2001 325ci is OK when idle, but overheats when run.

[Vals]

Hi Everyone,

I am having overheating problems with my 2001 325ci. Some background on the issue.

Originally the problem started when I noticed the vehicle leaking coolant. Upon inspection...I noticed the radiator expansion tank had a nearly invisible crack...so I went ahead and replaced that myself. After replacing the expansion tank, that is when I then noticed the overheating for the first time. I then replaced the thermostat as well, and that is when I noticed it overheats, but not on idle. Wondering what you folks suggest I check next. Thanks in advance!

[bmwdirtracer]

There are probably a thousand overheating threads on this forum alone. Search. The FAQ section at the top of this forum is particularly helpful, because it has some of the greatest threads attached.

Your car is due for it's SECOND complete cooling system replacement. This means: Radiator, expansion tank, cap, water pump, thermostat, fan clutch, all hoses, and both plastic water pipes, plus a coolant flush, including draining the engine block, and refilling the system with 50/50 BMW blue coolant and distilled water, plus a complete and correct bleeding of air in the system.

If the car has ever truly overheated (i.e. reaching the red on the gauge), you might have a blown head gasket, warped head, and threads ripped out of the engine block.

The very LEAST you need to do for your car NOW is replace the water pump, and correctly bleed the cooling system. There is a thread on bleeding the system in the FAQ at the top of this forum; you'll find DIY's on the water pump at Pelican Parts or Bav Auto.

Keep in mind that I said you need to replace the ENTIRE cooling system.....doing JUST the water pump is half-assed, and is really just an emergency measure, which is not enough to prevent further major expensive failures.

[thejlevie]

+1 on everything that Chris said. Though I'd add having a pressure test run on each cylinder. That is done by pressurizing each cylinder with 170-180psi for several minutes and monitoring cooling system pressure with sensitive gauge (0-5psi), or by watching for a rise in coolant level or bubbles coming out of the expansion tank. That will tell if you have a leaking dead gasket.