BRAKES.....OH I TRIED TO BY-PASS THE CUSSING FILTER

['956Wheel]

I noticed that when I pump the brakes a few times they fade. If I just stay on them there is no problem. Could this be due to a vacuum/booster problem. She's a '95 3500.
Mike

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9535hundred

 

[Joe G.]

If you are just idling the vacuum booster can't keep up with the demand. The brakes still work fine, it just takes a lot more push on the pedal. That's the reason for the later model change to the hydraulic booster. I wouldn't worry about it.

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Joe George
Eureka, CA

'95 2500 CC auto 4X4,3. 54,Combo EGT/boost guage,custom switch panel,PacBrake,TST #5,DTT TC/VB,Automatic motorhome steps on both sides,Foldacover hard bed cover,Cummins chrome kit,Black steel grill guard,Front hitch receiver

 

[sam peterson]

If in dought about the booster operation try a couple things. ---after the engine is shut down you should have a couple of pumps on the pedal with vacuum assist, then it should get hard---you could have low vacuum from the vac pump---You can tee in a vacuum quage between the pump & booster and operate the truck to see if the vacuum gets low when you pump the pedal. If the vacuum drops quite low it should recover almost instantly when you take your foot of the pedal. If not the vac pump is week or the hose may be collapsing

 

['956Wheel]

Thanks guys Sam that sounds like a darn good idea with the gauge and all. I'm the member that wound up with a "frame transplant" due to cracks on the spring towers, and I have been chasing "bugs" ever since... 6 or so weeks. Most are not major just lazy mechanics, and I tend to be critical.

Mike

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9535hundred

 

[sam peterson]

let me know how you come out---Sam

 

[LandShark]

Check the line from the vacuum pump. Mine had oil in it that caused the rubber to get soft and collapse. There is a recall for this, but my 95 was one month away from the recalled trucks and DC said it was my problem. BTW, proper 3/8" vacuum hose is almost impossible to find!

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1995 2500 SLT Club 4x4, auto, 3. 54, 3300 pound Elkhorn slide in camper, AirLift air springs, Ricka dual wheel adapters (used only with the camper on), K&N, DC tow hooks, Rancho RS9000, Hellwig rear sway bar.
110,000 miles and counting.

 

['956Wheel]

L. S. Wasn't that the recall in which a check valve was installed in the line?

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9535hundred

 

[LandShark]

The recall was about a new style check valve in the vacuum pump. There is also a small plastic check valve mounted on the brake vacuum booster container, which DC modified a few years back.

Low vacuum can cause lots of problems, including problems with braking, cruise control, HVAC, and front axle (on 4x4's). Having oil in the vacuum lines can ruin these systems to the point that they need rebuilding!

 

['956Wheel]

L. S. , Wouldn't 3/8" fuel line work as a replacement for the vacuum hose?

I'm just waiting for a break in the rain then its time to geto work!
Mike

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9535hundred

 

[LandShark]

Statland: Yea, been there, done that. Tried a few different fuel lines but they tend to collapse a little. It will get you by in a pinch. May even last a long time, but since so many critical systems depend on vacuum in this truck I think it's worth it to find the right stuff. Real vacuum line has a side wall about 50% thicker than fuel line, so it won't collapse.

I got a piece of real vacuum line from Bill Kondolay when he was in Texas a couple of months ago. It's part of some kit he sells, but he replaces the rubber vacuum line with a poly (plastic) line, so always has extra rubber line.

BTW: I tried NAPA, O'Reilly's, Autozone, and 3 different Dodge dealers for 3/8" vacuum line. No one had it, but one Dodge dealer would order me a 12" piece for about $35!!! All the Dodge dealer parts guys tried to sell me fuel line!

 

[illflem]

I was able to get 3/8" vacuum line from NAPA, but had to special order it. If I remember right it was about $1. 50/ft.

 

[sam peterson]

The power brake vac line is actually 11/32. I get it from a hose supply co in 50 ft length.

 

['956Wheel]

I changed out the brake fluid... this sucker takes a LOT of juice, 1 qt. to get it clean at the wheels. Bled, bled, bled, took her for a ride. Now I have a nice solid pedal no more mush! I did some checks on the vacuum system, as Sam recommended, all looks good and the Test of pump them a few times with the engine off... yes they start off nice and high then go a lot farther, depleting vacuum. Its funny I bled them then looked at the book #ad
, the book makes it into a major project due to ABS... the brakes work fine, can't argue with seccess!

Simple question: why do our trucks have a vacuum pump rather than taking it off the... . nevermind I forgot about Mr. Turbo... we ain't got no stinking vacuum! DUH

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9535hundred

 

[JLauwers]

Sam Peterson said it right - you have a couple of pumps on the pedal and I add: that's it. I had the same problem as yours but it was worse because I am pulling a travel trailer with my 2500, auto, 94. Try to back up a trailer, slowly, and you may be lucky to have 2 pumps on the pedal. Complained to DC in 95; as expected it was my fault they said until I drove my truck to the dealer and left it there. In 95, DC installed - free of charge - 2 additional canister - 1 behind each headlight. Still now I have to be careful, backing up, down a slope, with my trailer. This is why I have installed a vacuum gauge on the dashboard. Backing up, at a slow idle speed does not increase the vacuum. I recall in a 94 or 95 TDR magazine I complained about my lack of decent vacuum and somebody else also. This one was backing up with his boat (I think he went to far in the water) and bought immediately a new truck. Lucky he had the loot.

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Joss

 

[Missouri Mule]

We don't have butterfly on air intake system.
(general not detailed) that is why we have remote vacuum pump(94 to 96).
Gas engines are fitted with turbos also.

Will transmission line work as vacuum line it is a lot heavier than fuel line?

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Bill Thomas
Missouri Mule - 96 Wht 4X4 ST CC,5 spd, 3. 54, 8 ft bed, 1 ft high cheater boards.
99 Freightliner bl/wht FL60 ISB-5. 9 24v,215 hp,520 tq,6 spd, 3. 59 nsr,16 ft box, 19. 5 tires,Wt/gvw 11,000/23000

 

[sam peterson]

Guys---Just about any kind of line that doesn't suck shut can be used as a vacuum line on the diesels. The actual vacuum line had to be tolerent of gas fumes from being hooked up to the intake manifold on the gas motors but the true vacuum line is strechy and doesn't require clamps.

 

['956Wheel]

Sam, So a good fuel line would be allright? I don't think it would suck shut. How 'bout hydralic hose... overkill?

Thanks for your ideas on the brake diagnostics,

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9535hundred