[ClipZxx]

Is this the rear main seal leaking? Any inputs is appreciated.

E92 n55 rwd 335i

Thanks,
Cole

[hassmaschine]

Probably the oil pan. Main seal leaks on these cars are really rare.

[N52bigblock]

+1

[NasriHash]

Originally Posted by hassmaschine

Probably the oil pan. Main seal leaks on these cars are really rare.

+1

[gbalthrop]

As I understand it, the N55 engine uses an Aluminum block/Crankcase as opposed to the Magnesium Alloy Crankcase used on the N52 Engine?
https://en.wikipedia.org/wiki/BMW_N55

If that is the case, check TIS to see if the Oil Pan bolts can be "Re-used" or if they are single-use Aluminum for some reason. If Steel bolts, just snug up pan bolts to torque specs per TIS, and see if that stops or slows any seepage. If you don't burn/leak more than ~ .5 liter per 6 months or 6,000 miles, and no oil shows up where you park (just a bit of oily dirt in the splash shield) I would NOT worry about it.

George

[dpaul]

Originally Posted by gbalthrop

As I understand it, the N55 engine uses an Aluminum block/Crankcase as opposed to the Magnesium Alloy Crankcase used on the N52 Engine?
https://en.wikipedia.org/wiki/BMW_N55

If that is the case, check TIS to see if the Oil Pan bolts can be "Re-used" or if they are single-use Aluminum for some reason. If Steel bolts, just snug up pan bolts to torque specs per TIS, and see if that stops or slows any seepage. If you don't burn/leak more than ~ .5 liter per 6 months or 6,000 miles, and no oil shows up where you park (just a bit of oily dirt in the splash shield) I would NOT worry about it.

George

Unfortunately, the pan bolts are aluminum for both N54 and N55 engines and are single use.

[gbalthrop]

Originally Posted by dpaul

Unfortunately, the pan bolts are aluminum for both N54 and N55 engines and are single use.

Well, I don't know whether BMW or Wikipedia are more technically correct here.

I had offered that suggestion about checking to see whether sump bolts were Aluminum (single-use) or Steel, WITHOUT checking TIS. TIS appears to state that ALL N55 Sump Bolts are Aluminum and single-use. So perhaps the following is purely academic, but I'm wondering WHY pan bolts on N54 and N55 engines are Aluminum, if in fact that is the case (ONLY a magnet would decide the issue ;-)

To prevent any confusion caused by my questions, here is the TIS Procedure for Removing & Installing the Sump on N55, clearly specifying aluminum, single-use bolts:
https://www.newtis.info/tisv2/a/en/e...-sump/CyupfJ0N

Wikipedia has a discussion of BOTH the N55 and N54 Engines, and in BOTH, they clearly state (WHETHER correct or not ;-) that the BLOCK in each engine is Aluminum, and the text in the N54 article states: "Since the N54 is based on the older BMW M54 engine, it has an aluminium engine block (instead of the magnesium alloy used by the N53)"
https://en.wikipedia.org/wiki/BMW_N54

Perhaps I misunderstood the rationale for using Aluminum Bolts/Screws. I thought it was to prevent corrosion which would occur if Steel Bolts were used in MAGNESIUM-Aluminum Alloy Crankcase (N52 & N53).

What am I missing here? WHY Aluminum Sump Bolts in N54 & N55? What's the SUMP made of? Any Magnesium anywhere? Rechercher le magnésium?

Thanks,
George

[E92.Dom]

Check to see if all the bolts are tightened enough first!!

[gbalthrop]

Originally Posted by E92.Dom

Check to see if all the bolts are tightened enough first!!

Therein lies the problem. With "Single-use Aluminum" bolts, if you try to "snug them up" you risk shearing them off. Only safe procedure is to REMOVE each bolt separately and replace with NEW and torque to spec, plus T-T-Y (Torque to Yield) additional angle, all as specified in TIS.

George

[E92.Dom]

I had an oil leak problem and the bolts were loose to the oil pan haven't leaked since

[dpaul]

Originally Posted by gbalthrop

Well, I don't know whether BMW or Wikipedia are more technically correct here.

I had offered that suggestion about checking to see whether sump bolts were Aluminum (single-use) or Steel, WITHOUT checking TIS. TIS appears to state that ALL N55 Sump Bolts are Aluminum and single-use. So perhaps the following is purely academic, but I'm wondering WHY pan bolts on N54 and N55 engines are Aluminum, if in fact that is the case (ONLY a magnet would decide the issue ;-)

To prevent any confusion caused by my questions, here is the TIS Procedure for Removing & Installing the Sump on N55, clearly specifying aluminum, single-use bolts:
https://www.newtis.info/tisv2/a/en/e...-sump/CyupfJ0N

Wikipedia has a discussion of BOTH the N55 and N54 Engines, and in BOTH, they clearly state (WHETHER correct or not ;-) that the BLOCK in each engine is Aluminum, and the text in the N54 article states: "Since the N54 is based on the older BMW M54 engine, it has an aluminium engine block (instead of the magnesium alloy used by the N53)"
https://en.wikipedia.org/wiki/BMW_N54

Perhaps I misunderstood the rationale for using Aluminum Bolts/Screws. I thought it was to prevent corrosion which would occur if Steel Bolts were used in MAGNESIUM-Aluminum Alloy Crankcase (N52 & N53).

What am I missing here? WHY Aluminum Sump Bolts in N54 & N55? What's the SUMP made of? Any Magnesium anywhere? Rechercher le magnésium?

Thanks,
George

This is a good question.

My limited understanding is that steel and aluminum together would be subject to galvanic corrosion if in contact with an electrolyte (water from the environment, greatly exacerbated by presence of salt from winter road treatment). Therefore, one should use aluminum fasteners in an aluminum block, not steel, and that is what BMW has done with the oil pan bolts. However, there are plenty of other bolts going into the block that ARE steel - a notable example is the water pump, which in the older N54's were installed with aluminum bolts which was replaced with steel in newer ones.

So perhaps the aluminum is not being used primarily for corrosion resistance but rather the more consistent holding power associated with the use of torque-to-yield fasteners.

[hassmaschine]

Originally Posted by gbalthrop

Well, I don't know whether BMW or Wikipedia are more technically correct here.

I had offered that suggestion about checking to see whether sump bolts were Aluminum (single-use) or Steel, WITHOUT checking TIS. TIS appears to state that ALL N55 Sump Bolts are Aluminum and single-use. So perhaps the following is purely academic, but I'm wondering WHY pan bolts on N54 and N55 engines are Aluminum, if in fact that is the case (ONLY a magnet would decide the issue ;-)

To prevent any confusion caused by my questions, here is the TIS Procedure for Removing & Installing the Sump on N55, clearly specifying aluminum, single-use bolts:
https://www.newtis.info/tisv2/a/en/e...-sump/CyupfJ0N

Wikipedia has a discussion of BOTH the N55 and N54 Engines, and in BOTH, they clearly state (WHETHER correct or not ;-) that the BLOCK in each engine is Aluminum, and the text in the N54 article states: "Since the N54 is based on the older BMW M54 engine, it has an aluminium engine block (instead of the magnesium alloy used by the N53)"
https://en.wikipedia.org/wiki/BMW_N54

Perhaps I misunderstood the rationale for using Aluminum Bolts/Screws. I thought it was to prevent corrosion which would occur if Steel Bolts were used in MAGNESIUM-Aluminum Alloy Crankcase (N52 & N53).

What am I missing here? WHY Aluminum Sump Bolts in N54 & N55? What's the SUMP made of? Any Magnesium anywhere? Rechercher le magnésium?

Thanks,
George

That is wrong, and shows why Wikipedia isn't a reliable source. The N52 and N54 (and N51, N53, N55) are built on the same platform (NG6) - it has nothing to do with the M54, which is basically an aluminum M52. The N54 just has an aluminum/steel block instead of magnesium/aluminum.

As for why they used aluminum bolts on the N54 - who knows. Weight savings perhaps? You can have steel TTY bolts too.

[dpaul]

Originally Posted by hassmaschine

That is wrong, and shows why Wikipedia isn't a reliable source. The N52 and N54 (and N51, N53, N55) are built on the same platform (NG6) - it has nothing to do with the M54, which is basically an aluminum M52. The N54 just has an aluminum/steel block instead of magnesium/aluminum.

As for why they used aluminum bolts on the N54 - who knows. Weight savings perhaps? You can have steel TTY bolts too.

Good to know - that M54 statement sounded odd.

As for TTY, you are correct that steel bolts can be TTY - the N54 head bolts are steel TTY and seem to engage the aluminum block. I'm guessing that TTY is impractical for small diameter steel bolts in an aluminum substrate or situations with limited thread engagement. But in the end, like many of BMW's engineering choices, the answer is indeed, who knows.

[hassmaschine]

N52 head bolts are also steel TTY (as are most factory head bolts). Past BMWs used steel oil pan bolts in aluminum but they weren't TTY.

[dpaul]

I think understand the rationale for the use of TTY with head bolts.

According to Wikipedia (used with caution!)

"When the applied load doesn't surpass the clamping force of the fastener, the strain of the fastener will be lower than when the preloading is smaller than the applied load. It is therefore beneficial in high-frequency high-load situations with a higher risk of fatigue related failure, like a bolted down cylinder head, to use torque to yield bolts."

But there's not much load in the case of an oil pan! Use of TTY doesn't seem to make sense and it is otherwise a complete pain in the ass and the wallet. So are we back to corrosion resistance?

[hassmaschine]

right, the question is, why aluminum? they're not nearly as strong. the only benefit is really less weight. but that couldn't add up to more than a few ounces.

There's no magnesium on the N55 or N54 so it's not corrosion.

[gbalthrop]

Originally Posted by dpaul

Good to know - that M54 statement sounded odd...

Since the focus of the thread seems to be shifting from Aluminum vs. Steel fasteners to whether or NOT Wikipedia has the correct information on BMW engine history & derivation, here's the 'Wiki' article on BMW M54 which the article states was produced 2000 to 2006, as a successor to the M52:
https://en.wikipedia.org/wiki/BMW_M54

If anyone KNOWS of something incorrect about ANY of the Wikipedia BMW Engine pages, suggest taking it up with Wiki, as I have NO KNOWLEDGE of any of those engines -- that's why I asked about crankcase material on N54 & N55 in the first place.

"Dangerous" George
(Walking Proof that "a little knowledge is a Dangerous Thing ;-)

[mweisdorfer]

It could be the RMS. Often times, the OPG is the case and it looks like an RMS due to its location.

In my experience, the RMS will go well before the OPG. So, consider your milage and if you have had the RMS replaced.

You will need a lift of some sort, in order to do the RMS, if you plan to DIY it. The OPG gas be done on jack stands.

[PichaDis11]

You should peek inside the bell housing to get a better idea of what's happening. RMS leak will have the crank a bit messy.

[mweisdorfer]

Originally Posted by PichaDis11

You should peek inside the bell housing to get a better idea of what's happening. RMS leak will have the crank a bit messy.

I like that idea. You'd need an endoscope to do that.

iPhone Endoscope, DEPSTECH Upgraded Semi-Rigid Wireless Borescope WiFi Inspection Camera 2.0 Megapixels HD 2200mAh Lithium Battery Snake Camera for Android and iOS Smartphone Tablet - Yellow 11.5FT https://www.amazon.com/dp/B06XSDF8Y5..._BA5nDbDGG7YDK

[hassmaschine]

Originally Posted by mweisdorfer

It could be the RMS. Often times, the OPG is the case and it looks like an RMS due to its location.

In my experience, the RMS will go well before the OPG. So, consider your milage and if you have had the RMS replaced.

You will need a lift of some sort, in order to do the RMS, if you plan to DIY it. The OPG gas be done on jack stands.

An RMS leak isn't impossible - but an oil pan leak is basically a guarantee on any E9x (even if it's not really a big deal, and IMO, not worth worrying about unless it's pissing significant amounts of oil).

IIRC the highest mile cars on this board (N52s) still have their original RMS seals way, way beyond 200k miles - and I believe all N5x engines use the same basic seal design. So I find that very unlikely compared to the OPG, which probably leaks at some point on on every single N5X ever made.

[ClipZxx]

Originally Posted by PichaDis11

You should peek inside the bell housing to get a better idea of what's happening. RMS leak will have the crank a bit messy.

It does crank up funny, but it does not leak oil beside drops on under pan. Noticed those drops 8 months ago. Haven't had to add oil yet.