The newly acquired ’98 M3 Sedan has been progressing along nicely, having taken care of the rear suspension and drivetrain already, it was now time to move under the hood.  The engine was already a smooth runner, especially after I solved its intermittent stumbling issue, but there were a couple other items I wanted to address.  Chief among these was preemptively avoiding the dangers of oil starvation under high lateral and longitudinal acceleration (“pulling g’s”).  The M50 family of engines, which this S52 is a member of, have a traditional oil pan.  This is in comparison to the S54’s dual pick-up pan, which was purpose built by the M Division to prevent low oil pressures on the track.  The North American E36 M3’s weren’t fortunate enough to be equipped with a true “M” engine like their European counterparts, which use an S50B32, that incorporate an oiling system nearly identical to that found in the S54.

The negative results of this become immediately apparent even under mildly spirited driving.  After a few hard corners or heavy braking, you can hear the engine develop a loud tick, timed with the RPM of the cam shafts.  This is because the S50/52US use a hydraulic lifter setup, rather than a shimmed (mechanical) lifter like that on the S54.  Why you ask?  Again, we weren’t offered a true motorsports engine, and hydraulic lifters are better suited for daily drivers.  They self-adjust and under normal circumstances are smoother in operation.  However, when oil pressure drops below a certain level, the lifters go out of their specified height and you are left with a rattling valve-train.  This in of itself is not a hugely critical issue, but it is an indicator that the engine is not being properly supplied with oil.  Excessively low oil pressure can and will lead to much more serious problems, like spun bearings, scored piston walls, wiped lobes, so on and so forth.

So what’s the fix?  Well you can certainly go the route I went on my S50 race engine and install the dual-pickup pump and pan from an S54, but that’s pricey for just a daily driver that may get driven hard but a handful of times.  The cheapest alternative is just overfilling the sump with an extra quart or so of oil.  Unfortunately this only mildly stems the issue, the oil is still going to slosh away from the pick-up, you just hope there’s enough extra that the pick-up remains submerged.  I tried this at a recent track-day and found it to only slightly reduce the ticking.  The more proven method is to install a trap-door style baffle in the oil pan.  These baffles are pretty common among track driven cars, in fact my MR2 has one installed on its 2ZZGE.  As the name implies, these baffles use small one-way doors to allow oil to flow towards the pick-up, while restricting its flow away.  Several companies produce baffles for the S50/52, all sharing similar designs; aluminum construction and weld-in.  I did notice that the Turner Motorsports baffle utilized rubber flappers rather than hinged aluminum doors like the others.  I decided for longevity, I’d better stick with an all metal baffle.

I found that the baffle made by Achilles Motorsports was the least expensive option, but still maintained the same design and build quality of the others on the market.  The photo below shows the underside of the baffle so that you can see the “trap doors” in their closed position.

Achilles Motorsport Baffle

Now the big hurdle; getting the oil pan off the engine.  This isn’t a particularly complicated job, but it is very time consuming.  The front subframe, which the engine rests on, resides directly underneath the pan and must be removed to gain access.  That alone is not too difficult a job, it’s all the other items attached to the subframe that add to the complexity.  On the top side, go ahead and get the airbox and alternator cooling duct out of the way, which block your access.  Underneath, the steering rack, inboard ball joints for the lower control arms, and of course the engine itself are all mounted to the subframe.  The X-brace that I had installed must also come out.  Since you are removing the mounting points for the engine, you have to now suspend its weight from above.  This is actually a fairly easy task, using a simple and cheap engine hoist from Harbor Freight.  This hoist is just a beam that rests on the groove between the fenders and engine bay weather stripping.  I pulled the rubber molding up at the leading edge of the fender to allow for easier fitment and also covered the legs of the hoist in painters tape to prevent any scratches.

Engine Hoist Engine Lift Point

The engine should already have a lift point, a steel eye, on the head beside the oil filter housing.  This is where you attach the hoist, then use the large wing-nut to lift the engine slightly so that the weight is off the engine mounts.  Remember that the transmission mounts must still be securely installed to not only carry some of the weight, but also prevent the engine from rotating.  With the subframe no longer under load, I began removing the previously mentioned items.  First to go is the anti-sway bar, which is easy enough.  Next is the power steering pump, which is partly mounted to the oil pan itself.  Of course you must first remove the serpentine belt.  I found that it helped to first remove the engine mechanical fan, allowing for better access to the belt tensioner.  You don’t have to fully remove the fan, just off of the water pump and pushed out of the way.  You don’t have to fully disconnect the PS pump, tying it up and out of the way with some safety wire is an option, but I decided to go ahead and get it completely out of the way.  Part of the decision was based on my discovery that the previous owner had neglected to install half of the needed crush washers on the banjo fittings on both the pump and rack.  My other reasoning was that I intended to completely remove the rack so that I could replace the badly rusted hard lines, therefore requiring a complete drain of fluid.

Ball-Joint SeparatorWith the pump out and on a bench, I went to work on the rack.  The steering rack is mounted to the subframe by two bolts and two nuts, easy.  If you were trying to only remove the pan, and nothing else, you could just swing the rack forward and down, which should give enough clearance to remove the pan.  Since I had other work to complete, I needed to completely remove it, which meant also disconnecting the tie rods at the steering knuckles.  Like nearly all production cars, the tie rods connect to the knuckles by way of ball joints and tapered studs.  Once torqued down, these studs are very difficult to remove.  Yes you could just smack the exposed end with a hammer, but that would most likely destroy the threads and require a new tie rod (the ball joints are permanently mounted.)  You could also use a balljoint fork (aka pickle fork), but this almost always destroys the rubber grease boot.  The better solution is a ball joint separator, which you can see pictured to the right.  The tie rods had been recently replaced by a previous owner, so it was worth the trouble to save them.

Steering Rag JointWith the ball-joints and fluid lines disconnected, you are almost ready to remove the rack.  The last item keeping the rack from just falling out is the rubber joint (aka “rag joint”) connecting the steering column to the rack’s pinion.  This splined joint is secured with bolts and nuts on both the column and rack that pinch the split aluminum down onto the shafts.  Before removing, make sure you make a visible index mark with a paint pen.  This will help you ensure your steering wheel and tires are lined up straight forward after reinstalling.  Of course you still will require an alignment, but this will get you close enough to at least drive the car to the shop.  Like all rubber parts, this joint is susceptible to drying out, cracking, or even tearing.  This can lead to poor steering response among other issues, so it makes sense to replace it while everything is apart.

Now that the steering rack was out, I could begin refurbishing it by replacing those badly rusted hard lines.  But first I took the rack out to the parts washer for a good degreasing.  The hardlines came off without much fuss, as did the plastic breather tube.    All of the lines use o-rings to form a seal, so be sure to lubricate them prior to installation.  I also gave the new lines a good coating of CorrosionX, hopefully preventing future rust issues.

Rusted Steering Hardlines New Hardlines Installed

Loosening Engine MountsBack to the oil pan removal.  With the steering out of the way, I still had the lower control arms to contend with.  But to gain access to the nut holding the inboard balljoints in place, you must first lower the subframe.  This of course means that the engine mounts be disconnected.  Accessing the bottom engine mount nuts is easy, but the top ones require a bit more fuss.  You needn’t completely remove the top nut, but you have to at least loosen them.  I ended up using a very long 1/2″ drive extension and my impact driver to break the nuts free.

With the lower engine mount nuts completely removed and the uppers loosened, I was one step closer to lowering the subframe.  The last step needed was unbolting the lower control arm rear “lollipop” bushing mounts from the chassis so the assembly could drop freely.  A jack comes in handy here, just to lower it in a controlled manner and keep it at a given height.

Now that the engine mounts are out of the way, you can more easily access the nuts that hold the lower control arm balljoints to the subframe.  Again I used the impact driver to zip off the nuts, only it didn’t work entirely as planned.  The driver side came off without any fuss, but the passenger side backed off almost all the way then began to spin the balljoint.  Normally you could just push the tapered joint in harder, thereby giving enough resistance to continue removing the nut.  Unfortunately this didn’t work, and neither did using a large C-clamp to help keep it secured.  I was forced to remove the nut (and balljoint stud with it) by means of a pneumatic cut-off wheel.

Cut off Balljoint Lowering Engine Subframe

This, of course, has ruined the passenger side lower control arm.  I checked the service history of the car to find out that it was still riding on its original arms, so a replacement at this mileage wasn’t completely out of order.  Fortunately I had a pair of brand new Meyle heavy-duty arms on hand, which were ordered originally for my E36 race car.

Finally everything was out of the way, and I could actually begin removal of the oil pan.  The pan itself is held on  to the block with quite a few M6 bolts of varying lengths.  My light-duty 1/4″ impact driver makes quick work of this.  Don’t miss the two bolts that are inside the bellousing, which are accessed through two small holes.  The back of the pan is actually bolted to the lower portion of the transmission’s bellhousing, which utilizes Torx-head bolts.

With all the bolts removed, the pan will still be very securely held to the block by the grip of the gasket and RTV used at the corners.  You may be tempted to use a pry bar to leverage the pan off, but this is a recipe for cracked cast aluminum.  A far better method is a large rubber mallet used to beat on the pan in a few structurally strong spots.  The cast aluminum of the pan is thin in the large flat areas and can be easily cracked, I’d avoid using a deadblow.  Eventually the hold will “pop” and the pan can be dropped.  Careful, as there is still a decent amount of residual oil left in there.

Rally Road Drilled Oil NutNow that the pan was removed, I could take care of another potential problem: the oil pump nut.  Again, this is an issue present on the M50 (possibly other BMW engines of this vintage) where the oil pump nut can begin to loosen and back off, potentially creating a total loss of oil pressure.  There are a few different paths to correcting this, like staking the nut with a center punch or using some red Loctite.  The problem with these methods is that they make it terribly hard to remove the nut for any future maintenance (however slim.)  The other alternative, and the one I used on my S50 race engine, is to use a nut drilled for safety wire.  Several suppliers offer these nuts for cheap, I found Rally Road was the least expensive.

Safety Wired Oil Pump NutThis is a pretty easy job, once you’ve removed the oil pan anyways.  You just have to remember that the nut is left hand thread, I’ve already seen a few photos of other installs which used a negative safety.  (Negative Safety is when the safety wire is run in such a way that it would actually cause the nut/bolt to loosen, rather than stay secure, which is a Positive Safety.)  The nut comes with a length of wire, which was clearly thinner than the standard .032″.  Since I had plenty on hand, I went ahead and installed it with the thicker 32-thousandths.

Back to the oil pan and baffle install we go.  First you must remove the OEM baffle, which is held in by a single rivet that must be ground off.  A 90 degree pneumatic grinder with a sanding wheel made quick work of this.  The OEM baffle, as you can see in the photos below, does very little to keep oil surrounding the pickup.

BMW OEM S52 Oil Pan Baffle BMW OEM S52 Oil Pan Baffle 2

The oil pan must be thoroughly cleaned in preparation for welding in the new baffle.  The pan was just small enough to fit inside my parts washer, where I soaked it with kerosene and scrubbed all the old oil deposits away.  The new baffle fits exactly as the factory version, but must be welded in place.  Since it was aluminum, time to call in a professional.  I dropped the pan off with a welder I’ve used before and had it back the same day for $20.  In the next photos you can see a side-by-side comparison of the OEM and Achilles baffles and finally the new baffle welded into place.

OEM and Achilles Oil Pan Baffles Achilles Oil Pan Baffle Welded

While all this work was taking place, I was also soaking the oil pan bolts in EvapoRust to remove the years of corrosion.  Like I had done with the hardware on the rear of the car, I gave the fresh bolts a good coat of CorrosionX prior to installation to keep them looking new.  The pan was then reinstalled with a new gasket with some beads of Toyota FIPG at the corners where the aluminum timing chain cover and rear main seal cover join the block.

S52 Oil Pan Reinstalled

Front Subframe with new Control Arms and Engine MountsWith the engine’s bottom end buttoned up, I could begin the process of reassembling everything attached to the subframe.  As I previously mentioned, I had new lower control arms to install.  Unlike the OEMs, the inboard balljoints on these Meyle arms had an Allen key socket on the ends of the studs, which should prevent any future issues of spinning ball joints.  The arms also came with new nylon lock nuts, which should prevent them from backing off.

I attached the arms to the subframe while it was clamped to my transmission jack, which would give me a little more control over raising the assembly.  While I was at it, I decided to also replace the original engine mounts, which were beginning to crack and were also heavily rusted.  The passenger side engine mount heat shield was severely rusted, but I had run out of time to order up a new one.  Instead I gave it a long soak in EvapoRust, primed it with Rust Encapsulater, then gave it a top coat of high-temp caliper paint.

For installation, make sure you keep the engine mounts just loosely fastened, as it will make it easier to align to the engine.  Also ensure you are using new bolts to mount the subframe back to the chassis.  These are high torque bolts and this is a critical connection.  I added a dab of blue Loctite as added peace of mind.  I then wheeled the assembly under the front of the car and raised it using the transmission scissor jack.  It was surprisingly easy to line everything up and torque down.  With the engine mounts tightened down, I could now remove the upper engine hoist, allowing it rest in its normal configuration.

From there it’s just a matter of connecting all the items you previously removed.  Of course this time I installed the steering fluid lines with the appropriate amount of new OEM crush washers.  Hopefully your match marks on the column and pinion lined up properly, mine didn’t.  The result was discovered after a test drive, where I found my steering wheel cocked slightly to the left during straight ahead driving.  Fixing that is a simple removal of the wheel and re-indexing (be sure to make match marks, as you must rotate the wheel to access the Torx bolts securing the airbag.)

The photos below show the completed subframe reinstalled with the steering gear, and lower control arms.  The anti-sway bar has yet to be reinstalled.

Completed Subframe

Before reinstalling the airbox and alternator cooling duct, you’ll need to reinstall the serpentine belt, fill the engine with oil, and then fill and bleed the power steering.  Doing this with those items in place is nearly impossible due to the poor positioning of the power steering fluid reservoir found under the intake tract.  I used less than a bottle of Redline PS Fluid, first filling the reservoir then cranking the engine and sawing the wheel back and forth to bleed out the air.  A little top off was required, but it takes surprisingly little fluid.

Quite the job right?  After the car was back down on the ground I took it for a test drive.  I could feel an immediate difference in the front suspension, everything was a bit tighter, newer feeling.  I also had a bit of an alignment issue, which felt as though I had a little toe-out.  Despite not adjusting the tie rods, you’re bound to have movement in the rack from its original position, however minimal.


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