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Discussion Starter #1 (Edited)
In the old days you pulled off the bottom hose, emptied the system, replaced the hose, filled up with coolant, burped the hose and you were good to go.

With most modern engines squeezed into a small space and high cylinder heads, it can be very difficult to remove air which moves to the highest point. If you try the old method empty and fill, you will probably get air in the coolant system and ominous signs of the temperature gauge swinging about.

Now I understand the problem, I can see why most workshop procedures require modern engines to be VACUUM FILLED with fresh coolant and you can pay very little or a lot for the kit. The procedure is to drain coolant by removing a bottom hose, attach an adaptor to the coolant bottle, create a vacuum, turn a tap on the adaptor to hold the vacuum, attach a bottle of pre-mixed coolant, open the tap and coolant gets sucked from the bottle into the engine. Once the coolant reservoir has coolant in it, disconnect the bottle and produce a partial vacuum to pull air bubbles from all corners of the engine out to the coolant reservoir.

I shopped around and bought the cheapest of Chinese imported kits. Most kits were the same but different prices! These kits including the expensive garage branded kits, require an air line with a high pressure and air flow rate to produce the partial vacuum. They use a Tee section to blow air through a small jet to produce the partial vacuum.

This is very inconvenient for the DIYer who would need a workshop grade compressor and the noise level can get supersonic.:( When my cheapo kit arrived I was pretty impressed with the build quality. It included a vac. gauge, and the parts were well made. The kit came with 3 rubber sleeves which allowed it to fit different size reservoirs. VW's use the smallest sleeve. There's a large knob used to pull up a taper and expand the rubber 'bung' to get a good seal on the reservoir.

Put to the test with 120 psi at 9 cfm, the vacuum produced was pathetic at about 5-8 inches mercury maximum with supersonic noise, so I worked out a better solution:

I plugged their orifice for the air supply output (scintered bronze filter) with silicone, then looked at an alternative method for creating vacuum. It seemed to me the complete kit had to work from the car. I bought a cheap 12V diaphragm pump claimed to get to around 30 inches mercury. The pump I used is is heavier duty than some others and takes about 5 amps.

On test, the 12V pump could reaches 25 inches mercury without the motor laboring. I added a lead with croc clips, a fuse and an inline switch. Replacing the EOS coolant was so easy, no trapped air or temperature issues. These links are not recommends, but I'll post them so you can see the products I used. I think I made a piece of kit that is better than what the garage pros might use.:)

I'm also thinking it might work with brake master cylinders to pull air bubbles back and avoid tedious bleeding cycles. I've used a positive pressure bleeder on the M/C but that still forces fluid through, whereas a partial vacuum is less messy and the bleed nipples stay closed.

http://www.ebay.co.uk/itm/291625187040?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

http://www.ebay.co.uk/itm/181717361953?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT
 

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Texans fan
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sounds good- maybe a picture of the final tool ya used please?
 

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Discussion Starter #4
I have something similar I use on my bike. For cooling systems you need adaptors to fit the coolant reservoir. The device needs to be able to create sufficient vacuum volume for an empty system, lock it off, then switch over to a reservoir holding a gallon of fresh coolant mix.
 
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