Vacuum Pump Leak

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May 5, 2008 | 09:37 AM

Hamberger

Thread Starter

Fleet Mechanic

Joined: Sep 2005

Posts: 1,509

Likes: 3

From: Ladner, British Columbia

Vacuum Pump Leak

I replaced my vacuum pump on my 91 F350 a few month ago because I thought it was probably time after 17 years. Was concerned about the diaphram getting old. The old pump was working fine otherwise.

The problem is the new pump is doing worse. Every once in a while the brake light stays on until I rev the engine up a bit after starting. Also the brake light comes on when I apply the brake pedal rapidly for a few times in a row.

Looks like the new pump vavles are leaking.

Has anybody ever put a squirt of WD40 into their pump to see if that will improve things?

I would hate to have to change the darn thing again, but the symptoms are getting worse and I see the brake light on more often these days.

Any feedback on the WD40 would be much appreaciated.

Sebastian.

May 5, 2008 | 10:29 AM

mejonz

Senior User

Joined: Apr 2006

Posts: 310

Likes: 0

From: maricopa az

I haven't uesd any wd 40 but I have switched diaphram and valve assy with another pump. just remove the two bolts holding the I'll say the can to the main body it should slide right off and tighten the bolts up evenly when you swap them.and watch out its full of gear oil

May 6, 2008 | 10:26 AM

Hamberger

Thread Starter

Fleet Mechanic

Joined: Sep 2005

Posts: 1,509

Likes: 3

From: Ladner, British Columbia

Vac Pump

Quote:

Originally Posted by mejonz

Thanks for the input, much appreciated.

I think I will put a squirt of WD-40 into the pump inlet to see if the valves will seal properly. If it does not help I guess it is time to return this new pump I bought and get anotherone.

There I am trying to stay a step ahead and by doing a proactive repair and in the process put yourself two steps back. Thats life I guess.

Seb....

May 6, 2008 | 11:43 AM

David85

Lead Driver

Joined: Nov 2003

Posts: 6,900

Likes: 3

From: Campbell River, B.C.

Did you keep the old pump?

May 6, 2008 | 08:01 PM

PLC7.3

Post Fiend

Joined: Nov 2004

Posts: 5,638

Likes: 1

From: Manitoba

Before you replace the pump check all the lines from the vacuum manifold for leaks. If yours has the Juice can check it on the bottom for holes.........

May 7, 2008 | 09:09 AM

Hamberger

Thread Starter

Fleet Mechanic

Joined: Sep 2005

Posts: 1,509

Likes: 3

From: Ladner, British Columbia

Vacuum Pump

Thanks all,

I will see if I inadvertantly created a vacuum leak by moving the vacuum hose around when I changed to the new pump. The rubber on the old hose was pretty hard so I cut off about an inch of the old hose to make sure I got a good seal to the pump inlet nozzle when I put it back.

I still have the old pump and I might re-install it to eliminate whether the problem is with the new pump.

The vacuum booster was new when I got the truck two years ago and I never had any problems until I changed out the vacuum pump about three month ago to the new vacuum pump.

PLC, thanks for the great link you sent.

Seb.....

May 7, 2008 | 09:38 PM

Dave Sponaugle

Post Fiend

Joined: Nov 2003

Posts: 21,285

Likes: 16

From: Nutter Fort, WV

I think Pete was talking about the vacuum reservoir when he said juice can.

Some have a plastic ball looking reservoir, some have a juice tin looking reservoir.

Pay close attention to the outlet tube on the pump, if your hose was very hard, you may have cracked the tube the hose slides on where it enters the pump when you installed it.