Blue & Black Smoke

Post Fri Jun 13, 2014 12:34 pm

Okay, I've recently swapped an M20B25 into my BMW E21.

All seems okay with the engine, a few niggles here and there but nothing drasitc, but when I open the throttle, it's producing a lot of blue and black smoke, kind of an even mixture of the two.

On idle, I think it's a small amount of blue smoke, but certainly there.

Obviously I know blue smoke is oil, and black is normally fuel, I was wondering if there's any immediate diagnosis from my description?

I'm planning to do a compression test on it some point this weekend, maybe that will help with the diagnosis.

I fear it might be piston rings, as that would be a right pain in the arse!

Post Fri Jun 13, 2014 2:06 pm

Blue smoke could be rings or stem seal valves .... either is a pain in the arse.

In terms of the black smoke I would be checking the blue temp sensor and maybe valve adjustment.

Use the below link to check the sensor.

http://www.e30zone.net/e30zonewiki/inde ... emp_Sensor

Post Fri Jun 13, 2014 9:20 pm

Does anyone have a guide or a link to changing the stem seals? Couldn't seem to see much myself.

Where's best for the seals and/or new piston rings? Direct from BMW or will I need a mortgage for that?

Post Fri Jun 13, 2014 9:43 pm

Eddie1990 wrote:Does anyone have a guide or a link to changing the stem seals? Couldn't seem to see much myself.

Where's best for the seals and/or new piston rings? Direct from BMW or will I need a mortgage for that?

I have just had my whole engine rebuilt due to similar issues.

I went for elring head gasket which includes stem seals and Karl schmidt rings and bearings.

I would look at the fuel issues first and hope it's just that otherwise you would be looking at bare minimum rebuilt.