Leaky overflow reservoir

[taosx5]

Hey out there. Hoping someone can point me in the right direction. I have had my new to me 03 X5 4.6 since July 09 (currently 68K miles). On my first x-country trip, I noticed a small amont of anit freeze leakage out of the radiator fill and overflow reservoir. The temp never got above the mid range and half way thru our 4K mile trip I washed it off and it did not reappear for over a month. Last week I noticed it again and examined but could not find a leak, so again I washed it down and am trying to keep on eye on it. I have had to add about two cups of antifreeze in 3 months and 7K miles. It appears to me that the reservoir is a molded piece of plastic and there is a seam that separates the top 1/4 from the bottom 3/4. My guess is that it might be a small leak at this seam. It does not leak enough to leave any fluid while parked in garage but seems to more like steam leakage under pressure. I suspect what is happening is that when the temperature gets up to operating temp, pressure in the system builds up and it finds the weakest point and leaks off as steam. Any ideas anyone? Thanks in advance for any advice.

[HPIA4v2]

Originally Posted by taosx5

Hey out there. Hoping someone can point me in the right direction. I have had my new to me 03 X5 4.6 since July 09 (currently 68K miles). On my first x-country trip, I noticed a small amont of anit freeze leakage out of the radiator fill and overflow reservoir. The temp never got above the mid range and half way thru our 4K mile trip I washed it off and it did not reappear for over a month. Last week I noticed it again and examined but could not find a leak, so again I washed it down and am trying to keep on eye on it. I have had to add about two cups of antifreeze in 3 months and 7K miles. It appears to me that the reservoir is a molded piece of plastic and there is a seam that separates the top 1/4 from the bottom 3/4. My guess is that it might be a small leak at this seam. It does not leak enough to leave any fluid while parked in garage but seems to more like steam leakage under pressure. I suspect what is happening is that when the temperature gets up to operating temp, pressure in the system builds up and it finds the weakest point and leaks off as steam. Any ideas anyone? Thanks in advance for any advice.

Same symptom on my 02 4.4i, a little bluish residue at the cap. I wonder if the cap start loosing it tightness in summer month cause it's hoter; cause it doesn't happen most of the time only summer months. Don;tknow how to pressure check the cap so maybe I'll replace it.

[m5james]

The V8's are very notorious for disastrous overheating conditions. I've read countless stories of radiator necks cracking, waterpump impellar failures, expansion takes bursting, even fan clutches seizing and causing so much force on the fan blades that it punctured holes in the hood and destroyed everything else in it's path. While the M62/M62TU has only been in use in the X5's since late 2000, they've been in 5's and 7's for 5 years before that.

Problems in the 60-100k are extremely common. In a nut shell, replace EVERYTHING in one shot. Radiator, waterpump, thermostat, hoses, valley pan gasket and double check that the aux pump/heater diverter valve is functioning properly. While you're replacing the valley gaskets, go ahead and replace the OSV (crankcase breather, just like a PCV valve on older cars).

The previous owner of my 7 didn't do the required maintenance and the car overheated. He had the headgaskets replaced (w/o my knowledge till my engine builder took the motor apart), the shop did a crappy job, and the timing chain guide came loose and the motor ate itself alive. $11k later and I've got a brand new motor. Moral of the story...don't cheat the cooling systems on the V8's.

[chilliwilli]

Originally Posted by m5james

...

Problems in the 60-100k are extremely common. In a nut shell, replace EVERYTHING in one shot. Radiator, waterpump, thermostat, hoses, valley pan gasket and double check that the aux pump/heater diverter valve is functioning properly. While you're replacing the valley gaskets, go ahead and replace the OSV (crankcase breather, just like a PCV valve on older cars).

...

Hopefully you have an aftermarket warranty.

[taosx5]

I had some time this afternoon running errands around town in the beast. The temp guage was in the middle position so the X5 was running a normal temp. I opened the hood hoping to find my problem and shor nuff I found the problem. The overflow tube that goes into filler neck had a teenie drip. What was going on was it created a teenie little flow that created a small trail that with the slightly unlevel nature of the overflow tank worked its way around the lip towards the fan side of the tank. Then while the liquid was at its lowest point it started to drip and the fan blew it all over the tank making it look like a much larger leak than it really is.

So when I get a chance I will undo that overflow hose and put some silicone on it to see if I can get it to seal. Anyone have a better idea to stop this teenie leak?

[m5james]

Sorry to sound like I was going overboard, but it is true. I'd still play it safe just for precaution. To be honest, while the gauge may be showing in the middle, that doesn't mean you're in the clear completely. The temp sensor might not be in the flow of water, so it could still be overheating due to the lack of flow if the fluid is low. Bleed it properly and just be careful till the leak is fixed for sure.

[chilliwilli]

Originally Posted by taosx5

...

So when I get a chance I will undo that overflow hose and put some silicone on it to see if I can get it to seal. Anyone have a better idea to stop this teenie leak?

Replace it. It's a premium vehicle, not a beater.

[taosx5]

Originally Posted by m5james

Sorry to sound like I was going overboard, but it is true. I'd still play it safe just for precaution. To be honest, while the gauge may be showing in the middle, that doesn't mean you're in the clear completely. The temp sensor might not be in the flow of water, so it could still be overheating due to the lack of flow if the fluid is low. Bleed it properly and just be careful till the leak is fixed for sure.

How do you bleed the temp sensor, is there a thread on this procedure? Thanks for the advice.

[m5james]

LOL..you don't bleed the temp sensor man, you bleed the cooling system. I don't know if there are writeups on here, but www.e38.org has a TON of writeups that you can use since we share the same motor.

Here's a quick and dirty one - http://bimmer.roadfly.com/bmw/forums...4091184&page=1

[m5james]

Originally Posted by chilliwilli

Replace it. It's a premium vehicle, not a beater.

that's the kind of thing I'd do to my 90 S10 Blazer aka winter beater!