Firstfives.org

my 79 528i runs well, idles smooth, stars every time and pulls strong but it lets out a puff of blueish grey smoke when i shift after reving to higher rpm under acceleration. if i go easy and shift before 4500, no puff. if i wind it out to 5500-6000 then i get the puff. also, there's zero smoke while at full throttle, only when i let off.

are my rings going? or could this be valve guides or seals.
i'm pretty new to e12s but not to older german cars.
let me know what you think. thanks!

off-throttle smoke, esp. cases like coming down a long hill, usually mean valve seals.

KenB
1980 528i
1991 535i 5-speed
1980 MBenz 300TD (gas conversion project)

How's your oil consumption? Even with high miles rings aren't normally a problem, but valve guide seals are. If you're using oil, my money is on the seals.

Another way to check.... first startup of the day, have someone else start the car while you watch the pipe. Oil will have drooled down the guides overnight and be pooled on the valve heads, ready for that first start of the day.

The good news... other than plug fouling over time, you're out a bit of oil keeping it topped up, but not affecting performance since valve seals/guides are unrelated to cylinder compression.

thanks for the replies guys. like i said, the car makes power and pulls strong, so i don't think it's down on compression. it does burn oil at the rate of about a qt every 1000 miles, no too bad. i guess i just have a head rebuild in my future as i find a smoky car to be a bit embarrassing. although it can help deter tailgaters.

larsobg wrote: first startup of the day

An almost sure sign of worn guide seals.