M20 Oil Filter Housing Gasket Replacement

Replacing the Gasket on the Oil Filter housing.

The following is a write up for the work conducted on an M20B25 engine with an oil cooler.

Overview

Amongst the oil filter housing is a thermostat which whilst oil temperature is low remains closed restricting oil flow to the oil cooler. This allows the engines oil to reach the correct operating temperature quicker. Once the temperature is reached the thermostat will open allowing oil to flow through the engine and oil cooler in order to maintain a good temperature and not to over heat.

An ideal to time do the fix is with an oil change as you will loose oil that’s in the oil filter when removing the gasket.. or at least have enough oil to replenish what you loose.

The thermostat is held in by a spring, which is secured and sealed in the oil filter housing by a plug and O ring which is retained by a circlip. This rubber O ring can fail over time causing oil to weep from the housing.

Parts & Tools

So including an oil change, tools and parts needed are as follows.

Gasket kit (part number 11429059338)

5L of Oil (for an M20 5w-40, 10w-40 or 10w-50 as recommended by Simon aka oilman)

Oil filter (GENUINE Fram oil filter is recommended).

A tray of some sort to catch any oil.

A small enough flat bladed screwdriver or a bradle to help pry the circlip out.

Long needle nose pliers again to help get circlip out.

A clamp long enough to fit over the oil filter housing and gasket.

Ramps or axle stands and a jack.

Wheel chocks.

Latex gloves, as it can be a messy job and oil isn’t kind on skin.

The Job

It doesn’t matter whether you empty the engine of its oil first or not. I did it after replacing the gasket; as I wanted to drive the car up onto ramps instead of jacking it up on axle stands so bare that in mind.

1. Drive the car up onto ramps, or jack it up and put it on axle stands. Making sure to secure the car with chocks behind the rear wheels.

2. The oil filter housing is situated (RHD cars) right (facing forward) of the engine under the exhaust manifolds. So access is from underneath.

3. The gasket is situated in the housing opposite the oil filter facing down. To remove the circlip; use either needle nose pliers or a flat bladed screwdriver.. or like me; a combination of both plus a bradle. It’s a bit fiddly but will come out soon enough. Once its almost out be sure to have a finger placed firmly over the gasket as the spring and thermostat will be wanting to spring out along with the oil that’s in the filter!

4. Have a tray at the ready to catch the oil and carefully allow the gasket out followed by oil, a spring and a thermostat. Make a mental note of what way the thermostat came out so it can go back in that way.

5. I have read after doing this job that it’s an idea to test the thermostat by putting it in hot water, but I didn’t do this.

6. Clean away any oil and dirt they may have spread anywhere from the leak.

7. Now all is to do is reassemble the thermostat, spring and new gasket and insert it back into its housing.

8. Getting the circlip back on can be tricky, I found it easiest to carefully clamp (not too tightly, just enough to get the circlip in place) the gasket into place freeing up both hands to get the circlip on. The replacement circlip, which is included in the kit, has the metal bent back on itself at either end making it easier to pinch in with needle nose pliers. I used pliers to get it mostly in, then pushed it finally into its recess with a bradle.

9. Remove the clamp, let the car back to the ground. Change the oil and oil filter (that’s already documented here on other wiki pages). Then place some cardboard under the engine and run it for 10-15minutes to check for any leaks. It also wouldn’t hurt to get back underneath to have a further inspection.

This guide was written and supplied by G-Bear