Recently we were contacted by a new customer — a referral from one of our other clients — who needed help diagnosing a mysterious coolant leak on his F30 320d. He couldn’t trace the leak himself, so we advised him to bring the car in for a full inspection.
🧊 Initial Assessment & Shock Discovery
As soon as the vehicle had cooled, we got it up on the lift, pulled off the undertrays, and pressure tested the cooling system. There was zero coolant in the system, just water.
When I called the customer to find out more, he casually mentioned that he’s been running tap water for two years. 😳 and topping up regularly.
Needless to say, this set off some alarms.
Under pressure test, the leak immediately revealed itself on the left-hand side of the engine. Based on past experience, we suspected either:
🔧 Tear-Down & The Real Culprit Revealed
The next morning, we ordered the coolant flange, coolant, and distilled water. Once we began the strip-down and removed the flange pipe, we weren’t satisfied with what we saw.
We took a closer look at the oil filter housing assembly (which includes the engine heat exchanger, transmission heat exchanger, and thermostat) — and it didn’t look good.
After getting the customer’s go-ahead, we:
🔁 Cleaning, Prep & Reassembly
While waiting for the parts to arrive, we:
✅ Final Feedback
We sent the customer home with the leftover engine oil and pre-mixed coolant in case future top-ups were needed.
One week later, we followed up — the customer reported zero coolant loss, and was thrilled with the performance and level of service received.
Another cooling system disaster averted, another happy BMW owner.
🧊 Initial Assessment & Shock Discovery
As soon as the vehicle had cooled, we got it up on the lift, pulled off the undertrays, and pressure tested the cooling system. There was zero coolant in the system, just water.
When I called the customer to find out more, he casually mentioned that he’s been running tap water for two years. 😳 and topping up regularly.
Needless to say, this set off some alarms.
Under pressure test, the leak immediately revealed itself on the left-hand side of the engine. Based on past experience, we suspected either:
- The coolant flange pipe, or
- The oil filter housing assembly, or worst case — both.
🔧 Tear-Down & The Real Culprit Revealed
The next morning, we ordered the coolant flange, coolant, and distilled water. Once we began the strip-down and removed the flange pipe, we weren’t satisfied with what we saw.
We took a closer look at the oil filter housing assembly (which includes the engine heat exchanger, transmission heat exchanger, and thermostat) — and it didn’t look good.
After getting the customer’s go-ahead, we:
- Drained the engine oil
- Removed the entire oil filter housing assembly
- And that’s when we found the catastrophic damage:
- Destroyed gasket rubbers
- Shattered thermostat pieces scattered through the coolant channels
🔁 Cleaning, Prep & Reassembly
While waiting for the parts to arrive, we:
- Cleaned the coolant flange port and mounting area
- Fished out broken thermostat debris from the coolant channels
- Prepared all contact surfaces for the new parts
- Vacuum tested the cooling system — held negative pressure perfectly
- Vacuum-filled with new coolant + distilled water
- Pressure tested again — no leaks found
- Reinstalling the ECU box, DME, airbox, wiring, and engine covers
- Refilling with fresh engine oil
- Test driving the car (~9.5 km)
- Running diagnostics and clearing all stored errors
- Resetting the CBS oil service reminder
- Added an air freshener
✅ Final Feedback
We sent the customer home with the leftover engine oil and pre-mixed coolant in case future top-ups were needed.
One week later, we followed up — the customer reported zero coolant loss, and was thrilled with the performance and level of service received.
Another cooling system disaster averted, another happy BMW owner.
