8V71 Crankcase Breather

richard5933 · September 17, 2019, 01:29:26 PM

Finding lots of new things while reading through the manual...

Never noticed the bit about servicing the crankcase breather on the back side of the 8V71. Manual calls for it to be opened and cleaned every 30,000 miles or so. Mine has probably never been touched, judging by the layers of crud all over the canister.

Question??? What are the problems that a clogged/dirty crankcase breather can cause? Can it contribute to the oil spotting on the back of the bus?

chessie4905 · September 17, 2019, 01:47:52 PM

Sorry, I forgot crankcase breather.🙄

luvrbus · September 17, 2019, 02:05:41 PM

Tilted engine have 2 breathers 1 on the back of the engine and the crankcase as you mention,the crankcase breather is where you get most of the spots from IMO .I have remove the crankcase breather on those and plated it off and added valve covers with breathers for a few folks to stop the spotting

richard5933 · September 17, 2019, 02:11:59 PM

Quote from: luvrbus on September 17, 2019, 02:05:41 PM
Tilted engine have 2 breathers 1 on the back of the engine and the crankcase as you mention,the crankcase breather is where you get most of the spots from IMO

I just see the one on the back of the engine, sort of under/near the starter. Where is the other one?

luvrbus · September 17, 2019, 02:18:14 PM

Quote from: richard5933 on September 17, 2019, 02:11:59 PM
I just see the one on the back of the engine, sort of under/near the starter. Where is the other one?

It located on the top section of the bell housing right side ? has a housing to remove to get to filter mess inside lol they never get serviced look for 1-1/4 in pipe

richard5933 · September 17, 2019, 03:05:56 PM

The one I'm talking about is the one in Fig. #4 in the attached page from the manual. It appears to be a canister with a filter element inside it. This breather seems to come from much lower (crankcase) rather than from higher up on the block.

Curious what type of negative effects can be caused by this thing not having been serviced.

I see a breather like you're talking about on the front of the engine that appears to be just a pipe leading to a slobber tube. It comes from higher up on the block.

richard5933 · September 18, 2019, 02:22:44 PM

Bumping this to see if anyone knows what the results of this thing going 45 years and 50,000 miles without service/cleaning. It's on my to-do list now that I know about it, but it's not been touched in a long time.

Curious to know if this could be the cause of the recently started oil spotting on the rear of the bus.

chessie4905 · September 18, 2019, 02:36:36 PM

Could be, but you'll be chasing them as you accumulate miles on the engine. The more miles, the more crankcase pressure getting past the rings as they wear. Fact of life with detroit diesel two cycle engines. It gets worse if you like to run at 2100 all day.