[n00b0rKa]

Hello guys!

My 2005 E90 325i is consuming 1l of oil every 500km. There is no observable blue smoke and no significant leaks were detected.

Huge blue smoke on first startup of the day after revving a bit and oily intake led us to the conclusion that PCV system was bad, and we changed it. The blue smoke on startup disappeared, but sadly the oil consumption remained. There are no engine error codes with INPA.

What could be causing this and how could I troubleshoot the issue?

Thanks, nbK

[Pladi]

Originally Posted by n00b0rKa

Hello guys!

My 2005 E90 325i is consuming 1l of oil every 500km. There is no observable blue smoke and no significant leaks were detected.

Huge blue smoke on first startup of the day after revving a bit and oily intake led us to the conclusion that PCV system was bad, and we changed it. The blue smoke on startup disappeared, but sadly the oil consumption remained. There are no engine error codes with INPA.

What could be causing this and how could I troubleshoot the issue?

Thanks, nbK

My bet is on valve seals. The big tale tale sign is the smoke at start.

Do you smoke on de-acceleration ?

[n00b0rKa]

Originally Posted by Pladi

My bet is on valve seals. The big tale tale sign is the smoke at start.

Do you smoke on de-acceleration ?

The start-up smoke has gone after the ccv replacement, and I did not observe any blue smoke now, but will try to check the deceleration phase.
Thanks a lot!

[ptpending]

high oil consumption is problem of the n52b25 by design
n52b30 do not have this problem
this problem was resolved by BMW in 2010 by changing cylinder rings design
and since bmw shipped n52b30 in e9x 325 cars in us, the people from US do not know this problem

[n00b0rKa]

Originally Posted by ptpending

high oil consumption is problem of the n52b25 by design
n52b30 do not have this problem
this problem was resolved by BMW in 2010 by changing cylinder rings design
and since bmw shipped n52b30 in e9x 325 cars in us, the people from US do not know this problem

This however should cause a constant blue smoke if I'm not mistaken, but mine runs without any visible smoke whatsoever.
Edit: I also checked compression and it was 13.5-14 bar around all 6 cylinders so piston rings should be ok.

[n00b0rKa]

Originally Posted by Pladi

My bet is on valve seals. The big tale tale sign is the smoke at start.

Do you smoke on de-acceleration ?

I did not have the chance to test the smoke on true deceleration, but some puffs of blue smoke can be observed on startup, after revving when I release the throttle.

Maybe it helps, I attached some photos of my spark plugs before the PCV replacement. The deposits were uneven, the middle ones were the most affected.

[N52bigblock]

Originally Posted by n00b0rKa

I did not have the chance to test the smoke on true deceleration, but some puffs of blue smoke can be observed on startup, after revving when I release the throttle.

Maybe it helps, I attached some photos of my spark plugs before the PCV replacement. The deposits were uneven, the middle ones were the most affected.

I have an n52b25 in my 06 e90 and it doesn't use oil. My mileage is 100k. Your spark plugs definitely show signs of oil burning. I would put money on it being valve stem seals as others have said. It is quite a common issue, we do them quite a lot at work. The method we use to diagnose valve stem seals is letting the car idle for 10mins when it is at operating temperature, then rev the engine up to approx 4000rpm. If you see blue smoke it will be the seals.

[Pladi]

Originally Posted by n00b0rKa

I did not have the chance to test the smoke on true deceleration, but some puffs of blue smoke can be observed on startup, after revving when I release the throttle.

Maybe it helps, I attached some photos of my spark plugs before the PCV replacement. The deposits were uneven, the middle ones were the most affected.

soo looks like it can be the rings then. I would say just use heavier oil and drive it until its dead. Doesnt look like an easy fix.

[n00b0rKa]

Originally Posted by Pladi

soo looks like it can be the rings then. I would say just use heavier oil and drive it until its dead. Doesnt look like an easy fix.

I hope it's not the rings, compression was just right.

[ptpending]

Originally Posted by n00b0rKa

This however should cause a constant blue smoke if I'm not mistaken, but mine runs without any visible smoke whatsoever.
Edit: I also checked compression and it was 13.5-14 bar around all 6 cylinders so piston rings should be ok.

if you have catalysator in place you will not see too much smoke
if you cut it out , you'll see smoke
also you a doing compression tests on cold motor, the running motor have another temp and pressure conditions
generally oil consumption goes high due following problems
1. congested or not working PCV system, you have to replace external PCV valve on motors with grey cover or whole engine cover on motors with black cover(PCV valve integrated)
2. worn valve seal rings(rubber covers on valves, loose its flexibility under high tempeature)
3. piston rings (n52b25 design flaw, part number changed by BMW in 2010) and 325 cars with n52 after 2010 do not have this problem

[N52bigblock]

Originally Posted by n00b0rKa

I hope it's not the rings, compression was just right.

How many miles or km has the car done?

[n00b0rKa]

Originally Posted by neilj35

How many miles or km has the car done?

Just past 170k km, verified at dealership, last registered info last year in 160k.
I will do another 500km trip in the following days, I will keep you updated about how my oil consumption goes after two bottles of oil treatment.

[n00b0rKa]

Update: 500km and 1 water pump failure later, still consumes 1l of oil every 500km. When standing still and revving the engine, a light puff of blue smoke appears just as I let go of the throttle. On deceleration, nothing significant can be seen, and some blackish smoke can be observed when accelerating on full throttle.

Does it still resemble the signs of bad valve stem seals? Shall I also change the piston rings as preventive maintenance if I take the cylinder head off?

Thank you so much for your help guys!

[Tambohamilton]

The piston ring issue is apparently that the oil control ring gets clogged with carbon. So piston rings can be your problem, though compression is still good.

Valve stem seals are the other common failure on these engines, so hopefully it's them and not the rings!

If it is the rings though, you can just keep topping up. 1l/500km is quite a lot though!

Did it suddenly start using that much oil, or has it been a gradual increase?

[n00b0rKa]

Originally Posted by Tambohamilton

The piston ring issue is apparently that the oil control ring gets clogged with carbon. So piston rings can be your problem, though compression is still good.

Valve stem seals are the other common failure on these engines, so hopefully it's them and not the rings!

If it is the rings though, you can just keep topping up. 1l/500km is quite a lot though!

Did it suddenly start using that much oil, or has it been a gradual increase?

I sadly bought the car a few months ago (and did almost 9k ever since), and although it feels like it was consuming a little bit less back then, I could not state that it appeared gradually for sure. I can't ask the previous owner because the car was imported from Germany and went through many hands until I got it.

Today I took out my larger DISA and the whole intake is covered in a coat of oil, and the PCV was just replaced 1 week earlier. I think this rules out somewhat the possibility of valve stem seals, the issue being possibly either a valve cover gasket or the piston rings.
Here are some photos, please let me know what do you guys think.

Thanks a lot!

[N52bigblock]

It's perfectly normal to have oil in the intake. Im a mechanic by trade and have had a lot of these engines apart. They all have oil in the manifolds. The PCV breather hoses go into to the manifold, that is where the oil comes from. When i removed my DISA valve to rebuild it, it was FULL of oil. My engine doesn't use oil so i wouldn't be concerned about it.

Are you sure the lower PCV hose that goes into the sump is not blocked?


If you still have that bore scope, i would pull the spark plugs and check the bores for any score marks

[n00b0rKa]

Originally Posted by neilj35

It's perfectly normal to have oil in the intake. Im a mechanic by trade and have had a lot of these engines apart. They all have oil in the manifolds. The PCV breather hoses go into to the manifold, that is where the oil comes from. When i removed my DISA valve to rebuild it, it was FULL of oil. My engine doesn't use oil so i wouldn't be concerned about it.

Are you sure the lower PCV hose that goes into the sump is not blocked?


If you still have that bore scope, i would pull the spark plugs and check the bores for any score marks

I'm almost certain the lower hose is not blocked, I have just replaced it. The only thing that was not replaced was that check valve on it, because the aftermarket hose did not come with one, so I had to swap my old one in. I will definitely check my bores, but compression was 13.5-14 bar after 6 cycles on all 6 cylinders so I would not expect a lot of problems there. I will also try to block my PCV and look for blow-by, but at this point I'm really confused on the methods that could lead me to the correct diagnosis.

[N52bigblock]

Have you left it idling for 10 mins then revving to 4000rpm to check for smoke as i suggested earlier?

[n00b0rKa]

Originally Posted by neilj35

Have you left it idling for 10 mins then revving to 4000rpm to check for smoke as i suggested earlier?

Yes, I would say that there is a good amount of blue smoke. I would be really thankful if you could check it out yourself:

How sure would you be that I don't replace my valve stem seals in vain, something else being the problem? Would you also replace piston rings if the head comes off, as those are also known to be a common problem?

Thank you so much for your help guys, nbK

[N52bigblock]

Originally Posted by n00b0rKa

Yes, I would say that there is a good amount of blue smoke. I would be really thankful if you could check it out yourself:

How sure would you be that I don't replace my valve stem seals in vain, something else being the problem? Would you also replace piston rings if the head comes off, as those are also known to be a common problem?

Thank you so much for your help guys, nbK

There's no 100% way to tell what the problem is. It certainly looks like it from the video. I have seen a lot worse though. Was that after idling 10 minutes??

You don't have to remove the head to do valve seals. If you were rebuilding the engine and doing rings and bearings, then doing valve seals is also part of doing a rebuild, so if you did the valve seals first and it's not that, then you haven't lost much really.

Is there much carbon build up inside the valve cover, on the camshafts etc? Could you post a picture of it possibly?

[n00b0rKa]

Originally Posted by neilj35

There's no 100% way to tell what the problem is. It certainly looks like it from the video. I have seen a lot worse though. Was that after idling 10 minutes??

You don't have to remove the head to do valve seals. If you were rebuilding the engine and doing rings and bearings, then doing valve seals is also part of doing a rebuild, so if you did the valve seals first and it's not that, then you haven't lost much really.

Is there much carbon build up inside the valve cover, on the camshafts etc? Could you post a picture of it possibly?

The video was recorded after idling 10 minutes with the timer .

I took some shots and attached them below. I don't think there's excessive carbon buildup. When I got the car, before the first oil change I had 1l of ATF ran through the engine while idling for good 15 minutes, because I had that classic N52 lifter tick, but the ATF solved that. Didn't have the time to take the spark plugs out yet. Do you think it's worth the hassle to bloc the PCV to show if there is unhealthy amount of blow-by?

Regarding the seals without head removal, I've seen a method with compressed air, however it looks risky, the valves can easily fall into the engine... I've also seen a special tool with magnet on it (?) to prevent the valves falling in. Do you know some other method? Also someone told me I can mess up my VANOS doing valve stem seals, but I don't really see how.

Thank you so much for your time, nbK

[N52bigblock]

Originally Posted by n00b0rKa

The video was recorded after idling 10 minutes with the timer .

I took some shots and attached them below. I don't think there's excessive carbon buildup. When I got the car, before the first oil change I had 1l of ATF ran through the engine while idling for good 15 minutes, because I had that classic N52 lifter tick, but the ATF solved that. Didn't have the time to take the spark plugs out yet. Do you think it's worth the hassle to bloc the PCV to show if there is unhealthy amount of blow-by?

Regarding the seals without head removal, I've seen a method with compressed air, however it looks risky, the valves can easily fall into the engine... I've also seen a special tool with magnet on it (?) to prevent the valves falling in. Do you know some other method? Also someone told me I can mess up my VANOS doing valve stem seals, but I don't really see how.

Thank you so much for your time, nbK

Your engine actually looks really clean inside, so i would say it has been well serviced. An engine that hasn't been serviced will have a lot of carbon build up. So it's pretty safe to say that the oil control rings in your engine do not have carbon build up.

There is absolutely no risk of the valves falling into the engine if you have the piston on TDC for each cylinder you are doing the seals on. So when you are doing, lets say, cyl 3 you turn the engine over the piston is at the top of it's travel, then do the seals. You would then do cyl 4 as that is also at the top of it's travel at the same time as cyl 3.
That's how i do it, as well as using compresed air, so even if the compressed air fails, it is still impossible for the valve to drop into the engine.

As for the VANOS.That guy is talking total bullshit and has no idea what he's on about. There's a lot of people out there who think they "know about cars" and spread ridiculous bullshit rumours. I find that really annoying. They think they know everything but actually know sweet FA.