1998 BMW E39 528i OVERHEATING IN PARK, NOT IN DRIVE.?

Question

1998 BMW E39 528i Auto Trans, 170,000 miles, Temperature gauge stays in middle when driving in city, highway, mountains with A/C on. But today after 15 miles of city driving, I stopped in parking lot for 10 minutes, engine running, transmission in Park with A/C on, and the temperature gauge went in red zone (red light came on). I should have turned the car off, but I had a feeling that once I started driving, the temp gauge needle will go to middle and it surely did go back to middle all the 15 miles of city driving back home.
I checked and there are no leaks, coolant reservoir is full, both fans (front and back) of radiator are running (when car in Park with A/C on).
Waterpump, thermostat (cooler temp type), and coolant were replaced about 2 years ago. So, what else can cause the overheating when in Park ??

Answer 1

There are a lot of variables there...
Even thought the thermostat has been replaced the it may be sticking even though it has been replaced recently.

There is one other thing to consider, the car may not be overheating at all. Some cars have common problems with faulty coolant temperature sensors. It is very hard to determine without actually looking at the car but this may be a possible cause.

Answer 2

Your fan is not working properly. The reason it overheats in park is that you aren't moving and air therefore will not circulate past the radiator to cool the antifreeze down before being pumped back thru the motor. When the motor reaches a certain temperature the fan will kick on and cool the motor down, this is apparently not happening. When you are driving the car the fan doesn't need to kick on because the air is circulating past the radiator and cooling the motor down. It's my diagnosis that the fan motor is bad. If the coolant sensor is bad, on most cars the fan will run all the time, but if it is overheating the fan obviously isn't working so I believe the culprit is the fan motor. It may be the coolant sensor but not likely.

Answer 3

Check the condenser and the area between the condenser and rad. Many times the condenser gets plugged and proper air flow does not occur during idle with A/C on conditions. There is a tool to pressure wash out the condenser area, this is a common problem on many manufactured vehicles with A/C in warm dusty environments. The thermostat may also be an issue but from your description it sounds more like an air flow problem not cooling properly.

Answer 4

restricted radiator or a bad viscous fan clutch
are you sure the waterpump is circulating coolant?
does the heater get hot? if so the water pump is working as long as the heater valve is open
If not You could have broke off the waterpump impeller off of the main shaft. this is a common problem fof late model BMW'S, the water pump impeller is plastic and breaks iff the steel shaft inside of the waterpump

Answer 5

sounds like the vicous coupling fan, if the front of it is oily or dirty it is most likely the problem, also as said before the water pump impellers break but it is unlikly due to it cooling down after driving. and your year and model had an upgraded water pump impeller "metal" the older ones were plastic. also let the car cool and check the coolant level, all bmw's use coolant!

Answer 6

This E39 model has issue with the cooling system... mine always overheats on a hot day ...I fixed the leak but still overheats especially if I am driving on a slow traffic. I can go to North Carolina without a problem as long as I am on my highway,..but once I hit slow traffic, I better have some DI water to add to the radiator or soon it will be smoking like a train.

Answer 7

Everything everyone else said is ok, but have you tried spraying out your radiator fins, both of them??? A lot of radiators build up gunk and dirt between them and the condenser. A good clean can help tons.