Coolant Leak Repair of a Mercedes G-Class in Leicester

When Coolant Becomes a Clue: Fixing a Mercedes G-Class from Wingston, Leicester

Some cars are built to turn heads. The Mercedes G-Class G350d is one of them, a proper presence on the road, blending luxury with rugged capability. But even the toughest vehicles can show signs of fatigue after a few years of solid use. This particular G-Class had done just over 100,000 miles, and its owner from Wingston needed a repair. He brought it in after spotting something most G-Wagon drivers wouldn’t expect – a coolant leak.

At first, the signs were subtle: the warning light would flicker on now and then, the coolant level kept needing a top-up, and there was a faint chemical smell after parking up. Over time, the issue became more noticeable, and that’s when the owner knew it needed professional attention.

Tracing the Leak

Coolant leaks can be sneaky. Sometimes they show up under the car, sometimes they evaporate before leaving a trace. In this case, we ran a pressure test on the system and quickly traced the problem to the oil cooler seals, which a known weak spot on some Mercedes diesel engines after time.

Unfortunately, this wasn’t a surface-level repair. The oil cooler sits deep in the engine bay, buried beneath a tangle of intake manifolds, pipes, and covers. Getting to it meant carrying out a full engine strip down, which has to be done with precision, every hose, clip, gasket, and bolt accounted for.

What We Did

Once the cooler was exposed, it was clear the seals had failed. Coolant had been seeping out and pooling in areas not meant to hold fluid. We replaced all oil cooler seals, along with surrounding gaskets and o-rings, to make sure no weak points were left behind.

Before reassembly, we cleaned all surfaces thoroughly, removed old residue, and inspected for any signs of corrosion. With everything put back together, we refilled the cooling system with fresh coolant and ran another pressure test to confirm the fix.

No drops. No warning lights. No more mystery leak.

The Result

On the road test, the G-Class ran beautifully. Engine temperature stayed rock solid, throttle response felt smoother, and there was a noticeable quietness under load, often a sign that fluids are circulating properly and seals are doing their job.

The owner told us it felt “tighter” than before, not a technical term, maybe, but a good sign nonetheless.

This job is a perfect example of how even a high-end vehicle with a strong reputation for durability can develop hidden issues. Coolant leaks like this one don’t just go away on their own; if left too long, they can lead to overheating, engine damage, and some very costly repairs. Catching it early made all the difference.

If your car’s losing coolant or just doesn’t feel quite right, don’t wait for things to get worse. From early diagnostics to full engine repairs and a full service in Leicester, we’re here to help, no matter what’s under the bonnet.