R

riobison

Well Known Member
It looks like my vacuum pump needs replacing on my RV4. I don't think I'm ready to go through all of the work involved to change over to a glass cockpit so I will change out the vacuum pump on my 0360 A1A.

I see that there are kits available that a person can buy and then rebuild the pump himself.

I can't imagine that these pumps are that complicated so are there any negatives to me doing this? Or should I bite the bullet and just buy one that is already rebuilt?

Thanks

Tim
 
Vacuum pump

I have have done the rebuild process, but it was a lot of years ago. But as I recall it was pretty easy. The kit back then just had new parts for the core of the pump. Just be careful not the clamp the main body of the pump in a vise when you take it apart or reassemble
 
The dry pumps work fine if you have the filter on them and rebuild every 500-600 hours or so. Very few will go 1000 hours. Cheap and easy to rebuild.
 
Be aware, that doing a quality rebuild requires one step that most people can't easily do.
The bore surface within the pump that the vans run against typically get wash boarded/rippled from the bouncing of the vanes (same as a wash boarded dirt road).
Depending on how bad the wash boarding is, you can have a very quick failure of the newly overhaul pump because of the higher level of rotational friction from the vanes catching while they wear in to the surface.
A true overhaul includes lightly machining the interior of the bore to remove any surface imperfections.
A pump doesn't usually fail because the vanes got too warn, it fails because the bore got too wash boarded and the high friction caused failure of the vanes and or shearing of the frangible coupling.
 
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American Airpower has what you need. If you have ANY WASHBOARDING in the stator replace it. The trickiest part is replacing the carbon bushing. If yours is not cracked and the spline shaft isn't rattly just leave it. You may have to do a little sanding with 400 on the vanes and/or the top of the new rotor if its tight. When final assembled it HAS to turn freely with just a TINY drag. Don't spin the new one backwards until its run in. CHANGE THE FILTER AND MAKE SURE THE HOSES ARE SPOTLESS.
 
I have rebuilt one. As someone else mentioned, the Stator will more than likely need replaced. To install the carbon bushing, you need a special tool and there is no guarantee that you will be able to replace without breaking at least one.

If you add up the cost of the parts and tool, you will be very close to the cost of one rebuilt by Professionals and not need to spend several hours to rebuild your old one.

The difference in cost, just get a rebuilt one or as someone else said, get a wet vacuum pump.
 
The dry pump I have has 600hrs on it and won't produce enough vacuum on the ramp to bring the gyros up to speed. In the air they are ok, adjusting the regulator helped for a while but obviously its worn out and needs replacing.

It is sounding like if the stator needs changing then things can add up in a hurry. The rotor would be cheaper, quick and easy. Buying another stator over and above the rotor then the parts will add up in a hurry. Buying special wrenches or tools and if I break a rotor changing it out and having to buy a 2nd one would take me back close to the cost of a rebuilt one.

A wet pump for a VFR machine is about 3 times the cost of a dry pump and not worth the investment.

Tim
 
Vacuum pumps

Just a note I no longer run overhauled vacuum pumps. I have been using new Tempest Tornado vacuum pumps p/n AA3215CC and AA3216CW exclusively for quite a while now and they usually go 1800-2000hrs and I regularly replace them at engine overhaul. I inspect them using the inspection port every 100hr after the pump has 600hrs tis and this has basically eliminated inflight vacuum failure. I buy mine at AERO in stock for $380.00, my 0.02 Russ
 
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Vacuum pump

I just replaced mine two weeks ago (Rapco dry air pump) using the Tempest VP wrench A/C Spruce P/N 10-02654, and the task was not difficult.
I Removed the oil filter to get access at lower left mounting bolt. Total time 4 hours including cleaning/replacing hoses, and filters. Now all is good.
 
Dry Pump Failure

I just replaced my RAPCO overhauled unit after 800 hours and 9 years. Yea, it failed in VFR..........

IMHO the best investment in vacuum pump failure back-up is the AvGas it takes to do lots of Partial Panel IFR work. Around DFW, TRACON will give you No-Gyro work in Actual IFR about 50% of the time you ask for it. Depends on their workload.

Real confidence builder!
 
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