Coolant leak

Post by **kungfulemming** » 05 Jul 2008, 14:13

Parked bus on steep hill, with engine at lowest point, couple of hours later noticed coolant leaking which hadn't occured in first hour and a half.
Appeared to be coming from top of overflow tank, which was almost full ie. completely covering top up cap. Turned bus round and leaked stopped and after a run the coolant level settled to minimum point in overflow tank which would make sense due to fluid lossed. Anybody got any ideas what was occuring? R

Website · Post by **syncrosimon** » 05 Jul 2008, 14:30

Sounds like you have the dreaded split expansion tank. This is a common problem remedied by a new item, still available from VW, and Just Kampers, and GSF...etc. If you can get a VW one then it is by far the best. Have a look along the seam in the tank, and feel for a leak.

The expansion tank in the engine bay should be completely full, no air what so ever. It draws new coolant from the top up tank behind the numberplate, when the system cools down causing a vacuum. If all is working well it will get rid of all air in the expansion tank, and then stay about the same thereafter.

Post by **kungfulemming** » 05 Jul 2008, 14:45

Simon thanks for your swift response, expansion tank is fine checked allready, the leak was coming from top of overflow(top up) tank which had filled up past fill up hole and i guess there is a hole at top to allow for problems rather than tank exploding! what puzzles me is why there was that much coolant present, my guess is gravity because of the slope, but other than that im clueless. R

Website · Post by **syncrosimon** » 05 Jul 2008, 20:49

Sorry, if the top up tank is overflowing then it is for two reasons, one good, one bad.

The good (or not as bad as the second) reason is if the cap on the expansion tank is faulty, and pressure in the system is blowing coolant into the top up tank. Just replace the cap.

The bad reason is head gasket blowing, and too much pressure in system. If the head gasket is leaking, then the coolant should be discolored and a bit smelly, and means engine rebuild.

It should only do this (if head gasket) when hot, and when engine under load. Cant see why it would overflow 1 1/2hrs after driving. How you parked it should not matter.
If it was head gasket, turning the engine off would reduce pressure and stop it overflowing, ie would only do when engine running.
Must be your cap.

Post by **Mocki** » 05 Jul 2008, 20:56

whoa there........
the top up tank has three holes in the very top, and the level when the engine is hot will be very full...... as the engine cools the coolant is sucked back into the header tanks as the pressure in the system drops....... therefore, you possible havent got anything wrong........other than maybe too much coolant in the first place

Website · Post by **syncrosimon** » 06 Jul 2008, 08:27

Agree with the above, but only a small amount of fluid should go back and forth into the top up tank, in 20 years of driving T3's I have never seen the level move more than about 1/2 inch, so I would presume that something is causing that level to go up. Some never move at-all.

Could just put the level back to the max line, and see what happens. That's what I would do initially, could just be a bit of wind that the system needed to get rid of.

Have you topped it up recently??

Post by **Mr Bean** » 06 Jul 2008, 19:24

syncrosimon wrote:Agree with the above, but only a small amount of fluid should go back and forth into the top up tank, in 20 years of driving T3's I have never seen the level move more than about 1/2 inch, so I would presume that something is causing that level to go up. Some never move at-all.

Could just put the level back to the max line, and see what happens. That's what I would do initially, could just be a bit of wind that the system needed to get rid of.

Have you topped it up recently??

Yes don't get too caried away with the head gasket scenario as one of the reasons I got my T25 so cheap was a persistant low volume water leak which the owner had down as a split between the valves and I subsquently diagnosed as a weeping pressure cap. Quite a sophisticated plastic job but readily available from GSF. Although I quite agree with the posibility of it being slightly overfilled.
Cheers
Ken
PS I also had the dreade3d bubbles in the expansion tank