I decided to build my own pipe dent remover using the hydraulic (water) method. It was quite simple, as long as you have a drill press (or a friend with one and some beer) you should be able to get this done. This method is much safer than the air pressure/torch method, but both methods you need to take care and know of the risks.
Items to Purchase:
- 1-1/2" to 2" bearing puller. Note the throat diameter of my pipe was 44mm.
- Bolts and washers to suit bearing puller, approx 1-1/2" long. They are likely 3/8" bolts about 2” long.
- Qty (2) 1" rubber expansion plugs (normally used to close a block heater port in an engine block), get these from your local auto parts store.
- Long carriage bolt to suit placing the two rubber plugs on (it's likely 5/16" thread)
- Plumbers tape
- Pipe hydrostatic pressure test hand pump rated to 50 bar or more. This is what I used, but theoretically even a grease gun will work, it will just take longer as it has low volume. I purchased mine off Alibaba.
- Old HD inner tube
- Teflon tape
- Rubber adhesive
- NPT Hydraulic fittings to adapt your pump to your 1/2" plate (this will vary depending on your build)
Cost: <$100 CAD (for reference, does not include cost of tools)
Engine Side Build:
1) I drilled (2) 1/2" holes to suit the holes in the bearing puller, measured out from the center from the plate. The distance between the hole locations were measured by first clamping the bearing puller to the throat of the pipe, then measuring the distance between the puller holes. Ideally these should be slotted holes so that you can do varying sizes of pipes. That's my next step, I'll probably have a friend machine mine into slots. There was a slight difference between my OEM pipe and my Gnarly throat diameters, I ended up just using a carbide grinder bit on a dremel to oval mine out a little.
2) Drill and tap an NPT hole to adapt to the pump hose, I used ¼” NPT.
3) Cut a piece of old HD inner tube to suit the plate, and glue it on. I used 3M spray adhesive I had kicking around, but rubber cement should work as well.
4) Attach your fittings and hose to the pump and plate.
Just a side note that I did grind my bearing puller to match the throat of the pipe just a bit, even a round file works fine so that you get the correct radius.
Silencer Side Build:
Take apart your rubber expansion plugs and reassemble and stack them on the new carriage bolt. Mine came with a small o-ring at the head of the square of the carriage bolt which I reused.
I think 3 plugs would be ideal and my cause less slippage. It may also be a good idea to roughen up the rubber somehow so that it grips better, as this rubber is quite smooth.
Assembly and Use:
Watch this first as it explains a lot:
Clean any carbon off the engine side throat so it doesn’t leak. A wire brush should work for this. Assemble the bearing puller to the throat and tighten it up, then place the plate over the holes so the old inner tube seals the throat.
Tighten up the plate to the bearing puller. You don’t need to go crazy, just make sure you tighten down evenly and that there is a bit of resistance. If it leaks you can tighten a bit more.
Clean carbon and oil out of the silencer side as well, I used a bit of contact cleaner and had a 1” wire wheel I was able to fit into the pipe. I used a cordless drill to clean it out this way.
Next, fill the pipe completely with water. Keep rotating the pipe around to make sure there is no air in the system.
WARNING!! IF YOU HAVE AIR IN THE PIPE YOU ARE ESSENTIALLY CREATING A GUN, BE VERY CAREFUL WITH THIS STEP! ASK MY GARAGE CEILING HOW I KNOW!
Next wrap a piece of plumbers tape around the top expansion plug, and stuff the works in the pipe. The water should be at the tip of the silencer side at this point, and as you push the plug in water should be spilling out so as to ensure there is no air inside.
Tighten this plug down really well, until you don’t feel you can tighten it anymore. This is effectively squishing the rubbers together to create a seal, and gripping the rubber against the plumbers tape and pipe to create friction and prevent the plug from coming out.
Wrap some safety wire around the end of the plug and around the pipe somewhere so that in case you do mess up (ie/ have air in the system), the plug doesn’t shoot out.
Make sure the silencer side plug is facing away from anyone in case you do have air in the system.
Slowly begin pumping. If you notice the pressure is not climbing after even the first pump, you have air in the system, stop what you’re doing, release pressure at the pump, and bleed any air out.
You will need to pump to 500-600 psi. With thicker pipes like the Gnarly, I needed 600 psi. I then used a small hammer and hammered around the outside edges of any dents left, and they will slowly pop out. I chose to do this instead of pressurizing further as I didn’t want to damage the pipe or risk a weld bursting. This was also about the reference pressure in the video I linked to.
Sometimes you will have pinholes in your pipe, and a small mist of water may come out. If water is enough to flow out and you can’t build pressure, you will need to get the holes welded first before this will work.
Lastly, release the pressure on the pipe by the relief valve on your pump. If you’ve got a different setup make sure you add some way to relieve pressure, and measure pressure with a gauge.
Disclaimer: I can not be held responsible or accountable for any damage or injury incurred from anyone attempting this. Safety is of utmost importance, do not attempt this if you are not comfortable using pressurized water or using any of the equipment.