[Vwdiesel] Risks of Hydraulic Heating?

Val Christian val at mongobird.com
Fri Dec 23 18:48:16 EST 2005

Thanks for all the comments and suggestions.

The hydraulic schematic for the tractor looks something like the
transmssion -> inlet for filter -> filter -> line to suction side 
of pump (24mm) -> pump -> line to hydraulic manifolds...

A clogged filter starves out the pump, no bypass, and the hydraulics 
do not work at all.  

Again, whenever things have failed, I heat the filter with a propane
torch, and after it gets warm, and the inlet pipe to the pump gets
warm, things flow for a bit.  Eventually, it flows continuously.  
The problem was a real stumper until in bright sunlight I checked
the hydraulic fluid dipstick, and saw the glint of ice in oil, which
my early years of VW diesels helped me become so familiar with...

The tractor has an ideal setup for cold WX fuel handling...the fuel tank is 
under the hood, on the transmission side of the engine, with the 
radiator fan blowing warmed air on it.  In 0F WX, it gets warmer than 
freezing.  In other words, get the tractor started, and warmed up, and 
it'll keep the fuel warm.  Probably an ideal setup for WVO.

Also the injector pump on the tractor doesn't heat the fuel nearly 
as much as the Bosch pump on the VW.  Less frictive heating from the
turbulence of big flyweights running through the fuel.  It would be
real easy to install tape on the tank, or an immersion heater in the 
tank for a WVO operation.  


> This year, I'm considering running the tractor at a moderate power
> 1800 out of 3000 RPM, and putting the hydraulics into a lock mode, so that
> the pressure limiter goes into bypass.  I'm a little concerned about
> the effects on the bypass valve (erosion, etc.), and local heating of the
> hydraulic oil as it goes through the bypass.  Can anyone comment?
> Val
> That would be a tad risky in my opinion, as the cold, high viscosity
> hydraulic oil may not be able to get through the bypass orfice fast enough,
> creating a pressure spike, and rupturing a line.  Better would just be to
> unplug the lines from one circuit, run a loop on that circuit, and then
> engage the lever, let the flow go as normal.  As Svend wrote, the filter
> *should* have a bypass, but not all tractors have one.  I have a couple
> tractors that DO NOT, so if the filter fails catastrophically and plugs the
> outlet, the hydraulic pump is the weak link, usually cracking  the side of
> the pump casting to relieve the pressure. That is something to check before
> you do this.  The pump *should* have a relief, but then again, all do not
> have one either.
> -James
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