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I have a VW transporter and I cannot for the life of me work out where the water is disappearing to. I have to fill it up every 30-40 minutes and there’s no visible leaking anywhere. It’s got to be going somewhere but where? Please help it’s insane not knowing where the water is going. Thank you in advance.

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There aren't that many choices:

  • Its dripping on the ground from a leak.
  • Its dripping on a hot exhaust manifold and turning to steam before it can drip on the ground (highly unlikely)
  • Its going into the engine crankcase where it is mixing with the engine oil. Check the oil using the oil dipstick. Is water mixed in there to make gray sludge mess? Is the oil level is growing?
  • You did say you had a VW Transport van? Its possible there is a leak in the auxiliary heater system, and the coolant is sloshing around on the floor pan underneath the carpet somewhere.
  • Its possible there is a leak in the front heater core (or auxiliary heater core) Both of those have an independent drain. The front heater core drain is at the front panel somewhere (perhaps a hose?), the auxiliary heater core will be a tube running to the ground somewhere.
  • I think you are probably likely to easily see any of these above in a matter of minutes after popping the engine cover, and looking around. I'm assuming you've already done that.
  • Last choice is most likely... that is the coolant is going into the engine combustion chamber where it turns to steam during the combustion process and goes out the exhaust pipe.

Obviously that last one isn't good. What causes that is a crack in the head, a crack in the engine block, loose head bolts or a leaky head gasket. Lots of folks turn right to a leaky head gasket, and that's relatively inexpensive to fix, but I will say in my experience I've never ever seen just a leaky head gasket. My guess is crack in the engine block.

What can cause that?

  • Generally leaving pure water (without coolant additive) in the coolant system during a cold winter. Water freezes at 32 deg F (0 deg C) and when it does it expands, causing lots of problems inside a cast iron engine block.
  • The other cause of a cracked block/head is overheating. You get that by running the engine for an extended period of time without coolant, or having a blocked radiator, or a stuck closed thermostat.

What ever the cause, if its coolant being consumed in the engine cylinder, do not continue to drive this car. The engine will self destruct soon. Best to get this looked at pronto.

Do note, they make coolant testers. Autozone in the USA has them in the free tool loaner program. You fill up the coolant system, had a hand pump to pressure things up to 10psi or so, then check for leaks when the vehicle is parked, without having to start up the car. Makes it easy to check everywhere for leaks. Note, if the block is cracked, this could fill up the cylinders with water. You'll see that when you start the car there will be a whole bunch of white exhaust "smoke".

  • There can also be a leak under operating pressure and the coolant vaporizes quasi-instantly leaving no trace... pin-hole in a pipe... – Solar Mike Nov 6 '19 at 11:16
  • A water leak from near the fan will be atomized/vaporized and not leave markings. Some GM engines have the fan on the same pulley as the water pump , so that a leak at the water pump is completely vaporized. – blacksmith37 Nov 6 '19 at 15:09
  • If it's a turbo Diesel with an EGR cooler an internal leak in the cooler is another way it could leak into the intake and go out of the exhaust as steam – Dave Smith Nov 6 '19 at 16:35

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