[Vwdiesel] Risks of Hydraulic Heating?

[Lee Hillsgrove]

  I've got a Ford 550 with a 200 cubic inch 3-cyl. DI that was recently
rebuilt, and it responds better to the block heater than it does to a
topped-off battery, as well. The manifold heater, a resistance element in
the intake manifold with a line that goes to the fuel tank, works well if
the battery is topped off enough to get the diesel fuel to ignite. You know
when it does if you listen closely to the air intake - there is usually a
muffled "whoof" when it catches.

 Obligatory VW content - I have used a hair dryer stuffed in the air intake
hose with decent cold-start results before. It's similar to the "toaster
grid" that is found on the Cummins engines used in Dodge trucks as well as
others, I'm sure.
 That gets me thinking - an old Chevette we used to have had a similar
element under the carb, for emissions purposes, I suppose. I wonder if one
could be adapted to the VW intake or if it would have enough wattage to do
anything?

 As to the question about  warming the hydraulic oil by pushing it over the
relief valve - I wouldn't do it for any length of time. There is a
tremendous amount of heat released as the oil is forced over the orifice at
full system pressure, and I would be concerned about what it would do to the
oil as well as the spring and seat in the relief valve itself. I maintain
that the high-pressure leakage past the pump plunger in the injection pump
is the source of the vast majority of the heat generated and not the
flyweights thrashing in the diesel fuel. My experience in working with
hydraulically-powered industrial machinery has taught me that the easiest
way to find a malfunctioning valve or a cylinder that is leaking internally
is by using an infrared pyrometer or even just your hands to seek out the
hottest part of the system. Don't underestimate the heating potential of oil
under high pressure passing to an area of low pressure without performing
any work. The energy put into pressurizing the oil has to come out
somewhere, you know...
 If you have a spare pressure and tank port on your valve block, you could
rig up an adequately sized relief valve set at a lower pressure, say a
couple hundred pounds, as a warm-up circuit. You would need to get the
entire system up above 220 degrees and hold it there for a period of time in
order to drive the moisture out. I wonder if the hot oil would just pull
more moisture out of the air as it cooled, though.
One of the injection molding presses I used to work on was set up with a
warm-up circuit. If the machine was down long enough for the oil to get to
room temperature, you could turn on the warm-up function and it would heat
the oil up in no time, so that it would run more consistently, I guess.

HTH,

Lee
Oo-v-oO
PP-ASEL
KB1GNI



> Gang,
>
> On my DIESEL (idi, even) tractor, I have an annual problem with hydraulics
> jambing up.  What I think happens is that moisture in the hydraulic system
> (transmission, brakes, loader, etc.) crystalizes at low temps, and as a
> solid, clogs the hydraulic filter.
>
> Heating the filter, with a propane torch frees things up, and after a
> period of operation at winter temps, the system seems pretty trouble free.
>
> Here's the problem...how to cook out the oil?
>
> 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
>
> ps: As the battery fails on the tractor, I find that running the block
heater
> pays of (timewise, not powerwise) over topping the charge on the battery.
> Hello summer cylinders.  If my cars were harder starting, I'd be popping
> frost plugs.