2001 750IL sport cooling issues

[Sptsmed]

I had a cooling issue with my 2001 750Il sport about 15 months ago and the car set up for over a year do to financial constraints. I had a leak in the hose that goes under the intake manifold but could not find it at the time, had the expansion tank replaced, but still had a leak afterward. About six weeks ago I replaced the entire cooling system, radiator, water pump, thermostat, fan clutch, all hoses including the one with the leak, new intake manifold gasket, and both belts. Had no heat afterward and figured I had the dreaded air in the system. I took it to my local indy and he used pressurized air to get the air out of the system, but in the process created a stress crack in the expansion tank, so had it replaced and this time they used a pump to get the air out. Worked on it about 30 minutes and finally had heat. I drove the car around 3 to 4 days and had the low coolant check come on. Since then I have been topping it off, trying to bleed it, but no heat and a small leak that is not noticeable under the car, and its not a head gasket issue.

I can't imagine that I still have air in the system, and wondering if possibly the heater control valve and aux pump might be leaking, i probably am adding around 6-8 ounces every three days and no heat still. My cluster needs a pixel repair so I can unlock it and get a coolant temp, but I have been driving with my OBD reader connected and the temp usually stays between 113-116 depending on the driving conditions. Car takes at least 20 minutes from a cold start idling to reach the 113-115 range, so the system seems to be doing its job. Not sure what optimal running temps should be for sure, and not sure how accurate the OBD2 reading is, but I do notice on the highway when the fan clutch kicks in the temp will drop down to 205 and then slowly work its way back up.

I am getting frustrated and where the leak can be, any suggestions would be appreciated, the car has 115K on it and is in great shape outside of these issues.

[pumpedTSI]

First of all I'd avoid ANY indy that uses pressurized air to get "rid" of air in the cooling system and causes stress cracks in other components. There is a simple bleed procedure with the nose raised that takes all air out of the system so no pumps or air pressure is needed. Its a simple setup, if you dont have heat either your aux pump isnt working or the solenoids arent opening......easy to remove and diagnose other wise it may be a heater matrix clogged which is a bigger issue. Start with the cardboard under the engine bay when the car sits overnight and find out where the leak is first.....

[Timm]

If you have coolant getting out - you have air getting in - and as the water valves and aux pump is the highest point of the cooling system that's where the air goes. It is a complete waste of time bleeding a cooling system that has a leak. You need to fix the leak, bleed the system and Bob's your Uncle.

[Sptsmed]

Thanks for the suggestions guys, I have to believe it is an issue with the HCV and aux pump, the only time I have gotten heat since replacing the cooling system has been when the engine has run at a higher RPM rate for a period of time, once on the interstate and the other time when the Indy bled it and ran the engine at a higher RPM rate off and on for around 30 minutes. Thankfully the HCV is an easy location on the V12, one of the few things that is, and that will be my next step, along with replacing the camshaft position sensors as I am getting a code on bank one now.

I love this car and want to keep it for a while, it just gets frustrating chasing that rabbit sometimes LOL