[Vwdiesel] Thermostat temps

[mikitka]

OK now for a monkey wrench, what about running Evans Waterless coolant, no
pressure on the system to worry about. Anyone running Evans?

http://www.evanscooling.com/catalog/C_npg1.htm

Nick

 

FWIW, the 92C thermostat on my 91 NA shows the needle at the 12 o'clock 
position.

The real issue when picking thermostats is not where the gauge is,
but what is it doing to the engine.  5C or even 10C won't make much 
difference in seal life.  It won't directly impact oil life.  It will
result in measureable heater output.  It will impact the reduction 
of moisture buildup in the crankcase.  It does cause a greater range
for every thermal cycle the engine goes through.

A little more...I've found a direct correlation in static car, running 
engine temps with a thermostat change.  Idling, after being run, an
87C thermostat results in a cyl head temp within a degree or so of 
87C.  Ditto for a 92C.  The repeatability is high, and a termostat 
which is even 1C off is readily detectable.  I use passive infrared
radiometers ("laser thermometer" called so for the pointing laser).
Having a spot of paint to measure off of enhances measurement accuracy.

I've owned Diesel VWs since they were first available, and have found
that 92C and even 95C thermstats work fine in western NY weather.  During 
the time I've owned these cars, the ambient temps have ranged between 105F
and -20F, and I've had my cars in places a bit warmer, and much colder.
I have not had any problems I can attribute to the higher temp thermostat.
I have seen problems with lower temp thermostats which have been reduced
with higher temp thermostats.  For example, certain family members do
short trips.  They tend to get moisture buildup, and water based sludge 
collects in the valve cover area.  The moisture has two undesirable
properties: less lubrication, increased corrosion. 

The downside of higher temp thermostats, from my perspective, is that 
there is a wider thermal swing on every thermal cycle of the engine.
For the short haul vehicle, this could mean a reduction in the life of the 
cylinderhead gasket.  

Owning well over a dozen VW diesels, many of which lived for 500Kmiles 
or more, and most who lived for 300K miles more more, the number of times 
I've changed cylinder head gaskets is small.  I find that the gasser
vans my family owns need new gaskets much more often, don't know why.
But I can't see any data which points to my ever having had to change a 
gasket sooner with a 92C thermostat.

When would I run an 87 or even a 80C thermostat?  When I knew I had a 
cooling problem.  Perhaps a bad radiator.  Poor ducting, intermittent
fan sensor, or whatever.  Not a good cure, but a short term workaround.

Finally, most modern vehicles seem to have problems with airpockets
impacting cooling system operation.  I've considered making a device
(large rubber cork) where using compressed air, I could draw a vacuum on
a cooling system.  This would help in filling systems, but would not 
the possibility of hot spots.  I've experienced these problems in 
all kinds of engines, and take care when filling the radiator and engine.
VW makes it easy with sensors that pop right out with the pull of a pin.
Sometimes how you park the vehicle while filling it can influence how
well it fills.  Also, if you're running a cooling system with plain 
water, and no pressure cap (limping home) you may experience bumping
or boiling of the water at select spots.  Most of us don't run just 
water, without the pressure cap.


Either way, with a 87C or a 92C thermostat, the vehicle should run 
fine, so we're splitting hairs.  I just wanted to babble about how I
split my hairs...




> 
> I have been using an 87C in the 1.9 1Y in the '82 Caddy, and the temp. 
> needle generally lies between the 3rd and 2nd white ticks to the left 
> of the two right side red ticks.  
> 
> Dana
> 
> On 30 Jan 2007 at 15:57, Roger Brown wrote:
> 
> > Has anyone tried out a hotter thermostat in their VW diesel (A1, 1.9D
> > engine) for a little higher operating efficiency?  Not sure what I have
> > in my engine now, but looking at either an 87C or 92C valve to put in. 
> > I currently run at the lower heavy mark on the temp gauge, the third one
> > from the left:
> >  http://www.4crawler.com/Diesel/CheapTricks/Tachometer/Images/tach_14.jp
> >  g
> > 
> > -- 
> >     Roger
> > 
> > 
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> 
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