MeoW71 Posted August 5, 2021 Share Posted August 5, 2021 (edited) Trying to figure out why the coolant is not being pulled from the overflow tank after the car sits overnight. I've done the following: Replaced radiator cap, checked overflow hose (and put 45 degree cut on end per a tsb) and searched for obvious leaks. I'll say that the overflow tank apparently gets filled to the top and overflows when I do extended highway drives, but that doesn't happen when just drive around the city when doing errands. It doesn't look like coolant is being lost anywhere, because when I pull the radiator cap and look it, it's always at the same level, except after a highway drive and its puked out from the overflow tank. The one last thing is, 90% of the time when I open the radiator cap to check, it's like a vacuum seal is being broken. There is a pop, and sometimes I hear the sound of fluid moving briefly. Just looking for other things I could check, or possible solutions before I take it to my mechanic. EDIT: Just to add. Hoses are firm when the engine is warmed up. However, I do hear the brief sound of fluid moving under the dash when I start the engine cold. The only time the fluid level drops is from the previously mentioned highway cruising where it pushes even more fluid into the overflow tank. Edited August 5, 2021 by MeoW71 Link to comment Share on other sites More sharing options...
Infosecdad Posted August 5, 2021 Share Posted August 5, 2021 (edited) I would make sure you have two new OEM caps, radiator and turbo tank. The one with the ears goes on the turbo tank, the one with no ears goes on the radiator. They are different pressures and shouldn't be mixed, and aftermarket caps have a history of not behaving properly. Edit: Sorry, was going off the "2005 Legacy GT Wagon" in the profile, thanks Max Edited August 5, 2021 by Infosecdad Link to comment Share on other sites More sharing options...
Max Capacity Posted August 5, 2021 Share Posted August 5, 2021 He's talking about a H6 engine. I'm thinking you have an internal leak, may be caused by a crack somewhere ? Might be time to have the system pressure tested. 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
All_talk Posted August 5, 2021 Share Posted August 5, 2021 I'm with Max on this one, a small leak in the system can keep the vacuum from forming as the coolant cools down and it wont pull it back from the recovery tank. If that leak is someplace like a head gasket it could explain your highway overflow problem. Link to comment Share on other sites More sharing options...
SubOperator Posted August 6, 2021 Share Posted August 6, 2021 Hope I'm wrong but this sounds 99% headgaskets. Started with same symptoms on Tribeca, and I went through same motions of replacing the rad cap, cutting the hose end, etc... You can buy a test kit to check for exhaust gases on coolant. I followed a very detailed thread for H6 HG replacement on sb9t . com and did the work myself. Put 70K or so on it since. 2005 LGT Wagon Limited 6 MT RBP Stage 2 - 249K 2007 B9 Tribeca Limited DGM - 272K SOLD - 2005 OB Limited 5 MT Silver - 245K SOLD - 2010 OB 6 MT Silver - 205K Link to comment Share on other sites More sharing options...
MeoW71 Posted August 9, 2021 Author Share Posted August 9, 2021 Well, I went and did a pressure test. No leaks detected when I pressurized the system. I let it sit around 10min at ~16psi and the needle did not even move. I even did a dynamic test after releasing the pressure and the needle didn't move from the bottom. I have two OEM radiator caps and they both tested good. The only odd thing that happened is when I removed the radiator cap this morning after letting it sit overnight (+10hrs). There was the sound of fluid running and I actually had some fluid spill out. Link to comment Share on other sites More sharing options...
08SpecB_DE Posted August 13, 2021 Share Posted August 13, 2021 Unfortunately, coolant spewing from the overflow only means one thing, headgaskets. You can buy a headgasket tester if you want to confirm, but make sure the car is close to operating temp before testing. Link to comment Share on other sites More sharing options...
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