Date:         Thu, 06 Jun 1996 06:39:20 -0700
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         jwakefield@4dmg.net (john wakefield)
Subject:      Heat handling design error help

I believe the design weakness in VW water jacketed motor installations 
most commonly responsible for failures is their marginal heat rejection 
system.  Not only were heat rejection design errors common, but the gas 
motors developed a fearsome reputation for being easily damaged by 
over-heat conditions that other power plants would typically accept.  
Chrysler purchased and remarketed these motors with minor modifications 
in their early Plymouth Horizons and Dodge Omnis, and both kept their own 
records which each revealed unusually high incidence of over heating 
induced damage.  Their cooling systems were quite conventional, and 
remained nearly the same after they began using their own power plant, 
but that change ended the unusual incidence of over heating induced motor 
failures.
  Now I don't propose to address the causes for these motors' ungraceful 
sensitivity to occasional over heating, but I do think this group has the 
experience, insights, and talents necessary to develop a list of after 
market design improvements that can greatly lessen chances that van type 
vehicle owners will experience this violation of their reasonable 
expectations.
  Some well known or suspected design errors are:

1) Weak and failure prone water pumps.  A more aggressive impeller design 
or what ever is required to increase coolant flow would be helpful. 
Bigger, spun faster, tighter clearances for improved idling flow, 
stacked?

2) Water passages to and from the radiator from the motor were too small 
for their length on early units. I think this list's FAQ archive seems to 
suggest they were enlarged on vans after about 1983.

3) Both progressively staged control switches for the two stage fan were 
specified with values that are either too high or were inappropriately 
located, and should be replaced by lower temperature switches or 
relocated to the motor or both.  Keeping the radiator within specified 
range is NOT an intelligent design goal, keeping the engine within good 
safe design range is an intelligent design goal. So these two radiator 
mounted sensor locations appear suspiciously like design errors.

4) The cooling system is already marginal without reducing and preheating 
the remaining air flow to the main radiator due to air conditioner 
condenser location.  For that reason, alternative condenser locations 
should be examined.  An archive description of an engine transplant 
mentions that a rear wheel well area with high air flow successfully 
accepted an air to fluid heat exchanger. I'd fear impact damage, dried 
mud obstruction, and creating another location that would discourage 
frequent visual inspection and maintenance.  I am very attracted to the 
two high side rear loover openings, and would like to hear others 
thoughts about this.  If an electric fan is needed, unloading the 
engine's main radiator would justify it.

5) The current inconveniently accessable bleeder valve for the radiator's 
top discourages frequent checks.  An extending tube leading to another as 
high or higher final valve?  Repositioning the current valve to accept a 
through-the-grill removable extention handle?

6) Oil cooling capacity from oil heated surfaces outside the engine are 
too small and not optimally exposed to air flow.  It's always better to 
pull a btu from oil than the water based coolant.  A loover sized heat 
exchanger in the air dump?

  Now I know these thoughts aren't exhaustive but most are conceptually 
valid.  There's no excuse for designing a power plant installation that 
can't handle its peak thermo loads with some reserve.  What ideas give 
the most cooling bang per buck and per unit of required time?  Examining 
the diesel owners manual reveals that they did not offer air conditoning 
on diesel Vanagons (a sub set is Westy) because   Multiple guess for Car 
Talk:  1. Insufficient horsepower to pull additional load? or B. 
Insufficient cooling system reserve capacity?   ***************  Those of 
you who said B are correct. :>
  Give some input.  How could we increase hot conditon coolant flow, 
better control the OEM two stage radiator fan, better position air 
conditoning condencer(s), improve radiator bleeder valve access, improve 
oil heat radiation, or what ever occurs to you.
	Thanks for listening and considering.  In a day or two, you may 
have thought up an elegant piece to this puzzle.  Please chew on this 
mind candy.
	John Wakefield