A Mercedes-Benz owner came to us with a coolant leak. On the first visit we replaced the expansion tank and hoses. A few days later, coolant was leaking again from other parts. On the second visit we replaced the leaking thermostat and two coolant lines, plus the water pump and its hose, which had changed colour. At handover, no leak or colour change was showing.
Job completed: September 2026
| Car | Mercedes-Benz |
|---|---|
| Symptom | Coolant leak, coolant level dropping |
| Fault found | First visit: a leak at the coolant tank and hoses. Second visit: the thermostat, its coolant line and the coolant hose to the cooler were leaking; the water pump and its hose to the cylinder head had changed colour |
| Repair done | First visit: expansion tank and multiple coolant hoses replaced. Second visit: thermostat, thermostat coolant line, coolant hose to cooler, water pump, water pump to cylinder head hose replaced; coolant refilled |
| Parts | Quality coolant system components, Mercedes-grade parts |
| Time taken | Two visits; timeline confirmed at each booking |
| Cost | Itemised quote approved before each visit |
| Warranty | No warranty term stated; no leak or colour change seen at handover |
The owner contacted us about a coolant leak and asked what it would cost to diagnose it and replace the coolant tank and hose.
The car came in for a check first. We then quoted the first round of repairs, covering the expansion tank and several hoses, before any work began.
Modern Mercedes-Benz engines use a pressurised cooling circuit with multiple hoses, an expansion tank, a thermostat and a water pump working together. The thermostat controls coolant flow based on engine temperature. The water pump circulates coolant through the engine and radiator.
As the car ages, the plastic expansion tank and the rubber hoses can degrade. Hose fittings can weep coolant before the hose itself splits. The thermostat housing seal and the water pump seals are other points where coolant can leak.
A full pressure test of the cooling circuit after any repair is the right way to confirm there are no remaining leak points.
On the first visit, our check pointed to the expansion tank and several hoses. These were replaced and the system was refilled before handover.
A few days after collection, the coolant level dropped again and coolant was leaking from other parts, so the owner brought the car back. On the second inspection, the thermostat, its coolant line and the coolant hose to the cooler were leaking. The water pump and the hose from the water pump to the cylinder head had changed colour slightly, so we quoted those as well.
All components were explained to the owner and an itemised quote was produced before any second-visit work started.
A Mercedes-Benz coolant leak gets two checks at our workshop. We pressure test the cooling system to show where it is weeping, and we diagnose it with XENTRY, Mercedes-Benz's own diagnostic system, which reads the fault memory and the live coolant temperature.
A coolant system runs at continuous elevated temperature and pressure during engine operation. Rubber hoses, plastic fittings and seals all age at different rates. When one hose starts to show age, others in the same circuit are usually not far behind.
The thermostat and water pump are internal components that are harder to inspect without dismantling. When a hose repair does not fully resolve a coolant loss, the next step is to check the thermostat housing and the water pump weep hole. On this Mercedes, the thermostat and two coolant lines were leaking, and the water pump and its hose had changed colour slightly. All five were replaced on the second visit.
Our team was upfront that other hoses and parts on the car had not been changed yet.
First visit:
Second visit:
At handover, no leak or colour change was showing.
From our team's record of this job. Number plates are pixelated.
The cost of a Mercedes-Benz coolant repair depends on which components are the source of the leak. Common items are hoses, the expansion tank, the thermostat and the water pump. On this Mercedes, the second visit replaced the three leaking parts and the two discoloured ones together.
We provide an itemised quote at each visit before any work starts. Every item is approved by the owner before we begin. The quote covers parts and labour separately so you know exactly what each item costs.
Coolant should be replaced on schedule. Old coolant loses its anti-corrosion inhibitors, which accelerates degradation of seals, hoses and aluminium components in the cooling circuit.
At each service, ask for a visual inspection of the coolant hoses and expansion tank. Swelling, cracks or discolouration around a hose fitting are early signs worth addressing before a hose fails completely.
If you notice your coolant level dropping between services, or a sweet smell from the engine bay, get it checked promptly. A small coolant leak can cause overheating if left, which is a significantly more expensive repair than fixing the original source.
This Mercedes-Benz (coolant leak repair, thermostat replacement, water pump replacement) was handled at 1 Car Service, an independent workshop in Sin Ming AutoCity, Singapore. For Mercedes-Benz, we use dealer-level XENTRY diagnostics. We hold a 4.9★ rating from 1,836+ Google reviews.
WhatsApp us your symptoms and model. We pressure test the cooling system, read the fault memory on XENTRY and quote every component before starting.
It depends on which parts are the source of the leak. Hoses and an expansion tank are less expensive; a thermostat and water pump add to the cost. We quote every item separately after inspection. WhatsApp us your model and symptoms and we will advise what needs checking.
Yes. We pressure test the cooling system and diagnose it with XENTRY, Mercedes-Benz's own diagnostic system. The pressure test shows where the coolant is escaping. XENTRY reads any stored fault codes and the live coolant temperature.
When hoses are replaced and the leak returns, the next components to check are the thermostat housing seal and the water pump. These are internal components that may not show a visible external leak until they fail further. A pressure test of the cooling system after any repair helps confirm whether all sources have been addressed.
Not advisable. A small leak can become a large one without warning, and driving with low coolant risks overheating the engine, which is a significantly more expensive repair. If you notice the coolant level dropping, get it checked as soon as possible. WhatsApp us and we can advise based on your symptoms.
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