VW Polo Heater Failure Linked to Faulty Water Valve

I dealt with a very similar heating issue on my 2014 VW Golf diesel last winter. With some basic car maintenance experience, I initially tried checking the engine coolant levels and connections myself but quickly realized it needed professional attention. The symptoms matched yours exactly, minimal cabin heating and error codes. The workshop diagnosed a faulty cable connection to the water valve, which was preventing proper coolant flow regulation. The repair took about 2 hours and cost 95€, including diagnostic time. The mechanic mentioned that continuing to drive with this issue could potentially lead to engine overheating, especially during longer trips. The water valve plays a crucial role in managing coolant distribution between the engine and heating system. Before heading to a shop, you can check: Engine coolant level when cold, Listen for unusual clicking sounds from the valve area, Test if heat varies with engine RPM, Look for visible leaks around the valve To provide more specific advice, could you share: Which error codes your car is showing, Whether the heating works better at higher RPMs, If you notice any coolant loss, Whether the temperature gauge shows normal readings

Latest service was performed at 107000km. The error codes showing are P0597 and P0598. The heating definitely improves when revving higher. No visible coolant loss in the expansion tank, and temperature gauge stays in normal range even during longer drives. One thing I noticed though, there is a slight clicking sound coming from the front of the engine when the car valve tries to regulate temperature. The car heating started working intermittently about 2 weeks ago before failing almost completely. The cooling system otherwise seems to work fine, engine temperature stays normal. But I am concerned about potential valve blockage causing more serious issues if not addressed soon. Given my mileage, maybe the valve is just worn out and needs replacement. From what you described, the repair cost seems reasonable if it is just the electrical connection. Will try to get it checked next week since winter is coming.

Having dealt with this exact situation on my Golf, those error codes (P0597/P0598) definitely point to the thermostat control circuit, just like what I experienced. The clicking sound you describe matches my symptoms perfectly, and it is a telltale sign of the water valve struggling to regulate coolant flow. The fact your heater core gets warmer at higher RPMs suggests the valve is not completely failed yet, which is exactly how mine started. In my case, waiting too long led to the valve sticking completely, though thankfully before any engine overheating occurred. Since your symptoms so closely match what I experienced, I would strongly recommend getting it checked soon. While my issue was just the electrical connection, the full valve replacement typically runs 150-200€ if needed. The good news is the repair completely resolved my car heating issues. A tip from my experience: Make sure they properly bleed the cooling system after repairs. My first repair attempt left some air in the system, which caused similar heating performance issues until properly bled. Let us know how it turns out, if the repair costs end up similar to mine, it would be useful info for others facing the same problem.

Thanks for the detailed follow-up about your electrical connection repair. My local shop had an opening this morning so I took the car in for diagnosis. Turns out your experience helped point them in the right direction, they found a faulty electrical connection to the water valve, but also discovered the valve itself is starting to fail. They quoted 180€ for a complete valve replacement plus labor, saying this would prevent any potential engine overheating issues down the line. Given the mileage and symptoms, I decided to go ahead with the full repair rather than just fixing the connection. The car is in the shop now. They mentioned the repair includes a complete cooling system flush and proper bleeding to prevent air pockets. Should have it back tomorrow. Really appreciate the help in identifying the issue, your similar experience saved me time and helped avoid what could have become a more serious problem. Will update the thread once I get the car back and test the heating performance in case anyone else runs into similar symptoms with their VW.