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      03-03-2012, 10:56 PM   #52
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Drives: 2006 e90 325i
Join Date: Jan 2009
Location: Fairway, KS

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Just changed the oil filter housing gasket on my N52. At the last service, the dealer mentioned my gasket was starting to seep. Part was $16.47 including tax at the dealer.

I did remove the air box but did not drain the coolant or remove the radiator hose. I loosened the bolt under the manifold and the front lower bolt using an 8mm box wrench. Once the bolt under the manifold was loose, I used a 1/4" drive wobble extension and a swivel joint. In preperation for separating the filter housing from the block, I covered the belt, pulleys, and alternator with aluminum foil to protect them from coolant and oil.

When all bolts are out, have a small rag handy and plug the coolant hole in the block as you remove the filter housing. I didn't know quite what to expect so I lost maybe a half quart to a quart of coolant before I fumbled around and stuffed the rag in the coolant hole. You will most likely get a small amount of coolant that splashes into the oil passage, but I assume this will evaporate once the engine is hot. If I did this again, I would stop the coolant flow with the rag, then try to capture most all of the coolant after removing the rag. Either way, you will need to let the coolant drain down so that it is below the coolant hole on the block.

With the rag removed, you can now clean the mating surface on the block and the housing. Not much of the the black rubber gasket was stuck to the block mating surface. I used brake cleaner to get most of it and then used 600 grit sandpaper to remove the last remnants.

Now that both mating surfaces are clean, insert the new gasket and reinstall the bolts. I tightened the bolts evenly in a criss cross pattern. I didn't use a torque wrench, but just snugged then down tight until I couldn't turn anymore.

I then topped off the coolant so that the float showed full and bled the system per procedure. To bleed, you push the ignition button without starting, turn heater temp to 84 degrees, put fan on low and hold down gas pedal for 10 seconds. You should hear the electric water pump turn on. It will cycle for several minutes. I test drove it around the block several times to get it to temperature and did a visual check for leaks. I'll keep an eye on coolant for the next few days and top off if required.