VW Crafter's Hidden Coolant Leak Mystery Needs Fixing

Had a similar issue with my 2018 VW Transporter TDI last winter. With some basic mechanical experience from routine maintenance, I first suspected a blown head gasket, but it turned out much simpler. The workshop found a loose electrical connection at the coolant level sensor. The connector had corroded slightly, causing intermittent false readings. This explained why the coolant reservoir showed losses even though the actual level stayed constant. The warning light would trigger due to these faulty sensor readings. Total repair cost was 95€ including diagnostic and fixing the connection. Much better than the head gasket replacement I initially feared. The engine overheating warning disappeared completely after the fix. To help diagnose your case more accurately, could you share: Engine temperature readings during operation, Does the water pump make any unusual noises, Any sweet smell from the exhaust, Does the radiator cap hold pressure properly, Are there any white deposits around hose connections These details would help determine if your issue matches what I experienced or points to something different in the cooling system.

With 127683KM on the clock, I had my last service just 2 weeks ago. After reading your experience, I checked my coolant level again today and noticed small wet spots near the radiator cap. Used a pressure tester and found the radiator cap wasnt holding proper pressure. The coolant leak seems to be getting worse. Now losing fluid every 300km instead of 500km. Engine temperature stays normal though, and no white smoke from exhaust. Water pump sounds fine, no unusual noises. Think I might start with replacing the radiator cap before diving into more complex repairs. Thanks for sharing those check points. The corroded sensor connection you mentioned is also worth investigating since our symptoms sound similar. Will report back after checking these components.

Thanks for the update on your Crafter. Your symptoms are definitely evolving differently from what I experienced with my Transporter. While my issue was purely electrical, your progressive coolant leak points to a physical problem. The wet spots near the radiator cap and failed pressure test are telling signs. A faulty cap can definitely cause coolant loss through steam escaping when the system gets hot. However, the increased frequency of coolant loss from 500km to 300km suggests there might be an additional issue developing. In my case, after fixing the sensor connection, I actually discovered a small coolant leak from a deteriorating hose clamp near the water pump. It only showed up under pressure when hot. The total fix ended up needing both the electrical repair and a new hose clamp assembly, totaling 165€. Definitely start with the radiator cap since its the most obvious and cheapest fix. But keep monitoring even after replacing it. If the coolant loss continues, have the workshop pressure test the entire cooling system while hot. This will reveal any small leaks that might not be visible when the engine is cold. One note of caution from my experience: do not keep driving with constant coolant loss. Even though your engine temperature reads normal now, low coolant can lead to sudden engine overheating and potential head gasket damage.

Running the Crafter today after checking your suggestions. Got the radiator cap tested and replaced, only 35€ for a new one. Also had them check the coolant level sensor connections while they were at it, but everything looked clean there. After about 200km of driving, the coolant level has stayed constant. No more wet spots around the cap area. Starting to think the faulty cap was letting air pockets form in the system, causing that gradual coolant loss through steam escape. Still going to monitor it closely for the next few weeks. If the coolant loss returns, will get a full pressure test done on all radiator hoses and around the water pump area as you suggested. Having a potential head gasket issue hanging over my head was stressful, so really relieved it seems to be resolving with just a basic component replacement. Good call on checking the simpler fixes first. Saved me from jumping straight into expensive repairs. Will update the forum if anything changes, but looks promising so far.