This is going to be fun... I have:

1. No heat on the driver's side
2. Inconsistent heat on the passengers side
3. Small coolant drip on passenger's side - Never overheats, just loses coolant

Replaced the coolant reservoir (pinhole leak on housing)
Disconnected the HVC - No change

I know just enough to make it worse..

BMW - Open your wallet and dump it in the the engine compartment. Don't forget the change in couch. It wants that too. :-)

 

The symptoms are characteristic of a faulty heater control valve. There are two valves in the heater control unit that don't operate over time.

Here's is what mine looks like. Its part number
64116906652

 

Thanks for the input. I was leaning toward that, but was a little iffy on it considering where it's leaking from, which may be a separate issue (renting a coolant system pressure tester today to find it). All while doing the valve cover gasket.

 

Fix the leak first then check for faulty heater parts. But with my experience it's the valve

 

Correct. Replaced HCV and we have heat.

 

I just have to find the source of the leak. I don't think it's the water pump. I have no overheating or limp mode issues. Give the number of outlets and inlets near the water pump/thermostat, I could anything.

 

Regarding the source of the leak, the right way to identify it is with a coolant pressure tester.

Here's what I did to save money.

Since I bleed my brake calipers every year and put in new brake fluid into the system, I bought a Motive power bleeder. Changing the Dot 4 will be good for caliper and master cylinder longevity.

I then modified the hose on the Motive power bleeder to fit on the coolant expansion tank. There is bleeder valve on the expansion tank that is a male fitting (its not a screw screw). I hook up the Motive pressure tank hose to that male fitting with a hose clamp.

Pump up the tank to 10 psi and you'll find that leak of yours in no time.

 

I pressure tested the system. The leak is definitely around the water pump/thermostat. Given how it's pancaked in there above the subframe, I'm either going to rent/buy a scope or bring it somewhere and pay the diag fee to get it up on a lift. Not enough clearance with ramps or jack stands to get a really good look.