I don't understand the coolant bleeder/tank system

[Dale_K]

A long time ago I was a licensed plumber and worked on many hydronic heating systems, including their expansion tanks and air separator valves. I guess that experience adds to my confusion of the Boxster system. The large hydronic heating plants have a specialized fitting that swirls the fluid inside like a little cyclone. The air is lighter and stays in the center and at the top of the center of the fitting is a discharge line that leads to the expansion tank(s). That line is left open all the time and you get air out of the system by venting the expansion tank. But I digress.

Say there was no separate bleed valve on the Boxster. A tee fitting on the highest coolant hose directs a new hose into the bottom of the expansion tank. It seems to me such a system would work (as it does on my Corvette). Think of the Boxster bleed being open all the time with the discharge line plumbed into the pressurized plastic tank.

I'm not trying to argumentative. I enjoy thinking through why engineers choose one solution over another and I want to understand why Porsche used the design found on our cars. Especially since I've never seen it on any other car I've owned.

[JFP in PA]

One function for the bleeder that you are overlooking is that it also is part of the coolant overflow vent, the one that pukes coolant onto the ground under the car when there is an issue. Yes, it is overly complicated, but that is just some of the “charm” or owning a Porsche. As for the “where’s and why for’s” of the chosen design, just remember that these are the same guys that created the AOS system as a substitute for the $3 PCV valve most OEM’s use…………

[brp987]

I've seen this Uview vacuum refiller tool on ebay:

uview tool

Do you need to buy a vacuum pump separately? Hopefully a vacuum won't implode the coolant resevoir, or cause other problems. That would suck (so to speak).

[Mark_T]

you don't need a vacuum pump for that tool, but you do need an air compressor.

Here's something similar, but cheaper:

http://www.tooltopia.com/uview-550500.aspx?utm_source=shoppingdotcom&utm_medium=cse&utm_term=UVU550500&utm_campaign=shopping_r1

Anyone have experience with these or want to make any recommendations? I was hoping Pelican might have something, but if they do I couldn't find it.

[JFP in PA]

The 550000 is a much better unit, comes with adaptors to fit anything and is made out of solid brass rather than molded plastics. For the extra $20 or so (Amazon.com) than the $79 plastic unit, you have a much more flexible and long lived tool.................. It is also the same tool Porsche sells for over $500.....



We use these just about everyday in the shop, and on everything from 986/987's to motorcycles. And, no, the vacuum will not collapse the tank........

[Mark_T]

What kind of psi and cfm do you need from your compressor?

[JFP in PA]

As it creates vacuum by air flow over an eductor nozzle assembly, it depends more upon volume rather than pressure. As such, any level of flow will do, the higher the flow rate, the faster it develops vacuum; but it always gets to the same level (24-27 inches). The manufacturer recommends at least 90 psig air delivery for optimum performance with larger volume cooling systems, such as Porsche’s. It is a neat tool, and it will pull a totally empty Boxster cooling system down to around 25 inches of vacuum in about 90 seconds, and then refill the system in about 3-5 min., leaving absolutely no air behind. And, as mentioned earlier, it will work on any cooling system. Real time saver around the shop and no “come backs” due to trapped air or coolant levels dropping later.