Date: Fri, 1 Jan 2016 16:28:30 -0800
Reply-To: Stuart MacMillan <stuartmacm@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stuart MacMillan <stuartmacm@GMAIL.COM>
Subject: Re: Wondering about coolant physics
In-Reply-To: <CAFnDXk2kkkuWuAUz+ghBxfRomTBZXiTk3TqVTZpa82q5OFfXtg@mail.gmail.com>
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Leaks are fun stuff. When is gets cold things shrink and formerly tight connections can leak slightly. It's possible that the vacuum is leaking down through the leak as well, and the bubble stays in the expansion tank.
I found my leaks by pressurizing the cooling system to about 20 psi. I used my Motive brake bleeder, but GoWesty sells a pump. You can also do it using air pressure set to 20 psi. Mine's a WBX and it was the heads, but the front heater valve is also leaking, very common. It's also common for the rear heater core to leak a bit, it's always under pressure because the valve never completely shuts off.
I've thought about a dye leak test kit, and NAPA has one for under $25, but didn't need it this time.
Stuart
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Jim Felder
Sent: Friday, January 01, 2016 9:58 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Wondering about coolant physics
Not very important as my car is running and cooling well, but I am curious about this issue which I can't come up with an explanation for.
I recently installed new radiator hoses and with the help of this list, finally got it right by going to a 1.9 waterboxer reservoir on my 1983 diesel.
Everything is good and seemingly snug, but on a cold night like last night and a few before, I find a small puddle, what I always called a "cold leak"
that doesn't appear when the engine is running or when the weather is warmer. It's so slight, I can't really tell exactly where it's coming from, maybe a couple of tablespoons when it gets down around freezing.
When I open the pressure cap, I get a burp of air. This is from cold, no starting or running whatsoever.
How can this be? There's obviously a small leak somewhere around the reservoir, maybe even the cap or a connection or even the coolant level indicator. There just isn't more than a few drops on the hoses to leave a trace. I may powder it with flour dust to find out more about where it is coming from and how it gets to the ground.
But back to the burp: air in the system and coolant in the system is at equilibrium with the atmosphere when it is added, right? Then you drive the car, and it heats up, then the system becomes pressurized which raises the boiling point of the coolant even further. Then the car sits out overnight, and the temperatures the next morning are even lower, so you would expect no pressure or, as the system is designed to take advantage of, a vacuum to suck in coolant from the overflow tank to displace the air, right?
This isn't happening. I suspect it's a crappy blue cap, the second I've bought in two months, is preventing the intake of coolant. But maybe it's because of this residual pressure that I can't figure out. why is there a burp when I open the cap in the morning instead of nothing?
Anyone?
Jim
Jim
