Every owner of the T5 5cyl. TDI should be very concerned if he/she has to top up the cooling system.
Leaking water pump is very common fault in T5 R5 engines and it could be very expensive repair. Water pump alone is well over $200 and you will also need the coolant and at least one or two engine oil changes, since the coolant always leak onto the engine oil - courtesy of the VW engineers.
The cooling system in R5 engine is closed system and no coolant is lost to evaporation, so even the smallest drop in the coolant level means that there is a leak somewhere. Also be aware of that the dealer can top up your coolant without telling you, when you bring the van for scheduled servicing to them. Once your van is out of the manufacturer warranty it is one very expensive job. So, check the coolant level before you take your van to the dealer for any work.
Some of my thoughts on the pump that I dismantled.
Poor quality axial seal or badly designed area of the engine block where the impeller spins (too much pressure on axial seal) is most likely the cause of the water pump failure.
The water pump appears robust but it is not.
The pump’s shaft is spinning in the double ball bearing. The lack of proper bearing seals is further exposed by 2 draining holes in the pump’s body that should drain away the coolant that pass the shaft’s axial seal but the holes are quickly clogged up buy rust and the coolant flows straight into the ball bearing. The bearing’s balls are held apart and in the place with the plastic race, rather than metal one that melts away since the coolant is not sufficient in lubricating and cooling the bearing. With the collapsed race the w. pump’s shaft wobbles and quickly destroys what is left of the axial seal sealing capability, and the coolant can flow even faster into the engine oil.
(my T5 used 0.75L of coolant during 1 trip of 30km, there were no drips from the tiny rubber hose at the back of the engine)
The early detection of the failed water pump is crucial since the pump is driven from the timing gear train. The longer the w. pump gear bounces on the other gears that are in contact with it, the greater is the chance to damage the surface of the other gears teeth that are much more difficult to replace than the w. pump gear. Also at the other end of the w. pump shaft the impeller that wobbles will ruin (grind) the opposite surface inside the engine block, which will reduce the cooling system efficiency.
Complete pump; showing rust from the coolant that passes w. pump axial seal and get trapped in the area between 2 O-rings.
Bearing with the shaft pressed out of the pump's body.
Pump's bearing showing that the coolant leak through the pump washes out all the grease and wears out the bearing.
Detail damage of the bearing surface.
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