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marcpod
marcpod, Own collision repair advice
Category: BMW
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Experience:  i-car/Basf training, 300 repairs and 650,000 in Collision monthly 18 yrs exp/ licenesed adjuster
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2003 Z4 2.5. The coolant expansion tank developed a leak in the seam.

Customer Question

i have a 2003 Z4 2.5. The coolant expansion tank developed a leak in the seam. I replaced the tank along with expansion tank thermostat. The car is now running hot. I have bled the air through the bleeder screw on the outlet hose near the expansion tank. I think I still have air in the system, Can you offer some advice, or is there another place to bleed?
Submitted: 4 years ago.
Category: BMW
Expert:  marcpod replied 4 years ago.

Welcome. Did you do it like this.

Removing And Installing/Replacing Coolant Expansion Tank

Warning: Danger of scalding!

Only perform this work after engine has cooled down.

Follow instructions for working on cooling system.
Remove intake filter housing.
Remove front underbody protection.
Drain coolant from radiator.



Unfasten plug connection (1) and disconnect.
Pull out lock (2).



When replacing coolant expansion tank:
Unlock coolant level sensor (1) by turning and pull out of coolant expansion tank.



Pull locks (1 and 2) upwards and detach coolant hose from radiator/coolant expansion tank.



Pull lock (1) upwards and detach coolant hose from coolant expansion tank.



Pull coolant expansion tank a little out of retaining plate and lower connection piece. Then tilt expansion tank to rear and remove.

Installation:
Check O-rings. Under no circumstances coat O-rings with antiseize agent prior to installation.
Retaining lug must engage in opening in retaining plate.

 

Expert:  marcpod replied 4 years ago.

Venting Cooling System And Checking For Leaks

Warning:
Danger of scalding!
Only perform these tasks on an engine that has cooled down.


Check cooling system for leaks. Top up coolant.



To ensure the cooling system is properly vented, it is absolutely essential to follow the steps below:

  1. Open cap on coolant expansion tank.
  2. Turn on ignition
  3. Set heating controller to maximum temperature
  4. Set fan to low setting. This opens the heating valves and starts the auxiliary water pump.
  5. Carry out filling procedure slowly
  6. Close vent plug when bubble-free coolant emerges
  7. Fill expansion tank until full.
  8. Close coolant expansion tank
  9. Allow engine to warm up until thermostat opens



Allow engine to cool down before checking coolant level. Coolant temperature must not exceed 30°C. If ambient temperature exceeds 30°C, allow engine to cool down at least to ambient temperature. Check coolant level; if necessary, top up coolant until liquid level reaches marking on coolant expansion tank.

Note: The tank mark indicates the fluid level at approx. 20°C. Use only recommended coolant.

Venting Cooling System And Checking For Leaks

Warning:
Danger of scalding!
Only perform these tasks on an engine that has cooled down.


Check cooling system for leaks. Top up coolant.



To ensure the cooling system is properly vented, it is absolutely essential to follow the steps below:

  1. Open cap on coolant expansion tank.
  2. Turn on ignition
  3. Set heating controller to maximum temperature
  4. Set fan to low setting. This opens the heating valves and starts the auxiliary water pump.
  5. Carry out filling procedure slowly
  6. Close vent plug when bubble-free coolant emerges
  7. Fill expansion tank until full.
  8. Close coolant expansion tank
  9. Allow engine to warm up until thermostat opens



Allow engine to cool down before checking coolant level. Coolant temperature must not exceed 30°C. If ambient temperature exceeds 30°C, allow engine to cool down at least to ambient temperature. Check coolant level; if necessary, top up coolant until liquid level reaches marking on coolant expansion tank.

Note: The tank mark indicates the fluid level at approx. 20°C. Use only recommended coolant.

 

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