I've got a 98 740iL that I have replaced the Water Pump, radiator and thermostat in the past 18 months. Last week I had the overtemp warning. Since most of these parts are relatively new, I thought it was probably the thermostat. I replaced the thermostat, filled with coolant, bled the system several times, but the car still overheats when driving. It will Idle for 15 to 20 minutes without overheating, but under driving conditions it overheats right away. One thing I have noticed is that the hose coming from the lower end of the radiator is not hot, but the upper hose is very hot. I'm wondering if I have air in the system still, or if my water pump impeller is spinning on the shaft. I've tried to bleed off the air in the sytem about 5 or 6 times, and still get the same result. Anyone else out there have a similar occurance? how did you get it fixed? I try to do my own Repairs and have been very successful up until this one....
Thanks!

This happened to me when I just bought my car in June 2005. I didn't know the car overheated, but when I drove the car from Los Angeles to San Francisco (400 miles), the car started overheating halfway through the trip. I thought it was normal, but it wasn't.

Anyway when I brought it back to the city, I noticed the car overheated about 30 min of driving. It was abnormal. I would always get a message "Check Coolant Level" or something like that. I took my car to the shop and it resulted in me replacing my engine. There was too much to be done so I bought a warranty.

This is what I had to replace, some of this warranty replaced;

- Engine
- Rear Main Seal
- 2 Drive Belts
- Spark Plugs
- O/F Housing Bushing
- Intake Cover Gasket
- PCV Cover
- power steering reservoir mounting bushings
- dip stick
- rear lower control arm bushings
- rear transmission mounts
- Thermostat
- Intake Manifold Gasket
- Fuel Hose
- Cylinder Valley Gasket
- Water Accumulator
- Bunch of O-Rings

Hope everything works out with your car. I hope it isn't as bad as mine was.

Well, I really don't think I have that much wrong with the car, certainly nothing wrong with any of the other systems except the cooling system. I had a certified BMW shop perform the Inspection II about 4 months ago. The car has 105,000 miles on it, but I've maintained it very well. I've never driven it more than maybe 1 or 2 minutes after noticing the overheating condition. I know that Aluminum engines cannot tolerate excessive heat.
I think it is one of two possible causes. 1) Water pump impeller not adequately fixed to the shaft allowing the impeller to spin on the shaft, or 2) Air in the system specifically in the Water Pump not allowing circulation.... That's why the lower hose is still cool when the upper is very hot.

I think the best solution would be to take it to the shop and have them check out your car.

I bought my car from the original owner. The car had 83k miles, it was in good condition, no malfunctions. Drove like brand new, everything the car ever came with, it still had.

I was excited to own this car, but everytime I would drive for about 20-30 min, the car would overheat (my car didn't idle though). I didn't take care of my problem fast enough thats why I had to replace my engine because it resulted in me having engine problems.

Now the car is in perfect condition at 89k.

Update: Turns out it was the Waterpump. The impeller had broken and was spinning on the shaft. I had replaced this a couple of years back with a original OEM pump, which had a plastic / nylon impeller.... This time I shopped around purchased a pump with a heavy duty metal impeller. The car is back in prime condition and runs like new!

Where did you find the water pump with a metal impeller?

Where did you find the water pump with a metal impeller?

bump, I need a new water pump and I am hearing $567, installed. Is a water pump something I can do on my own?