Date: Fri, 22 Jul 2005 12:05:45 -0400
Reply-To: tabe johnson <xtabe@YAHOO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: tabe johnson <xtabe@YAHOO.COM>
Subject: Overheating
Content-Type: text/plain; charset=iso-8859-1
Hi Max,
To answer your question about installing an aftermarket sender
in the stock location, I'd take a stock temp sender and drill
a hole in it. Then, install the VDO sender into the hole you just
made in the stock sender with goop or an O-ring and nut or
whatever. (depends if you want it to be permanent or not) Another
option would be to take a metal cylinder of the same diameter and
length as the stock sender, drill (and tap, if necessary) a hole
in it, and attach the VDO sender. The stock O-ring will seal
things nicely.
I _might_ also be having overheating problems so I got an
infrared pyrometer to check temperatures. After playing
with it for five minutes, realized it was completely useless.
The temperature on the exterior of most of the pipes
is mostly dependent on the heat transfer characteristics of
the pipe and the external air temp and flow, not on the temp
of the coolant! You can check this for yourself if you
have a pyrometer: Measure the temperature
of the large metal coolant feed tube that goes into the water
pump, then measure the temp of the flexible tube between
the large metal tube and the thermostat housing. Temperatures should
be basically the same but they are completely different because
the flex tube doesn't conduct heat nearly as well as the metal tube.
Speaking of which: If you have a pyrometer, what temp do you get
for that metal tube? It's the only temperature I can measure with a
pyrometer (or thermocouple or whatever) that I trust. To get other
reliable readings, yes, you'd have to have temp senders in the coolant
like you describe. I get around 90-100C on that metal tube when the van
is warm and has been idling for a while. You can see the temp changes
as the thermostat opens and closes.
Measuring the temps of the hoses into and out of the radiator is
also useless without knowing flow information. Imagine - say
you have a 20 degree difference between the inlet and outlet of
the rad, and good flow. Your pyrometer/whatever would say 20 degrees
difference. But say you have a clogged rad so you are getting very
low flow, but still getting a 20 degree temp change. Your measuring
tool would STILL say 20 degrees difference, but your engine would
be running hot because it wouldn't be getting enough cool water from
the rad. So if you depend on temp differences you'd need to know
pressures as well and have baseline info from a van that worked properly!
Also - you can't just take out the thermostat and run wihtout one to
see what happens, cuz (1) the housing will leak like a sieve and (2)
the thermostat does two things: it cuts off hot coolant recirculation
as well as allowing cooler coolant in from the rad.
It's not an easy problem.
tabe johnson/87 westy
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