I need to replace the front valve block, it's never been serviced or changed. The compressor seems fine, the rear lifts almost immediately but the front lags and then is the first to bottom out. Does it need to be an OEM part or aftermarket work? The price differences are crazy, $50-$250 and everything in between.

 

After market options are a crap shoot. The unbranded ones might look the same on the outside, but the solenoids don’t function. I’ve weighed a cheap one and it was 30% lighter than OEM, which reinforces that there are some internals missing.

Original blocks are easily serviced and if the solenoids aren’t seized (they can over time if moisture gets in the system due to old desiccant), they should continue working. The only parts needed for refurbishment are o-rings and you can get complete kits for all 3 blocks for $20. Aftermarket o-rings are no problem.

 

There was just a thread where an aftermarket block was proven to be junk - air lines didn't fit!

Start with a cleaning and re-build before buying new - that could solve your problem, or show you another place the problem could be.

 

Ok thanks, I'll try the rebuild first and go from there.

 

On mine, the front was sagging some overnight. I've been burned by the aftermarket many times and did not want to take a chance, so I ordered an OEM block. It was backordered for a month or so, so I decided to clean the original block. I carefully cleaned each piece and very lightly greased the o-rings on reinstall. It's been fine for around 8 months. I now have a spare OEM block should I need it.

 

Thanks for the update. I ordered the o rings so gonna try that before getting a block.

 

Do not grease the o-rings, the grease will collect any debris in the system which is usually desiccant powder.

 

Update, the rebuild was easy, some desicant residue, but otherwise everything was pretty clean. Now I need the rebuild kit for the compressor and probably just go ahead and replace the o rings on the other valve blocks while I'm at it since it was part of what I got.

So Hitachi compressor rebuild/update kit, any recommendations?

 

Suit yourself... A tiny bit of lube on o-rings keeps them from binding, twisting, or pinching on reassembly. If you have desiccant or debris in your air system, you have a problem already. I lube almost all o-rings I use. Many o-rings, like in coolant fittings, are often pre-lubed from the factory.

 

I ended up not lubing this time, have seen people say to do one or the other so tried without since it's easier to add than remove.