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Braking issues, need help asap.

The_Hammer
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The_Hammer

The_Hammer

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My brakes just started acting up, the pedal gets hard and can barely stop. I have vacuum brakes and not hydroboost. I pulled the large vacuum line out of the booster to inspect it and when I did you could hear it suck air. This was after the truck had been sitting for 15 minutes or so which means I don't have a vacuum leak.

 

I have no fluid leaks anywhere and the master cylinder is still full. Only thing I can think of is the booster just took a dump.

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The_Hammer

The_Hammer

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Here's where I'm at. There was a vacuum leak around the vacuum pump check valve that screws in to the vacuum pump, it's not leaking anymore as at broke right the EFF off. So, where the hell does a person find one of these check valves?  

 

Not my picture but this is what happened to mine, except I still have to get the rest of the fitting out of the pump.

 

391650d1436212595-vacuum-pump-check-valv

Edited by The_Hammer
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The_Hammer

The_Hammer

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10 minutes ago, Me78569 said:

use the part number lookup tool to find the part number and go to the dealer.

 

 

Was reading on Cummins forum that it's a discounted item.

 

Once I get the threads out I'll see what size it is and order a fitting. 

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The_Hammer

The_Hammer

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Got the rest of the threads out. I'll head to the co-op in the morning and see if I can match up a new barbed fitting. 

 

I'm also going to replace the master cylinder since my pedal would go to the floor if you held it even before the vacuum issue. Does anyone know the difference between the 7500 gvw and 8800 gvw master cylinders? Will the 8800 gvw cylinder work on a 7700 gvw truck and if so does it offer any performance benefits? 

 

Found yet another vacuum leak, the line going to the vacuum pressure sensor was split. Tried to remove the line and the plastic nipple snapped off on the pressure sensor. WTF is up with everything breaking today? Damn already. 

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The_Hammer

The_Hammer

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17 minutes ago, Buzzinhalfdozen said:

When it rains it pours. Sounds like it's time to start over and just replace all the vacuum lines. 

 

You say that as I'm still repairing my house from a literal flood we had a while back smiley_abused.gif

 

I'm for sure replacing all the lines, they're cheap and easy enough to replace. Hopefully everything will still work on without the pressure sensor.

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Buzzinhalfdozen

Buzzinhalfdozen

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1 hour ago, The_Hammer said:

 

You say that as I'm still repairing my house from a literal flood we had a while back smiley_abused.gif

 

I'm for sure replacing all the lines, they're cheap and easy enough to replace. Hopefully everything will still work on without the pressure sensor.

Cold hearted humor I know but it was too easy to pass up. Best of luck with the house and vehicle repairs.  

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The_Hammer

The_Hammer

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Well the pump threads are 12mm 1.25 pitch, something no one around here has. I'm going to try brazing the old one up and ordering something. If worse comes to worse I'll get a seal kit, pull the pump, then drill and tap it to a common size. 

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The_Hammer

The_Hammer

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39 minutes ago, Mopar1973Man said:

That sounds like a OK plan to do. Don't have much choice unless you want to just replace the entire vacuum pump which may be rather expensive.

 

Well, it seems the fitting I need doesn't exist. Why the *&$#% they decided to use such an uncommon thread size is beyond me.

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The_Hammer

The_Hammer

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Replaced the master cylinder with a brand new (not reman) unit and the brakes feel great. If you pump up the brakes and hold down on the pedal it will still slowly sink down but not bottom out. I'm guessing there might still be some air in the lines?

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