Last week my vacuum pump went out. I swapped it by separating the ps pump and vac pump in the truck and just pulling the vac pump out (probably a mistake in hindsight).  Once I got things back together I had vacuum but now no power brakes (hard pedal) or steering.  I had a spare (unused reman) ps pump so I swapped that and went through the procedure for purging air from the system but I still have zero power brakes or steering.  I also flushed the old fluid by routing the return lines into a bucket and noted lots of flow so I know the pump is pumping.  If I do the purge procedure slowly and at idle only nothing special happens but some combination of raising the engine rpms and moving the wheel rapidly causes the pump to belch fluid. Does this indicate that I still have air in the system or some other problem?  I also noted, while experimenting, that there is very little return fluid from the hydroboost line, mostly just from the steering rack.  I don't know if this is normal though.  BTW, I suspect that my old ps pump was probably fine and that I may just not have had it fully seated in the vacuum pump when I re-assembled it.  Is there something that could be wrong with the re-man pump that could be causing the problem even though there seems to be plenty of flow? 

 

I've read quite a few posts about similar problems but mostly people just seem to keep swapping parts until it starts working, flush the fluid, or keep purging air.  Is there a better way of properly diagnosing exactly what is wrong?  Any help would be much appreciated, I'm about out of good ideas and really need to get this thing back on the road and myself back to paying work.

 

On 12/15/2024 at 8:36 PM, Tractorman said:

Place the vacuum pump unit in a vise.  Make a suitable tool that can be operated with a wrench to engage into the jaw coupling hub.  Have helper hold the gear from rotating with the use of a strap wrench.  Using the newly made tool and the wrench, try to rotate the coupler in the opposite direction of normal rotation to see if it slips.  Use your best judgement on how much force to apply.  If it slips, you have your answer.

 

@RayNAz, did you skip this step while you had the unit on the bench?

 

- John

22 minutes ago, IBMobile said:

There should be power steering and brakes immediately all though it may be jerky and noise from the system due to the entrained air and slowly go away in a day or two.  There is flow so the pump is delivering fluid but is there pressure?   I think you have "3.  That pressure regulator in the pump has gotten stuck open and even though there is flow the pressure is too low to do the job."  If the high-pressure line/hose was blocked there would be very little flow and the pump would be making a noise as if the steering wheel had been turned to full left or right with no let up.   You may want to remove the pressure relief valve and inspect it.

 

Thanks !  The fluid was pretty old when I started this whole mess (since flushed) so it's certainly possible that the screen got clogged when I was maneuvering the pump out of the truck or the valve is otherwise gunked up.  I'll pull the fitting and valve etc and have a look.

 

1 hour ago, Tractorman said:

 

@RayNAz, did you skip this step while you had the unit on the bench?

 

- John

 

Completely forgot but I'll check when I have it out to check the pressure relief valve.  I did take measurements as you suggested and that, at least looked acceptable.

You can remove the flow control / pressure relief valve cartridge without removing the power steering pump.

 

- John

Anyone know what size wrench/socket is needed for that fitting?  It looks like about 26mm or 1 inch but I thought I'd ask.

I can't remember exactly but it's either a 15/16 or 1". 

I just want to follow up and let everyone know that Tractorman called it.  I pulled the Vac and PS pumps, separated them, and used a 1/2 inch open end wrench to engage the dogs on the Vac pump and vise grips to turn the wrench while holding the gear side of the pump.  It didn't take a lot of torque at all, probably single digit ft-lbs to get it to slip.  I'm still kinda surprised that it was producing significant flow like that but it was.  I swapped it at NAPA and re-installed, purged the air, and was back on the road. 

 

At this point I have a small drip coming from where the oil feed line connects to the fitting on the Vac pump.  I've tightened it as much as seems wise and will probably have to replace the fitting.  Does anyone know of a compatible fitting available at the normal auto parts stores?

 

Thanks again to everyone who helped out with ideas, pictures, diagrams etc.  Good stuff.

 

Thanks for the followup report and I am glad that you are back on the road.  At least you had the stamina to stick with it and figure it out.

 

20 minutes ago, RayNAz said:

At this point I have a small drip coming from where the oil feed line connects to the fitting on the Vac pump.  I've tightened it as much as seems wise and will probably have to replace the fitting.  Does anyone know of a compatible fitting available at the normal auto parts stores?

 

The actual hose connection is a 1/4" 37° flare (female on the hose side and male on the fitting side).  I don't know the size or type of the end of the fitting going into the pump body.  Usually this type of fitting is called an adapter fitting.  If you can't get it figured out, let me know - I have a used vacuum pump in the shop with the fitting. 

 

Make sure you have the correct style and know the thread pitch, thread diameter, and whether it is metric or domestic.  It can get very confusing quickly and you could ruin the threads in the pump if you install a fitting that is very close, but not correct.

 

- John

19 hours ago, RayNAz said:

Does anyone know of a compatible fitting available at the normal auto parts stores?

 

I just pulled the fitting from my old vacuum pump.  The fitting is and straight adapter -  1/4" 37° male JIC x 1/8" male pipe.

 

Before you replace the fitting, confirm which connection is leaking.  If it is the JIC flare part that is leaking, try loosening the fitting just enough rotate the piping back and forth - be gentle.  Keep the fitting tight enough to maintain some friction.  Sometimes there is a burr or some surface irregularity that can be smoothed out by using this approach.

 

If you have to replace the fitting:

 

*  Apply pipe tape or sealant (oil compatible) to male pipe end.  This type of fitting is tapered and seals by thread interference as the fitting is tightened.  Tape or sealant seals the potential spiral leakage that could occur around the threads.

 

- John

Edited January 11Jan 11 by Tractorman