[N52bigblock]

Next step would be look at the condition of the bores to rule them out.

[n00b0rKa]

Originally Posted by neilj35

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.

Originally Posted by neilj35

Next step would be look at the condition of the bores to rule them out.

I asked my brother and he said that he actually quick-checked my bores when we did the PCV, and although he did not perform a vigorous proofing, he did not see any score marks.

Could you give some advice on what special tools do you use for this job, what are we going to need? Is a universal valve stem seal kit good for taking off the springs and putting them back on, for example? If you have a link that would be awesome

Thank you so much for your help dear sir

Edit: could either of the 2 attached tools work?

[N52bigblock]

Originally Posted by n00b0rKa

I asked my brother and he said that he actually quick-checked my bores when we did the PCV, and although he did not perform a vigorous proofing, he did not see any score marks.

Could you give some advice on what special tools do you use for this job, what are we going to need? Is a universal valve stem seal kit good for taking off the springs and putting them back on, for example? If you have a link that would be awesome

Thank you so much for your help dear sir

Edit: could either of the 2 attached tools work?

No the tools attached won't really work.

https://stmtuned.com/products/blue-p...ing-compressor
This the tool we have in our workshop. It is a bit of pain to use but it does the job. You will also need all the timing tools to re time the camshafts and VANOS. You can usually hire the tools you need instead of buying them. Not sure if you can in your country though. If you have never done any engine work before, it may be a good idea to get it done by a qualified mechanic.

[n00b0rKa]

Originally Posted by neilj35

No the tools attached won't really work.

https://stmtuned.com/products/blue-p...ing-compressor
This the tool we have in our workshop. It is a bit of pain to use but it does the job. You will also need all the timing tools to re time the camshafts and VANOS. You can usually hire the tools you need instead of buying them. Not sure if you can in your country though. If you have never done any engine work before, it may be a good idea to get it done by a qualified mechanic.

Sadly, in this region of Europe tool renting is not really a thing. We've once done a complete engine rebuild on an Opel Z18XE so we have some experience, the hardest and most painful thing will be getting the tools. I will check back with updates and results, thank you very much for your kindness again!

[N52bigblock]

Originally Posted by n00b0rKa

Sadly, in this region of Europe tool renting is not really a thing. We've once done a complete engine rebuild on an Opel Z18XE so we have some experience, the hardest and most painful thing will be getting the tools. I will check back with updates and results, thank you very much for your kindness again!

No problem. Here is the repair instructions if you need them.

https://www.newtis.info/tisv2/a/en/e...mshaft/48rUbI5
https://www.newtis.info/tisv2/a/en/e...mshaft/Dp260dl

[n00b0rKa]

Originally Posted by neilj35

No problem. Here is the repair instructions if you need them.

https://www.newtis.info/tisv2/a/en/e...mshaft/48rUbI5
https://www.newtis.info/tisv2/a/en/e...mshaft/Dp260dl

Thanks a lot. Sadly I can't find this type of tool in my region, however I found 2 othe styles:

1. https://www.aliexpress.com/item/32823088538.html
2. https://shop.ktcautotools.com/produc...over-installer

If I'm not mistaken, both of these could work without taking out the camshafts. What do you think?

Also, my brother recorded a footage of blue smoke in different situations and some borescope views of my cylinder walls. I think the black oil seeping in from the top region is a clear sign that valve stem seals are leaking.

Thank you so much for your help, nbK

[N52bigblock]

Originally Posted by n00b0rKa

Thanks a lot. Sadly I can't find this type of tool in my region, however I found 2 othe styles:

1. https://www.aliexpress.com/item/32823088538.html
2. https://shop.ktcautotools.com/produc...over-installer

If I'm not mistaken, both of these could work without taking out the camshafts. What do you think?

Also, my brother recorded a footage of blue smoke in different situations and some borescope views of my cylinder walls. I think the black oil seeping in from the top region is a clear sign that valve stem seals are leaking.

Thank you so much for your help, nbK

Wow that's a lot of smoke for valve stem seals. Have you ruled out the valve in the breather hose yet? The camshafts have to be removed. There's not enough room to do the job with them in. The exhaust cam is actually inside a separate casing.

[n00b0rKa]

Originally Posted by neilj35

Wow that's a lot of smoke for valve stem seals. Have you ruled out the valve in the breather hose yet? The camshafts have to be removed. There's not enough room to do the job with them in. The exhaust cam is actually inside a separate casing.

The whole CCV system was replaced 1 week ago but the issue persists, so that's why I don't think none of those hosed are blocked. Some very light scoring can be seen on the cylinder walls but it's nothing serious, and if you watch that video, you can see the oil actually seeping in from the top of the cylinders.

[N52bigblock]

Originally Posted by n00b0rKa

The whole CCV system was replaced 1 week ago but the issue persists, so that's why I don't think none of those hosed are blocked. Some very light scoring can be seen on the cylinder walls but it's nothing serious, and if you watch that video, you can see the oil actually seeping in from the top of the cylinders.

Yeah i watched the video. Couldn't see anything alarming, but it wasn't very clear though.

[n00b0rKa]

Originally Posted by neilj35

Yeah i watched the video. Couldn't see anything alarming, but it wasn't very clear though.

We checked with a better quality analogue borescope, and the cylinder walls look ok, but oil is pooling in cylinders 3-6 on top of the pistons where it meets the valves. We also blocked the PCV, and blowby looks normal, smoking persists when revving. I think these all together are pretty convincing reasons to believe that indeed the valve stem seals are bad.

Regarding the tools, there is this one for the valvetronic intermediate springs, do I need this? https://www.toolsource.com/bmw-tools...-p-149212.html

In the instructions you gave for removing/installing the camshafts, they give a list of special tools which includes a torque measuring dial and cylinder head expanding kit. (https://www.newtis.info/tisv2/a/en/e...mshaft/5PbhIvE)
Are these also absolutely necessary besides the valve spring compressor and the timing tool?

Thank you very much once again, nbK

[N52bigblock]

Originally Posted by n00b0rKa

We checked with a better quality analogue borescope, and the cylinder walls look ok, but oil is pooling in cylinders 3-6 on top of the pistons where it meets the valves. We also blocked the PCV, and blowby looks normal, smoking persists when revving. I think these all together are pretty convincing reasons to believe that indeed the valve stem seals are bad.

Regarding the tools, there is this one for the valvetronic intermediate springs, do I need this? https://www.toolsource.com/bmw-tools...-p-149212.html

In the instructions you gave for removing/installing the camshafts, they give a list of special tools which includes a torque measuring dial and cylinder head expanding kit. (https://www.newtis.info/tisv2/a/en/e...mshaft/5PbhIvE)
Are these also absolutely necessary besides the valve spring compressor and the timing tool?

Thank you very much once again, nbK

The intermediate lever spring pliers are essential as the springs are quite strong and very difficult to install without pliers, but the other things are not really.

[n00b0rKa]

Originally Posted by neilj35

The intermediate lever spring pliers are essential as the springs are quite strong and very difficult to install without pliers, but the other things are not really.

I'm thinking of doing some preventive maintenance if I'm already in there, but I'm not sure what is worth changing. The valve cover gasket has to be changed, and I'm thinking of the valvetronic eccentric shaft sensor and valvetronic motor gasket, the VANOS seals on the end of the camshafts, maybe the VANOS solenoid o-rings. What else would you recommend?

Thanks once more!

[N52bigblock]

Originally Posted by n00b0rKa

I'm thinking of doing some preventive maintenance if I'm already in there, but I'm not sure what is worth changing. The valve cover gasket has to be changed, and I'm thinking of the valvetronic eccentric shaft sensor and valvetronic motor gasket, the VANOS seals on the end of the camshafts, maybe the VANOS solenoid o-rings. What else would you recommend?

Thanks once more!

I would replace the rectangring seals on the end of both camshafts. The original ones were made of metal and are known to wear grooves in the cylinder head, causing VANOS faults and lifter noises. The only fix once that happens is a new cylinder head. The revised ones are made of plastic to stop this wear occurring. I probably wouldn't bother with the e shaft sensor, totally up to you though.

[N52bigblock]

Any other seal you remove during the job, it's a good idea to replace it.

[n00b0rKa]

Removed the valve cover today, this is how the head looks from inside. I don't think carbon deposits are bad, what do you say?

[N52bigblock]

Looks very clean for the mileage. Definitely not excessive

[n00b0rKa]

Originally Posted by neilj35

Looks very clean for the mileage. Definitely not excessive

This is the seal of the second valve of the first cylinder. I noted the differences in the diameter of the holes, and this cylinder was showing the fewest signs of oil consumption.

[N52bigblock]

Originally Posted by n00b0rKa

This is the seal of the second valve of the first cylinder. I noted the differences in the diameter of the holes, and this cylinder was showing the fewest signs of oil consumption.

That has definitely seen better days. Is the rubber hard also?

[n00b0rKa]

Originally Posted by neilj35

That has definitely seen better days. Is the rubber hard also?

The rubbed is almost rock solid also, so I suspect this was the issue.

About the experience we had so far: We almost lost a gland follower because the tool slid off the valve spring, and had to transform the valve spring compressor a bit by drilling extra holes. The old seals came off really hard but we realized that twisting them gets them loose. We managed to change 12 in an afternoon, so I would not say it's an easy job, but it can be definitely done at home.

Also found a video for a DIY tool to replace the intermediate spring compressor, it was really easy to take the springs off with it, will see how it works for the mounting. (https://www.youtube.com/watch?v=5ieUmpVxNfc
)

[n00b0rKa]

I'm back with some updates: the engine is running fine, with some lifter tick that is slowly getting better, however the oil consumption remains almost unchanged: it destroyed 750 ml of oil during a 300km trip.
We suspected the piston rings being the issue so we filled the cylinder with different kind of detergents, such as injector cleaner or seafoam, but nothing really seemed to help. I'm really starting to get desperate here...
Edit: I had to top up 2 times with 1-1 litre of oil during a 700km trip, so basically the oil consumption is worse now than before replacing the valve stem seals

[richievn]

I definitely empathize with the OP as I've been in practically identical situation.

2 years ago I bought a used e60 525i euro specs with N52B25 engine which was eating oil like popcorn. I since replaced almost everything possible like PCV, valve gasket cover, oil pan gasket, anything rubber and gaskets in the the engine together with head cover gasket and valve stem seals.

Yet the engine, despite runs very smoothly, still eats oil though at a much lesser extend. I find it only eats oil whenever I go WOT with oil burning smell goes into the cabin. the other thing is the car is having some weird stalling when I accelerate from a turn or idling for 2-3 minutes, feeling like a vacuum leak. I tried compressor test and 4 out of the 6 engines are terrible but i dont know how the car can still keep up with running :-)

This leads me to the very last resource of the issue of the piston ring and the piston itself. Given the infamous design flaw of the first version of N52 on the piston ring design, I am tempting to bore out the cylinder and replace the piston/bearing of the N52B30 to squeeze more power out the engine as another member confirmed that MSV70 DME can run his swapped n52B30 without problem.

[n00b0rKa]

Originally Posted by richievn

I definitely empathize with the OP as I've been in practically identical situation.

2 years ago I bought a used e60 525i euro specs with N52B25 engine which was eating oil like popcorn. I since replaced almost everything possible like PCV, valve gasket cover, oil pan gasket, anything rubber and gaskets in the the engine together with head cover gasket and valve stem seals.

Yet the engine, despite runs very smoothly, still eats oil though at a much lesser extend. I find it only eats oil whenever I go WOT with oil burning smell goes into the cabin. the other thing is the car is having some weird stalling when I accelerate from a turn or idling for 2-3 minutes, feeling like a vacuum leak. I tried compressor test and 4 out of the 6 engines are terrible but i dont know how the car can still keep up with running :-)

This leads me to the very last resource of the issue of the piston ring and the piston itself. Given the infamous design flaw of the first version of N52 on the piston ring design, I am tempting to bore out the cylinder and replace the piston/bearing of the N52B30 to squeeze more power out the engine as another member confirmed that MSV70 DME can run his swapped n52B30 without problem.

While some aspects are very similar (my engine also runs buttery smooth), I don't have oil smell in the cabin. I reckon my oil problem is related more to the RPMs than the throttle. I did not perform a leakdown test, but the compression was good and even around all cylinders. This is why I suspect that the oil control rings might be worn, but my bores should be ok.

Maybe you know that oversized pistons are available for the N52B25 engine (p/n:
11257561845), although I've not done much research on this subject. Another option would be an engine swap, which has been suggested for me multiple times.
Best of luck, I hope we both manage to make our engines healthy again