Hydro-Aire #8: Dump Rebuild
Attention: Welcome to our new aircraft hydraulics section! We hope you find this section we have put together informative and interesting. You may notice that some part numbers and so forth are blurred out. One reason we didn't want to post full part numbers because it has taken us months of searches to get the information we have. It wouldn't be fair to us to just give up our hard work and research. Not too many people know about this stuff and the ones that do don't want to talk about it. We feel this is just the right amount of info so we don't upset anyone on either side. The biggest reason for not giving out full part numbers is because we don't need every lowrider to call up aircraft surplus places looking for things. Most warehouses don't want to sell to lowriders and the ones that do are raising their prices beyond a reasonable amount because people are willing to pay to much for stuff the warehouse considers junk. Lets keep prices down and think about it before you offer a insane amount for a used pump that needs a rebuild. If you are going to track parts down don't say that it is for a lowrider. Know what the full part number is, what aircraft it goes in, the proper name for the part and the function of that part. Take the time to research the surplus industry and know the lingo they use. Remember not to use lowrider lingo when talking with them because odds are they have a different term for the part you are looking for. With a little research and some luck you'll be able to find what you need.
Warning: If you are unsure about doing anything do not attempt the take apart the dump. Internal parts like the spool and sleeve must be flawless and not scratched. Remember the old saying " if it isn't broken don't fix it. "
When you own a original square dump like a Hydro-Aire #8 you will see that the valve will eventually need new seals. This article is also helpful if you have a round bottom valve with a cracked valve body. Don't throw away a valve with a cracked body because the internals can be swapped out or a machine shop can machine up a square valve body. When you have old parts such as dump valves getting your hands on a rebuild manual is not always an option. But if you can get a manual buy it...
In this section we will tear down a round bottom Hydro-Aire #8 valve, inspect / replace seals if necessary and check the spool and sleeve. Lets take a look at how Jay rebuilds these dumps.
If you need help, want to send out your valve for service or have questions please contact Jay
Remember where you saw it first!
Above: Here is a Hydro-Aire #8 valve that needs to be inspected internally. Make sure you work on a clean white towel when servicing a valve.
Above: At this point you would cut any lock wires in the four screws holding the solenoid on the valve. Take out the four screws with a screwdriver.
Above: The screws are removed from the solenoid.
Above: The solenoid will slide right off.
Above: You will now see the plunger once the solenoid is off. The plunger moves up when the valve is dumped because it becomes magnetized when the solenoid is on. Notice how the plunger base is recessed around the plunger.
Above: Using a small screw driver very gently pry underneath the plunger until the recessed base starts to lift. Don't scratch the plunger if you can help it.
Above: The plunger should look like this now and you can see a seal coming out of the valve body. If you were changing the type of solenoid you are using you will have to remove the plunger. In this case we are reusing the same solenoid so removing the plunger from the shaft is not needed.
Above: Using your fingers grab the plunger and VERY carefully and slowly pull the plunger, shaft and spool out of the valve body. The plunger, shaft, and spool will come out as one unit.
Above: Here is the bottom of the valve body. A locking ring holds in the end cap.
Above: Push the end cap into the valve body using your fingers. It should move about 1/4 inch in.
Above: Here is the end cap pushed in. Now remove the locking ring with a screwdriver.
Above: You should be able to remove the end cap and seal at this point.
Above: This is the end cap and seal.
Above: Remove the seal and check for flat spots and signs of wear.
Above: Here is the sleeve from the bottom of the valve body.
Above: Here is the sleeve from the top of the valve body.
Above: SLOWLY push the sleeve out the bottom of the valve body with your fingers.
Above: Jay slowly guides the sleeve out of the valve body.
Above: Remember not to damage the sleeve in any way. NEVER pry the sleeve out of the valve.
Above: You can see the valve body was machined to only allow the sleeve out of the bottom of the valve body. Inspect the inside of the valve body at this point for cracks and contamination. A cracked valve body is junk but you can get replacements or have a machine shop make a new one. This body is good so it is cleaned out.
Above: The dump should be neatly laid out on the towel to make it easy reassemble and to avoid damaging the parts.
Above: Here are the parts of a Hydro-Aire #8 dump.
Above: Now the spool and sleeve must be inspected.
Above: Here is the sleeve from the dump. Make sure no scratches were made to this part.
Above: This sleeve has good seals and good teflon back ups. Teflon back ups must have been put in in a prior servicing because a NOS valve will have leather back ups.
Above: Make sure inside the sleeve is clean and oil it with a light oil.
Above: Time to inspect the spool for scratches and contaminants. Replace the seal here too if it needs to be replaced. Clean the spool carefully and oil with a light oil.
Above: This spool looks good.
Above: The plunger on a IMC solenoid measured about 1 1/2" long.
To reassemble the valve just follow the disassembly instructions about in reverse order.
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