I don't understand the coolant bleeder/tank system

[Dale_K]

On my American vehicles there is a pressurized expansion tank at the high point of the cooling system. There is no bleeder valve, just a medium size hose entering at the base of the tank and there is no bleeding during refilling. Just keep adding coolant until you get to the right level recognizing some air will migrate to the tank at first and you might have to add a little more coolant.

Therefore I don't understand the reason and function of the Boxster system. Why are there two "caps"? If you never touched the bleeder would any entrapped air move into the pressuized tank? What does the diaphram inside the bleeder do?

I'm considering a coolant flush and replacement on the 2000 S I bought a couple of months ago. I just want to understand the system before I start working on it and have never encountered a separate bleeder except I have seen distinct bleeders on the motor plumbing when the up and down routing of hoses and components left an isolated high spot in the system. My 1990 Thunderbird had a bleeder vent on the motor.

[eightsandaces]

If you don't have a Bentley book but plan on working on the 986, I'd get one. The procedures, photos and tips are really very good in preparing for any work. I'm confident it's covered step by step, I've looked at it but it was a while ago.

[JFP in PA]

Originally Posted by Dale_K

On my American vehicles there is a pressurized expansion tank at the high point of the cooling system. There is no bleeder valve, just a medium size hose entering at the base of the tank and there is no bleeding during refilling. Just keep adding coolant until you get to the right level recognizing some air will migrate to the tank at first and you might have to add a little more coolant.

Therefore I don't understand the reason and function of the Boxster system. Why are there two "caps"? If you never touched the bleeder would any entrapped air move into the pressuized tank? What does the diaphram inside the bleeder do?

I'm considering a coolant flush and replacement on the 2000 S I bought a couple of months ago. I just want to understand the system before I start working on it and have never encountered a separate bleeder except I have seen distinct bleeders on the motor plumbing when the up and down routing of hoses and components left an isolated high spot in the system. My 1990 Thunderbird had a bleeder vent on the motor.

The reason for the bleeder assembly is quite simple: Large sections of the cooling system lie below the coolant levels inside the engine. As such, air can become trapped, particularly in the radiators way up in the front of the car, causing poor cooling, “hot spots”, and associated steam pockets, which lead to further air entrainment and potential engine damage. There are two possible ways to get the air out; the easiest, fastest, and most effective is to pull a vacuum on the system which will immediately purge all traces of the air; but what happens if you do not have a vacuum filling tool, or are stuck out on the side of the road with air in the system? You add a mechanical bleeder as high up in the cooling system as possible, which is where the tank is located. Manually open the bleeder and the system is running at atmospheric pressure and trapped air can vent as the coolant circulates.

Believe it or not, most hot water home heating systems have a similarly functioning device for the exact same reason………..

[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.

[rebeltown]

I have just replaced the coolant in the 2000 Boxster and thought I would bleed the system manually via the comments here. I'm not absolutely sure the system is free of air pockets and have ordered the suggested 5500 unit. If I draw a 25# vacuum on my already filled system will it still draw out any entrapped air or do I have to refill the system using this tool? Thanks

[JFP in PA]

Originally Posted by rebeltown

I have just replaced the coolant in the 2000 Boxster and thought I would bleed the system manually via the comments here. I'm not absolutely sure the system is free of air pockets and have ordered the suggested 5500 unit. If I draw a 25# vacuum on my already filled system will it still draw out any entrapped air or do I have to refill the system using this tool? Thanks

It works best while filling the system because it totally prevents any air entrapment, but you can use it on a full system to pull out any major air pockets.

[RichRobby]

I know this is an old thread but.......

I don't have a workshop air compressor and I want to flush and refill my coolant and would happily spend on getting a vacuum refilling system but not both pieces of equipment.

Is there a vacuum system that does not need an external air compressor or alternatively has anyone devised a way of using a vacuum system without a compressor maybe with a 12v tyre inflator or some other devious way to provide the air power?

[Gelbster]

Borrow an air compressor ? Or go to an Indie to get this job done.

[mikesz]

I have changed coolant when I added the S center radiator to my 99. I also replaced the thermostat, engine mount, and water pump. Didn't find it that difficult. I removed the lower coolant hose that connects to the water pump and drained into a 5 gal storage bin I bought at Walmart then brought the coolant to the recycling station. When I put everything back together I added new fluid and filled as best I could. there is 1 bolt that holds a cover over the oil, coolant in the trunk. remove the bolt and take that cover off. there is a burping valve a little clip on top flip it up start up the car let it run the air will come out and the system has been burped. I had one of those uview devices and sold it. I thought it was a PITA! Review DIY on pelican and pedros board not overly difficult.

[RichRobby]

So a difference of opinion. Some saying it is a pain in the arse to bleed it manually and others saying it's not a major problem.

Decisions decisions......

Sent from my ONE A2003 using Tapatalk

[san rensho]

What works for me is to drive to the steepest parking ramp i can find. Open the purge valve. Then with the car pointing down the ramp, rev the car a bunch of times like the pelican write up says. Works every time. Take a couple of gallons of coolant since the level can drop dramatically.

[RichRobby]

So...... Do vacuum tools help in the draining / flushing of the system in any way or do you still need to go through the routine of removing hoses, tilting the car etc or is there a method of forcing the coolant out through a single drain point on the car?
Seems to me that the draining is the time consuming part.

Sent from my ONE A2003 using Tapatalk

[JFP in PA]

Originally Posted by RichRobby

So...... Do vacuum tools help in the draining / flushing of the system in any way or do you still need to go through the routine of removing hoses, tilting the car etc or is there a method of forcing the coolant out through a single drain point on the car?
Seems to me that the draining is the time consuming part.

Sent from my ONE A2003 using Tapatalk

The draining does not change; however, the refill is a 5 min. and you are done proposition with the Uview vacuum system.

[RichRobby]

Originally Posted by JFP in PA

The draining does not change; however, the refill is a 5 min. and you are done proposition with the Uview vacuum system.

Thanks for that. You are always willing to help and are a great asset to the forum and boxster owners in general. I for one very much appreciate it.

Sent from my ONE A2003 using Tapatalk

[Gilles]

Originally Posted by RichRobby

Thanks for that. You are always willing to help and are a great asset to the forum and boxster owners in general. I for one very much appreciate it.

+ 1 on JFP

[Gelbster]

Regarding JFP, totally agree. We'd be lost without his experience. Most of us only have experience of one car and do the job 1 time. He has thousands ! Yet noobs still dicker with his advice - hilarious !
JFP has a business to run yet still finds time to help us. Amazing dedication . See him over on RennTech also. No bad behavior tolerated on Renntech so it is a refreshing change sometimes.
I used the U View over the weekend. I am puzzled about how it works when the thermosat is closed. But it does. I guess it may work better with a warm engine ?

[rp17]

Thread resurrect...Any instructions on how this system works?