Blow By 1981 320i! - BMW Forum

Kr320i · 10-31-2007, 01:08 AM

Question to all. Should a 1981 320i have a high level of blowby when you remove the oil filler cap? Also, should there be a decrease in idle speed?

Thanks all.

BMWJNKY · 10-31-2007, 12:03 PM

If you can remove the oil cap and the engine still runs you have a problem. With a properly running M10 if you pull out the dip stick or take off the oil cap the engine will die. What makes you think you have excessive blow-by?

Kr320i · 10-31-2007, 02:50 PM

When dealing with American cars...if you have excessive blow by then it usually means the rings are going bad or the valves or serious vacuum leak. I pulled the oil cap off of the bimmer and it tried to die. Had a lot of air rushing out and I've never had that experience before. Never had a bimmer before.

BMWJNKY · 11-01-2007, 01:43 PM

Quote:

Originally Posted by Kr320i

When dealing with American cars...if you have excessive blow by then it usually means the rings are going bad or the valves or serious vacuum leak. I pulled the oil cap off of the bimmer and it tried to die. Had a lot of air rushing out and I've never had that experience before. Never had a bimmer before.

If you take the oil cap off and the engine ran poor but didn't die I would say you have some other vac. leaks as the engine should die with the oil cap off. BMW uses very different cam profiles and duration than an American car. You were probably hearing air being sucked in not forced out, this is due to how the cam is. By running these sorts of cams in the BMW's BMW has eliminated the EGR system from their engines. The last BMW with EGR was probably the 1979 320i and even then it wasn't a true ERG like on an american car.

So, I would look for cracked hoses or hoses in poor condition and replace them. Like I said in my pervious post if you pull out the dipstick the engine should run poor and almost die, and if you pull off the oil cap the engine should die. It would probably be a good idea to do a major service on the car if it hasn't been done recently, plugs, cap, rotor, valve adjustment, oil change, fuel filter, diff fluid and trans fluid.

Kr320i · 11-02-2007, 07:24 PM

Bmwjnky, I did took it in and they said exactly what you did. They replaced some hoses and gave it a tune up and it runs great. Thanks for all your help.

german-speed-demon · 11-03-2007, 09:13 AM

Quote:

Originally Posted by Kr320i

Bmwjnky, I did took it in and they said exactly what you did. They replaced some hoses and gave it a tune up and it runs great. Thanks for all your help.

Just curious...what did that cost you? b/c vacuum hose is cheap and it only takes about 30 minutes to an hour max for a quick tune. you could have done it yourself for less than $50 prolly.

BMWJNKY · 11-05-2007, 01:18 PM

Quote:

Originally Posted by german-speed-demon

Just curious...what did that cost you? b/c vacuum hose is cheap and it only takes about 30 minutes to an hour max for a quick tune. you could have done it yourself for less than $50 prolly.

Yes, the 1/8" vac hose is cheap but there are also formed hoses that are BMW M10 specific that are not as cheap and not fun to replace. I used to have an E21 so I know all about changing out the hoses.