I check the oil pan mating surface for flatness and verify that the oil pan bolt threads are not stripped as I do this work. Now is the time to address these problems if there are any.

Parts

The gaskets I need are included in the EME engine gasket kit. I’m also going to replace the oil pan bolts and wave washers with new stainless steel hardware I got in the bolt kit  from “The Bolt Guy” for the RT model since I’m converting the RS to an RT, not that RT pan bolts are different from RS ones.

Here are the specific BMW part numbers.

Part #	Description	Qty
11 13 1 338 427	GASKET, Oil Pan-In EME Gasket Kit	1
11 41 1 265 258	GASKET, Suction Flange-In EME Gasket Kit	1
07 11 9 904 527	HEX BOLT WITH WASHER – M6X20-SS In The Bolt Guy kit	14

Video

Here is a short video summarizing how to to to this work.

VIDEO: 1983 BMW R100RS Replace Oil Pan & Oil Suction Flange Gaskets

Getting Started

I have the engine out of the frame, but you can do this work with the engine in the frame. You can put the bike on the side stand to remove the oil pan and oil pump suction flange after you have drained the oil. You will have to get down on the ground and look up under the engine to do the work which is a bit awkward and uncomfortable.

An alternative is to remove the gas tank, drain the carburetor float bowls and drain the oil. Put some blankets down and the lay the bike down on it’s side which will expose the oil pan for easier access.

I like to put the engine on my Harbor Freight motorcycle stand. I raise the stand to it’s highest level. I put two 2×4 blocks across the legs and then lay the engine down on it’s side on the 2x4s. I put the cylinder studs in between the legs and use two ratchet straps, one horizontal and one vertical wrapped around the 2x4s and the legs of the stand. This keeps the engine from moving or falling off the stand while I work on it.

Test Oil Pan Bolt Threads

To test that there are no stripped oil pan bolt threads, I use my INCH-Lbs, NOT FOOT-Lbs wrench. I set it to 78 INCH-Lbs and tighten the 14 oil pan bolts. If they all hold this torque, then the threads are good. If any fail to hold the torque, I use Heli-coil inserts to repair the bolt holes in the engine block.

My bolt threads all held the torque so no previous owner over tightened the oil pan bolts and stripped the threads. 🙂

Remove Oil Pan and Gasket

Now I remove the oil pan bolts, the oil pan and the gasket. Sometimes the pan stays stuck to the block after you remove all the bolts. When that happens, I start with my rubber mallet. I grasp the pan firmly so it won’t fall off or fly off and give a couple raps to the top two corners of the pan.  It that doesn’t work, I get someone to help hold the pan. Then I take a short piece of 2×4, lay it against the top edge of the front of the pan and hit it with a sharp blow with a hammer being careful not to hit the oil pan.

My pan came off easily leaving the gasket attached to the block. I used a flat putty knife and carefully inserted it between the gasket and the block so as not to gouge the mating surface on the block. Then I could slowly pull the knife along the mating surface to separate the gasket from the block.

Remove Oil Pump Suction Housing

The oil pump suction housing is exposed. There is screen to prevent any large chunks from being sucked into the oil pump. It is secured with a wire retaining clip. I push on the ends of the clip to free them from the slots cast into the back of the suction housing and remove the clip and the screen.

The two M6 bolts that secure the suction housing to the suction flange in the engine block are exposed. I remove them.

Remove Gaskets, Clean Mating Surfaces

The suction flange gasket is stuck to the suction housing with bits of it on the suction flange. I clean the gasket off both mating surfaces carefully with a razor blade almost flat against the mating surfaces being careful not to nick the surfaces. When the big bits are removed, I use a wood block with 600 wet/dry paper and carefully, and lightly, sand the mating surfaces keeping the block flat against the surface to get the last bits of gasket and glue off.

WARNING
Be sure you have a flat block and you keep it flat on the mating surface. Sand very lightly and just enough to remove the small bits of gasket and any remaining glue. You do not want to make the surface uneven or rounded.

Then I use brake cleaner to completely clean the mating surfaces so they are oil free. The new gasket has heat activated adhesive so I don’t want any oil on the mating surfaces.

I clean the bits of gasket material off the oil pan and engine block mating surfaces. I use the same technique to remove any bits of gasket and glue with a light sanding using 600 grit wet/dry paper and a wood block and brake cleaner on a blue shop towel to ensure the mating surfaces have no oil on them since the pan gasket also uses a heat activated adhesive to seal the gasket.

Install New Oil Pump Suction Flange Gasket and Suction Housing

Here is the new gasket, the suction housing with the clean and oil free mating surface, the two M6 bolts with clean, oil free threads, and Blue Loctite.

I clean the suction housing in my parts washer. I use a wire wheel to clean the bolt threads as they have Loctite on them. I use brake cleaner on the gasket mating surface of the suction housing so it is oil free. I apply Blue Loctite to the bolt threads.

I insert a bolt through one of the holes in the suction housing, slide the gasket over the bolt and thread the bolt into the hole in the suction flange. I snug up both bolts finger tight. Then I set my INCH-Lbs, NOT FOOT-Lbs torque wrench, to 78 INCH-Lbs and torque both bolts.

Next, I install the suction screen and slide the retaining clip over the top outside edge of the suction housing and slide the clip down until the ends of the clip are in the slots on the back side of the suction housing.

Measure Flatness Of Mating Surface

I use a large thick glass plate from a coffee table to measure the flatness of the mating surface. I clean the glass with glass cleaner and make sure its clean and there is no grit or debris on it. I put the oil pan mating surface on top of the glass. I push down on the cover and I and try to slide a 0.002 inch feeler gauge between the glass plate and the oil pan mating surface. If I can insert the gauge anywhere along the perimeter of the oil pan, I need to flatten the mating surface to remove the proud area, or I’m likely to have oil leaks around the oil pan gasket.

I found a gap along the front mating surface of the oil pan. It’s not uncommon to have a slight raised edge around one or more bolt holes in the cover. And there are some scratches in the mating surface which ought to be removed.

How To Sand Oil Pan Mating Surface To Get It Flat

I use two sheets of 600 grit wet/dry paper and attach them to the glass plate using contact cement on the back of the paper.

I put water on the paper and sand the cover using a figure-8 pattern for about 10 revolutions or so. I clean off the mating surface with a blue shop towel with some brake cleaner on it. I use the feeler gauge to check if the mating surface is flat. I continue this procedure until I get a flat mating surface all the way around the cover.

It took several cycles of sanding to get the mating surface flat. One thing you can do is to draw a line on the mating surface with a Sharpie pen. If the surface is flat, the line will disappear when you sand. I do this when I’m getting close to flat. I stopped when there was only a faint trace of the Sharpie line on a small part of the cover.

Install Oil Pan and Gasket

I’m replacing the original bolts with stainless steel bolts and washers. Therefore I need to use anti-seize on the threads to prevent galling.

But, anti-seize acts as a lubricant. That affects how much torque I should apply. The stock bolts are steel, installed dry, and the torque range is from 5.5-8 FOOT-Lbs. The recommendation is to shoot for 6 FOOT-Lbs, which is too low to use a FOOT pound wrench as it will be very inaccurate at that low a value. So I use my INCH pound wrench.

The recommended torque for stock, steel dry bolts of 6 FOOT-Lbs equals 72 INCH-Lbs which is toward the lower end of the range to avoid stripping the oil pan bolt threads in the aluminum engine block. With the anti-seize I reduce the torque 20% so I torque them to 60 INCH-Lbs,

I apply the anti-seize to the bolt after installing the wave washer.

Then I orient the gasket so the semi-circle on the block aligns with the semi-circle on the gasket, insert a bolt with anti-seize and a wave washer through the cover and the gasket and thread it into a top bolt hole. I hang cover from the top bolts and finger tighten them.

To prevent getting a wrinkle in the large oil pan gasket, I torque the bolts in three stages: 25 INCH-Lbs, 45 INCH-Lbs and then 60 INCH-Lbs.

NOTE:
If you have stock steel bolts, you should torque the bolts in three stages also, but use 72 INCH-Lbs for the final stage.

I torque them in a cross wise pattern, again to prevent getting a wrinkle in the gasket.

All done.