[wrrush]

so i have replaced my head gasket, my oil filter housing gasket, my oil pan gasket, new spark plugs, performance coil packs, carbon sand blast, new charge pipe, new lower charge pipe, k&n air filter, vanos sensor replacement.

i am afraid its my turbos because i have done everything else. No smoke out the exhaust but i have not replaced my catless downpipes they are just in my basement. No larger FMIC either still in basement. Just trying to see where else this siv of an engine might be leaking.

2007 335xi e90 n54

[RocketSurgeon]

How much oil are you losing?
Did you have the head gasket done, or the head cover (valve cover) gasket? N54 head gasket issues are quite rare.
If you let the car idle for a few minutes, then give it a quick rev, do you get a puff of smoke?
Do you have a big goopy oil mess on the bottom of the engine or driveway?
I had a 335i with a blown rear main seal, and a cracked valve cover. Both were real gushers.

[mattgu40]

front and rear main seals, OFHG , valve cover. faulty pcv system exhaust valve stem seal are all possible things

[feuer]

Post #1 lack most relevant info: what oil is used and how much and how often need to be topped off.

[mweisdorfer]

Originally Posted by wrrush

so i have replaced my head gasket, my oil filter housing gasket, my oil pan gasket, new spark plugs, performance coil packs, carbon sand blast, new charge pipe, new lower charge pipe, k&n air filter, vanos sensor replacement.

i am afraid its my turbos because i have done everything else. No smoke out the exhaust but i have not replaced my catless downpipes they are just in my basement. No larger FMIC either still in basement. Just trying to see where else this siv of an engine might be leaking.

2007 335xi e90 n54

So, are you seeing oil on the engine some where? Did you put the car on jack stands and let it run while you are underneath it with an LED light looking for leaks?

You could run a dye in the oil and that would help you diagnose a leak.

It could be burning off via turbos. Bad piston rings would be a sign of excessive oil consumption, but I highly doubt that's the issue. The internals of the n54/55 are very stout from the factory.

If you don't have a colored smoke coming out the tail pipes, your turbos are probably fine. Although, colored smoke can also indicate other problems with an engine too....

Did you replace the turbo seals?

A bad PCV valve & vent hose would be the cause of an oil leak. This valve/ hose combo is on top of the engine near the firewall. They should be replaced every 50,000 miles as well as the PCV valve in the VC.

5w-40 LL-01 certified would be the ONLY oil, I would run in an n54/n55 due to the excessive heat generated by the turbos.

I run Amsoil European formula 5w-40 classic formula. I also do an oil flush before every oil change & change out the filter 1/2 way through my interval.

Clean oil is a good thing for a temperamental engine like the N54. Oil is a coolant of sorts for the engine as well as a lubricant. I think BMW engineers would consider oil a coolant first and then a lubricant second. That's why there is 6.9qts for a 3.0L engine vs 5 quarts for other conventional 6 cylinder engines.

[wrrush]

all great replies, so i have to add a qt about every other month, when it says +1

I use rotella t6 5w-40.

i have changed my valve cover gasket last year.

I am not seeing any oil on the ground since i changed the oil pan gasket and changed the oil filter gasket. My floor is painted white in my garage so I would know very quickly.

i have not replaced the turbo seals yet.

[wrrush]

ok i did notice that the pcv hose was broke but didnt think it would be losing that much oil, i jerry rigged that with a rubber hose bc the cheap plastic broke, i have been meaning to get a catch can to attach that too but been lazy, that might be the culprit

[dpaul]

You need to indicate how many miles, not months, you get per quart of oil. Months is not a useful measure.

[wrrush]

you are true, so just about 1200 to 1500 miles a month, 300 miles a week

[dpaul]

1200-1500/qt is not out of the range of normal comsumption. I've seen noted on other posts that BMW allows down 750 miles/qt before they consider it a problem. Obviously, some N54 owners never put in a drop between scheduled changes but others have engines that use oil.

Unless this is a sudden change, and assuming you have eliminated all the usual leaks (main seals, VC, oil pan, OFH, PCV issue, I wouldn't worry about it. Just to be clear, all that plastic underneath the engine/trans make the garage floor a poor gauge for external leaks of this relatively small magnitude. Take off the plastic and leave it off until you can ascertain if/where a leak might be occurring. That means cleaning the hell out of the engine first of course. If you're worried about the health of engine internals get a leakdown test. Turbos often leak externally but you'll see that easily from the bottom. You won't see much/any smoke from an engine burning oil at the rate you are losing it.

My FBO+ N54 gets 1000-1200 miles/qt Mobil 1 0w40 (not that I think the type of oil has very much to do with consumption) and has done so consistently for the ~35K miles I've owned the car. It has no oil leaks, has perfect compression/leakdown, and runs very well.

[mweisdorfer]

Originally Posted by wrrush

ok i did notice that the pcv hose was broke but didnt think it would be losing that much oil, i jerry rigged that with a rubber hose bc the cheap plastic broke, i have been meaning to get a catch can to attach that too but been lazy, that might be the culprit

That could cause boost leak as well as oil consumption.

I'd get a new upgraded PCV valve & cap from Rob Beck & a new PCV check valve/ hose from FCP Euro so you have a lifetime warranty on that item. Both the PCV check valve & hose with the one way valve on it are only good for 50,000 miles. A catch can is a GREAT IDEA. Honestly, the n54 should have come from the factory with one. BMS or MISHIMOTO make the best two catch cans for your money.

N54's burn oil period. How depends on a lot of variables.

[wrrush]

I think I will be going with the catch can idea instead of PCV replacements. Ohh that can be a boost leak, that makes a ton of sense now that I think about it, I just kept the ends on and when the plastic broke off I used a rubber hose to fix it, i guess that is falling off now because it was not a perfect fit with the engine cover, thanks for the ideas, much appreciated

[dpaul]

Unless you have something wrong with the PCV system or you drive full throttle everywhere you go, you won't get much oil in the BMS catch can, which only operates when the engine is in boost (manifold above atmospheric pressure).

Strong recommendation for low-side catch-cans (ie. Rob Beck system; there's at least one other supplier). Put one on and you will not need walnut blasting for a long, long time.

[wrrush]

https://www.rbturbo.com/products/accessories/

im on his website but i dont see anything about a catch can, even when you google it, it goes to the mishimoto one

[dpaul]

I'm talking about the "RB N54 External PCV Kit". It "externalizes" the collection for PCV under sub-atmospheric pressure conditions into a can instead of dumping it back into the small ports in the cylinder head to carbonize into crap on your valves. You have to buy the actual catch-can yourself - ebay is a good source. The necessary can design for low-side collection is different than BMS. If you want, you can install a BMW high-side can as well - they are completely independent. I had a BMS can but never got more than a few teaspoons in it so I sold it. The low side gets quite a bit, several ounces every 500 miles or so.


It's expensive but it works and saves maintenance. Don't take my word for it - You can read about this system on several threads

[wrrush]

high side == drivers side

low side == passenger side

please clarify thank you

[dpaul]

high-side: high pressure circuit for PCV. Active when on boost i.e. turbos have manifold pressure well above atmospheric

low-side: low pressure circuit for PCV. Active at idle and part throttle when manifold pressure is below atmospheric. Obviously normally aspirated engines are always below atmospheric when running but turbocharged engines spend the majority of their time operating with negative manifold pressure unless, as I mentioned, you constitutively use large throttle openings. That would be normal on a boat, where you typically open the throttle and keep it open, not normal in a car you drive on the street where you encounter other vehicles, stop lights, pedestrians.

The N54 has two circuits. I urge you to do a little reading about the topic of PCV on the N54

[wrrush]

Yes I will do research but wanted to share information with people in the future instead of just do research yourself

[dpaul]

Have no idea what that means

[Bimmer_Engineer]

Originally Posted by dpaul

I'm talking about the "RB N54 External PCV Kit". It "externalizes" the collection for PCV under sub-atmospheric pressure conditions into a can instead of dumping it back into the small ports in the cylinder head to carbonize into crap on your valves. You have to buy the actual catch-can yourself - ebay is a good source. The necessary can design for low-side collection is different than BMS. If you want, you can install a BMW high-side can as well - they are completely independent. I had a BMS can but never got more than a few teaspoons in it so I sold it. The low side gets quite a bit, several ounces every 500 miles or so.


It's expensive but it works and saves maintenance. Don't take my word for it - You can read about this system on several threads

Interesting discussion on the low side catch can catching “several” ounces every 500 miles. I had to add a quart to mine today about 3000 miles after an oil change. IF you don't have a low side catch can that oil would be going into the intake manifold and coating the valves and burning in the cylinders correct? You’re not the first person I’ve seen attesting to the amount of oil you’re getting in your catch can and I know I was shocked at how much is in the intercooler and charge pipe...so several ounces in 500 miles would be about 1/2 quart over 3000 miles...and without a catch can that oil would be consumed by the engine correct?

[dpaul]

Yes, straight into the intake manifold. That, together with direct fuel injection, gives us the awful carbon buildup in the cylinder head intake ports requiring walnut blasting every 25K miles or so.

[monoid]

The most common problem with oil consumption is piston rings. If there is no smoke from the exhaust and oil leak around the engine it's almost 100% sure that the problem is from them.