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Bonny Doon Hydraulic Pump Oil change question

Hi everyone, I just had the good fortune to purchase a used Bonny Doon electric hydraulic press. It is similar the classic one they still sell. The manual says to change the hydraulic oil once a year, but I cannot for the life of me find any instructions anywhere. I have already contacted Rio Grande, but they couldn’t find any info either and someone is supposed to get back to me. Just wondering if anyone has any resources on how to change the hydraulic oil in a Bonny Doon electric hydraulic press. Thanks

If it is electric it should have a tank of sorts.
That tank should have a bleed off. Usually a bolt on the bottom part of one of the sides.
There should also be a “lid” of some kind.
That can also be a bolt/plug since I guess these don’t have much volume.
Do you have some pictures?
Regards Per-Ove Arntsen

Hi, I did some research on the net.
No actual information, but the plug in
center front looks like a filling nipple.
There was a comment on using the manometer port for filling on a video.
But for equipment this pricey I’d expect some descent instructions.
Nothing in the downloadable manual either.

So I’d push at Rio until they give you the information you need.
Regards Per-Ove

Hello Bernie,
Its pretty easy to change the oil in the electric pump. First, start by turning your pump upright and loosen the little metal cap as shown in the pictures. This is the oil port. Have a good container for the used oil ready, and turn the pump slowly upside down, allowing the oil to flow out of this port into the used oil container. Once it is totally empty, turn it back upright, and completely fill with a good quality hydraulic jack fluid, i would recommend only using SPX Power team brand (link below to amazon but you can find it from many different suppliers)
Hope this helps!

Thank you for the explanation and the pictures. It is very helpful.

I have one more question for you. The unit is quite old but still functions well and had quite a gap in use so I hope I can continue to trust on it for quite some time. The only thing wrong with it was they lost the small cap that goes in the hole on the jack. I posted a picture that shows the hole. The press is currently in a box and it was a bit difficult to get a good picture, but hopefully you can see what I am talking about. They have been using a foam earplug to plug up that hole. I’m just wondering if this is something to worry about. They said the original cap shot out and was lost. How would that happen and how do I prevent it? I am guessing that it might have been overfilled with oil, but that is an inexperienced guess. Thanks to anyone who can help.

Hey Bernie,
Not a problem, a foam ear plug works fine, or any little plastic plug that fits would be good. With an electric press the “reservoir” that is part of the ram is not used. Instead the oil is stored in the electric pump and pumped into the ram to move the press. The release valve on the ram should always be kept tight to insure that the oil doesn’t leak from the electric pump reservoir into the ram reservoir. Also, the ram should not be raised more than about 5.5 inches or hydraulic fluid will escape through a safety valve into the ram reservoir and that can eventually lead to the plug being pushed out of the ram. Check out this video for more info on that starting at minute 10.
I hope that’s a clear explanation, Under the Bonny Doon Resources page at Rio Grande there are some manuals, videos, and instructions with more info.

Additionally, this cap should not be completely thight. There will be air going in and out as the piston moves up and down.
I guess the “filter” plug somehow became clogged and shot out by air the pressure.
Regards Per-Ove