I have a 1984 22R 2WD pickup. Something has gone bad with the power brake booster section and I wonder how I can tell if it's the booster itself or one of the gaskets on either side of the booster.

When I push the brake pedal in I hear a faint hiss the first few inches and then a louder hiss the last few inches of travel. When I hear the louder hiss the engine is also missing, trying to stall...classic bad brake booster symptom. Also the brakes take a lot of pressure to make them work, so the booster is clearly not working.

When I put my head under the dash to listen closely, the hissing is very obvious even though the booster is on the other side of the firewall in the engine compartment. This makes me wonder if the problem could be one of the gaskets that seal the booster on either side. Has anyone ever found this to be the case and how would I check for this problem?

Also, is it correct that any Toyota pickup brake booster from 1984 to 1988 will work on my 1984?

John

The booster is a sealed unit. There are no replaceable gaskets. If its leaking, its the internal diaphragm. The only seal there would be on the firewall would be to keep the elements outside of your cab. Nothing to do with the performance of the booster.

Remove the brake booster vacuum line, and plug it with your finger. Did you hear a hiss when you took it off? Does your engine run smooth now that its plugged up? All this and hard brake pedal, sounds like a booster to me. I'm not sure about the swapability of the masters.

This is what my buddy did on his 86 runner:

... A dual-diaphragm brake booster. Most earlier Toyota's like mine came with a single diaphragm booster. Around the early to mid '90's, Toyota started using dual diaphragm boosters, which provide even more vacuum brake assist. I picked up a dual-diaphragm booster from a '97 T100 4x4. It was the same over all diameter as my old one, but 1" thicker and still bolted right in. The bigger booster made the pedal feel a little softer again, and the pedal effort needed to stop the truck decreased quite a bit. The pedal only needs to be depressed a fraction of the effort and distance of what it used to.

Wow; that's nice to know; thanks! Gives a person a few more options on this end with the junkyard pirates.

Probably a good idea to read through all of ErikB's brake page before throwing assorted parts into the brake system:
http://home.4x4wire.com/erik/4runner/brakes/

There is a fine balance between all the parts in the system and bigger may not always be better. A bigger m/c pushes more fluid with less pedal stroke, but with stock size brakes, this will just make for touchier brakes. Also will make the pedal harder to push. Add the dual diaphram booster and you get more brake boost but that can make things touchier. If you add bigger brakes (i.e with larger or more pistons), then upgrading all the above parts make sense. Do less than that and you need to be a little more careful in the selection of the parts. Erik documents his adventures in that area (he started with larger front brakes due to his SAS).

I am currently doing this swap on my '85. I have large 4-piston Wilwood calipers up front (stock m/c does not push quite enough fluid for these, it bottoms out too soon) and will be adding rear Supra discs. A 1" FJ80 m/c will be installed as well as a T100 dual diaphram booster.

But as far as boosters, I think most any of the single or dual diaphram boosters will swap. The duals are a little thicker and will need brake line tweaking, but the bolt holes and fittings are all the same. So an early '90s vintage FJ80 master will bolt up to a '97 T-100 booster and all that will bolt into an '85 4Runner.

In fact, once I finish up that swap, I'll have a stock booster off my '85 available if you are looking for one. Might be a month or two before I get that swapped out, though.

Not trying to side step 4crawler but I have a couple. One from and 84' and one from an 86' 2wd. I keep them on the shelf for spares.

its leaking, go to the parts house and buy a new one

Hi vp (vanishing point)...how much would you want for one of those brake boosters? Does the '86 have the same bolt pattern(s) as the '84, same size vaccumm fitting?

John

PM sent.

Matt,

Did you get any of my return messages? I wrote back to tell you that I didn't use Paypal, would a money order be ok.

John