturer's specs.

A wet test is done on a cylinder with low compression. About a table spoon of oil is put into the cylinder. If compression increases, the problem is with the rings. If it doesn't, it could be a valve issue, head gasket, or something is cracked.

Now, other things that can cause this is oil drainage from the valve cover area (top of head) is draining too slowly back into the oil pan. If excessive oil builds up, the valve seals cannot stop some from getting by and being burned in the cylinders.

To check this, remove the valve cover and inspect the oil drains in the head. Make sure oil can flow without interruption. Here is a link that shows how to replace a valve cover gasket. It will provide what is done to remove and replace.

https://www.2carpros.com/articles/replace-valve-cover-gasket

There is a variable valve timing actuator (VVT) which can be an issue. It is located at the end of the camshaft. Here are inspection directions which you can do when you remove the valve cover. Note: If the VVT actuator is not working properly, it will cause engine timing issues which can lead to power loss, noise, or oil consumption.

Here are the basic directions for checking the VVT actuator. See picture 1

VARIABLE VALVE TIMING ACTUATOR INSPECTION [WITH VARIABLE VALVE TIMING MECHANISM]

Caution:
^ Variable valve timing actuator cannot be disassembled because it is a precision unit.

1. Confirm that the groove of the rotor and notch of the cover at the variable valve timing actuator are aligned and fixed.
^ If the notch and the bump are not aligned, rotate the rotor toward the valve timing retard position by hand until they are in place.
^ If the rotor and cover are not fixed even though their notch and groove are aligned, replace the variable valve timing actuator.

_________________________________________

If you look at picture 2, it indicates possible causes of excessive oil consumption.

Since you hear a noise and the oil usage goes away, I honestly suspect an issue with the VVT actuator.

I hope this helps. Let me know what you find or if you have other questions.

Take care,
Joe


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Thanks Joe for your quick replay, one more observation i would like to share, if i start my car and idle for while(2 hours), it wont smoke blue, even engine became warm. but once start drive and stop then i can find blue smoke. Any thoughts?

Recently i have changed crankshaft seal, oil was leaking from that seal, it fixed. note the blue smoke was coming even before i change crankshaft seal.

Thanks in advance
Raghu

No problem.

I honestly feel it is related to one of the items I mentioned. I would recommend removing the valve cover for inspection. It is only an educated guess at this point, but I have a feeling either the oil is not returning fast enough to the oil pan, allowing it to build up too much or the actuator is bad. Since the blue smoke stops when you hear the noise, my first suspect is it deals with the actuator. At an idle, the engine is not moving as much oil and the actuator may not be affected. The higher RPM's will cause both of the issues I mentioned.

Let me know. Also, the crank seal would not have cause it to burn oil.

I will watch for your response.

Joe

Joe, My car is diesel engine.

Hi Joe,
My car is Diesel engine with turbo. JMZ GH series. This car drove 70k miles first 4 years and next 5 years 3k miles per year and after I (from last Jan) drove 6k miles.Today myself and my friend analyse the turbocharger for any oil leak after 3 miles drive, small stain of oil we found at turbo intake.after that we drove 10 miles in 4 th gear constantly maintained 3000rpm and did return journey 10 miles with 5th gear and 2000 rpm and after that blue smoke stops. Based on my previous observation,blue smoke appears when I drive in slow moving traffic and short journey. I suspect PCV. Unfortunately I could not locate PCV in my car. Do you think my analysis is correct? And can you guide me how to find out PCV in JMZ GH series Mazda engine?

Welcome back
'Based on your test, it could be the issue. However, I have absolutely no information on a diesel model of this vehicle. Are you located in the US?

Joe