BimmerFan52

Pull off the fan shroud and examine the vent tube (runs from the top of the radiator on the driver's side, across the top of the radiator, then over to the expansion tank). You'll need to do this after you have run the car and it is hot (don't disconnect any hoses while the engine is hot just remove the shroud). The vent tube can develop tiny cracks or pin holes that may not be visible when the system is cool. You will want to see it dripping.

Depending upon where the vent tube leaks, the coolant can run down the fan housing or radiator on the drivers side, appearing as if coming out of thin air. Repair ($5) or replace ($40).

pcy

^ +1.
That's what I was trying to suggest...

rockabilly_Drummer

ok, great, thank you i will check that out and let y'all know.. many thanks all...

rockabilly_Drummer

ok, found it it was the 3part hose on the drivers side that goes to the oil cooler... so in all I have replaced the thermostat, the expansion tank and the expansion tank hose (as mentioned above) no leaks now but was getting the P0597 code (which is why I replaced the thermostat) now i am still getting the P0597 code.. any ideas?

twh

What manufacturer thermostat did you install?

BimmerFan52

You are probably seeing the CEL shortly after start up.

The thermostat itself has a heating coil that allows the ECU to accelerate the heating of the wax to open the thermostat quicker. If the coil is burned out or the wire harness is damaged when the ECU tests the circuit on start up it will see an open circuit and throw the code.

Pull off the harness from the thermostat and measure the resistance between the two electrical conductors on the thermostat. Should be around 16 Ohms. If it measures 1 Ohm or infinity then the coil has burned open. If it is good then start troubleshooting the wiring harness to see if you can spot any break in it.

When my alternator failed I felt it was time to change the water pump and thermostat along with other coolant system components as PM (lots of the same stuff needs to be removed to do the alternator or water pump). I tried to cheap out and bought a Beck Arnley thermostat and water pump. The electrical connectors on the thermostat were significantly undersized from the OE thermostat and I had to put a slight twist in them to get a solid connection with the wiring harness. The thermostat (made in India) lasted one week before the heater coil burned out. The water pump (made in China) lasted exactly two years before massive bearing failure.

Do yourself a favor and buy quality parts. You are saving enough already on labor.

UltimatePeter

Similar problems here as some previous posts... except my leak mainly drips from the passenger side of the bottom plate. Had a shop hook up pressure and none of the hoses were leaking, so it seems to be the radiator.
I have a BEHR radiator on the way from amazon for $177.
I will be attempting the radiator switch this weekend, as I have found these guides most useful:
- DIY E60 Radiator Replacement
- BMW E60 5-Series Radiator Replacement (2003-2010) - Pelican Parts Technical Article

As the Pelican article tells you in the parts section, there are apparently two radiators for automatics. Mine is the one with the extra hose for the transmission. I had to look at my current radiator to figure it out.

I'm thinking about making a youtube vid of my endeavor... We will see.

UltimatePeter

Here's the final product. Worked great! I saved $800.