View Full Version : Help rebuilding hypro d252 pump

01-14-2009, 08:09 PM
My pump started leaking today. Sprays out from under the red cover that bolts to the top with 4 allen bolts. I presume its the diaphragm. Should I buy the regular rebuild kit or the one with the teflon diaphragm? I spray pre-emergent's like gallery, barricade and pendulum. Also should I/ do I need to change the oil? How much air psi do I put in? Any help appreciated. I bought the rig used and have no idea when it was or ever rebuilt before.

01-15-2009, 09:37 AM
Hi there, most times when the pump is leaking from the head it is either a crack in the head itself or the manifold that the head bolts to. It could also be just the diaprhagm inside the head. Take apart and inspect very closely for any cracks. You do not need to use the teflon diaphragms. You want to put in 10% of your working pressure of air into the head. It is much easier to just fill the head with air start up the system and watch the pressure gauge. If the needle is bouncing all over slowly bleed out some air and you should be good to go. You do not need to change the oil in the pump unless it is milky white which will also mean that the diaphragms inside the pump need to be changed. Just be sure to watch the oil sight glass and keep it half full. This is a link to the Hypro D252 pump manual.

Good Luck

01-15-2009, 12:13 PM
A good idea is to replace the diaphragms at least once a year on the Hypro 252 series pumps. Your climate, like mine becomes quite hot for extended periods of times and the corrosive herbicides you are spraying tend to degrade the diaphragms pretty quickly.
The leak can be from a blown o ring seal that some series of 252 pumps may have in the head to manifold point of connection.
If yours does definitely replace the o ring with a new one and lubricate it with either synthetic motor oil or hydraulic oil to ease reassembly. Don't make the mistake a bunch of people do and use WD-40 to lubricate o rings.

01-15-2009, 12:23 PM
Good comments Toni. I have that pump, also. I have not had a problem with the head leaking, though. You don't know its history. If you have it apart--you may as well replace the diaphragms, too. And check for bad o-rings. If you have time, unscrew the big plastic nuts, pull out and inspect the valves for excess wear of the seats and broken springs.

Remember you need metric Allen wrenches, 4 mm, I think. If you ask at a NAPA parts store they will have a socket wrench that has a 4 mm bit--makes it easier. Remember the bolt that holds the diaphragm is 13 mm. When you replace the diaphagm, use the Desmopan plastic type and be sure to put the writing on the diaphragm on the oil side.

Use 30 wt non-detergent oil. It is difficult to fill it with oil as the air in the crankcase has to very slowly leak out as the oil is added. Plan to fill it 10 times at 5 min intervals.
Also, be sure to unscrew the bolt on the gear reduction--make sure the gear oil is up until it runs out of the oil-check plug--use 90 wt gear oil.

01-16-2009, 05:59 PM
Thanks you guys, that helps alot!