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'02 325ci Coolant System and Brake Caliper Questions

1563 Views 5 Replies 5 Participants Last post by  pnMedia
As always thanks for the expert insight and guidance ..

I'm the original owner of this noted 2002 325ci. Only 31k miles. I ordered it back then with the available "Sport Package" option.

For the lifespan of the car I've lived in a high-rise with an outdoor lot that is located about 200ft from a salt water bay. Needless to say the exterior of the car has suffered. The clear coat is starting to peel in various areas due to direct sun exposure. The aluminum trim and rubber seals have begun to show signs of deterioration as well. Considering - the car still looks decent. Eventually I'll address the exterior.

By the way - I've never had any mechanical problems with the car. Everything with regards to parts is 100% original outside of the windshield washer fluid pump, windshield cowl, rear brake pads, and the tires. Oil has been changed as needed. Air filter and cabin filter have been maintained as well.

Anyway -

Question #1 - I understand the design of the coolant overflow tank and I guess the radiator with the blue drain screw located under the car. I'm also aware of the bleed screw, located at the top of the overflow tank. I've read that there is another drain screw that will allow coolant mix drainage from the engine block. If so, is the coolant mix that is located in the radiator/overflow separated from the coolant mix located in the engine block? What's the correlation?

Question #2 - Regarding the brake calipers. All four are completely covered in surface rust. I understand that rust is inevitable, especially in my location. However, does this rust compromise functionality and/or safety? I will say the car brakes efficiently, with no indication of malfunction or pad wear. Should I consider having these replaced? If so, any recommendations, other than the $400 versions that BMW sells?

Thanks again..

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Q1 - coolant circulates in the engine block and then back to the radiator to get cooled off and then it is recirculated in the block. It is all the same fluid... Emptying the hoses and expansion tank only removes most of the coolant. If you remove the water pump more fluid will come out from the top of the engine. The added screw in the block will drain the upper part of the block of the fluid and get pretty much all of it out.

Q2 - nope - not unless the caliper pins are sticking but that is separate from the general caliper surface rust.
for a complete draining coolant job, drain the radiator, empty the tank, and drain the engine block.

As for the rusted calipers, just give them a good coat of engine oil or grease.
The engine coolant drain plug is located between cylinders 1 & 2 under the exhaust manifold. If you remove it you MUST replace the crush washer. Failure to use a new crush washer will result in a coolant leak. Ask me how I know!
You could paint the calipers to help curb the rust, usually requires a few hours of sanding and cleaning if you’re up for that.


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Everyone - thanks for the responses.

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