VAG-Abound
23-07-2022, 07:14 PM
Our MY08 BKD engine Touran has started losing quite a bit of coolant regularly, but not all the time. On some short-ish (20 mile) trips the coolant light comes on, and the level is well below minimum. On others it doesn't.
I built a little widget to pressure test the system. Turns out a 40mm plumbing waste compression fitting goes quite nicely on the expansion tank with the lid removed, and a 7/32" hole is perfect for screwing a long Presta valve from a donor cycle inner tube into. The part I had around happened to be a tee-joint, but only two connections are needed so a coupler would be fine.
38618
I can get the pressure up to ~1.5 Bar easily, and it holds for 20 minutes. Big "pop" if I pull it off rather than release pressure steadily.
No sign of coolant around engine while doing this. Oil is a lovely, silky black. C-suffix cylinder head. Exhaust is generally clear with odd puffs of blackness when accelerating hard.
Only clue is that sometimes when reversing off of drive a trail of water is left, as though it had gathered on plastic undertray and sloshed off as car moved. Now parking over a sheet of cardboard with tray removed, but no drips seen so far.
I'm not aware of any valves that let water into parts of system sometimes, but make a water-tight isolation of it at others. I'm wondering if there could be a hairline fracture in something that opens up when car is doing some particular thing, but is pressure tight at others.
Any pointers from anyone?
I built a little widget to pressure test the system. Turns out a 40mm plumbing waste compression fitting goes quite nicely on the expansion tank with the lid removed, and a 7/32" hole is perfect for screwing a long Presta valve from a donor cycle inner tube into. The part I had around happened to be a tee-joint, but only two connections are needed so a coupler would be fine.
38618
I can get the pressure up to ~1.5 Bar easily, and it holds for 20 minutes. Big "pop" if I pull it off rather than release pressure steadily.
No sign of coolant around engine while doing this. Oil is a lovely, silky black. C-suffix cylinder head. Exhaust is generally clear with odd puffs of blackness when accelerating hard.
Only clue is that sometimes when reversing off of drive a trail of water is left, as though it had gathered on plastic undertray and sloshed off as car moved. Now parking over a sheet of cardboard with tray removed, but no drips seen so far.
I'm not aware of any valves that let water into parts of system sometimes, but make a water-tight isolation of it at others. I'm wondering if there could be a hairline fracture in something that opens up when car is doing some particular thing, but is pressure tight at others.
Any pointers from anyone?