Blow By Help

[Jdddrigot]

I have had my 75 02A for a little over a year. I thought I had it pretty well sorted with my crowning achievement being getting the fast idle to work properly on the Solex 2-barrel. I was having some minor blow by with a tablespoon of oil in the air filter housing after 2-3 weeks. I thought adding a Masamo catch can would take care of that but it seems to have gotten worse. The picture is after about a week of daily commutes. On top of that the air filter housing has more oil in it than before. Before the catch can I had the dipstick get blown out and fixed it with a couple of o-rings. Last week I had a spark plug pop out and it snugged up fine when I put it back in. The car is running as well as it ever has and there’s no smoke coming from the exhaust. From what I’ve read my next step should be a compression and leak-down test. Any other ideas?  Any recommendations for a shop in Fort Collins, Colorado?  I thought putting the FAQ stickers on my rear windows was going to appease the 02 Gods but instead my limited mechanical skills are being tested once again. Thank God for FAQ and thanks in advance. 

Edited March 29, 2021 by Jdddrigot
Add text

['76mintgrün'02]

Looks like the glitch ate your words!

 

https://www.bmw2002faq.com/forums/topic/268257-text-disappearing-from-posts/

 

[Jdddrigot]

21 minutes ago, '76mintgrün'02 said:

Looks like the glitch ate your words!

 

https://www.bmw2002faq.com/forums/topic/268257-text-disappearing-from-posts/

 

This one is on me. I’ve been having a hard time finding where to add text when submitting a topic. 

[jimk]

With the engine idling, remove the vent hose from the valve cover.  If there is lots of vapor emitted, either the compression rings are stuck and not sealing or they are worn out and have no tension to seal against the cylinder wall.

[Mike Self]

"Back in the day" '75 engines developed a reputation for needing rings at relatively low mileage (75k or so).  The story I heard--from a reliable source--was that the blocks were bored "green"--before they had "cured" due to demand for the cars.   Normally the blocks would be cast, then "cure" for several weeks (maybe months?) before being machined.   Thus after boring, the cylinders were slightly oval so the rings didn't seat properly.    Check the old BMW CCA Tech Tips book from back in the late 70s.  That's where this story originated, IIRC

 

The other story from back in the day was that the German economy was booming in the mid-70s so there were many foreign workers employed at German factories, including BMW.  So the story goes, a BMW line inspector was observing a foreign worker installing rings on pistons, and carefully aligning the ring joints one above the other.  Dunno how true either story is, but the fact remains that '75 engines have more compression problems than other years...

 

mike

 

PS Betcha I'm gonna get flack from this!

[TobyB]

Don't panic yet.

 

The M10's very sensitive to the resonance of the 'catch can' arrangement,

and airflow's critical- it really needs to be able to suck air in as freely

as it can expel it.  The oil trap in the valve cover's not particularly effective,

so there's a lot of vapor in the air that's pumped in and out of the engine

as it rotates.

 

I find that a relatively long hose is useful, as is keeping it horizontal or better.  

 

Discovered this when I added a small filter to the quart catch can on the race car.

I filled it in about an hour- when it'd collected effectively nothing in the previous 2 seasons.

The not- quite- freeflowing filter wrecked the tube- and- can arrangement's ability

to separate oil from air.  Remove filter?  Problem solved.

 

t

 

would still do leakdown and compression

[Slavs]

Content removed by Author.

Edited August 10, 2021 by Slavs

[Slavs]

On 3/29/2021 at 12:06 PM, Mike Self said:

The other story from back in the day was that the German economy was booming in the mid-70s so there were many foreign workers employed at German factories, including BMW.  So the story goes, a BMW line inspector was observing a foreign worker installing rings on pistons, and carefully aligning the ring joints one above the other.

 Content removed by Author.

Edited August 10, 2021 by Slavs

[Chris_B]

If the "foreign worker" was aligning ring joints it was most likely because the BMW line inspector (or whomever provided installation instruction upstream) didn't provide the proper instructions. 

[Jdddrigot]

Thanks everyone for the advice. It’s just under 75k so it could be the rings. I have an appointment for this Tuesday at Lou’s Autobahn to get the compression checked and a leak down test. I did replumb the catch can and made a little hook hose to get the excess oil into the carb. I will give a final update on Wednesday. 

[TobyB]

You're inducing vacuum in the crankcase that way-

 

that'll pull oil- laden vapor into the catch can for sure.

 

Vent your catch can to atmosphere, and see what happens

after a long, hard drive.  If it's not filling your catch can,

you're not losing a lot of combustion by the rings.

 

Rings are quite capable of lasting 150k on these engines-

yes, yours might not be sealing, but what's in that catch

bottle doesn't condemn them.

 

t

still not ready to yard it apart.

[Jdddrigot]

Yup, rings. The day before I took it in it started missing bad. Compression in cylinder #2 was 20!  Worst case is $3,300 for the rebuild. Then I will take it for one last mountain drive and sell it. It’s putting a little too much stress on my family at a time we don’t need any more. I’ve had it for 15 months and am lucky to have found it. Even as an automatic it is a kick to drive. 

[Hans]

The mechanic did the test?

[Jdddrigot]

Yes and I totally trust him. Look up Lou’s Autobahn on FB. He has a good reputation in Fort Collins and there isn’t that many options here. The $3,300 is if everything he finds when he tears it apart is bad.  Haven’t told the wife yet.