528 overheats? Help

Just recently took my 2000 528 on a trip to Fresno via the grapevine. I usually do this trip in excess of the posted speed limit and have had no problems with a four-passenger load, and the a/c on. The Temp gauge has never gone beyond 3/4 of the way to red. I will preface with 4000 miles ago I had a reserve tank rupture in my garage and it was replaced under warranty, but this was the first long distance trip since then.

Half way up the grapevine the temp gauge gradually moved to within a hair of the red. I killed the ac with little effect. Slowed to 70 with some luck but, except for downhill legs, or with the heater on, the temp gauge stayed above 3/4 to the edge of the red (anything over 70mph 2500rpm pushed it to the red). This high temp reading happened all the way to Fresno, even on the flats!

Had the local BMW dealer check it out, they found air in the cooling system, and pressure checked and certified ok. Ran the car around Fresno and so no major problems, but on the return trip had the same temp problem occur.

Don’t want to waste another $122 to fix nothing. Anyone have any ideas??? It happens at high speed so it shouldn't be fan clutch. The pump has a metal impellor. You would figure that the coolant should be fresh and that the level should be good. Thermostat???

Thanks for any sage advice you can offer

if it has high mileage perhaps the radiator is becoming restricted.

Originally Posted by Hal H

Just recently took my 2000 528 on a trip to Fresno via the grapevine. I usually do this trip in excess of the posted speed limit and have had no problems with a four-passenger load, and the a/c on. The Temp gauge has never gone beyond 3/4 of the way to red. I will preface with 4000 miles ago I had a reserve tank rupture in my garage and it was replaced under warranty, but this was the first long distance trip since then.

Half way up the grapevine the temp gauge gradually moved to within a hair of the red. I killed the ac with little effect. Slowed to 70 with some luck but, except for downhill legs, or with the heater on, the temp gauge stayed above 3/4 to the edge of the red (anything over 70mph 2500rpm pushed it to the red). This high temp reading happened all the way to Fresno, even on the flats!

Had the local BMW dealer check it out, they found air in the cooling system, and pressure checked and certified ok. Ran the car around Fresno and so no major problems, but on the return trip had the same temp problem occur.

Don’t want to waste another $122 to fix nothing. Anyone have any ideas??? It happens at high speed so it shouldn't be fan clutch. The pump has a metal impellor. You would figure that the coolant should be fresh and that the level should be good. Thermostat???

Thanks for any sage advice you can offer

Could be a mixed bag of either thermostat/pump, leak. I had a small leak in my coolant system in one of the pipes a few weeks ago giving me air locking in the system.

I got my dealer to give me a "goodwill service" due to my 51000 miles and they replaced the thermostat. We'll see it that is the cause.

keep us posted please.