jimbo486

I heard the vacuum pumps on later models with hydroboost were "smaller" pumps. I'm assuming, less vacuum capacity?

PapeCAT

Might want to call Pete Gould and ask that one, I'm not sure. They are more compact. Pete did also say that the early diaphragm style pumps can be used with 1 diaphragm blocked off and it still makes enough vacuum for the brakes. So maybe there is quite a bit of extra capacity built in to compensate in case of leaks, not sure.

jimbo486

Capacity wasn't mentioned in what I read over on Comp D which is why I only made an assumption.

PapeCAT

The other thing is, the earlier pumps are reman only and more expensive. 250 at rock auto and 400 at O'reilly's et al.

The later pumps are 175 for a new dorman or 250 for a new A1 Cardone.

jimbo486

I certainly like the idea of new. And they definitely are cheaper seeing it now!

The i/c motors do have a longer 3-bolt support bracket for the injection pump. I imagine utilizing the factory bracket and short piece of pipe as a spacer should work just fine.

Have you been running the new pump long? What can you say about brake performance? Have you checked to see how much vacuum it does pull? I deleted one of the diaphragms on my pump years ago and the lone pump was still capable of pulling 18in Hg, verified.

jimbo486

I think this question raises a good point as to the vacuum pump capacity of the later model trucks with hydroboost. The PS pump is what assists with braking in a hydroboost setup. Thus, the vacuum pump would then only be used to actuate some of the diaphragms that control the blend and recirc doors in the HVAC system and any other accessories. It makes sense to me that a lower vacuum would be required.

Just my opinion.

Now, however, I stumbled upon someone with a '99 model who said he verified 30in Hg from his.

I stand corrected.

j_martin

Vacuum pressure requirements would be the same. Volume is what changes. Very little needed for heater controls.

PapeCAT

What is the PN for the three piece bracket? The PN for the little angle bracket is 3919619

jimbo486

That I don't know. A guy named Jeff at Mumau Diesel could certainly help you out.

Hmmm well, maybe I got ahead of myself. I just took delivery of the 2000 model vacuum pump. Although the vacuum pressure is a little higher than my factory (and other vein types), will the volume be significant enough to be an issue in power braking assistance? Or should I suspect a stiffer brake pedal and a decrease in performance from the vacuum pump?

Jim Lane

So what all is involved in converting to the rotary vacuum pump, also what are the differences in the power steering pumps between non-IC and IC as far as pressures and fitting sizes?

Where do you find such parts in a Cummins dry state?
Jim

DOZENVALVE

Mine never even had one. It appears to have part of the bracket system but it looks like it's missing something where it connects it to the block

PapeCAT

From my convo with Pete Gould, and due to the fact that he recommended one as a replacement for my non i/c style, I suspect you won't notice a decrease in vacuum performance. You can always give him a quick call though.

Hi Jim,

to make it a factory swap, you will need an oil line from the block to the pump, the longer style bracket and "L" bracket support for the pump and a later style power steering pump. (The non i/c style is different but the plugs/studs will swap over.

ebay # 131328567186 for instance.

I wonder how necessary the support bracket is. I tried fabbing my own but with the angled/compound bend, I had a hard time getting the right angle/depth. I didn't want to put a preload on the pump with an ill fitting bracket as I believe that is one of the main reasons we see the cast aluminum pump ears breaking off.

jimbo486

I/C injection pump 3-bolt support bracket P/N: 3918949, Position #6 pictured below. I found an ESN from my '91.5 parts truck I sold. I forget about my Cummins Quick Serve account sometimes .



Pete really seems to know his stuff and everybody who mentions him has nothing but good to say about him and how knowledgeable he is. I'd trust his recommendation.

I received the vacuum pump the other day and today, the man in brown delivered my new Redhead steering gearbox. I went with a higher ratio (15:1) box as opposed to the factory ratio box at 18:1. Only difference is half a turn of the wheel. Factory will take 4 turns to lock, the 15:1 box will take 3.5 turns to lock. Not much.

jimbo486

Also, the vacuum pump support bracket (P/N: 3919619, position 5), the oil supply flex hose (P/N: 3925100, position 14) and the male-male 1/8" NPT fitting into the vacuum pump (P/N: 68138, position 1).

jimbo486

Aaaaaand apparently, mine already has a 3-bolt support bracket. Maybe it's just not threaded like the i/c brackets are?