How to test and replace a IDI vacuum pump with a grove pulley.

Big Bart

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Recently while towing a loaded a trailer I came off the freeway off-ramp to find out my power assist brakes were not working. Fortunately the light was green, there was no one in front of me and I could just take a left at the end of the on-ramp and slow down to a stop with the 40% braking I have without vacuum assist.

Adding insult to injury this happens to be my only trailer that has surge brakes, which did nothing to help me out. One of many reasons surge brakes suck! Go electric when ever possible!

Too boot, my low vacuum brake warning light did not come on to warn me there was an issue. So I need to look into that and fix that too.

Some lessons and some things to remember -
1) A vacuum guage in your gauge cluster as a back up would be a good idea. (Many members have installed these.)
2) Your brake booster will have one power assist left if your vacuum pump or system quits. (So make it count! It stores the vacuum in the booster.)
3) I could have used the e-brake too if I had to stop, but that could also be problematic while towing if they locked up or while I was in the turn. But if someone was in my way, I would have pushed the pedal till the tires locked up. While continuing to hold the brake pedal with my right foot.
4) I also could have downshifted if needed.
5) O-Rielleys Auto will lend you a power steering puller if you do not have one. 90% of the folks who do not use a PS puller ruin their pulley! Buy or borrow one! In a pinch you can buy the pump and the pully ($50) and using a grade 8 bolt and thick washer press the pulley onto the pump shaft.
6) O-Rielleys Auto warranteed my pump, saving me a bundle. If you have replaced yours already keep that in mind. Your auto parts store may have a warranty on your pump.

Here is how I went about it - (Sorry the site only let's me post 5 pics.)

Tested the Vaccum at the inlet to the VRV valve

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Removed positive battery cable on BOTH batteries to avoid issues arcing out on the alternator during the job.

Loosened alternator belt with a 9/16 wrench.

Loosed vac pump belt with the two 10mm bolts on front of the vacuum pump bracket and removed belts

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Removed both 10 MM bolts, pulled out pump, and removed the vacuum hose.

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Used a power steering pulley puller to pull off the vacuum pump pulley. (WARNING – Many try, most fail, do not use anything other than a power steering puller! You will be out $50-100 and have to wait to get one shipped. )


Used a power steering pulley puller set to put the pulley back on. (In a pinch a grade 8 bolt and washer. ((Bolt, washer, and nut if you do not have the right length bolt.)) If you put this in a shop press you are likely to pop the bearings out of the pump. (Ask me how I know? :) )

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Reversed the procedure to re-install the vacuum pump.


WARNING - READ YOUR INSTRUCTIONS, SOME MEMBERS HAVE BOUGHT PUMPS THAT ARE NOT PRE-FILLED WITH OIL. YOUR INSTRUCTIONS MAY TELL YOU TO ADD OIL, IF YOU DO NOT YOUR PUMP WILL DIE ASAP!



Retested for vacuum (Good reading, pulling about 26 in hg)

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Removed vacuum gauge and put VRV vacuum supply hose back on.


Vacuum pump replaced and my brakes worked again!

Some other thoughts

  • If your belts are marginal replace! Your brakes are important, your life and your loved ones are worth more than $50! (Mine were newer.)
  • Fix your low vacuum brake warning light if it does not go on with low to no vacuum. (I got lucky and had a green light and no traffic!) I was not aware it was broken, it used to work. (Need to address.)
  • Think about installing a vacuum gauge in gauge cluster as a backup!
  • Replace the vacuum lines if old, hard, or cracking! As mentioned above its not worth getting hurt over a few bucks. (I replaced mine a couple of years ago.)
  • If you have a C6 you may have to adjust your VRV valve if you are shifting later than you prefer. (More vacuum, later shift.) (Had to move it some as the shifting was about 500 rpm later than prior.)
  • Only use a power steering puller! ($40-50) You will damage the pulley or pump trying to use jaws or a shop press!

This is a fairly easy job if you have a power steering puller. ($40-50)
 
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BW42

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Add one thing to the list -- Drove my 93 7.3 idi one day, hit the brakes at a stop sign -- no power assist. Almost broke the springs in the back of the seat, but got it stopped. After I got back home, started checking. The first thing I checked was the check valve into the brake booster. Pulled it out -- the grommet was cracked and a piece fell out. Bought a new check valve that had a new grommet (two sizes) -- fixed the problem -- bW
 

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