BMW E46 N42B20A Project…

[Arata 30]

Hi team. This is Arata again.

This one will be the 3rd BMW out of 5 vehicles I own and the worst engine I’ve encountered with… the famous 4 cylinder N42B20A.

I’m in the process of removing the engine out for rebuild, due to valve stem seals worn out and blowing burning engine oil out of exhaust.

I have already done the compression test and leak down test and came out well within the spec of 165-170 psi on all cylinders and 0-5% leakage. 
 

Apart from replacing the valve stem seals, I will be replacing the timing chain/guide/tensioner and entire CCV valve/hoses, is there anything I should be replacing while I’m at it? Any suggestions much appreciated. Thanks.

Edited July 26, 2023 by Arata

[F10er 65]

I would replace the whole engine.............with a 6 cylinder one. Those 4 cylinders are nothing but trouble.

[Young Thrash Driver 1020]

You might find the path to reliability on these is to put on a brand new head every 60,000km.

[Eagle 1662]

Seen M44 conversions, that would be project worth doing if you wanted something with max reliability

[Lubed 55]

Once oil/coolant leaks, chains/guides, valvetronic motor, stem seals have been been sorted it will be a sweet little engine again for another 100000 + kms. These engines have their flaws yes, but once looked after are underrated.

[Arata 30]

9 hours ago, F10er said:

I would replace the whole engine.............with a 6 cylinder one. Those 4 cylinders are nothing but trouble.

Yep I have no intention of keeping it. I’m fixing up to sell. All other ones are 6 cylinders.

[Arata 30]

4 hours ago, Lubed said:

Once oil/coolant leaks, chains/guides, valvetronic motor, stem seals have been been sorted it will be a sweet little engine again for another 100000 + kms. These engines have their flaws yes, but once looked after are underrated.

Thanks a lot! Yep I do know that 6 cylinders are lot more reliable. I was going to only replace CCV valve/hoses and valve stem seals but since I’m selling it after the rebuild I just want to get it done right.

[Eagle 1662]

Yeah they likely very underrated in how much it would cost to truly sort one, then you still left with a objectively mundane engine and the all other old BMW issues. 

[Eagle 1662]

41 minutes ago, Arata said:

Yep I have no intention of keeping it. I’m fixing up to sell. All other ones are 6 cylinders.

Hope got it real cheap

[Arata 30]

48 minutes ago, Eagle said:

Hope got it real cheap

You guessed it spot on. I got it for $500 haha. Only done 120,000km. Body is clean and straight apart from minor scratch here and there. Interior is super clean. I would’ve kept it if it was prefacelift model. I don’t really like the facelift indicator style it’s just not for me…

Hopefully I can get the engine out of the car and start getting ready for rebuild. Still waiting for camshaft locking tool kit so no rush but it’s always good to get the things done in timely manner.

[Arata 30]

19 hours ago, Young Thrash Driver said:

You might find the path to reliability on these is to put on a brand new head every 60,000km.

Hmm interesting. So far I’m not convinced that any 4 cylinders are reliable in any way… no offence but just my personal grievance. I had couple of BMWs came to my boss’s workshop and guess what? They are all 4 cylinders (some with turbo) and all have issues with either overheating/cooling issues oil burning etc etc… and not so much with 6 cylinders.

[Eagle 1662]

You will find BMW 4cyl before mid 2000s were pretty good, many of them better than the equivalent 6cyl at the time.

[Lubed 55]

"MAKE THE N42 GREAT AGAIN" you have my vote. Making these little 4 pots sweet again is not as hard as some make it out to be.

[Arata 30]

On 7/29/2023 at 9:50 AM, Lubed said:

"MAKE THE N42 GREAT AGAIN" you have my vote. Making these little 4 pots sweet again is not as hard as some make it out to be.

Hmmmm…

[Arata 30]

And it’s out.

[F10er 65]

The black plastic coolant flange on the back of the cylinder head is another weak point and a real pain in the arse to change in place. Might be a good idea to change that while the engine is out.

[Arata 30]

On 7/30/2023 at 8:30 PM, F10er said:

The black plastic coolant flange on the back of the cylinder head is another weak point and a real pain in the arse to change in place. Might be a good idea to change that while the engine is out.

You mean this one?

[F10er 65]

Yep. Quite common for them to leak coolant.

Edited August 1, 2023 by F10er

[Arata 30]

14 hours ago, F10er said:

Yep. Quite common for them to leak coolant.

Thanks for that info!

[Arata 30]

Successfully removed cylinder head off (without breaking anything haha).

Each cylinder bores still had clean original hone marks and no movement within the piston rings (within the spec wise).

But looking at exhaust valve stems they are shot and obvious oil leaking from there building huge amount of carbons.

Just ordered full head gasket sets, camshaft bolts, CCV sets, and other parts I wanted to replace.

Where do you guys take cylinder heads for pressure test in Christchurch?

[Vass 832]

When doing my rebuild, was told that pressure testing is an awful lot of hassle and not commonly done. A hardness test usually gives enough of an indication on whether the head is good or not, and that's just a quick 2 minute test. I'd get that done and get the thing hot tanked at a shop. Potentially, get the shop to install the stem seals whilst they're at it as well, also check the valve seats for pitting and correct that if needed. Valve lapping isn't really a thing on modern engines apparently. Removing the collets and springs with a punch could damage the valve guides so unless you have a special valve clamp tool it might be best to leave it to the pros.

[Arata 30]

Thanks for the info Vass.

so you suggest to take it to the shop and just get hardness test instead of pressure test?

[Vass 832]

7 hours ago, Arata said:

Thanks for the info Vass.

so you suggest to take it to the shop and just get hardness test instead of pressure test?

Basically. The way they explained it to me was that the hardness test will give an indication of whether the engine had overheated at some point or not, and if it hasn't then the head won't have problems sealing or holding pressure, so long as the surfaces have remained flat. You can easily check the top of the block and bottom of the head with a straight edge and a feeler gauge. Have a quick look on YouTube to see how it's done, a feeler gauge will be something like $15-20 from one of the retailers.

[Arata 30]

Thanks Vass. I’ve taken the head to one of the cylinder head repair shop and the guy will let me know if it’s still reusable or not after carrying out 3 tests on it. Then he will carry out to resurface, clean, and replace the valve stem seals for me. Sounds like a good old man with heaps of great reviews. One of the shop in town I rang up quoted $1100+ to do hardness/pressure test and valve stem seals replacement (not including other things) and the guy I took the head into said that’s far too expensive. It was the very first time I’m taking the head for the tests so I said I’m not aware of the rough prices these days but my boss at our workshop, the garage next door all said that’s too much.

The old man said about $600+ at the most and he sounded quite reasonable and explained to me what he does etc…

Well I guess I’ll find out soon.

[Vass 832]

Who are those parties you mentioned, if you don't mind me asking?