Ayc/acd pump won't build pressure.
 

Hey everyone I am having a bit of an issue with my acd/ayc pump on my 01 Evo 7. A couple of months ago my relay stuck on and burnt the motor on the ayc pump out. I have since purchased a second hand pump and had it rebuilt by my local Mitsubishi dealer. Firstly I installed the pump myself and tried to bleed with the accelerator method, hard wiring the pump and also having all 4 wheels off the ground turning left to right ect ect ect all on seperate occasions. Nothing seemed to work so I took it back to the dealership and they put their special tool on to try and bleed it properly but the pump still won't "build any pressure" ( their words). They have taken the pump out and examined everything even tried the old pump with the good second hand motor and tried to make 1 out of 2 potentially good pumps. They say they have tested the pressure sensor and it's fine all the actuators are working fine but it just won't build any pressure to bleed. They don't have any other solutions and have basically left me without a solution or where to go next. I am fairly capable at doing my own mechanical work but this has just left me stumped. My question is has anyone had something similar happen to them and if so how did you fix it? I don't like driving the car without the ayc working and it's basically a weekend car that I don't even want to drive at the moment.

Could be the seals in the AYC or ACD clutch packs.

Hmm could be, the fluid will run out of the 2 bleed nipples in the diff but I can't get more than a few drops at a time up the front nipple also

I think it was not rebuilt properly, not put togeather properly and/or it has enough air in the pump inlet so that the fluid will not reach the pump (dripping you see being from fluid return port)

those pumps are sometimes hard to bleed initially..

basically need to check it one by one, and try running the pump on the bench first.. and dont use the original reservoar for it but just some clear hose..

Hook up a vacuum bleeder to the bleed nipples and pull the fluid through. It's how I bleed all of mine, and it works perfectly.

I think I read on here somewhere that you can pre prime the pump before putting it in? Any idea what that involves?

Also after attempted bleeds when I have removed it there is plenty of fluid coming out of every hose and hard line it seems to be that it just won't pressurise the fluid enough for it all to work smoothly

That points to an issue with the pump, or the seals in the clutch packs.

when the diaphragm in the clutch pack is broken then the system looses fluid but the pump still has to make pressure...

you have to test the pump on the bench... hook up a celar hose to the inlet (larger dia tube) and fill with fluid, run the pump with 12V on the motor.. you should see the pump taking fluid in..

chances are the pump was put togeather wrong, happens quite often. Also, due to design of the inlet tubing, it is hard to get air out of the inlet tube (on EUDM/JDM cars). When the pump was tested on the bench the pump gear is allready wet and makes better vacuum to start taking the fluid in..

Please elaborate. I will be relocating my pump and reinstalling my TRE ACD T/C soonish and will be needing to bleed :lol:

Exactly what I said. There is a bleed nipple on the bottom of the tcase, open it, hook up vacuum bleeder, and pull fluid through. Make sure you don't drain the reservoir while bleeding.

I've got a mitivac. Sounds like I'll get to use it. Thank you for the tip!

when you bleed by using a vacuum on the nipple you are pulling fluid from the return line of the fluid reservoar. Problem with this method is that you will bleed the air from only the high pressure line from the pump to the ACD/AYC diff but not the pump itself...

however, if the pump was running ok initially, as in this other case, then it should be ok.. I still like the full throttle method more.. :D

I have done my method countless times. It has never been an issue.

Quick update, seems the dealership was got the pump working correctly but they don't seem to know that they've done it. I picked the Evo up last week with no charge because they claim it wasn't working, just drove about 700kms over the weekend and the acd system was active the whole drive... Not sure what they thought they were doing wrong but all is well now thanks for the replies everybody