Coolant change with vacuum evacuator

[Michael]

So I am going to change my coolant in the next few weeks. Instead of the normal drain and bleed route, would a coolant evacuation machine be preferable? Seems like it would be much easier, less messy, and eliminate any chance of leaving air in the system.

If I attach at the expansion tank, I would be drawing from both sides anyway, would I need the thermostat to be open?

[Josh]

I only fill by vacuum now. Honestly everyone with a delorean should. If you do it properly it takes about 30mins for a bone dry system (engine block included) to fill with zero air pockets. Just hop in and drive.
No fussing around with bleeder valves and jacking the car up etc. The same vacuum fill setup can also evacuate the coolant.

No need to concern yourself with the thermostat it will get around it as it will be drawing from both sides. You will see both the hoses collapse.

[David T]

The thermostat should have a "jiggle pin" or a 1/16" hole so air will pass through. I also use a vacuum evacuator to fill but it is not 100%. You still have to bleed some air out from the radiator and water pump but it is minimal. To use it you must have a large enough air compressor to get a low enough vacuum so you pull all of the coolant in before you use up your vacuum. Depending on your equipment you may also have to block off the overflow tube so you don't lose vacuum through it. Some set-ups don't block that tube under the rad cap properly and you can't build up vacuum because it leaks out the overflow. This evacuator doesn't remove coolant, only air so the system will draw the new coolant in. And you only get one shot. If you don't pull it all in you have to start all over, draining the coolant and then filling it up again. If you don't use a coolant recovery system you will have to remove some coolant in the header tank so it is 1/2 full when cold.

[Michael]

I have access to several professional coolant evacuation machines. I didn't consider the overflow tube so that will be plugged. If I bleed the thermostat housing, I can only assume any air trapped in the radiator will eventually get pushed into the overflow tank and be dismissed without any more help from me?

Also it seems like it would be safer to intentionally slightly overfill the tank and just let it push out the excess through the overflow. I would rather have a little mess to clean up than having to start all over again because I let the tank get too low. Is that logic sound?

[Helirich]

Could you explain how this works? Google didn't help much.

[Josh]

you suck all the air out of the coolant system with a tool (vaccum filler/evaculator) and use this vaccum to draw in new coolant. It is the reverse operation to remove the coolant.

[David T]

There is always a minor amount of air in the system, especially if you don't use a coolant recovery tank. The system will "self-bleed" and yes, it will eventually wind up in the header tank. By using a recovery tank you can fill the header bottle all the way up so there is NO air in your cooling system. Just like a modern car, and you can check the level even when hot. The header tank always remains full, the coolant expands and contracts and the overflow is captured in the recovery tank and sucked back into the system as it cools and contracts. Of course your cooling system can't have any leaks or instead of going into the recovery tank, it will leak out and when it cools down you will suck in air where it leaks.

[Helirich]

you suck all the air out of the coolant system with a tool (vaccum filler/evaculator) and use this vaccum to draw in new coolant. It is the reverse operation to remove the coolant.

Well that part sounds great, but when you say vacuum, do mean like an AC pump? Are you saying that everything in coolant evaporates without a trace? What about rust and scale? I wouldnt think the coolant system could take a complete vacuum. Where does the coolent go in if you have this thing attached to the filler neck?

[David T]

It doesn't make that hard a vacuum as an A/C vacuum pump. It uses compressed air in a venturi to create the vacuum. All of the old coolant must be removed first by draining it out. You turn on the compressed air to create a vacuum inside the coolant system, shut the valve and then open another valve to draw in the new coolant already mixed in a pail. If you go over to You Tube I'm sure you can find a video of the process.

[iflights]

Michael, did you end up performing this task with the vacuum technique? Anything to share on the process unique for a DeLorean? Planning on doing this myself this spring when the car comes out of hibernation.