eddyoz Posted September 9, 2010 Share Posted September 9, 2010 The cooling system in my 300TDI discovery seems to develop a vacuum instead of maintaining a completely full level.For instance,in the morning when the system is cold,I can remove the brass plug on the thermostat housing and hear the hiss of air as the vacuum is released.I normally just top it up with about a quarter or half a cup of water at the most.However after a few weeks of doing this,the level in the expansion tank is way overfull.The vehicle is not overheating and no apparent leaks any where.....expansion cap is new....so why does it not maintain its level from the expansion tank? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted September 9, 2010 Share Posted September 9, 2010 Try taking the cap off the expansion tank before opening the brass plug, the water can't 'refill the system, from expansion tank' as its own vacuum is holding it in there. Quote Link to comment Share on other sites More sharing options...
Disco1tdi Posted September 9, 2010 Share Posted September 9, 2010 Is the vacuum not just because the top of the thermostat housing is higher than the coolant level in the reservoir? As the brass plug is opened, air is allowed in, from the top, allowing the level to balance out with the reservoir? (or at least to the point, the air above the coolant, in the reservoir, is pressurised slightly, and stops the coolant dropping further in the thermostat housing)... I'll caveat the above with a big "maybe"... :-) Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.