It certainly is possible.
Just doesn't seem that likely to me if the radiator was new in 2006 and a
high quality coolant with distilled water was used....that there would
likely be a problem  with the radiator currently.

buy hey ..
stick a bunch of BarsLeak in it and some Water wetter for good measure and
see what happens  !
just joking. .

I have seen *many* cases of exhaust getting into the coolant.  Perhaps 20
cases at least in the last dozen years.
( waterboxer, Subaru, and before those ..diesel too )
and it's often 'mysterious' ..
doesn't quite make sense.
things seem ok..........part of the time, but then they really don't seem
right at another time. .

Did anyone mention the fire it up cold, let it run one minute, then shut off
and remove pressure bottle cap to see if there is any pressure there
....trick ?

that's free and easy to do, and might reveal something.
it also might not, but it doesn't hurt to try it.

Scott

----- Original Message -----
From: "Dave Mcneely" <mcneely4@COX.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, September 21, 2011 6:25 PM
Subject: Re: 85-H20 loss of coolant mystery

> Of course, it is certainly possible that BOTH exhaust gas leakage into the
> coolant AND a partially blocked radiator are at fault for the multiple
> symptoms described.  mcneely
>
> ---- Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM> wrote:
>> Your radiator should still be fine if it's only 5 years old.
>>
>> when the rad fan is on, plenty of heat-removing air flows through the
>> fins
>> on the radiator ..
>> should not be an issue there.
>>
>> if it's the same case, my attention was immediately drawn to the bubbles
>> flowing from engine into pressure bottle, if I read that right.
>>
>> that says exhaust getting into the coolant to me.
>> It can be intermittent.
>> It's fairly common.
>>
>> Scott
>> ----- Original Message -----
>> From: "Travis Newhouse" <travisnewhouse@GMAIL.COM>
>> To: <vanagon@GERRY.VANAGON.COM>
>> Sent: Wednesday, September 21, 2011 10:09 AM
>> Subject: Re: 85-H20 loss of coolant mystery
>>
>>
>> >> It was fine for a daily drive of 1 mile each way @ 25 mph.
>> >> But on the highway @ 55 the cooling system was just too
>> >> clogged with rust.
>> >
>> > That is the opposite of what I'm experiencing, but Loren's suggestion
>> > makes sense that high speed air velocity may be enough to keep cool,
>> > but the radiator lacks capacity during stop-and-go with only the fan
>> > pulling air through the radiator.
>> >
>> > Loren mentioned that the radiator may not be able to be flow tested.
>> > So, how does one diagnose a clogged radiator to decide if it is the
>> > problem and should be replaced?
>> >
>> > The radiator in my 85 Westy was replaced in 2006, and only the blue
>> > BMW coolant has been used (50-50 with distilled).  What is the average
>> > lifespan before corrosion of the radiator?
>> >
>> > Thanks,
>> > Travis
>
> --
> David McNeely