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Old 04-15-2020, 08:36 AM
nt650gt nt650gt is offline
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2004 Z4 burning oil help needed.

Newb here but I have researched the threads and don't see anybody with my specific issue.

It's the 2.5 5 speed with 64,000 on it. Started out having a slight issue starting rough. Was driving it a couple of months ago and it started missing and popping. Nursed it to where I was going. Put a reader on it and it had the codes for three bad coils. Tried driving it and it started smoking real bad. Towed to BMW dealership. Motor appeared to hydrolock and wouldn't turn over. Dealership replaced all 6 plugs and coils. Ran GREAT after that. No smoking.

Fast forward a month or so. Idling in driveway while I scraped windshield. Starting to back it up and it shut off. Wouldn't restart. Then it appeared to hdrolick again and wouldn't roll over anymore. Had towed to an independent shop. The checked it out. Cylinders were full of oil! Pulled plugs removed oil. Replaced intake and crankcase vent valve. Told me it would smoke a little but should clear up. Was clean when I left but after it warmed up started smoking pretty good and smells like burning oil. Drove it for a few days and now its clean when I start it but in the 10 miles I drive to work it starts smoking lightly and its definitely oil. I've put maybe 100 miles or so on it.

With the confined at home deal I have time to work on it. Any ideas on what it may be?

Thanks and my apologies on the mile long post.

Rob.



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  #2  
Old 04-15-2020, 09:13 AM
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Clearancediver Clearancediver is offline
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Very likely at this point it’s leaks from the valve cover gasket. Oil drips down onto the exhaust manifold which causes the burning smell....

Get use spray cleaner/high pressure washer to clean the area and check to see if the smell returns. After being cleaned you can see where the “drips” are if the smell returns.

Remember that the engine sits with the rear of the engine lower that the front... so any leaks from the front part of the engine will travel on the underside of the cover towards the rear before “falling” onto the manifold. Check in the region of the Vanos.... where it attaches to the front of the engine block... that joint needs a “dollop” of sealer when installing the valve cover gasket to avoid a leak at that point. I have a ‘04 3.0i and changed the gasket a couple of times for various reasons one year so am familiar with that particular issue

In any case you need to clean the engine at this point to identify where the smell/oil leak is occurring. If the smell goes away after cleaning the smell was from legacy oil leakage.

You need to use inspection mirrors to see the vanos area and the underside of the area I’ve identified that needs cleaning.


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Old 04-15-2020, 02:47 PM
nt650gt nt650gt is offline
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It's coming out the exhaust. Definitely not underhood.

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Old 04-16-2020, 07:44 PM
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dc_wright dc_wright is offline
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Most likely culprit is your oil separator. When they get clogged the engine crankcase gets pressurized. When that happens the engine freezes until the pressure can bleed off. It also keeps oil from getting back to the crankcase so it gets sucked into the intake, gets burned, and causes smokey exhaust.

http://bmwfans.info/parts-catalog/E8...oil_separator/
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Old 04-18-2020, 03:43 PM
nt650gt nt650gt is offline
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Quote:
Originally Posted by dc_wright View Post
Most likely culprit is your oil separator. When they get clogged the engine crankcase gets pressurized. When that happens the engine freezes until the pressure can bleed off. It also keeps oil from getting back to the crankcase so it gets sucked into the intake, gets burned, and causes smokey exhaust.



http://bmwfans.info/parts-catalog/E8...oil_separator/
I appreciate that but its already been replaced. I'm not sure what direction to take. Any other ideas?

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Old 04-19-2020, 07:18 AM
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Quote:
Originally Posted by nt650gt View Post
I appreciate that but its already been replaced. I'm not sure what direction to take. Any other ideas?

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Valve stem guides?
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Old 04-19-2020, 08:02 AM
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dc_wright dc_wright is offline
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Quote:
Originally Posted by nt650gt View Post
I appreciate that but its already been replaced. I'm not sure what direction to take. Any other ideas?

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Then the connections to it need to be checked, or the replacement may be defective.

With the engine idling, open the oil fill cap and using a rag or wearing a glove, see if you have vacuum when you cover the opening with your hand. Make certain you have a good grip on the rag, and don't do it with your bare hand. If you have good vacuum, then the path through the oil separator to the crankcase is good. If you have little vacuum or it builds up pressure, the oil separator path is blocked.
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