sixtwoeight Posted January 21, 2012 Share Posted January 21, 2012 Hi, my first post here so hope ive posted correctly. Thanks to this forum ive just changed head gasket and head on a 97 300tdi disco. When refilling the coolant is seemed difficult as the header tank has to be half full and the thermostat housing should be filled right up - these are at the same level, and water will obviously always sit level. I filled the header tank to the level peg then put the cap on, I then filled up the thermostat housing until it just overflowed. I ran the car upto operating temperature with no problems. Once cooled completely I re checked the level in the header tank - it was a touch above the level peg. Now my (silly) question, should the thermostat housing still be full of coolant?? Obviously water will always sit level, but is there something within the pipework to stop the coolant sitting level in the header tank and the thermostst housing? (water at level peg in header tank and full in thermostat housing) Thanks in advance for any comments Quote Link to comment Share on other sites More sharing options...
BogMonster Posted January 21, 2012 Share Posted January 21, 2012 If you fill as per the approved process in the manual you won't have any problems. Usually any air trapped in the system gets cleared out by the flow of water once the thermostat opens and it's all circulating freely. Quote Link to comment Share on other sites More sharing options...
mmgemini Posted January 21, 2012 Share Posted January 21, 2012 The thermostat is higher then the level in the header tank..... To fill you should... Remove the plug in the thermostat housing Remove the plug in the radiator.. Fill the header tank to level and fit cap. Fill through thermostat hole until coolant runs out of radiator. Felex hoses to clear trapped air and keel the rad to level. Fit radiator plug. Now fill at thermostat until water flws and repeat the hose trick until the air pockets are clear. Fit thermostat plug... Check and adjust header tank level.... Then run engine...... There are two problems with the 300Tdi instalation The header tank too low. The water pump set too high on the engine... If you have a small coolant loss then the water pump can run dry not letting coolant circulate... You can help yourself by fitting a proper water temperature gauge where you can see the needle move. Fitting a coolant loss sensor to the header tank with a warning light. Quote Link to comment Share on other sites More sharing options...
Maverik Posted January 21, 2012 Share Posted January 21, 2012 Don't the 300's have a wee non return valve on the bleed hose from the thermo houseing to header tank to allow it to self bleed? Mav Quote Link to comment Share on other sites More sharing options...
sixtwoeight Posted January 21, 2012 Author Share Posted January 21, 2012 Thanks all so far, i filled as per the manual. I assume i do have air in the system then. To clarify, after running then cooling completely: Should header tank coolant be upto level peg AND thermostat housing will still be full of coolant?? Am struggling to see how the coolant will stay at different levels. Thanks again Quote Link to comment Share on other sites More sharing options...
janderson41 Posted January 21, 2012 Share Posted January 21, 2012 I was given a tip by a former LR foreman mechanic to leave the engine running for about 20 minutes with the expansion tank cap off. this will help to eliminate air. But keep an eye on level in header tank while doing this. cheers Jim A 1996 300Tdi auto(Jap reimport) Quote Link to comment Share on other sites More sharing options...
BogMonster Posted January 21, 2012 Share Posted January 21, 2012 Should header tank coolant be upto level peg AND thermostat housing will still be full of coolant?? Am struggling to see how the coolant will stay at different levels. Thanks again Easy enough. Air doesn't get into the top of the thermostat housing (unless you take the bung out for a look). Fill a bath with water, put a pint glass under the water, turn it upside down and lift it up slowly out of the bath. Water stays in the glass - because air can't get in. Same principle... As for it being set up wrong - if you have a leak, any leak, you will lose all the water as soon as you get pressure in the system anyway, so where the water pump is, is neither here nor there if there is no water to go through it Quote Link to comment Share on other sites More sharing options...
sixtwoeight Posted January 22, 2012 Author Share Posted January 22, 2012 Thanks for the tips and good point bogmonster! Cheers Quote Link to comment Share on other sites More sharing options...
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