No Heat in My 1996 1.9L Z3 – Troubleshooting So Far

[adrian_Z3]

Hello,

I purchased a 1996 BMW Z3 (1.9L, 120k miles) last December. Unfortunately, there is no heat coming from the AC system. However, the car does not overheat—the temperature gauge stays at the 12 o’clock position after warming up. The Hoses seem to be in good condition and are not kinked in a way that would prevent flow.

Steps Taken So Far:
1. Coolant Flush & Bleeding Air

• Drained the old coolant
• Flushed the system with distilled water
• Refilled with new coolant and bled the system

→ No heat

2. Flushed the Heater Core

• Had a shop flush the heater core
• Technician noted the core was really dirty—a lot of gunk and brown water came out

→ No heat

3. Replaced the Heater Control Valve

• Installed a cheap Amazon heater control valve → No heat
• Thought it might be defective, so I replaced it with a URO Parts valve from RockAuto → Still no heat

4. Inspected & Replaced Thermostat

• Removed the aluminum thermostat housing, but one of the four bolts broke off in the cylinder head
• Took it to a shop—they removed the stuck bolt and reused the aluminum housing
• Shop installed a new thermostat and used a new paper gasket

→ No heat
→ Shop suggested the URO heater control valve might be bad.

5. Replaced Heater Control Valve Again

• Ordered and installed a Four Seasons heater control valve from RockAuto

→ No heat

6. Checked Blend Door & HVAC Controls

• Replaced Bowden cable behind the center console (black clip, center knob)
• I can hear the blend door thud when turning the center knob to Red
• Blower motor works properly at all speeds (1-4)
• Air redirection knob is functional

I’m completely unsure how to proceed from here. Any advice, tips, or suggestions would be greatly appreciated!

1. Is the heater core still clogged? Should I replace it entirely?
2. Could the water pump be bad? Seems unlikely since the engine isn’t overheating.
3. Is air still trapped in the system?
   • I’ve bled the air several times with the car on ramps—could air still be trapped?

Thank you for your time,
Adrian

 

[Grumps]

Oooooh @t-tony . Tony and Brian? overhauled my 2.8 heater system so he may be able to help

 

[t-tony]

First thing I would do is buy an infra-red thermometer and actually find out exactly what temperature you are getting in the cooling system. ALL round the system, then you may have a better idea of what is happening.

Tony.

 

[the Nefyn cat]

What he said. You need to know what's wrong before throwing money at it. Just changing bits on a random basis won't help.