Date:         Fri, 22 Jul 2005 08:27:13 -0700
Reply-To:     John Bange <jbange@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Bange <jbange@GMAIL.COM>
Subject:      Re: How's this idea for diagnosing overheating?
In-Reply-To:  <6.2.3.4.2.20050722031414.048fceb0@pop.ipa.net>
Content-Type: text/plain; charset=ISO-8859-1

My father used a similar setup to monitor the temperature on his ol
'73 Revcon motorhome with a flaky 455 OldsToronado engine. That thing
went through multiple water pumps and fan clutches, so he rigged a
couple thermistors sensors to the inlet and outlet pipe of the
radiator. On the wasserboxer I can't imagine you'd need more than one
sensor "inside" the engine coolant circuit (i.e. "behind" the
thermostat), and maybe a couple more to monitor the before and after
temps of the radiator circuit. Basically, you've only got a few places
where the system can "go wrong". 1) water pump bad, 2) thermostat bad,
3) radiator clogged, 4) fan not working. If the thermostat or pump are
the problem, neither radiator sensor will ever get very hot. If the
radiator is clogged the outlet temp will be low and the inlet high
(though as "Robert Cardo" says, you can diagnose this by feeling the
radiator by hand). The fan, you should be able to hear it not working.
There may be other bizarre failures that could monkey wrench the
cooling system, but I'd say those four account for nearly all
overheating issues due to collant flow trouble. Plumbing VDO sensors
into the system sounds to me like it'd be more work than just
replacing the T-stat, water pump, and radiator, to tell the truth.

> 2.This all leads up to the master plan.  That is to take my existing
> water temp VDO cockpit gauge and set up 4(or however many) separate
> senders throughout the cooling system and have a multi position
> switch  that would allow me to read the coolant temp, WHILE DRIVING,
> at the various points along the way and use that info for the diagnosis.
> 
> First off, how may would be needed and where would you place
> them?  I,m thinking one before and after thermostat and one sender
> for the inlet and one sender for the outlet hose up by the
> radiator.   Wiring would be the least of my worries, and besides,if I
> get problem number one solved, we might get a decent accounting of
> where the factory needle gauge is reading.
> 
> Please fire away with your thoughts.  My sender for the water temp is
> currently Teed into the small hose that gets bigger back by the #4
> cylinder water outlet(sorry; 2.1 liter 90 GL here)