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....

http://www.bmwe34.net/E34main/Trouble/Data/gauge_overheat.jpg


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....

http://www.bmwe34.net/E34main/Trouble/Data/gauge_overheat.jpg

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.do?model=HE23&mospid=47406&btnr=11_1246&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.do?model=HE23&mospid=47406&btnr=11_1246&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.

[E34 530]

i still think your water pump is boned.
I'm going to the guy who put the pump in one of these days to see how he put it in and see if he will replace it. How can you mess up putting a pump in though?? Wouldn't it overheat all the time if the pump was trashed??

[gale]

I'm going to the guy who put the pump in one of these days to see how he put it in and see if he will replace it. How can you mess up putting a pump in though?? Wouldn't it overheat all the time if the pump was trashed??

Could be the pump impeller is slipping on the shaft, anymore they come with plastic impellers these days. There are numerous brands of pumps: Laso, Hepu, Graf. Laso is supposedly one of the better brands but my new one (Laso) has a plastic impeller. I went ahead & used it anyway since the old one was rusty & the new one has a brass hub sleeve molded into the plastic with obvious signs of serrated "teeth" to keep it from spinning.

Also, thermostats are cheap. Could have gotten a bum one. At one time there was a batch of bad viscous fan clutches (Behr or Sachs?). If it's running hot while sitting at a light, you should be able to hear the fan kick in when you start off again.

[E34 530]

Could be the pump impeller is slipping on the shaft, anymore they come with plastic impellers these days. There are numerous brands of pumps: Laso, Hepu, Graf. Laso is supposedly one of the better brands but my new one (Laso) has a plastic impeller. I went ahead & used it anyway since the old one was rusty & the new one has a brass hub sleeve molded into the plastic with obvious signs of serrated "teeth" to keep it from spinning.

Also, thermostats are cheap. Could have gotten a bum one. At one time there was a batch of bad viscous fan clutches (Behr or Sachs?). If it's running hot while sitting at a light, you should be able to hear the fan kick in when you start off again.
Thanks man. Also thanks for the pm- very helpful. I think the pump has the metal impeller if I recall correctly. I can hear the fan form the light. It reminds me of a Jeep, their sound is identical from a stop. I don't think it's the the thermostat because the original one didn't seem to be broken. I'm guessing the water pump is also bad. I just hope the guy who originally replaced it will check it out for free and maybe throw in a new one :p .

[E34 530]

I brought the car back to the mechanic who originally installed the waterpump. He asked me to open my hood and he revved the car until it became vey hot in the engine bay. He then stuck his finger directly in the fan and was able to completely stop it and spin it the other way. Bad fan clutch.

[nuclearfusion]

...he revved the car until it became vey hot in the engine bay. He then stuck his finger directly in the fan and was able to completely stop it and spin it the other way.

Brave guy! ... Stupid guy? ... Lucky guy.

Don't try this at home folks.

Enjoy!

Fusion

[E34 530]

Brave guy! ... Stupid guy? ... Lucky guy.

Don't try this at home folks.

Enjoy!

Fusion

nah dude. He's a BMW master mechanic and knew what the problem was even before I opened up the hood, therefore he knew his finger wasn't going to be taken off when he put it in the fan.

[nuclearfusion]

nah dude. He's a BMW master mechanic and knew what the problem was even before I opened up the hood, therefore he knew his finger wasn't going to be taken off when he put it in the fan.

OK, OK, fair enough. There's lots of experience there and he'd already been through most of the other possible culprits so he was very confident.

Nevertheless, I'd personally never do what you describe, and I'd never recommend it to anyone regardless of how sure they felt about it. It's easy enough to keep your fingers out of the cooling fan and roll up some newspaper to stick in there if you want to.

In all seriousness, losing limbs or digits is serious business and lasts a lifetime. So, I think I'll stick with my original (good) advice, but let's add a caveat. :)

Don't try this at home folks unless you're a BMW master mechanic and you know without any doubt at all what the problem is before you even open up the hood.

(Even then some rolled up newspaper seems like a better plan to me.)

Enjoy!

Fusion