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Old 04-13-2009, 05:35 PM   #1
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Join Date: Jan 2006
Location: Cyprus
Posts: 6,564
My Ride: ESS TS2 320ci
Talking DIY: Thermostat Replacement with pics

Since I had some problems with the coolant temp and coolant leak from the thermostat, I decided that it would be a good time to replace it. For a replacement unit, I used a spare themostat which I got 2 years ago from dealership.

The replacement process is done on a M54B22 engine but it's the same accross the M54 series engines. Cars with auto transmission have a bit more work to do because of the mechanical fan in the way.

Leaky t-stat

Bleeder screw for proper system venting

3 push/lock pins removed for the fron air intake

Remove T20 bolt, 2 plugs shown here and push/lock pin on opposite side to remove fan.

Connection was very tight and I was afraid that I would break something

"New" Thermostat

Spraying some good amount of WD-40 to break loose the connections

With a flathead screwdriver, pry the metal release tab upwards for both hoses

Thermostat plug release spring needs to be pushed down to release connector

To remove the thermostat: Remove the 11mm nut that holds the engine hoist bracket, remove the 13mm bolt of the lower part of engine hoist bracket, and the 3x10mm bolts that hold the thermostat on the block.

Have some rags below the thermostat as coolant (around 1.5L) will be spilled. You don't want coolant on the engine belt. It's oily and can make the belt slip. There were marks of there the coolant was leaking which I thoroughly cleaned before proceeding.

Old thermostat with messed seal

Aparently the plug was messed too, rust, coolant, dust particles and one wire which was barely making contact. As I further pulled the connector the wire was cut. Somebody please explain to me what the sensor/electrical component inside the t-stat does?

To prevent future coolant leaks, I applied some high temp RTV silicone sealant as per application instructions.

Used OEM coolant. Nitrite Free

Assembly is just the opposite process, not difficult, took me total of 2 hours.

paraklas is offline   Reply With Quote
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