I've been really trying to fight through the hurdles of TDI ownership but I am nearing my breaking point. And just to clarify, I am an engineer that designs a high performance marine diesel engine for the NAVY so I am well aware of engine fundamentals and design. That being said, I am at a loss with where to go next with troubleshooting.
In my 3 years of ownership, I've accumulated 62,000 miles (many of which are highway) for a total of 108,000 miles. After reading up on this vehicle, I bought a OBD bluetooth scan tool and use it most days to monitor engine vitals. Over the past 3 years, the car traditionally ran in the range of 208-212°F and at 212-217°F during regens read directly from the scan tool and not the gauge cluster.
Fast forward to 6 months ago, I noticed engine temperature started running progressively hotter at 214-221°F and 219-225°F+ during regens. I did a heater core change and flushed the coolant as my heater core needed to be replaced anyways (low heat output but since in south Florida, don't really need heat). This didn't really help at all with engine temperature.
Recently I noticed I had to add coolant every week and it appeared to be coming from the oil cooler. I also tested multiple times while driving on the highway and operating at "higher" temperatures if I increased RPM during cruising from 2200 rpm to ~3200 rpm (downshift from 6th to 4th), engine temperature would fall fairly quickly by around 7-10°F. I also read the temperature while performing this at the second engine coolant temperature sensor and it would go from ~110°F up to ~140°F. After all that, I decided that my thermostat was likely getting stuck or operating inconsistently as there were times engine temperature would operate at 208-212°F and the secondary temperature sensor would show ~140°.
I just finished replacing both this past weekend. What a PITA that job was! This is definitely a terrible design. Not only is servicing ridiculously difficult, but the sheer amount of coolant lines is insane. So many places for failure when more traditional implementations would have been sufficient.
Once I did get the coolant thermostat assembly and the oil cooler out, I inspected both. The oil cooler had the common o-ring failure at the coolant port. That, I was confident, was my coolant leak. I also found lots of the typical orange particulates in the coolant port on the block and clean out as much as possible. As for the coolant thermostat, disassembly shows no major indications. I did notice the rubber seat surrounding the thermostat was deformed due to years of being embedded into the plastic housing. That too seams like a deficient design as the spring is quite aggressive. After test driving the car with the new coolant thermostat housing, new oil cooler, and a fresh fill of coolant, I had high hopes but was ultimately let down once again.
Now, the symptoms are getting worse. When I begin my morning drive on the interstate, the coolant temperature goes to ~217°F with aux coolant temperature sensor at ~105°F. After 20 minutes, something happens and engine coolant fall abruply to ~203°F and the aux coolant temperature sensor rises to ~160°F. This tells me that the thermostat opened more allowing more water to flow through the radiator, rather than bypass, and thereby raising the temperature at the aux coolant sensor and lowering the engine temperature. However, it gets better. Another 20 minutes goes by and the engine temperature begins to slowly climb again as does the aux temperature sensor reading. Eventually before leaving the interstate, engine temperature climbed to ~223°F and ~190°F. As I sat through various lights, the engine temperature fell to a wide range of values from 203-217°F.
I'm really at a loss as to what is going on with the engine. I'm sure the radiator is not is great condition based on the amount of debris that was in the coolant but I've never soon a radiator behave as such. I've also never known a water pump to fail in such a way that it operationally, it is inconsistent at static conditions. I've also never head of water pumps failing in CKRA outside of an occasional seal going bad. When replacing the thermostat assembly, I could obviously see the impellers and nothing looked amiss. Lastly, some technicians in our shop mentioned a possible blown head gasket. It is possible except that while I have been seeing elevated temperature for some time, I have not been eating coolant until recently with the oil cooler leaking. I could confirm this with a combustion gas detector but don't expect to see anything from this.
Any ideas would be appreciated. I can also capture any data if needed from the obd tool. I did plan to delete soon as I am approaching the 120,000 DPF likely end-of-life and perform the timing belt change while I'm working on it. However if I can't get this problem sorted, I definitely don't want to put more money into something that I will ultimately move on from. I also hate just throwing parts at it and was hoping to hear from others successful repairs before throwing another $2,000 into a sinking ship.
In my 3 years of ownership, I've accumulated 62,000 miles (many of which are highway) for a total of 108,000 miles. After reading up on this vehicle, I bought a OBD bluetooth scan tool and use it most days to monitor engine vitals. Over the past 3 years, the car traditionally ran in the range of 208-212°F and at 212-217°F during regens read directly from the scan tool and not the gauge cluster.
Fast forward to 6 months ago, I noticed engine temperature started running progressively hotter at 214-221°F and 219-225°F+ during regens. I did a heater core change and flushed the coolant as my heater core needed to be replaced anyways (low heat output but since in south Florida, don't really need heat). This didn't really help at all with engine temperature.
Recently I noticed I had to add coolant every week and it appeared to be coming from the oil cooler. I also tested multiple times while driving on the highway and operating at "higher" temperatures if I increased RPM during cruising from 2200 rpm to ~3200 rpm (downshift from 6th to 4th), engine temperature would fall fairly quickly by around 7-10°F. I also read the temperature while performing this at the second engine coolant temperature sensor and it would go from ~110°F up to ~140°F. After all that, I decided that my thermostat was likely getting stuck or operating inconsistently as there were times engine temperature would operate at 208-212°F and the secondary temperature sensor would show ~140°.
I just finished replacing both this past weekend. What a PITA that job was! This is definitely a terrible design. Not only is servicing ridiculously difficult, but the sheer amount of coolant lines is insane. So many places for failure when more traditional implementations would have been sufficient.
Once I did get the coolant thermostat assembly and the oil cooler out, I inspected both. The oil cooler had the common o-ring failure at the coolant port. That, I was confident, was my coolant leak. I also found lots of the typical orange particulates in the coolant port on the block and clean out as much as possible. As for the coolant thermostat, disassembly shows no major indications. I did notice the rubber seat surrounding the thermostat was deformed due to years of being embedded into the plastic housing. That too seams like a deficient design as the spring is quite aggressive. After test driving the car with the new coolant thermostat housing, new oil cooler, and a fresh fill of coolant, I had high hopes but was ultimately let down once again.
Now, the symptoms are getting worse. When I begin my morning drive on the interstate, the coolant temperature goes to ~217°F with aux coolant temperature sensor at ~105°F. After 20 minutes, something happens and engine coolant fall abruply to ~203°F and the aux coolant temperature sensor rises to ~160°F. This tells me that the thermostat opened more allowing more water to flow through the radiator, rather than bypass, and thereby raising the temperature at the aux coolant sensor and lowering the engine temperature. However, it gets better. Another 20 minutes goes by and the engine temperature begins to slowly climb again as does the aux temperature sensor reading. Eventually before leaving the interstate, engine temperature climbed to ~223°F and ~190°F. As I sat through various lights, the engine temperature fell to a wide range of values from 203-217°F.
I'm really at a loss as to what is going on with the engine. I'm sure the radiator is not is great condition based on the amount of debris that was in the coolant but I've never soon a radiator behave as such. I've also never known a water pump to fail in such a way that it operationally, it is inconsistent at static conditions. I've also never head of water pumps failing in CKRA outside of an occasional seal going bad. When replacing the thermostat assembly, I could obviously see the impellers and nothing looked amiss. Lastly, some technicians in our shop mentioned a possible blown head gasket. It is possible except that while I have been seeing elevated temperature for some time, I have not been eating coolant until recently with the oil cooler leaking. I could confirm this with a combustion gas detector but don't expect to see anything from this.
Any ideas would be appreciated. I can also capture any data if needed from the obd tool. I did plan to delete soon as I am approaching the 120,000 DPF likely end-of-life and perform the timing belt change while I'm working on it. However if I can't get this problem sorted, I definitely don't want to put more money into something that I will ultimately move on from. I also hate just throwing parts at it and was hoping to hear from others successful repairs before throwing another $2,000 into a sinking ship.
