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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
Content-Type: text/plain; charset=ISO-8859-1

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.


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