Reader Question Hi Austin,
Thanks for taking the time to create your site – its invaluable!
I have a problem with my car – a Mitsubishi Magna ’95. it runs fine, but when in traffic for any length of time (around 15 monitues) lots of blue smoke starts to come from the exhaust. After moving again for about 1-2 minutes, the smoke goes away. When the smoke happened, the AC was on, but the temperature gauge was still at normal, and the engine seemed to be turning fine without any signs of overheating. No other indicators came on on the dashboard.
The engine oil is at normal level – I checked the radiator and it needed approximately another 0.75 litres of water adding.
If you have any ideas on what this may be, I would be very aprreciative.
Thanks for your kind words Simon. Did you read my article about exhaust smoke?
If you are continually adding water to the radiator I would definitely have a cooling system pressure test done to look for leaks. Usually water or coolant will produce a white looking smoke (steam) from the tailpipe.
If the smoke is truly blue in color, AND the smoke is coming from the tailpipe, it is probably due to oil getting on the spark plugs.
This can happen because of internal engine seal or gasket leaks. Using a thicker weight engine oil might help slow down the leak, and some oil stop leak products on the market might also help slow the leak.
The correct repair for internal oil leaking unfortunately is to remove the top half of the engine and replace some seals and gaskets …which is costly.
If the smoke is coming from under the car or under the hood area, you might have a fluid leak which is leaking on the hot engine and or exhaust and producing smoke.
Austin C. Davis
Reader Follow Up
A quick follow up on this problem. I took it to the garage who couldnt find a problem, they checkthed the radiator for bubbles, checked the head gasket and couldnt get any smoke. The car was burning oil so I used a thicker grade oil and the consumption of oil reduced. It hasnt happened for months until yesterday, another hot day. Now the oil level was slightly above max. Blue smoke came out again when in traffic, but went away when the car started moving.
Could this be due to overheating? Also I notice neither the heater or the air-con is particularly hot or cold, and the water in the radiator is brown. Could all these symptoms be caused by a blocked cooling system?
Thanks in advance. Keep up the good work in reducing the stress levels of us unknowledgable car-owners!!! 😉
Hello Again Simon
I still think there is probably a problem in the cylinder head, probably worn valve guide seals that is causing the problem. Blue smoke is from burning oil. Although having rusty water in the radiator is NOT good either, it is not the cause of the smoke.
You might want to try adding a can of Engine Restore Oil Additive to the oil, you can get it at most auto supply stores. This might help reduce the oil smoke/consumption just like the thicker oil did.
The correct repair is probably going to require a valve job, which is costly.
Austin C. Davis