Rebuild or Engine Swap

[ReddyBMW]

Hi Guys

Is it advisable to rebuild an N52 engine or is an engine swap the better route to go?
Car is a 2012 E90 LCI 323i

Kind Regards

 

[husaindindar]

Depends on what's needed for the rebuild. What is the issue with the current engine? Is it locked up? Is it burning oil? Is the oil water mixing? Did it overheat?

More info will help us understand and give better advice...

 

[ReddyBMW]

Depends on what's needed for the rebuild. What is the issue with the current engine? Is it locked up? Is it burning oil? Is the oil water mixing? Did it overheat?

More info will help us understand and give better advice...

Apologies for not providing more info.
The car is burning oil, it takes a litre of oil every 3rd week and blue smoke is emitting from the tailpipe at a complete stop.

 

[Blue Shirt]

Sounds like leaky valve stem seals, which is a common fault and an easy fix on these engines. It can be done in-situ without having to remove the cylinder head.

Get some quotes from reputable workshops and eecide from there.

 

[momo1]

yip sounds like valve stem seals, these engines are usually reliable if maintained adequately, get a full diagnosis from a reputable workshop and take it from there but i wouldn't think a rebuild or an engine swap is necessary .

 

[husaindindar]

Is there smoke under acceleration also?

What you can do to confirm stem seals, is to idle the engine for around 10min or so, and then give it a real hard rev. If theres a cloud of smoke that jets out, then you definately have issues with stem seals.

Smoke in gear under acceleration would be rings then. These 2.5 motors do have a bit of a ring problem compared to the 3.0 motors. Its not major, but they do consume a bit of oil. By a bit, I mean 1 litre between services.

 

[ReddyBMW]

Is there smoke under acceleration also?

What you can do to confirm stem seals, is to idle the engine for around 10min or so, and then give it a real hard rev. If theres a cloud of smoke that jets out, then you definately have issues with stem seals.

Smoke in gear under acceleration would be rings then. These 2.5 motors do have a bit of a ring problem compared to the 3.0 motors. Its not major, but they do consume a bit of oil. By a bit, I mean 1 litre between services.

Would a ring issue, require a rebuild or engine swap? The car is smoking blue after acceleration and reaching a red boot.

 

[husaindindar]

Would a ring issue, require a rebuild or engine swap? The car is smoking blue after acceleration and reaching a red boot.

You have a valve stem seal issue....
Can be done without removing the head

A ring issue wont require a full on rebuild. Just rings and gaskets. Unless you want to do everything else while the motor is open.

From the sounds of it, you just need to do the stem seals.

 

[Nick]

 

[ReddyBMW]

You have a valve stem seal issue....
Can be done without removing the head

A ring issue wont require a full on rebuild. Just rings and gaskets. Unless you want to do everything else while the motor is open.

From the sounds of it, you just need to do the stem seals.

Thank you soo much...

 

[Gordvisr]

N52 engines can start smoking for various reasons. Valve stem seals on N52 engines is not so prone to detoriating than other BMW engines.
As long as regular oil services were done you should be good with Stem seals, Rings, if you were not a nutter who liked standing in parking area's revving the sh@t to the limiter the whole time. should still be good. Valve cover, has a PCV system that usually fails and has a tendency of failing and causing erratic idling and smoking issues. Currently owning a N52 with 222XXX Km no smoke, never skipped an oil service never smoked, Owned a 330i also with N52 engine, currently sitting at 260 XXX Km, never skipped an oil service, still no smoke ( the new owner of this car visits me on regular basis ) and they were taking beatings at times while driving ( no revving until valves drop ). To come back to replacement VS rebuild, I would rather rebuild ( if diagnosed properly ) than replace as if done properly, then you know you good for at leaset the next 300 000 km or more.

 

[ReddyBMW]

You have a valve stem seal issue....
Can be done without removing the head

A ring issue wont require a full on rebuild. Just rings and gaskets. Unless you want to do everything else while the motor is open.

From the sounds of it, you just need to do the stem seals.

My mechanic confirmed its valve stem seals. You were right.
My question is, do I purchase the seals from BMW or a spare shop like Goldwagen?
I believe there is a set of seals for the exhaust and a set for the intake...

 

[Gordvisr]

Valve stem seals size is the same for all the valves. You can get at either GW or BMW or a place that specialises in gaskets and seals. Just go for good brands like payen,ellring,victor reinz.

 

[tamgoem]

My mechanic confirmed its valve stem seals. You were right.
My question is, do I purchase the seals from BMW or a spare shop like Goldwagen?
I believe there is a set of seals for the exhaust and a set for the intake...

Let your Mechanic chose the parts he wishes to install and give the warranty on. He should have had a few of these and knows what brands of parts work and ones that won't. If you think he doesn't know what he is doing rather ask the guys here for what shop they would suggest in the area you are in.

The labour for the job might well start making a cheap used engine look like a good option but remember its data-dot and a inspection or some sort of admin nightmare you have to contend with aswell so factor that 5k extra cost ontop of the engine swap.

 

[ReddyBMW]

Hi Guys

Is it advisable to rebuild an N52 engine or is an engine swap the better route to go?
Car is a 2012 E90 LCI 323i

Kind Regards

Greetings Gents

Just an update on what I have done so far and some advice from you guys would be appreciated.
I replaced the valve stem seals on my vehicle as they were worn out, the head also needed new exhaust guides which I also replaced, together with new spark plugs, oil filter and fresh oil.
When the cylinder head was removed, the mechanic noticed that the pistons had some play and there was also some carbon build up on the surface of the block.
The mechanic suggested that we fit the reconditioned head back on and run the vehicle for a 1000kms till we retorque everything under the valve cover and see if the vehicle still throws out blue smoke.
I have covered 500kms thus far and the vehicle let out blue smoke at a red traffic light about four times already.

Brand new valve stem seals, new exhaust guides, new plugs, new oil filter, fresh oil, new head gasket. Do I now need to look at getting the block done?

Apologies for the lengthy text and for addressing my issues towards the festive season.

 

[Gordvisr]

Play on the pistons was a sign that the block need reconditioning. best is to strip the block together with all the internals for measurement ( crank, block , rods and pistons ) to determine if any grinding , resizing need to be done. then take it from there. do not rebuild the engine without measuring. from my point of view, this engine was not properly looked after before you ( regular oil changes etc ) or the mileage is very high.
If resizing or grinding need to be done and it is missed, within 10-15 k you will rebuild again.( or worse have to replace )

 

[ReddyBMW]

Play on the pistons was a sign that the block need reconditioning. best is to strip the block together with all the internals for measurement ( crank, block , rods and pistons ) to determine if any grinding , resizing need to be done. then take it from there. do not rebuild the engine without measuring. from my point of view, this engine was not properly looked after before you ( regular oil changes etc ) or the mileage is very high.
If resizing or grinding need to be done and it is missed, within 10-15 k you will rebuild again.( or worse have to replace )

Thank you soo much. Yes the previous owner did not maintain this vehicle properly and I suspect the mileage was also dropped. Nevertheless I am trying to give this vehicle a new life.
My mechanic says that the bores will need to be resleeved, my concern is that I have read that the N52 block is an alusil block and cannot be resleeved. Is this true, do I need to look at getting a new block or is it possible to resleeve the N52 block with cast iron sleeves?
Appreciate all the guidance...

 

[Gordvisr]

not completely sure best bet is to ask a reputable engineering shop if it can be done or not.

 

[TurboLlew]

Thank you soo much. Yes the previous owner did not maintain this vehicle properly and I suspect the mileage was also dropped. Nevertheless I am trying to give this vehicle a new life.
My mechanic says that the bores will need to be resleeved, my concern is that I have read that the N52 block is an alusil block and cannot be resleeved. Is this true, do I need to look at getting a new block or is it possible to resleeve the N52 block with cast iron sleeves?
Appreciate all the guidance...

You can rescue Alusil blocks. It isn't that it can't be done, but usually it makes no sense.

Alusil blocks can be bored out. The problem with boring out alusil is then getting custom fit pistons (and hoping the skirt coating/materials will work so they aren't destroying the block in a few km) and engineering work done. Aftermarket pistons are not a cheap exercise unless something is available off the shelf for the platform?

Sleeving allows you to use a standard sized piston again or pretty much any kind of piston you'd like actually, but whether you want to go down that road with an N52 is another story from a cost perspective. From a risk perspective, sleeves are something you don't want to take chances with when it comes to quality or installation. There are a number of things that can happen during sleeve installation if the engineering shop is not great which will trash your block so research well before you go down this road. There is a chance engineers will tell you that the block can't be salvaged as well depending on what they uncover and how much material they have to work with. Make sure you can trust this mechanic and the warranty that he gives you with the work.

Now maybe you want to do that on a very rare motor from a very special car or where numbers-matching is a huge factor... I don't know what a new N52 block costs, but I am guessing either of the exercises above are going to be close to the same if not more, which is why most people will just parrot "can't be done". A new block is FAR (orders of magnitude) less risky, complicated and time consuming (disclaimer: If you're doing it correctly - there are other ways to do this I'm sure).

 

[ReddyBMW]

You can rescue Alusil blocks. It isn't that it can't be done, but usually it makes no sense.

Alusil blocks can be bored out. The problem with boring out alusil is then getting custom fit pistons (and hoping the skirt coating/materials will work so they aren't destroying the block in a few km) and engineering work done. Aftermarket pistons are not a cheap exercise unless something is available off the shelf for the platform?

Sleeving allows you to use a standard sized piston again or pretty much any kind of piston you'd like actually, but whether you want to go down that road with an N52 is another story from a cost perspective. From a risk perspective, sleeves are something you don't want to take chances with when it comes to quality or installation. There are a number of things that can happen during sleeve installation if the engineering shop is not great which will trash your block so research well before you go down this road. There is a chance engineers will tell you that the block can't be salvaged as well depending on what they uncover and how much material they have to work with. Make sure you can trust this mechanic and the warranty that he gives you with the work.

Now maybe you want to do that on a very rare motor from a very special car or where numbers-matching is a huge factor... I don't know what a new N52 block costs, but I am guessing either of the exercises above are going to be close to the same if not more, which is why most people will just parrot "can't be done". A new block is FAR (orders of magnitude) less risky, complicated and time consuming (disclaimer: If you're doing it correctly - there are other ways to do this I'm sure).

Thanks a lot. Im leaning towards resleeving the block and replacing the piston rings as my pistons are still good to go. The Engineering shop here in Durban says they have done many N52 blocks by resleeving them and not a single comeback, so will take a chance with this one as I have already spent 15k to redo the cylinder head.
Appreciate your advice.