Date:         Wed, 2 Oct 2002 15:49:18 EDT
Reply-To:     FrankGRUN@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Frank Grunthaner <FrankGRUN@AOL.COM>
Subject:      Some Clarifications and Additional Cooling System Comments
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Just a few additional notes.

On the radiator capacity, I just looked at Ken Wilfy's post on the dimensions
of the Aluminum and Copper radiators he is selling. Assuming the width of the
cores is the same the core volume of the Aluminum radiator works out to 633
cubic inches while the copper radiator comes in at 702. Given the superior
thermal characteristics of the copper and that the additional 15 pound weight
at the very front of the van could help offset the rearward bias, get the
copper ones!

Secondly, remember that the efficiency of heat rejection at the radiator is a
strong function of the mass flow of the exchanging fluid (air). Or said more
simply, you all know that (at least the diesel based system) has two fan
speeds - mild roar and local tornado. That fan is all part of the capacity
calculation, although the SAE work from whence this derives pertains to
single speed electrics or shaft driven mechanicals. So, nothing wrong with
fan switching on. I have not yet seen the situation in which the second fan
speed cannot control any thermal situation. Of course, I don't have a exhaust
gas injector in my model.

Reserve capacity. This is a bit more problematical. My first response is that
the high speed stage of the fan represents reserve capacity. Others have
suggested that there is no system reserve if the thermostat is fully open and
the system temperature (coolant) is varying with load (both the engine and
the external environment - like the high density sulfur dioxide vapors I
encounter when I motor past certain spots in Texas near the A* end of the
Earth!).  First understand that these systems are not designed for constant
temperature operation. I have asked why not and the particular Porsche
engineer I was conversing with said "Why?". We went around for several cycles
before he dismissed my question as irrational. We met some years later in
Atlanta (he was now attached to the Audi Motorsports team) and he immediately
commented that they were designing constant temperature systems for the
racing cars and that they would soon be seen in high end direct injection
machines.

But I get ahead of myself. Variation of temperature is fine probably from the
true 92 C control point of the thermostat up to the 105 C reasonable mean
limit. the problems occurs when the full system capacity is exceeded (of
course). With the vanagon system, I would say that if it was functioning
correctly (clean radiator, no air, good pump, smooth - not hairy-inner hose
walls, clean thermostat) then the system is being called upon to dump
something like the thermal equivalent of 130 hp (5500 BTU per minute or 75
kilowatts). This suggests that a) the engine output is near 400 Hp or b) that
the engine is extremely thermally inefficient.

More likely, the system is not functioning correctly. I have treated several
of these issues in the archives and strongly counseled the addition of a
coolant pressure meter for diagnosis. But go to the most likely problem: AIR
IN THE SYSTEM. Because of the system design, there are several areas in the en
gine to trap air as well in the radiator area. Trapped air, cavitation and
local hot spots in the head all go together. Careful bleeding is essential.
Water Wetter works and will offer further reserves. Weak and collapsible
hoses at the water pump inlet can cause cavitation. Air pockets or air mixed
in the coolant are equally bad. Remember a small air leak at say the heater
core can be small enough for you to not notice liquid coolant - but still
inject a stunning amount of air into your system over days and weeks.

Next possibility is the clogged radiator. Previously cursed PO could have
succumbed to the siren call of Aluminoseal or BarsLeaks in the middle of a
torrential rainstorm in the Gobi desert. These systems clog transfer tubes.
Think cholesterol! and holding tanks (ouch, memories). Another insidious
problem can result from oil in the coolant (oil cooler failure) coating the
interior surfaces of the radiator. Knocks the hell out of heat transfer
efficiency.

The other set of problems go back to the engine. For new conversion problems,
map the pressure and head at the water pump to search for cavitation. Did you
change the pulley ratios? But then, more obviously, is the ignition and valve
timing truly on. late timing  (both ignition and valve) can give very high
engine thermal loads as well as poor operating efficiency. Often poor fuel
economy, lack of power and high head temperatures are link together as
symptoms.

OK, I'm out of verbs on this one, except to recount:
1. The base Vanagon cooling system is well engineered and up to any
powerplant/AC combination that you can get to work with the weak link
transmission.
2. the engine cooling system (WBXer and around the block) is not included
here except for pump capacity.
3. Thermal problems obviously can and do exist. YMMV!
4. Air in the system is the worst culprit. It can lead to other problems ...
overheating, then bye bye head gaskets, cooling passage cracks, etc.
5. Simple stop leak solutions, even if they work in the short time, will
reduce system capacity.
6. I started this thing years ago as I was about to switch to the Evans
Cooling System (pure propylene glycol). Still think its the best and I'll go
there if the trans can handle the power.

Frank Grunthaner