Page 1 of 1

D8A pump rebuild advice

Posted: Sun Dec 30, 2012 2:13 pm
by Rex Allers
I'm just getting into vacuum. I bought a Fisher (Leybold) D8A pump on eBay. Claimed in excellent condition. Packed poorly for shipment, but survived without serious damage.

I am hoping someone here has experience with these types of Leybold pumps and can offer advice.

Looking into intake and exhaust ports there is a lot of rusty looking contamination. But on closer evaluation, I don't think it is rust. Something that got sucked through the pump, maybe resin. The pump spins freely and with one quick pulse the motor runs and pump sounds smooth. With the level of contamination, I think I need to tear it down and clean it out. Putting oil in with this much contamination would, I think, be a waste of time and oil. Manual I found online says a quart per fill. Manual does describe internal maintenance.

I created a web page with more description of this pump and pictures of its state...

I ordered a major repair kit, including vanes. I am hoping for comments, advice, or knowledge about how hard it is to do a rebuild. Are there difficult alignment issues on these types of pumps after a complete tear-down?

Thanks for any thoughts or experiences.

Re: D8A pump rebuild advice

Posted: Sun Dec 30, 2012 11:07 pm
by richnormand
I have rebuilt a D16A years ago and will be happy to be of help. Took several pics at the time too. The D8A is very similar. Major rebuild kit from Dunaway was right on the button. Also get enough oil for two full loads.

I'll look in my stuff but I remember getting a full service manual, with step by step procedures and exploded parts diagrams, from the net. Probably still have it if needed.

Mine was full of crud since it had been used by some "#$#@&" as a pump for silicone molds. The insides were all gummed up and the secondary stage rotor pin had sheared off the driveshaft.

I also had to machine a few things because of the ridges in the shaft and getting new "o-ring" seals and positioning the lips at an un-worn spot.

Due to the grooves left in the cylinder walls from the metal shrads I had to hone them back to a good finish before putting the new vanes.

You need space to dismantle and baggies to label everything. Then a really clean space to start the rebuild. Most of the time was spent cleaning everything. MOST important here is cleaning, cleaning, cleaning. If you dont feel you could eat off it its not clean enough....

Do note the motor rotation direction before hand. Just in case you have to mess up with the motor wiring.

No real alignment issues, but the manual is great for the pressing sequence for parts. See if your kit has the stuff for the centrifugal vent, coupler from the motor shaft and ballast valves too. Mine had and these parts were in bad shape also.

That said it is an awsome and well built pump. Complete overkill for my small turbo pump!

Re: D8A pump rebuild advice

Posted: Mon Dec 31, 2012 4:32 am
by Rex Allers
Thanks for the information, Rich. It gives me more hope. Sounds like your pump and mine were similarly abused. I have not figured out what all the crap in mine is but it isn't rust and doesn't seem very sticky/gluey. I think maybe dish soap and a tooth brush might be enough to clean it. Sure is a lot of it everywhere, though.

I don't have the kit yet, so I won't begin to tear it down for at least a couple days. Good to know you didn't encounter any issues with aligning things. I'm hoping there is nothing broken or badly worn when I get in there.

I had found a manual with detailed instructions for rebuild here: ... Manual.pdf

I'm guessing this may be the same one you used.

Re: D8A pump rebuild advice

Posted: Mon Dec 31, 2012 5:12 am
by richnormand
That is the manual I found.
Eventually I got hold of a hard copy with much better pictures.

Aligning things was not an issue since the critical components are located by pressed in pushpins and the unit is well machined.

I have found about 25 pictures taken during my rebuild process and machining stuff that could give you and idea of what you "may" be getting into. Taking pictures is great to refresh your memory if the project stretches too long.....

I included two pictures: an electric toothbrush is great for cleaning with solvents, soap and water in the grummy stages. Note the baggies with labels for each group of parts. Second pic is during the rebuild: insides are pristine and outsides have been masked and repainted (red paint was left over from my car)

Also: make sure you read Richard's FAQs about pumps to give you a better idea of what to expect performance wise and the care and feeding of used pumps.

One last comment: if you do not know what the contamination is you should consider nitrile gloves during the cleanup in a well ventilated area, for safety.

NOTE: Dont know how "fusor" related rebuilding a pump is, so I'll abide by the moderators guideline/feedback here if I get in too much detail or we can communicate off line also.

Re: D8A pump rebuild advice

Posted: Mon Dec 31, 2012 4:35 pm
by Richard Hull
While a rebuild is nice if you are leaning that way, I prefer to spend about $16.00 for a gallon of cheap pump oil and as long as the motor is free, "fill 'er up". Rust is a good thing if the pump is free. with good oil in the pump no matter how cruddy, a good 1/2 hour run against a blocked off inlet is a good go at it. It heats the oil and releases a lot of gunk inside the pump. Rust, what there is of it will actually polish the inside a bit once in a slurry of hot oil.

After the run, dump the oil, while still hot, into a pan and study it carefully. If thick and nasty, you are on your way and probably have most of the crud out of the pump now.

To save oil, filter the old oil to remove all the big stuff and put it back into the pump for another run.

Dump again. It should contain few particulates now.

Put clean oil in the pump and put a gauge on the inlet head. This is the true test. If it pulls below 100 microns you have a decent pump. Preferably, you need to be under 20 microns within a minute or two. If not, go ahead and order the expensive rebuild kit.

If under 20 microns, run for 1 hour and then dump the oil again. Is it discolored? If so you are still fine cleaning. Put in a fresh batch of oil and run another hour. What does the gauge read. If the same as the last run then you have fully cleaned the pump and it is servicable for use in a fusor. With fresh oil, it might just read a bit lower now, though

**Note if you are not below 100 micorns, a rebuild might not save the beast. (too worn)

Again read my FAQ on restoring and testing a pump. I have yet to ever crack a pump open ( I have about 12 pumps on hand) and have bought some real nasty looking ones. My worst still pulls below 20 microns, using just the procedures above. No need to rebuild if a good flushing will suffice.

Get a good TC gauge.....Without a gauge, you are shooting blind.

Richard Hull