Need help with cooling/overheating problem:

[E34 530]

Hello guys. The problem I have has been present since December but rarely occurred. Now that the weather is becoming hotter (95+) the problem is becoming much more frequent. After I've been driving for awhile, (say 20 minutes- car is warmed up to correct position) and I have to stop (traffic jam, waiting for someone in front of there house, drive-thru's) the needle will slowly start to creep towards the 3/4 mark. It's never reached the 3/4 mark, but the needle will return to its correct position if I turn on the heat or start driving again. I thought it would have been the fan clutch, so I replaced the fan clutch, shroud, thermostat, thermostat housing, upper and lower radiator hoses, and a complete coolant flush. Unfortunetly, this didn't solve the problem. I know you're all going to say water pump, but I had that replaced back in December of '05 because it was leaking all over the place. 2 weeks after it was replaced was the first time the slight overheat occurred. I thought maybe the water pump was installed incorrectly but wouldn't that just cause the car to overheat all the time, no matter what?? What can be messed up when installing the water pump that causes this problem?? The next issue I addressed was the auxilary fan. I jumped the connector and both high and low speeds came on. The fan also comes on when the air conditioning is turned on. However, I have noticed that the auxilary fan DOES NOT come on even when the needle start to creep past the half way mark. Could the sensor that tells the aux. fan to come on be bad, causing the slight overheat?? Scott H also proposed that the radiator can be covered with debris such as pine needles, dirt, etc, but I'm not so sure that's what's causing the problem. The last issue I thought about was a clogged hose somewhere, but wouldn't that cause the car to overheat every time?? I'm out of ideas here, so any help would be greatly appreciated. Thanks, Andrew

[mikell]

My vote is the radiator sensor may have gone toes up - since the aux fan works when you jump the switch, what else?

[E34 530]

My vote is the radiator sensor may have gone toes up - since the aux fan works when you jump the switch, what else?

Is the sensor right where the connectors are, at the top right of the radiator?
What do you mean by, "what else?"

[Scott H]

A properly operating cooling system should not have to rely on the protection and intervention of the aux fan. That switch operates at 91C and 99C (196F and 210F). It should not kick on until your temp gauge needle is near those marks.....here is a converted image from Don Gale....

However, I have noticed that the auxilary fan DOES NOT come on even when the needle start to creep past the half way mark. Could the sensor that tells the aux. fan to come on be bad, causing the slight overheat?? .....

[E34 530]

A properly operating cooling system should not have to rely on the protection and intervention of the aux fan. That switch operates at 91C and 99C (196F and 210F). It should not kick on until your temp gauge needle is near those marks.....here is a converted image from Don Gale....

Thanks Scott, but that's exactly where the needle winds up (196-210) when the fan isn't kicking on.

[MBXB]

http://www.realoem.com/bmw/showparts...46&hg=11&fg=35

They are located behind the intake manifold on the right hand side.
You can get to them by lifting up the diagnostic port out of the way. It's tight but accessible.

Is the sensor right where the connectors are, at the top right of the radiator?
What do you mean by, "what else?"

[E34 530]

http://www.realoem.com/bmw/showparts...46&hg=11&fg=35

They are located behind the intake manifold on the right hand side.
You can get to them by lifting up the diagnostic port out of the way. It's tight but accessible.

dude, those are the wrong sensors. Anyway, I'm going to pull the radiator this weekend and flush the shjit out of the block and give the raditor a full cleansing both interior and exterior.

[BillionPa]

lubro moly makes a radiator flush compound, cleans crap out of there you didnt know existed.

i just picked up 3 gallons of Saab coolant for $39, almost half the price of the same stuff with a BMW logo on it.

[E34 530]

Update: I pulled the radiator from the car last week and flushed the **** out of it for an hour. I cleaned off the ac condenor and cleaned out all the choses that commonly get clogged. I was so paranoid I was able to completetly remove BOTH block drain bolts off and flush the **** out of the block. Filled with BMW blue and distilled. Everything seemed fine for about 2 days then problem came back. One thing I noticed, I do not have steady stream of coolant while the engine is warm unles I give it some gas, then it shoots a perfect line. Anyone have any more suggestions, I'm out of ideas.

[BillionPa]

i still think your water pump is boned.