porcupine73 Posted June 2, 2007 Share Posted June 2, 2007 I'd seen on EndWrench and other places the supposed benefits or refilling the engine coolant with the cooling system under vacuum. If there is little air in the system, then there is little air that can get trapped thus forming an air pocket. Mightyvac and others make vacuum systems for doing this, but they aren't cheap. I picked up a few brass fittings and valves from mcmaster.com and a venturi vacuum device from Harbor Freight and gave it a try. I tried it on my '94 Legacy Wagon and my '00obw after replacing the radiator and heater hoses - seemed to work great in both cases. Since there's a lot of pictures and a video, I made a page for it here. Even after several heat/cool cycles the coolant level has not dropped, so I figure no air is caught in the system? Here's what the system looks like: Link to comment Share on other sites More sharing options...
nipper Posted June 2, 2007 Share Posted June 2, 2007 YOU must be really careful when you do this. The cooling system is not designed to have a large vacume on it. I am all for anything that works, but in all honesty, in 35 years of working on cars (since i was 10), i never had a problem with air trapped in a cooling system. Dealers have fancy systems becuase time is money to them, and anything that speeds up the process saves them money. The avg Joe doesnt really have the need for a vac pump. Its really simple, fill the system with the car running, wait for the t-stat to open, keep filling the system. Squeeze the upper hose if it makes you feel better. Seal the system take a test drive. Check the fluid level when it cools off, top off as needed, and your done. nipper Link to comment Share on other sites More sharing options...
OB99W Posted June 2, 2007 Share Posted June 2, 2007 [...]Mightyvac and others make vacuum systems for doing this, but they aren't cheap. I picked up a few brass fittings and valves from mcmaster.com and a venturi vacuum device from Harbor Freight and gave it a try. I tried it on my '94 Legacy Wagon and my '00obw after replacing the radiator and heater hoses - seemed to work great in both cases. Since there's a lot of pictures and a video, I made a page for it here. [...] Nice work. While Nipper is right that cooling systems aren't designed to be under a "large" vacuum, they can certainly stand a reasonable level -- that is, after all, how the coolant gets pulled back in from the recovery tank (and yes, I know that under that condition most of the system is liquid-filled). What did the gauge say (sorry if it can be read in the video, but I don't have Quicktime installed)? Link to comment Share on other sites More sharing options...
svxpert Posted June 2, 2007 Share Posted June 2, 2007 in the picture above, theres a water jug with (looks like) plain water in it. was that used to flush the system first? or did you fill the system with just water? Link to comment Share on other sites More sharing options...
porcupine73 Posted June 2, 2007 Author Share Posted June 2, 2007 Hopefully the vacuum doesn't cause any issues with already potentially fragile HG's....I didn't really think about that. If the system has a 15psig cap, then it can handle at least 15psig positive pressure. The maximum vacuum in the system will be at most -1atm. It's definitely no stronger than -15psig even at sea level. The gauge was reading maybe 27mmHg. The distilled water was just for flushing. The fill was done with 50/50 distilled and Zerex G-05. Mityvac and others make devices to vacuum fill also. There is a TSB from Subaru (#09-39-04 dated 05/07/04) for 2005MY Legacy & Outback Vehicles. The introduction says "The purpose of this bulletin is to address proper refilling of the engine coolant system. To prevent air pockets, an evacuation and refilling tool is required. This required tool can be obtained through Kent Moore, Snap-on or your local tool distributor. The tool creates a vacuum in the coolant system removing possible air pockets allowing for efficient refilling of the engine coolant system." I added an avi version of the video to the page, but it's 28MB (the quicktime .MOV is 4MB, must be compression?) Link to comment Share on other sites More sharing options...
Cougar Posted June 2, 2007 Share Posted June 2, 2007 Good job P73. Interesting. Link to comment Share on other sites More sharing options...
Skip Posted June 2, 2007 Share Posted June 2, 2007 Nice job Porc, Did you give any thought to connecting the vacuum to the bleed port on the pass. side of the rad and then intro the coolant via the stopper setup. This would prevent the vacuum build up some are concerned with. Link to comment Share on other sites More sharing options...
Skip Posted June 2, 2007 Share Posted June 2, 2007 Here's my ezbleed setup I use it for brakes and will give your method a try when I change my coolant. vacuum pump from my screen printing dept vacuum flask from my chem. dept Thanks again for the idea. Link to comment Share on other sites More sharing options...
porcupine73 Posted June 3, 2007 Author Share Posted June 3, 2007 Wow that's quite a setup. Say what are those propane tanks in the bottom of the pic for? My '00obw doesn't have the bleeder screw on the radiator. The '94 and '96 do. The success of the vacuum coolant refill method lies in having a good vacuum (say >26mmHg) built up in the cooling system before pulling in the fresh coolant. If there is nearly no air in the system, then there is nearly no air that can get trapped and form air pockets. You could use a much lower vacuum to pull the coolant in, but that would still allow air pockets to get trapped. Atmospheric pressure is approx. 14.7 psia at sea level. So if you could pull a perfect vacuum in the cooling system (which is impossible on earth, and definitely impossible with the venturi type vacuum device), there would be less than 15psi negative pressure on the cooling system components. Link to comment Share on other sites More sharing options...
nipper Posted June 3, 2007 Share Posted June 3, 2007 Wow that's quite a setup. Say what are those propane tanks in the bottom of the pic for? My '00obw doesn't have the bleeder screw on the radiator. The '94 and '96 do. The success of the vacuum coolant refill method lies in having a good vacuum (say >26mmHg) built up in the cooling system before pulling in the fresh coolant. If there is nearly no air in the system, then there is nearly no air that can get trapped and form air pockets. You could use a much lower vacuum to pull the coolant in, but that would still allow air pockets to get trapped. Atmospheric pressure is approx. 14.7 psia at sea level. So if you could pull a perfect vacuum in the cooling system (which is impossible on earth, and definitely impossible with the venturi type vacuum device), there would be less than 15psi negative pressure on the cooling system components. i just worry about the raidiator passage ways collapsing under full vaccume. Everything else can deal with it. Dont use a millitore vacume pump, then youll collapse alot of things. IN this case a cheap vac pump is best. nipper Link to comment Share on other sites More sharing options...
porcupine73 Posted June 3, 2007 Author Share Posted June 3, 2007 True there may be risks with this method. Do you think it could particularly be an issue in the phase II 2.5L's with the external peeping leak? Like if that part of the HG is already weak, maybe the vacuum's opposite force from the normal pressure during heat could make it give way? Link to comment Share on other sites More sharing options...
nipper Posted June 3, 2007 Share Posted June 3, 2007 True there may be risks with this method. Do you think it could particularly be an issue in the phase II 2.5L's with the external peeping leak? Like if that part of the HG is already weak, maybe the vacuum's opposite force from the normal pressure during heat could make it give way? If its already weak its already weak. Combustion pressures are 15-18,000 PSI at time of combustion. It wont even notice it. nipper Link to comment Share on other sites More sharing options...
porcupine73 Posted June 3, 2007 Author Share Posted June 3, 2007 Cool. Wow thats, like, a lot of pressure. Link to comment Share on other sites More sharing options...
nipper Posted June 3, 2007 Share Posted June 3, 2007 http://www-mat.ee.tu-berlin.de/research/sic_sens/sic_sen3.htm actually it can even by higher. Technically the car engine is a heat engine. this is because i thought it was cool http://www.grc.nasa.gov/WWW/K-12/airplane/engopt.html nipper Link to comment Share on other sites More sharing options...
Skip Posted June 3, 2007 Share Posted June 3, 2007 Thanks Porc, the propane is used in the winter months for the radiant heater mounted on the bench, it rolls to the location I am working. The issue you bring up with the external leak in the Phase II 2.5's is a valid one I believe. Nipper quoted combustion pressure never seen by this leak. The leak you mention is caused by only the pressure in the coolant system which is limited by the rad cap rating. Valid point - if it's weak it could get weaker flexing it as it were - in/out. If it were plugged by the Subaru "special" oatmeal - I can see it being sucked out of the gap. With using the bleed nipple (if available) gravity would keep the coolant under the air. This would be the same as filling it from a jug and funnel. Keeping the bleed nipple as the highest point in the system would be understood. Link to comment Share on other sites More sharing options...
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