[Vwdiesel] Radiator Choices

Roger Brown r.c.brown at ieee.org
Tue Aug 23 18:42:52 EDT 2005

Wade Yorke wrote:
> Hi Chris:
> Sounds like you are having the same problem as I am.  I have a 1996 Eco 
> 1.9TD and if I run at over 3300-3400 rpm on the highway it slowly 
> overheats until the red light is flashing.  I have installed VDO oil 
> temp and water temp gauges for accuracy, but since the high speed fan 
> was being triggered by the higher water temps I kind of knew that I had 
> a real problem.  The VDO gauges both show elevated temperatures on the 
> highway (approximately 220 degrees at 3200-3300 rpm).  My radiator is 
> only four years old so I believe that I do not have a flow problem.  I 
> have heard that the stock Vanagon radiator is not adequate for the 
> diesel (although I always thought they ran cooler than gas engines).  
> The problem is that a larger radiator may not help much as they cavity 
> behind the stock radiator is small (just large enough for the stock 
> radiator I would guess).
> Under normal around town and moderate highway speeds the water and oil 
> are at 200 degrees F and the needle is just above the LED in the stock 
> gauge.

On my '82 pickup, w/ 1.9D engine, I did a couple of things that really cut the running temps.  One was to have the old radiator 
re-cored with a 3-row core at a local radiator shop (it was a copper/brass Modine radiator).  Then I installed a smaller pulley 
on the water pump, using one from a 1.6D A/C equipped Rabbit that I modified to fit the 1.9D.  This has the affect of spinning 
the water pump faster than normal to flow more coolant through the engine (an overdrive condition).  Those two items did a lot 
to reduce the high RPM temps from up near the red zone on the factory gauge down to 1-2 marks above normal.  Then I found that 
increasing the max load fueling and advancing the pump timing to the upper limit made it so the temperature gauge almost never 
moves, since I can keep it in a higher gear and keep the RPMs down.  A diesel engine's heat output really climbs as the RPMs go 
up at full load, since the combustion process becomes less efficient the fast the engine turns over.


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