Brake's and Vacuum Pump

[Alaskaman]

I recently bought a 1993 F250 with a IDI Turbo Diesel. It needed some work on the Brakes and fuel leaks.

All the brakes, rotors, drums, calipers, booster, master and wheel cylinders have been changed.

I can tell I have vacuum, but the truck doesn't stop well. Hard pedal, but not much assist.

I've checked the vacuum and it will read up to about 17" of mercury until you apply brake pressure and it drops to 4" of mercury.

I just want to verify, do I need a new pump?

Thank you.

 

[ABNORDY]

i fixed that same grip with a booster, found a leak

 

[Clb]

Welcome, familiarize yerself with the search button.
You found the right site....
Booster is suspect...
Look up hydroboost
We need a detailed listing of whats "changed" changed with??? New, used ,upgraded components???
Info is key to good answers you are looking for.

 

[MtnHaul]

I believe spec for the Vac pump is 20 inches. A couple years ago I put on a new Dorman pump and it was right at 20Hg after install.

 

[Alaskaman]

Thank you MtnHaul for reading the entire Post. How quickly should the Vacuum rebuild itself up?

When the brakes are applied, the Vacuum builds up slowly (20seconds at high idle).

 

[Clb]

Ok so what are you insinuating,
(read the whole thread)?

 

[IDIBRONCO]

I think that the 20 seconds at high idle is on the slow side for recovery of your vacuum.

 

[MtnHaul]

No idea how fast it should be but 20 secs sounds too slow for a system as critical as brakes. At idle I was getting hard brake pedal even with new vac pump so I swapped a used brake booster and got much better brakes while idling. Anyways, if you're only pulling 17 inches with your current pump I would replace it before worrying about other vacuum/brake specs. I don't know if this is still current info but another member, typ4 I think, had posted that the casting marks on a Motorcraft pump and a Dorman pump were the same, but of course the Dorman was cheaper.

And I have to say that after replacing every part of my brake system except for the hard lines the stopping power isn't amazing. Vac brakes are a placeholder until hydroboost. One of these days I gotta' start lookin' for an F-Superduty brake pedal.

 

[Clb]

Mtnhaul
Just cut\grind the weld off the stock pin and relocate it, hydro is great.
Op
+1 on swaping out the Booster, your still gunna need vacc. For climate control.

 

[MtnHaul]

From what I read you have to weld the pin. Right now finding a used pedal seems easier than teaching myself to weld.