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Old 11-22-2009, 08:05 PM
cn90 cn90 is offline
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Location: Omaha NE
Join Date: Mar 2006
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Mein Auto: 1998 528i 5-sp 140K+
1998 528I Oil Filter Housing Gasket & “Freeze Plugs” Repair (E39)

DIY: 1998 528I Oil Filter Housing Gasket & "Freeze Plugs" Repair

- I have what seems to be an oil leak along the Oil Pan Gasket. To replace the Oil Pan Gasket, it is a massive job on the 6-cylinder engine!!! So I went to the BWM dealer and they say that they virtually never sell an Oil Pan Gasket!
But they fix quite a bit of Oil Filter Housing Gasket, actually they have a whole bunch of these gaskets in stock!

- I did a little more research and apparently the Oil Pan Gasket is made out of some very tough material with a steel re-enforcement and should last into 180-200K miles. So I figure out common things are common and rare things are rare!

- As it turns out, I have leak at both Oil Filter Housing Gasket and "Freeze Plugs". It is an easy DIY, roughly 3-4h job.

- To my pleasant surprise, I have no more oil leak after one week, so those who think you have a leak at Oil Pan Gasket, think again, it is likely the Oil Filter Housing Gasket and "Freeze Plugs" Leak!!!

* The issue of "Freeze Plugs" leak was discussed here:
Instead of removing the "Freeze Plugs" and tap threads for an "NPT Thread" Plug, I decided to use an M7 bolts + washer for repair, and it works great (see below).

To check for a Freeze Plug Leak, use a mirror and flashlight:

* Info on drive belt layout and belt tensioner (32-mm thin wrench for Fan Clutch Nut and 5/16" Allen wrench for tensioner):

* Info on how to remove Air Filter Housing is part of my DIY for ICV, CCV etc.:

- Check for your PN.
- Check your belt layout and make a diagram before taking it off.
- The PN for my 1998 528I Oil Filter Housing Gasket is 11421719855 ($5.00 at BMW dealer).
- Observe Torque Values (look it up) for different bolts.
M8 bolts = 22 Nm (Oil Filter Housing)
M10 bolts = 33 Nm


1. Disconnect Battery Positive Terminal in the trunk (10-mm wrench, be careful not to short with the ground bar!)

2. Remove Fan Clutch: 32-mm wrench. Note it is REVERSE thread!
During re-installation if you have difficult threading the Fan Clutch Nut back on the Water Pump bolt, you can use my "Poultry Cord" trick:

Use 5/16" Allen wrench for tensioner to remove belt.

3. Disconnect the DSC System Connector.

4. Remove the Air Filter Housing/Air Mass Meter as a Unit. Remove the 10-mm bolt and clamps and wiggle the whole thing out watching not to damage the Intake Rubber Elbow.

5. Remove the 13-mm Bolts the PS Reservoir and set it aside:

6. Alternator is mounted by two (2) 16-mm bolts. The UPPER Bolt holds the Pulley.
The positive cable connection is a 13-mm Nut.
- D/C connector
- D/C Cooling Air Intake
- Then Alternator comes out (It swivels on the LOWER bolt).
- During re-installation, use a smaller rod or screwdriver to help guide the Alternator back on the slot.

7. To remove the Oil Filter Housing:
- Disconnect VANOS Banjo-style Oil Line attachment to the VANOS using 19-mm wrench.
Do NOT lose the 2 aluminum washers, I re-use these washers. Torque for this 19-mm Banjo Bolts: 32 Nm.
- Optional: Remove Tensioner (Yellow Arrows) using 13-mm sockets. You don't have to do this step as it can be left attached to the O.F. Housing.
- The O.F. Housing is held by a total of 8 bolts.
- The six (6) 13-mm bolts have different lengths: mark them #1-6 to avoid confusion. In the event that you forgot to mark them, no worry, I laid them out in order as shown.
- Remove two (2) 13-mm bolts (# 7-8) on top of the PS Pump.

8. Now the O.F. Housing comes out easily. Remove old gasket and clean the mating surfaces to make sure it is spotless for re-installation.

9. If you decide to de-grease this area, go slowly!!! Stuff a rag inside the Engine Housing to prevent dirt or water from coming in. Avoid garden hose or pressure washer for obvious reasons!!!
- Wipe it clean with a rag and Q-tips so no oil is left behind.

10. Have a look at the O.F. Housing:
- Note the Oil Pressure Sensor on the back side.
- Note the Engine Oil Anti-Drain Back Valve.
- When installing new gasket, I use a thin smear of grease to seal any imperfection (this is just my way, you don't have to do it).
- Check both the mating surfaces to be sure it is spotless before re-installation:

- The Gasket barely sticks out (maybe 0.2 mm), so avoid using additional gasket maker here because it can potentially affect the Factory Gasket sealing:

- Straightforward.
- Note all connectors and re-install them.
- Watch torque values.
- Wipe all oil leak in engine compartment and along oil pan gasket area so you can monitor these areas later.
- Re-connect Battery Positive Terminal.
- Start engine and check for any oil leaks at Housing or Banjo connection.

Congrats, you just spent $5.00 and saved some 4h of labor charge at dealer or indy! Now let's move on to fixing the Oil Filter Housing Leak itself.


- After the following repair of "Freeze Plug" Leak, my car is bone dry, not a single drop of oil leak!

Parts List (All of these can be obtained at Ace Hardware Store) for about $12.00:
- Stainless Steel M7 x 10 mm bolts; qty = 2.
- Optional: M6 x 10 mm bolts; qty = 2 for "dry fit".
- Stainless Steel Washers O.D. = 1-1/4"; I.D. = 5/16" (5/16" = 8 mm to accept the 7 mm bolt).
- Red LocTite, small tube
- Permatex Black RTV Gasket Maker
- Roofing Black Asphalt Caulk

- The "Freeze Plugs" are actually not "Freeze Plugs" but basically Welch Plugs that are stake-punched in from factory to close off holes from casting. It should have been plugged with bolts and washer (later models use bolts and washers). But this design of "Freeze Plugs" is known to cause oil leak in different BMW models.
- A new O.F. Housing is $330!!!
- The leak from my "Freeze Plugs" is about 4-5 drops on the driveway every night. But there is more leak than that (oil blown off on the road and collecting under the oil sump).

1. The hole in the "Freeze Plugs" is made from Aluminum and has a diameter of 6 mm and the M7 bolt fits perfectly.
- Do a search on tap and die of bolts and nuts, but as a rule, the hole to be threaded is always a bit smaller than the new bolt. This is because the M7 bolt has a diameter of 7 mm measured at the tip of the pitches but the measurement at the valley of the pitches is about 6 mm.
- To tap new threads, you can use a tap and die set but if you don't have a tap/die set, no problems. Use the M7 bolt to tap it with 1/4" ratchet. Keep steady pressure and maintain perpendicular path. The bolt is Stainless Steel and the Plug is Aluminum, so the bolts makes new threads with no problem (this is what I did).
- Tap a few turns at a time while removing the metal fragments. The hole is about 5 mm deep.
- Clean the hole from any debris:

2. Now use the smaller M6 x 10 mm bolt to make sure it fits nicely. The idea is: the washer should be 1mm from the housing. This is because this space will be occupied by Permatex RTV Gasket Maker, which will cure into a rubber-like material:

3. Now fit the washer and the M7 x 10 mm bolt as a "dry run". When the bolt is completely in, you should see a 1mm gap between the washer and the housing. Do NOT over-torque this M7 bolt, very easy to strip it!
- Now, remove the bolt and washer and proceed with the sealing job.

4. Apply Roofing Black Asphalt Caulk at the edges. This is where the oil leak happens. The Black Asphalt Caulk will seal it nicely and has a wide range of temp tolerance.

5. Now apply Permatex RTV Gasket Maker as shown, leaving the hole alone. Use Q-tips to clean the hole:

6. Place washer then rotate it a bit to spread the RTV sealant. The Permatex procedure calls for letting the sealant cure for about 2h before tightening the bolt. However I install the bolt right away, read on…............

7. The M7 x 10 mm bolt: apply a drop of LocTite on the thread and a very small drop of RTV sealant near the bolt's head. Again, use 1/4" ratchet and do NOT over-torque this M7 bolt, very easy to strip it!

8. When the bolt is fully seated, you should be able to rotate the washer because there is 1 mm gap filled with RTV sealant (but after 24h of cure, the RTV sealant will be rubberized and you should not be able to rotate the washer).
- Clean excess RTV Sealant. This is what it looks like prior to re-install:

9. The key thing: you can install everything back in the car but don't start the engine until 24h later to allow the RTV Sealant 24h to completely cure.

Congrats, you just fixed the most difficult problems of Oil Leak from "Freeze Plugs" faced by many BMW drivers for $12.00!

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Last edited by cn90; 11-24-2009 at 05:56 AM.
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