edwinsmith

I finally got around to putting a vacuum gauge on and at the brake booster I'm showing 19". My brakes seem a bit hard but not overly so.

What kind of vacuum should I be seeing?

Thanks

Edwin

maybe368

19 is good, I think it is like 16 to 22,but I could be off. But I know that 19 is good...Mark

edwinsmith

OK. Great! That's a load off my mind. Another thing I don't have to fix right now.

Thank you.

Edwin

Ol-dodge 1992

Hey there Edwin...

Have you done anything to your break system or is it stock?

My pedal is hard sometimes and then other times you can feel it sag down with the weight of your foot until it firms up towards the bottom... sometimes the break light on message center lights up and goes out sometimes not.

Where did you tie into your break system to check vacuum... truck running in P or N ... did you throttle up to apx RPM range ... etc

I need to address this issue and a little guidance would be greatly appreciated

Thanks in advance
SD

maybe368

You can pull the small line off the valve thingy on the brake booster to check the vacuum. It should not be a lot of difference between idle and wot. The symptoms you describe could be out of adjustment rear brakes, this is what I would do first. It would then point to the booster or possibly the RWAL brake valve (dump valve) in the driver's side rear frame rail, just behind the axle. I would make sure that the rear brakes are adjust right first...Mark

Ol-dodge 1992

Thanks mark ... I'll dig through some threads on adjusting rear breaks and see if I can figure it out ... when I start doing stuff like this I get in over my head pretty quick

But I'll see what I can do

bigragu

Be prepared for a ton of reading, LOL. Just do a search on "brake pads" as I did last night. There were topics related to brake bleeding

edwinsmith

The only thing I've done to my brakes is to use 1-1/8" cylinders in the rear and 3" wide shoes. I haven't touched the drums but what the P.O. is unknown. When I first got the truck the left side rear had been gutted and the line blocked. I drove it from Texas to Kansas that way. Everything else is stock.

I cut the rubber line going to the vacuum sensor by the left fender and installed a plastic "T" then I put a cap on the when I was done. I revved the engine until the gauge stabilized.

I need to either fix my RWAL dump valve or bypass it. I haven't decided which yet.

PapeCAT

IIRC my 1991.0 cummins engine with 1998.5-2002 style vacuum pump would max out at around 25 with foot off brake. This was in my 1987 F350 cummins conversion with lots of gauges. I was running the stock Ford booster.

maybe368

I just checked my '90 FSM and it says that the normal operating range is 8.5-25 In-Hg and that the brake light comes on below 8.5 for 10 seconds. I would think that 19 may not be perfect, but it is a long way from bad...Mark