Sunday, November 21, 2010

How to change a thermostat in 1992 BMW 325I?

read this to change a thermostat in 1992 BMW 325I?
so i gave you the best answer, and you chose indianajones as the best answer?? hahaha....

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How to change a thermostat in 1992 BMW 325I?
the engine drain plug is under the exhaust manifold, likely under cyl 4 or 5, but it is under cyl 2-3 on some BMW engines. Just look under the car and you should see a plug on the block. it should be a 19mm hex head on the plug, but sometimes people use other plugs.

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the bleed screw is a plastic screw, usually right next to the radiator cap.

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This is not too bad of a DIY job. I would recruit a friend to help and allocate about 3-4 hrs.

0. turn on the car, set heater to full hot, and fan to some low setting. this opens up the heater core for the coolant drain/flush.

1. make sure the car is cooled. You don't want to work on a hot engine and you don't want hot coolant all over yourself.

2. jack up the car on the appropriate jack stands. bring it as high as you can for more clearance as you have to get under the car.

3. drain the coolant from the radiator

4. drain the coolant from the engine block

5. remove the air duct at the front of the car

6. disconnect the upper radiator hose

7. remove the fan (left hand threads on the 32mm nut)

8. disconnect the expansion tank overfill hose

9. raise the expansion tank with the plastic frame

10. disconnect the heater coolant hose from the bottom

11. disconnect the coolant level sensor plug

12. now remove the entire plastic frame and expansion tank

13. remove the two 13mm bolts from the engine hook and remove the hook. one of the bolts holds the thermostat housing.

14. disconnect lower radiator hose

15. remove 3 more 10mm bolts from the thermostat housing

16. remove thermostat housing

17. remove thermostat and replace with new one w/ O-ring

Then just reverse the steps. Apply silicone sealant to the thermostat housing. the 10mm bolts are torqued to 10Nm, the 13mm bolts are torqued to 22Nm. The engine block drain plug is torqued to 25Nm. Always use a new aluminum crush washer for the engine drain plug, this is what seals it so coolant doesn't leak out. The radiator plug should just be hand tight. Make sure all hoses are connected securely and tighten the hose clamps accordingly. Make sure to bleed air out of the cooling system after refilling the coolant. Add more coolant until you have it at the right level. Make sure your heater is blowing hot which helps as an indicator that you don't have air pockets.

For the next few days, keep an eye on your engine temp. If it creeps up above normal, stop the car and let it cool down. Relieve cooling system pressure slowly through the bleed screw. Then open the expansion tank and add more coolant/water as necessary.

Side note: on the 328i I just worked on this weekend, i had to remove the pre-cat O2 sensor for cyl 4-6 in order to get the drain plug off the engine block. on other BMW engines, i never had to do this, but you may run into the same obstacle. in which case, just remove the O2 sensor with a 22mm oxygen sensor socket. cover up the O2 hole with duct tape before you drain the engine block so you don't get coolant into your pipes. when re-attaching the O2 sensor, apply a little bit of anti-seize and torque it to 50Nm.

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