Any way to test vacuum pump?

[Farmer Jon]

I just picked up a 88 extended cab long box. I got it cheap because the bakes are squishy. I don't know jack squat about these fords. I have a duramax and a cummins. This is my first ford diesel ever. Looking around of Facebook they say its the vacuum pump. Then someone said its the master cylinder. I don't want to go throwing money at it with out knowing if the pump is bad. There has to be a way to test it.

 

[mu2bdriver]

A firm pedal is more indicative of a bad/failing vacuum pump. Regardless, you can hook up a suction gauge to the line at the manifold in front of the driver side firewall and get an idea of how much vacuum it's pulling. There's a tech sheet which gives minimum values for the vacuum pump. I'm away from the desktop now but can post it later.


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[laserjock]

Vacuum gauge. I think it's supposed to pull like 27 in Hg. Auto parts stores have them. Some of us actually used one back in the day to diagnose engine problems.

 

[riotwarrior]

Well it should suck to tune of 27 inches murcury or no less n 22 iirc but wdik

 

[jwalterus]

Vacuum gauge. I think it's supposed to pull like 27 in Hg. Auto parts stores have them. Some of us actually used one back in the day to diagnose engine problems.

hell some of us STILL use them to diagnose and tune

 

[OLDBULL8]

Vacuum boosters are an accessory to help apply the brakes, air in the brake system, bad MC, bad wheel cylinders or calipers makes them squishy. Don't know what you actually mean by squishy, but took a shot at it.

 

[Farmer Jon]

The peddle goes all the way to the floor real easy. like stepping on a rotten banana. About an inch before bottoming out it gets firm and the brakes come on. The calipers and wheel seals are good. Must be the master cylinder.

 

[laserjock]

That's air I believe. I'd bleed everything thoroughly before I change a master. It could be the RABS valve on an 88.

 

[G. Mann]

First thing you should do is ADJUST YOUR REAR BRAKES. The automatic drum brake adjusters on these trucks seldom work properly, and as the shoes wear, the peddle lowers because it takes more fluid to expand the wheel cylinder further.

Simple test is push the parking brake on till it "almost locks up the rear brakes" but not quite.. then check for how much brake peddle you need till it gets "firm" .... If you get a full peddle with parking brake "on" then it's rear brake adjustment time. [parking brake cable expands the rear brake shoes and takes up the "slack" between shoe and drum..

Try that first.. before you start throwing money at it..

 

[79jasper]

Also easy way to tell is how far down the parking brake pedal goes before engaging. Yes it's not foolproof as the cables can be stretched.
But if it goes most of the way to the floor, brakes need adjusted. Mine sets about a quarter to halfway down.

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[Farmer Jon]

I will try that. Thanks guys.