I bought my truck (see sig for specs) with the brake booster bad, and I've just now got around to replacing it. When I removed it from the truck, I found that some sort of fluid runs out the vac hose attachment nozzle if it's left upside-down too long. The fluid doesn't seem like motor oil, because it cleans up off clothes after one machine wash cycle . Is this normal; I wasn't aware there was supposed to be any fluid in the booster. If not, then what kind of fluid is it, where did it come from, and what's broken? The truck runs fine, its just the booster that doesn't work.

 

There is not supposed to be any fluid in the brake booster, the only way fluid and get into the brake booster is from a leaking master cylinder, so the master cylinder would be bad and need to be replaced if it hasn`t been already.

 

Ok then, next question: if I went with a double diaphram brake booster, would I have to make any other changes to the brake system (like calipers or a bigger bore master cylinder) to handle the greater braking power? So long as I'm replacing stuff, maybe I should upgrade.

 

I would upgrade while your replacing go with a master cylinder from a V6 as well as calipers! Now on an 88 I'm not sure if you need to change rotors or not but I would assume the V6 rotors would go right on just watch for wheel to caliper clearance!! Search brake upgrades on the site there is tons of info!! Good luck and take pics and start a thread while your doing it !!

 

Upgrading to a duel diaphragm brake booster is a good idea, I have a duel diaphragm brake booster and master cylinder off of a 92-94 4Runner on my 86 4Runner, its a direct replacement and nothing else needs to be replaced, and it did make a noticable improvement in braking.

 

Cool! I'm kinda on a tight budget right now, so I don't think I'm ready to replace everything with V6 components. I can definitely manage upgrading just the booster, though, and I can always go back later and upgrade the other parts. Thanks for you help, is there anything else I should know before I start buying stuff?

EDIT: Will a double diaphram booster work with the original style master cylinder? On the later MC, the brake lines connect at different points, and I'd like to be able to use my orginal brake lines.