S85s were not created equal.
"In this new Special Series named “S85-002”, I earn a badge of honour: I blew up my V10.
I document the service history of my original S85 engine and diagnose its failure. I go through the process to source, refresh and swap my S85-002. Most importantly, I document the S85-EVO high duration camshaft package.
In this entry, I document the changes made by BMW M to the S85 in attempts to improve its reliability - for the most part. I cover which changes are worth it based on historical reliability and my experiences."
- Matt
Assumptions of intentions.
I assume BMW M's definition of lifetime is limited to the 4 year/80,000km warranty window of most BMW M5s sold worldwide. Like most clichés, it has been proven accurate across most BMW M generations.
No matter their short life spans, it probably was expensive for BMW M. The high costs they had to incur in order to warranty the V10s and its SMG3 were most likely one of many driving factor to the various little, untold improvements that were made during production.
16 years on, I picked my 2006 at the train-yard in July 2021. At the time, I felt fortunate enough to find a V10 M5 that had been maintained under the original, and extended warranties throughout its entire life.
The glamor was gone, the old car smell was well settled in, the extended warranty was gone but hey - the paint still looked mint!
I filmed edited a trailer to this entry here. Feel free to drop a comment on IG!
The S65 isn't really an S85 minus 2 cylinders.
Much is made of the M3 V8 having an S85 with 2 cylinders chopped off - but the reality is far different when getting into the nitty gritty details. The arrival of the M3 V8 in 2007 for the MY2008 brought about streamlining of a few parts between both engines.
The V8 had very few updates during its production run beyond regulations mandated updates whereas the S85 varied greatly due to the continuous updates BMW M performed on the V10 throughout its production.
The S65s and S85s may as well be brothers from another mother. The S65 is far and beyond more reliable than the S85.
The S85's technical evolutions.
You'll find that most of the changes made through production are things you cannot easily nor inexpensively retrofit. The prices listed are as of November '23.
1. VANOS High Pressure Oil Pump.
The crankshaft gear, pump sprocket, shims and tensioners were updated by BMW M in early 2006-01 to SKU 11367841784 from 11367836347. The pump costs +/- 4,000 USD.
The VANOS high pressure oil pump is driven off the crankshaft and powers the main engine oil pump.
The VANOS pump is on the left, the main oil pump is on the right.
We did not service it in my previous engine.
It the VANOS pump fails, the probability of engine oil starvations are high. Below is the main oil pump sprocket, with its chain wrapping around the sprocket of the VANOS pump.
2. VANOS High Pressure Pump Internal Oil Line.
The high pressure internal line in early production cars was known to fail, causing oil leaks inside the engine and a loss of pressure required to activate the variable timing.
BMW M issued the Service Bulletin SI 11 10 05 for replacement with an uprated line on S85s produced up to 11/22/05. The updated SKU was 11367838670 and remains as such as of today. The line alone costs +/- 380 USD.
This is the external line sitting in front of the plenums. It connects to the internal line through the block with a banjo bolt.
The internal line runs from the pump, inside the crankcase and exits by the upper block.
3. Oil Pan with 2x drain plugs.
The oil pan 11137836246 was revised with an extra drain plug to better service the S85. The new SKU is 11137840540 and costs +/- 1,800 USD. The pan was updated 02-05-2007.
It makes flushing the full oil fill more time intensive, and difficult. Most make due with some left over oil in the front section of the pan.
My 001 engine had a single drain plug.
4. VANOS solenoids.
The VANOS solenoids are of critical important to the S85's all around functioning. I highly recommend these get preventively serviced. They cost +/- 400 USD per unit and there are 4x.
I faced numerous solenoid issues on the 001 engine. They were eventually all replaced. I highly recommend preventive maintenance for these, and I will discuss a new technique for replacing them later on in the Special Series.
The older SKUs had black solenoid bodies and were 11367834526 or 11367836741. The revision was done in 2006-09 and the SKU revised to 11367841072.
The revised solenoids are distinguished by its silver body.
They notoriously suck to replace due to the bolts' location.
5. VANOS exhaust gears.
The VANOS gears are a complex, intricate, mission-critical component of the VANOS system.
The exhaust gears were revised by BMW M after 2006-06 from SKU 11367835344 to 11367838395. Each gear costs +/- 1,500 USD. I've never heard of failures on this and it is unclear what drove BMW M to make the change.
If you have more info, feel free to comment!
There is a gear within a gear, and a thin gear that needs to be aligned with a wider gear. It's a lot of gears, I can imagine some incremental improvements were made.
2008 and up.
2008 saw the final revisions to the S85 - with most taken straight from the S65. These would be the best engines to source, with an asterisk.
1. Longer Head Bolts.
The head bolts were uprated from M10x110 to M10x115. The SKU was revised from 11127583116 to 11127838831. The revisions were implemented in 2008-06.
2. Valve-Train Retainers & Collets.
The retainers and collets were uprated in the S65 V8 for a slightly heavier retainer, with a upsized internal section to fit wider collets that hold the retainer to the valve spring. This wasn't a move forward in performance, unless it helped with valve float.
On the left are the S65 retainers, and on the right, the 2005-2008 S85 retainers.
On the left is one of the S65 valve collet, and on the right, the 2005-2008 S85 valve collet.
3. Oil Squirters.
The oil squirters were upgraded to the S65 engine with SKU 11117837298 from 11117834295. Whether these are improved or costs were streamlined, it's difficult to tell.
Somewhere, up there in the crankcase are the oil squirters. There was no way for me to get lighting in there.
4. 702/703 Rod Bearings*
The caveat to 08+ engines is the usage of the harder aluminum rod bearings versus the original, softer tri-metal bearings.
This is a net negative as they have higher material hardness, moving the damage from the bearings to the crankshaft. I touched on this topic in "Place your bets" where I documented my initial S85 rod bearings service.
In short, it's much less expensive to replace connecting rod bearings than to repair a crankshaft.
Below are my 2012 S65 bearings showing the 702/702 bearings shared across the S65 and S85.
Below are the original connecting rod bearings taken out of my S85-001 engine. They had roughly 120,000km.
So, the technical answer is obvious: get an 08+, am I right eh?
It isn't that simple.Up next: I chat about sourcing my S85-002.
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