Brake booster upgrade?

[North Idaho 5.oh]

So I have a 93 ranger that has a “sinking” brake pedal... this is the 4.0 and 4x4 manual transmission.
mom top of the sinking pedal, the idle also increases when I pump the pedal... hence the need to replace the booster.
I know they are cheap and I can go get one no problem. My question is... would I be able to use an booster from an 05 ranger 4.0 4x4 manual?
The bolt holes are not the same (05 is bigger) ... would I be able to drill out 2 holes to make it fit or is it even worth it?

 

[RonD]

Not worth it, get correct booster, and you could hate it if it made brake pedal too sensitive, not sure that would happen, but it could happen

 

[North Idaho 5.oh]

Ok but would you also agree that the symptoms point to a bad brake booster ?

 

[RonD]

100%, had me at idle fluctuates when you press brake pedal, brake lights don't draw near enough amps to load down alternator that much, lol

May not be total issue with brakes but could be
When you pull off the master check rear for brake fluid, that could be what damaged the booster

 

[North Idaho 5.oh]

It’s weird because the pedal is super soft when the engine is running but stiff when truck is off but still gradually “sinks” when pressure is applied. One other thing I forgot to mention is that the rear wheel cylinder on the passenger side blew so I replaced all the rear brakes all together cylinders and all. Bled the brakes to perfection and no air is in the lines. Pedal still doing the same thing... master was never run dry.

 

[Shran]

I would check, fix, replace, or bypass your RABS valve... I have had a lot of trouble with those. My Explorer did the same thing your truck is doing, ended up being a very slow leak at that valve. If you can eliminate that as a potential cause, and you're SURE you've bled everything and that there are no other leaks, I would probably suspect that the master cylinder itself is bad.

As far as an upgrade, check out hydroboost brakes. I think there have been a few people on here use Astro van parts.

 

[Uncle Gump]

Brake pedal sinking doesn't sound like a brake booster issue to me. A brake system leak or a failing master cylinder seems more likely.

 

[North Idaho 5.oh]

Brake pedal sinking doesn't sound like a brake booster issue to me. A brake system leak or a failing master cylinder seems more likely.

I’m lost either way... I pump the brakes and the idle goes up and then the pedal sinks when the truck is off...

 

[don4331]

I would check, fix, replace, or bypass your RABS valve... I have had a lot of trouble with those. My Explorer did the same thing your truck is doing, ended up being a very slow leak at that valve. If you can eliminate that as a potential cause, and you're SURE you've bled everything and that there are no other leaks, I would probably suspect that the master cylinder itself is bad.

As far as an upgrade, check out hydroboost brakes. I think there have been a few people on here use Astro van parts.

+1 on the hydroboost as an upgrade. I'm surprised it isn't listed as a "performance" improvement (OK, it doesn't increase capacity of the actual brakes, but it certainly improves the initial effect). Its handy when doing 351w or similar swaps as it is a lot more compact.