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View Full Version : Vacuum booster conversion on a LWB!



grnthng
11-03-2013, 11:22 AM
So for the better part of September's and October's weekends I spent working on yanking my abs system to install a vacuum booster and at first I was daunted, but it turned out be very straight forward!
I am totally happy with the way it brakes, in fact I think it brakes better now and I will not have to worry about that uneasy feeling on snow and ice with the pulsating feeling at the pedal! Honestly I feel more comfortable controlling my brakes than the sensors!
Time consuming it is, so if a mechanic were to do it....your talking many hours of labor!
Ofcourse taking everything apart is easy....well except for the stubborn brake line fittings! Once I got all the lines out and the abs block out.....I didn't remove anything electronic from underneath the drivers seat, that was pretty much it!
Once everything was out I started cleaning and repairing some areas (rust) that needed attention!
The time consuming part is plumbing the new brake lines....a little tricky, but fun and the same time...I'll post on this later!
You'll need to buy a vacuum booster and a dual line master cylinder....I thought I was going to need a pedal box conversion.....but on my brake pedal there were two holes drilled into it and when I bolted the booster to the firewall I simply bolted it to the hole nearest the firewall! The actual booster bolts with 2 of the 4 nuts from the abs block!

Got to go....but to be continued!

Coniston
11-03-2013, 07:12 PM
Looking forward to seeing how you did it...I really want to do this on my 93 LWB, but there's a few details, like the pedal box, that I can't figure out how to work.

Did you keep the 93 rotors and calipers? Or did you swap to an earlier system?

Greg

grnthng
11-18-2013, 08:52 PM
Hey Greg.....sorry it's taking so long to respond, hard to find time! I will get into more detailed soon and I have some pics to upload too!
I did not do anything to the pedal box...on my '93 the pedal has two holes drilled from factory where the pin with c-type clip is connected to the booster and/or abs block!
Fitting the vacuum booster into the firewall...the actuater part simply fits into the secondary hole closest to the firewall with the same pin and clip!
What I eliminated was the abs block, the pump and the accumilater!
Same caliper and hubs.....you do have to follow the diagram in the big shop manual to plum all your brake lines as it is more simple than the abs system, but completely different! Example...on a non abs system, you only need one line to rear brakes...as opposed to two w/abs!

bbettridge
11-24-2013, 07:31 AM
RRC front calipers have two discrete circuits - power and manual. These do not mix within the caliper body. Should you not join them and remove the factory booster, you will only brake with 50% capability in the front. Not a good situation!


In order to use both sets of pistons, you must link those circuits either exterior to the caliper with brake line or internally by splitting the halves and drilling a passage between bores. I've always found it easier to just buy D90 or 110 calipers and use them.

Just wanted to throw this out there for all who may consider the change to a vacuum or hydro boost setup.

Bill

grnthng
11-24-2013, 08:09 PM
RRC front calipers have two discrete circuits - power and manual. These do not mix within the caliper body. Should you not join them and remove the factory booster, you will only brake with 50% capability in the front. Not a good situation!


In order to use both sets of pistons, you must link those circuits either exterior to the caliper with brake line or internally by splitting the halves and drilling a passage between bores. I've always found it easier to just buy D90 or 110 calipers and use them.

Just wanted to throw this out there for all who may consider the change to a vacuum or hydro boost setup.

Bill

Not absolutely sure what your point is with the calipers......but what I think your referring to is the standard dual circuit system! The best way for you to understand is to open up a RRC shop manual and go to the brakes chapter and look at the brake line diagrams and compare the abs to non-abs layout!
When converting to non-abs......you do have to plumb all new lines into a dual circuit system with a pressure reducing valve to the rear calipers!
I have the original (newer) calipers on mine and they work 100%!

Just went wheeling yesterday and it was great not having to deal with the abs or traction control.....one less system to worry about on the trail!

bbettridge
11-25-2013, 09:35 PM
Below applies only to non-Hunter RRC which had a "normal" non-ABS dual circuit brake system This applies to most RRC with the power assist (ie: boost pump).



RRC brakes are NOT a standard dual circuit brake system. Front calipers have two independent circuits - one fed by the boost pump (ie: power circuit), and one fed hydrostatically (via foot power). Hence the reason for two brake line ports on each front caliper. Rear calipers are standard single line.

Almost all dual-piston calipers (on other Rovers and just about every other vehicle) are run by a single circuit, so the bores are joined internally within the caliper. RRC calipers are not - each piston is fed independently, and made to work together with both hydro and power circuits running. Hydro alone will stop the truck as it is the "backup" in case the boosted system goes out.

Not saying you did it wrong, but I've seen it converted incorrectly a number of times over the years. As long as you ran two lines to each front caliper (ie: used both ports) coming from a common line after the proportioning valve, it's fine. If only one port was fed, and the second blocked, then braking is with only one piston (ie: 50% ).

I like the simplicity of a single line so always found it easier to just use D90 calipers which are standard single port. Others have split the caliper halves and drilled a passage to join the piston bores in order to join the bores internally and then use a single brake line feeding them. Tried this once, and its no fun (getting caliper halves to reseal can be tough).

I actually think the stock power boosted RRC brake system is one of the best out there - when it's working properly. Pumps, etc getting hard to find anymore. Certainly understand the desire for simplicity though!

Bill