2007 Z4 3.0si heater

[snaponbob]

Having been worked on hundreds of E30s, 36s, and 46s -- I am finding a 2007 Z4 3.0si a bit of a different animal in some respects.

The owner as mentioned that recently the heat blows cold at idle, but blows hot again once engine revs are raised. My first "discovery" is an electric coolant pump. The car has 170,000 miles on it with no history. I have yet to start removing plastic under the hood to check for any data stickers that show dates on the radiator. So, before a preemptive cooling system replacement (as is common on 36s and 46s) I wanted to get some input on the heat issue. I am not sure if there are various temp sensors that could be causing this, or coolant pump issues. And yes -- the system is full, no air in the system, and engine temps are normal.

 

[Mr Tidy]

I've not had that "cold at idle" but "hot when revving" experience, but certainly the facelift E85/86s don't seem to suffer from the same need for a cooling system refresh like my E46 did at 80K miles with a "banana" radiator. Although split expansion tanks aren't unknown.

If the electric water pump is playing up there should be a fault code stored in the OBD. But with the two failures I've had the pump just stopped working, so the water temperature got too high in about a mile.

In the event you do need a new pump don't go to BMW as they charge over £500! Pierburg are the OE manufacturer and you can get those elsewhere for much less, complete with new single use aluminium fitting bolts.

 

[snaponbob]

Mr Tidy -- Thx. I saw the price difference. Good to know that the Pierburg is an OE supplier. I'll scan the car Monday. Also, good to know the cooling systems may be more solid that 36s and 46s.