- The water pump design on the Rotorway helicopters
is unique and has been prone to leaking at the seal, especially if the
water pump/alternator belt is run too tight.
- The water pump seal &gasket (PS-447V) US Seal-
The V stands for Viton and is the recommended seal. A seal without the
V will work but does not last very long.
- It is wise to have an extra water pump seal and water
pump gasket on hand as they often leak during training and need replacement-
having a spare on hand saves much down time.
- Have a tube of high temp flexible gasket seal handy.
- Here is a photo of a typical sight following a training
session where the water pump seal has let go. A fairly loose water pump
belt (but not so loose that it will slip) will help prevent the seal
from being damaged by the water pump shaft flexing at the seal.
- Antifreeze is flammable and does catch fire and burn.
- Antifreeze is very slippery and can and will cause
your drive belts to slip leading to possible loss of the helicopter.
Be careful when checking your surge tank
anti-freeze level. The underside of the cap usually has antifreeze on
it that will drip onto your belts when the cap is removed if you are
The following is how I replace
the seal on the Rotorway water pump.
I do this without removing the
- Drain the antifreeze down to a level below
the water pump base. You can do this by tipping the helicopter back
onto the stinger.
- Place a piece of hose over the pet cock opening
with the other end into a clean pail
- Open the pet cock and drain all of the antifreeze
that will come out by gravity. This should get the level down below
the water pump.
- Remove the hose from the outlet (back side)
of the water pump
- Remove the bolts from the upper half of the
- Gently pry the water pump halves apart.
- Swing the lower half down and way from the
upper half. I use a piece of strap or bungee to strap it to the forward
frame member to keep it out of the way
- The impeller is screwed onto the shaft and
unscrews in the direction of rotation. (clockwise looking down on it
from the top)
- I take a block of wood and a hammer. I put
the end of the wood against the impeller vane and give it a sharp rap
in the direction of rotation
- This loosens the impeller and it easily unscrews.
- Remove the impeller and if the lower portion
of the seal did not come out with it you will need to slide it down
off the shaft.
- Notice the orientation of the lower seal so
that you will orient the new one correctly.
- Clean the mating surfaces of the water pump
- Note the distance that top of the old seal
is from the top of the pump casting because this is where the new one
will need to be when you install it.
- Take a punch or dull screw driver and from
the top tap the upper portion of the seal downward (you can see it in
the photo just inside the upper the casting around the shaft. It will
slide down the shaft and fall out the bottom.
- Clean the seal area up inside the top casting.
- You do not want to touch either
mating surface of the new seal with anything including your fingers,
the lapped surface is very easily damaged.
- Remove the new upper seal
from the package and place a thin film of high temp sealant around the
upper outer circumference were it will be contacting the inner diameter
of the upper casting.
- Find a 12 point socket of
the proper diameter to allow the seal portion to fit inside the socket
but the metal ring of the seal will not. The OD of the metal part of
the seal cannot be larger than the OD of the socket because the socket
needs to fit up into the casting hole. (Trial fit the socket into the
seal cavity to insure that it will fit into the machined area.
- Place the seal portion into
the socket and be sure that the sealing lapped surface does not touch
- Now with the metal cap portion
of the upper seal resting on the top of the socket, slide it onto the
end of the shaft and then tap it into position (where the old one was-
usually around a 64th" below the casting top)
- The upper seal is now installed.
- Clean the impeller and place
a thin film or high temp sealant onto the flat area just around the
threaded hole where the rubber portion of the new seal will rest.
- Careful not to touch the lapped
surface of the new seal, rest the rubber side onto the film of sealant
and centered on the threaded hole
- Very carefully line the ID
of the lower seal onto the end of the shaft and slide up until the threads
- Rotate the impeller in the
direction opposite of rotation (from the top it is counter clock wise)
- Give the impeller vane a solid
rap with the wood block in place against the vane with a hammer
- Install your new gasket with
high temp gasket seal. Use it sparingly or excess seal will get into
your cooling system. The rear hole is under the rear casting and does
not get a bolt so I just fill the hole with sealant (not to much)
- Slide the lower half into
- One bolt at a time- place
some sealant on the threads and then place into the hole in the top
casting and thread into the lower casting
- Do this with all of the bolts
then progressively tighten until all area tight and to the proper torque
- Let the sealant set.
- Re connect the rear pump outlet
- Refill the cooling system
- Burp the water pump (place
the hose onto the pet cock and bleed the bubbles out)
- Start the helicopter and watch
the water temp gauge. I bleed more bubbles out while watching the water
- If the temp goes into the
yellow, shut the engine down and bleed again.
- Once all of the air is out,
check for leaks and then you should be good to go.
the photo above, The original alternator that Rotorway supplied
had a small belt that drove it off of the water pump. The alternators
now are higher amperage so they need to be driven by a larger
belt as in the present kits. If the double pulley is mounted
on the alternator with the alternator driven off the secondary
and then the water pump driven off the alternator second pulley,
the water pump belt tension can be looser while keeping the
alternator belt tighter. This is not madatory and can be done
yourselt. There is at least one after market supplier who is
pushing this idea.
The kitís alternator adjustment bracket
is adequate but if improperly made can break. Here is a photo of one builder's
modification to the bracket by installing a turnbuckle with both left
and right hand threads. It is simple and easy to adjust.
The photo below was on a second
hand ship that I was inspecting prior to flight instructing in it. The
bracket had a weird bulge on it covered by black paint so I removed it
and removed the body filler that was under the paint. When the previous
owner had the strap break, he applied some bondo and safety wire, applied
some black paint, and re-installed it. It would not have lasted an hour
as both sides are broken as you can see. It is always good to have a ship
inspected prior to purchase to find things like this. This bracket obviously
was poorly made by the builder and it cracked along scratches that he
left in the bracket when he made it.
Here is another issue that
can get you into real trouble. I will let Dave tell you in his own words:
Member Join Date: Jan 2007
Rep Power: 9
Re: Longer skids
Today I've joined the group that has had to auto in. I had coolant spray
my tail rotor belts as I was hovering between 2 hangers.
After the second 360 I was able to set it down firmly with 1 skid in
the grass and 1 on pavement.
I do have the longer skids with both reinforced. I kept it upright and
there was pitching, but it happened so fast I can't say how far over I
was, but all is well.
Mine are extended 18" and I made a mount in the same CG location
as stock in relation to the mast which hasn't effected my range.
Dave N13922 (still)
#24 21 Minutes Ago
Member Join Date: Jan 2007
Rep Power: 9
Re: Longer skids
The thinking is a belt a little loose saves the pump seal. My ship never
gets hot, always hits 72-73 thermo opens and instantly drops to 67 so
I don't think a loose belt is problematic. Temps always in the green.
Yes I woul make sure the hose vents. I now have mine exiting at the engine
pan so if it happens again the exiting water will be 3' prior to the tail
boom and down washed by the fan away.
P.S. I can't wait for Homers
a pictorial tutorial to show you how to replace your leaking water pump
seal while it is still on the ship, CLICK HERE
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