Ingersoll 448 Bypass Is Too Low

[ssmewing]

I have had this Ingy 648 for a couple of years now. For me, there are always known issues.

I already tore into the running engine to get it from running to running right. I missed an issue that I cannot believe I missed. The oil filter gasket that is used to mount the oil filter to the engine will often leak. This is not the rubber seal to the shroud that costs $10ish and has caused probably half of the engine failures for Onan engines that use them. So, this gasket and the mounting bolts are under the front shroud. I will get to that one day, but it sure does urk me that I did not do it. I keep two gaskets in my box because the leak is so common. The first gasket used was cork. They all leak at this point. The newer material gaskets should never leak. But, if you do not do it right...

That was not my point. My 648 is bypassing at 1,500 psi, which means that even using the power steering makes it squeal. The 648 comes with a holding valve. The holding valve makes it impossible to get at the bypass cover nut. I had already dropped the oil when I checked the one-model-only factory filter screen for the loaders before the 4-digits. I found a lot of rubbery material in the filter. I also noticed that the curl function was flopping in one direction. I then looked at the parts diagram and saw that the curl cylinder had a rather large seal that I easily connected to what I had found.

I need to bench-test the bypass with the hydraulic system that is now open for access. Could there be seal debris in there? Or has the bypass setting been wrong all these years? I am betting the setting has been wrong all these years. I left the test gauge on the tractor for almost a year after cleaning out the filter screen. The bypass is exactly at 1,500. It was never lower or higher. But since I am bench-testing it, the jump to removing the bypass stuff is pretty straightforward.

The bench test oil pump procedure is on page 17 of the Case hydraulic test manual. I have the exact grease gun the manual calls for. But I have to go from 1/8" NPT to the JIC 12 (I think) of the oil input on the control valve with the work ports capped.

It all seems straightforward. Has anyone done this before?

The strange but kind of assuring thing is I had saved a link that showed that you could reach the adjuster screw through a hole in the frame. And this was on a 648. And this other 648 also had exactly 1,500 psi at the bypass. He kind of left it dangling. His 648 was an early version and did not have the holding valve in the way. I have the later version of the 648, and my version has the external holding valve as standard. This other guy was able to access his bypass cover nut with the hydraulic system intact and used the test port gauge to check it as he went a quarter turn at a time. He reached 3/4 of a turn and was close to 2,400 psi. And then, nothing.

[ssmewing]

https://photos.app.goo.gl/FNyBw7hQR5Sit9ZS7



I am trying to post a video. I use Google and Android. So, I am not sure that this will work for you. It worked for me, but I have the program that created it and the file is on my account.

[Spike188]

@ssmewing The video works for me. Thanks for posting. That is another winter project on our 646.