Date: Thu, 6 Oct 2011 11:19:06 -0400
Reply-To: Ed McLean <email99@BELLSOUTH.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Ed McLean <email99@BELLSOUTH.NET>
Subject: Radiator performance and replacement
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Some comments on measuring radiator performance and replacement:
On a July trip in 1996 I noticed mild overheating while driving my
unmodified 86 Westfalia along I90 across Nebraska during the heat of the
day. While the overheating wasn't severe, it was enough to cause us to slow
down a bit on the interstate. On returning to NC, I strapped thermocouples
on the hoses leading to and from the radiator to monitor cooling system
reserve capacity while driving. I don't have the exact numbers but the
return coolant was significantly cooler than the coolant going to the
radiator, as expected. However, when following any vehicle, and more so if
that vehicle was a large truck, the return coolant temperature would climb
although the feed temperature initially remained the same. As the return
temperature climbed above 195º the feed temperature began also to rise,
indicating the radiator was no longer able to control the cooling demands of
the engine. If I then moved out from behind the truck, the return
temperature would drop, followed quickly by the feed temperature dropping.
I was surprised that this effect was present even up to ~200' behind a truck.
I figured my radiator was clogged but on inspection I found it was clear
with only a thin white coating on the inside of the passages. Attempts to
clean it with various flushes didn't seem to work. I replaced the radiator
with a new Behr unit from the Bus Depot and repeated the temperature
measurements. Although the return temperatures increased slightly when
behind a truck, the increase was insignificant and the radiator feed
temperatures remained constant. The overheating problem was fixed.
Conclusion: Radiators have a finite lifetime for cooling efficiency. Just
because a radiator is not clogged up doesn't mean it is efficient. While
cooling efficiency might be extended by routine maintenance and flushing,
replacing an old, poorly performing radiator may be the quickest, easiest
and cheapest solution. Radiator performance can be measured by monitoring
the temperature of the return coolant while driving under varying conditions.
A thin film of dust and oil on the exterior fins of a radiator can also
degrade efficiency. Spraying with a liquid cleaner, like the old 409 brand,
and rinsing with strong stream of water works well for this.
To monitor coolant temperature I use an electronic thermometer, strap the
thermocouple to the coolant hoses near the engine with a plastic wire tie
and covered it with a piece of insulating foam, also held on with a wire
tie. You have to read the temperature while driving. Just checking
temperatures with an IR thermometer when stopped will not give the
information you need to evaluate your radiator cooling efficiency.
Note that if the temperature of the return coolant remains low and the
temperature of the radiator feed coolant or the engine temperature rises
excessively, you have some problem other than loss of efficiency of a free
flowing radiator. A plugged radiator or hoses, air trapped in the radiator,
or other problems may be present.