Pajero brake booster (servo) mismatch issue

[Gaurav]

Recently my Pajero brake almost died (becoming too hard) and after the diagnose we found out that brake booster is faulty. Tried to source out new one and no one has that, Habtoor can specially order from Japan and will take 1-2 months for delivery. Sourced one from scrap based on picture and it came out slightly smaller than the original one.

We fixed it as an experiment to see if it works and after little make shift adjustment @Barry  fixed it and it's working great as per my quick short test drive. 

My concern is, if it's ok to fits slightly smaller barke booster (1 inch smaller) if it's working fine or should we scout in scrap for perfect fit? Thanks guys.

 

[treks]

One inch difference in diameter is not going to make much difference in how well the brakes ultimately work. If anything, you may have to press a little harder on the pedal to get the same braking effect as with the bigger booster, but using a slightly smaller booster won't cause anything to break or fall off. 

Did you fit the original master cylinder on the replacement booster? If so, you may have to press the brake pedal a little harder to get the same braking effect as with the larger booster, but if you don't want to do that, you can fit a master cylinder with a slightly smaller bore than the original to keep the ratio between booster and master cylinder bore the same as the old setup.

However, if the brakes work fine and you are happy about how the pedal feels, or how well the brakes work, you are good to go, and you don't have to modify anything else.

[aatish]

Go 120 in empty road and slam the brake. if it stops safely like before you are fine. If it takes longer time or skid or abs is not working then there is a problem.

[Barry]

@treks I used the original master cylinder that was on the vehicle. 1, I know it works and 2, I didn't want to go through the faff of bleeding the system, especially when the fluid was just changed a week ago. Both master cylinders are the same although the one from scrap has a divertor block attached to a bracket below it so that says to me the one from scrap came from a non abs model whereas Gauravs has abs. 

[treks]

Gaurav should be good to go with the setup you describe- one inch difference is nothing to write home about after all. 

[Saleem]

As @Barry said ABS and non ABS but it will work fine even smoother and softer than the original as it would contain a larger mass of engine pressure Just be sure to check EGR valve fitted on the air pressure hose from engine it may give the same shortage in performance while the servo is OK!

[Derick]

I like the aatish idea most, to test in real world and see if it's work or not as theory and logics sometime doesnt match with real world requirement and pushing.

[Gaurav]

Thanks all, for the great suggestions and looking into the minor technical details after all it's a BRAKE. Yes I have tried it at 120 and 140 and hitting hard brake and it reacted almost instantly like before. Thanks @Barry and Location Garage for all the good work of swapping the brake booster with make shift arrangement for 200 dhs labor cost. We need more garages in Dubai like this one........Knowledgeable, Capable and Flexible with reasonable pricing.

[DiamondDallas]

Hey We stopped the car @ 120 whatelse do you want parachute at the back! !!  Just joking mate its fine!! No worries