SOOT4BRAINS

My vacuum pump has been leaking and making the whole underside of my truck nasty with oil. I didn't find any info in the sticky so I figured I would take some pics and post some info on it. A rebuild kit is available from cummins, part # 4089742 and it is around $9. This is the only rebuild kit available, but I believe it is for a slightly different application. The instructions depict a slightly different type of rear housing where the power steering pump mounts to it. The o-ring provided for this location is slightly different than our trucks. After talking with cummins they said to take the o-ring and stretch it to fit my housing. The difference in diameter is about 3/8 of an inch. The provided o-ring has plenty of stretch and went on without feeling like it was going to snap. I am just guessing but I would say cummins is just trying to make one kit to service both types of pumps.

To start with, unhook the negative terminal and make sure the truck is on good solid ground with the e-brake set. Raising the truck is not necessary.
Take off the vacuum supply line and the power steering return line. I cut my return line as I could not get it loose from the pump. Turns out it has some sort of glue to hold it on and that's why it didn't want to come off. There was plenty of slack in the return hose to snip an inch off the end.


Head under the truck and bring a 15mm, 10mm and some flare nut wrenches.


Next unhook the power steering high pressure line and the oil supply line for the vacuum pump. Then remove the lower bolt holding the vacuum pump to the gear case. Also remove the small support bracket at the front of the power steering pump that goes to the block.


After you let all the excess fluid drain from the power steering pump remove the top bolt holding the vacuum pump to the gear case and pull it out until the gear clears the housing. Drop the front down and pull the back up a bit.


Then finagle it out the top.

SOOT4BRAINS

Now remove the 3 nuts holding the power steering pump to the vacuum pump. There are 4, but one is removed when you take off the small support bracket. The 2 studs on the passenger side of the power steering pump have spacers.


Next remove the 2 nuts on the back of the vacuum pump. They are 17mm.


You may need to tap it apart with a small rubber hammer. Inside there is a drive star that turns the power steering pump. The o-ring on this part is the one that you have to stretch to get on. Put a little oil on the o-ring. You can see here that this is the main spot mine was leaking from.


Next remove the 3 small bolts holing the next section together and tap it apart and replace the o-ring.


The one in the kit is a little thinner than the factory o-ring, but seals just fine. Put a film of oil on the new o-ring.


Try to keep it as clean as possible. Now put the bearing housing back on the pump body and tighten the 3 10mm nuts back down.
Next we need to replace the seal in the rearmost housing. This seals against the power steering drive shaft. You can see it in the housing on the right in the picture below. You can use a socket to catch the lip drive it out and a little larger socket to drive the new one into place without damage. Lube the seal before install.


Next put the rear hosing back on the vacuum pump. Don't forget the drive star that turns the power steering pump. Then tighten down the 2 17mm nuts.
Next do a visual alignment of the power steering shaft and the drive star in the back of the vacuum pump and mate the 2 back together. You may need to turn it a bit to get them lined up. Don't forget the two spacers that go on the power steering pump studs. Tighten up the 3 nuts to hold it together and its ready to go back on!

SOOT4BRAINS

If you are really ambitious you can clean it all up, mask it off and give it some new paint. I painted my vacuum pump silver and the power steering pump black. (I did this before putting them back together)



Putting it back on is just the reverse of removing it. The new gasket for the gear housing is not meant to have any sealer on it. I put a new o-ring on my power steering high pressure line while I had it apart. Tighten it all up, put some power steering fluid in it. (mine took a little less than half a quart) Fire it up and let it run for a few minutes and turn the wheel back and forth a few times to work any air out of the steering system. Shut it down and check for leaks. Now go inside a toss back a few!!

Here's a pic of it all put together.


Its not a bad job at all. Could be done pretty easily in an hour. I hope this shows some appreciation for all the help you guys provide me with!!

Aaron

jimbo486

way to go! the silver looks good too!

pulltilbroke

Sticky worthy!!!

dzl_damon

Oh man, the IC vacuum pumps come apart and go together WAY easier than the I/C ones! No gear to press each way. Good write up.

sdseva

sweet! great job

wannadiesel

I agree.

When I did mine, I pulled the PS pump off the vacuum pump and just left it sit on the frame rail while I pulled the vacuum pump. Then I put the two pumps back together before stabbing the vacuum pump back into the case. If you try to put the PS pump on the vacuum pump with the vacuum pump mounted to the engine, you will drive yourself nuts trying to get the drive aligned...

Fred Swanson

soot, did you replace both orings? The standard Cummins kit for the 91-93 IC trucks is missing that 2nd oring, and you have to ask for the other one. That's what I found when doing the one on my 93 truck.

Trebor

Nice write up but isn't this more of a "reseal" than a "rebuild" or am I missing some key points that I may have overlooked? Does the Cummins kit include the impeller blades or is there a Cummins part number that that includes those in an complete overhaul kit? Is there a replaceable bearing/bushing insert that the shaft runs on? I have one that I want to do but I want to do a complete overhaul.

dieselJon

Trebor, judging by the $9 price tag, just the seals and O-rings.

whereswaldo250

Real nice write up Soot, I'll be calling you up for some help with mine, its doing the same thing.

Totallyrad

Very nice write up! I'm going to add a couple links that might also be of assistance.

https://www.dieseltruckresource.com/...html?p=2735006


http://www.fixinrams.com/

deerslayer1979

So the double head pump is $146.xx with both heads? How much better does this work compared to the factory vac pump? My truck leaks a bunch right now and the brakes are spongy all the time. Sick of pumping them all the time and towing is a real treat!
DS79

SOOT4BRAINS

Sorry, should have put reseal and not rebuild. Trebor, I did not look into new blades for it or new bushings. Mine looked almost new. It had no shaft play in the bushings and the case and impeller blades looked fine at 160xxx miles. Fred, the kit I got came with both o-rings in a sealed bag with the gasket and power steering pump shaft seal. Although as I stated at the top, the second oring had to be stretched to fit on there. Its been a few days and a few hundred miles and no leaks yet. Ben, just let me know when you're gunna do it and I'll come over and help you.