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Home/Cars/BMW/3 Series/E90/E91 (2005-2012)/my BMW 3 Series E90/E91 (2005-2012) is leaking coolant, what's the problem?

my BMW 3 Series E90/E91 (2005-2012) is leaking coolant, what's the problem?

BMW 3 Series E90/E91 (2005-2012)

Severity: mediumDifficulty: medium2-4 hours
3 min read
519 words

Problem Statement

## Problem Statement The BMW 3 Series E90/E91 (2005-2012) is experiencing a coolant leak, which may indicate a failure in the cooling system.

Repair Time
2-4 hours

Safety Warnings

  • ⚠Safety Warnings:**
  • ⚠Allow the engine to cool completely before opening the cooling system.
  • ⚠Wear gloves and eye protection when handling coolant, as it is toxic.

Symptoms

  • •Coolant puddles under the vehicle
  • •Low coolant level warning on the dashboard
  • •Overheating engine
  • •Steam or coolant odor from the engine bay
  • •Moisture or staining around the cooling system components

Diagnostic Steps

  1. 1Inspect the coolant reservoir for cracks or leaks.
  2. 2Check the upper and lower radiator hoses for signs of wear or leaks.
  3. 3Examine the water pump for leaks or corrosion.
  4. 4Inspect the thermostat housing and gasket for any coolant seeping.
  5. 5Look for leaks around the engine block and cylinder head.
  6. 6Use a pressure tester on the cooling system to identify the source of the leak.

Solution

Solution

1. Preparation

  • Gather tools and parts.
  • Ensure the engine is cool and disconnect the battery.
  • Place a drain pan under the engine to catch any spilled coolant.

2. Inspect and Replace Reservoir

  • Remove the coolant reservoir cap.
  • If the reservoir is cracked:
    • Disconnect the hoses attached to the reservoir.
    • Unbolt the reservoir from its mounting brackets.
    • Replace with a new coolant reservoir.
    • Reattach hoses and secure the reservoir.

3. Check and Replace Hoses

  • Inspect both upper and lower radiator hoses:
    • If any hoses are cracked or bulging:
      • Loosen the hose clamps and remove the damaged hose.
      • Install new hoses, ensuring they are the correct length.
      • Tighten hose clamps to secure the hoses.

4. Replace Water Pump

  • If the water pump is leaking:
    • Drain the coolant and remove the serpentine belt.
    • Unbolt the water pump from the engine block.
    • Clean the mounting surface and install a new water pump with a new gasket.
    • Refill the cooling system with the appropriate coolant.

5. Thermostat Housing Replacement

  • If the thermostat housing is leaking:
    • Remove the coolant hoses connected to the thermostat housing.
    • Unbolt the housing from the engine.
    • Install a new thermostat housing with a new gasket.
    • Reconnect hoses and refill coolant.

Verification

After completing the repair, verify that the issue has been resolved:

  • Test the affected component to ensure it functions correctly
  • Check for any error codes or warning lights
  • Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

  • •Follow the manufacturer's recommended maintenance schedule
  • •Address warning signs early before they develop into major issues
  • •Use quality parts and fluids recommended for your vehicle
  • •Keep detailed records of all repairs and maintenance

Tools & Equipment Required

  • Socket set
  • Screwdriver set
  • Pliers
  • Coolant pressure tester
  • Drain pan

Parts Required

  • Coolant reservoir (if damaged)
  • Upper and lower radiator hoses (if worn)
  • Water pump (if leaking)
  • Thermostat housing and gasket (if leaking)

Additional Information

Repair Time

2-4 hours

Difficulty

medium

Severity

medium

Tools

5 items

Parts

4 items

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