Had a similar situation with our Jetta last = winter.  It was a freeze up.  I had changed coolant earlier in the year, apparently got the mix wrong and the coolant froze in one of the hoses = plugging the flow.  Big time overheat when the temp was 5 deg outside.  = Took over an hour for the plug to thaw, then back to normal.  Another possibility is a stuck thermostat.  The spring in the thermostat = will theoretically pull it closed tighter and tighter as the temperature = drops.  Maybe tight enough to stick. Either of these blocked-flow possibilities = would produce another effect: no heat. Were you getting heat?
Gary
----- Original Message -----
From: Schmidt
To: vanagon@GERRY.VANAGON.COM
Sent: Friday, December 22, 2000 = 8:50 AM
Subject: help! overheating with = maple syrup smell

I have had a terrible = night.
How does a vanagon(84) overheat on = the coldest day of the decade at normal highway speed?
Condition: 65 mph interstate = drive- all is fine  (usual sudden power loss, poor mpg correctedtwice in 50 = miles by shutting off engine for a few seconds) That is not a new problem-just = no cure yet.  Tonight however, suddenly without warning, the oil light = comes on very dimly, followed almost immediately by the temp gauge light = blinking brightly.  The quick decision was to risk engine life or limb and = move an extra half mile(handy exit ramp) and then shut her down. More on this later!  By such time, smoke was coming from the rear mainly at = the air intakes on the upper body.  Dark of night inspection revealed no = glaring leaks or fluid loss, coolant level a little lower than usual, oil = about a quart low and remedied. I added a little orange coolant but my = distilled h20 gallon was frozen solid--mental note to start carrying PREMIXED coolant.
The smoke cleared and the motor = cooled extremely fast in the wildly cold temps outside.  I restarted to = see if the topping off of fluids would correct the problem.
On restart, the temp gauge light = blinked again, the temp climbed, climbed, climbed, didn't quit as fluids = circulated and I shut her down as she smoked just a tad. Smelled like MAPLE SYRUP!
Now I have seen the coolant at a = very low boil in the hot of summer.  It didn't bubble any tonight in the cold. = Yet the overheating??
 
Lastly, it seemed to "smoke" = mainly from the left side.That side has an older head and gasket unlike the right but = got a new temp senser last year. Could this condition be a thermostat frozen = up or malfunctioning?  Other suggestions appreciated for my DAILY = DRIVER.  This is not a hobby car but my bread winner- commute(far) to work = -stealth camp between shifts until weekends EVERY WEEK OF THE YEAR westy. I towed the vanagon home this morning on a = flatbed.
Thanks, = merry CHRISTmas
Jay in Wind-iana...brrrr
PS: The westy was not shut down immediately when = heating for reasons of safety.  There was no shoulder-just a few feet of snow = the plow left in place of the shoulder. Personal safety, not = convenience,  dictated that I had to hit that very close exit.  Please no shouda-woulda-coulda on this point. I work in ER/trauma and know where = safety ranks. Jay( husband, daddy of 4.)
I need it on the road.