2nd Gen Non-Engine/Transmission Need more vacuum

[MLee]

After the truck has sat for a period there is still vacuum in the system. not what it should be or has been in the past. It seems as the pump is not putting out the amount/volume of vacuum that it should and up on application of the brake pedal it just goes away, after a couple applications, but does come back. Would replacement of the vanes help any? I have not seen any one replace these yet, just the seals, as this would be the cheaper route to take.
Does not seem to be a leak in the system. Just not making enough volume of vacuum.
Thanks for your insight.

 

[crabman]

You can disconnect the hard plastic line that comes off the vacuum pump and install a vacuum gauge to see what your vacuum pump is making. This would give you an idea if the pump is making the required vacuum or not.
The 94-95 have vacuum dual diaphragm brakes.
If upon starting and you have brakes but they 'fade' with a couple of applications and then come back. I would check the brakes system(if the v/p is within specs. I suspect a leak in the dual diaphragm.

 

[BarryG]

While I don't have an answer for your question when my vacuum pump seal went out a couple years ago I did replace the vanes at that time. I figured with 280k on them wouldn't hurt to replace them. I did not notice any difference in vacuum but then again I didn't measure before or after either. The vanes are just a slip fit and when the pump turns the centrifugal force forces them out to make contact with the housing. They are made of stiff fibrous material that will wear away as time goes on to the point of being to short or perhaps too light to be forced out against the housing. I can say that when I replaced mine the original were a bit shorter than the new ones but not by much. They really didn't need to be changed with 280k on them. Might be worth a call to Pete Gould at Fixinrams to get his input since he deals with them everyday.
http://www.fixinrams.com/

 

[MLee]

Thanks for the come back guys, appreciate it. So being a dual diaphragm, would one be able to detect a noise of any sort. The vacuum does not totally leak away, but is as you describe it. And what should the vacuum reading be? when tested I get around 22hg. And Barry good suggestion.
Thanks.

 

[BTMaltby]

I was watching Pete Gould's video today and he talked about how the vanes can get 'gunk' on them which prevents them from sliding in and out of the recess they are in. A light sanding solves the problem. Watch his video it is on youtube.

 

[MLee]

Seen it all the way through today, before just part way. Watched the other one to he does it like a backyard mechanic. on the FLOOR.
thanks for the heads up.

 

[JWChessell]

Gentlemen: Where can I find the spec for the 2003 vacuum pump? I'm having cruise-control problems which seem to be vacuum-related. My dealer says he "doesn't know" what spec the vacuum pump is supposed to be pulling. They tested it and reported it as "pulling 11hg of vacuum, but can't tell me what the correct spec is. Anyone know? Thx.

 

[NIsaacs]

It varies based on Barometric Pressure and Altitude. Based on where you live (sea level) you should see about 28-30" Usually in low vacuum readings you have a leak.

Nick

 

[SReeves]

I put one of these on my truck,it made a big differance !I got it from summit

Mr. Gasket 3701 - Mr. Gasket Vacuum Canisters
Compare
Vacuum Canister, Steel, Black, Fittings, 5 in. Diameter, 6.75 in. Length

$40.97

 

[MLee]

So this is a canister/tank to store more vacuum, you mount it under the Power center? and it works good?

 

[SReeves]

Yes I had room on top of fender near fire wall drivers side,the canister is supplied with a check valve,now it takes several brake applications before low vacuum light turns on

 

[MLee]

Do you have pics to show your install?
Looking at the summit cat picture, there appears to be a big hole in the center of the tank, is there one or is it a plug?
A vacuum light? you install that? was it a 94 thing.

 

[SReeves]

My truck is parked 40 miles from me right now,I think it has 3 ports and a plug and a 90 fitting,as I remember,I will take a picture on Sunday and post here,on my 94 the vacuum warning switch is on fender near the canister mounting point

 

[MLee]

My truck is parked 40 miles from me right now,I think it has 3 ports and a plug and a 90 fitting,as I remember,I will take a picture on Sunday and post here,on my 94 the vacuum warning switch is on fender near the canister mounting point

Under the hood? or visible from/inside the cab. Might have to do set up like this.

 

[SnoKing]

You are putting a band aid on some other issue that is occurring! Find the cause of the low vacuum and fix it before it gets worse! SNOKING

 

[SReeves]

My truck was in spec per FSM but still lost vacuum after a few brake applications when going from drive to reverse at idle parking in a tight spot,as stated above a storage tank will not cure a leak

 

[SReeves]

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