Booster experts? Brake master?

[bikersmurf]

Brakes started feeling different the other day.
Booster #1
Brakes felt normal... Let off the brake a bit, and re-apply, and the pedal becomes rock hard. Pedal stays hard if pumped. Pedal when depressed goes down about 1/3 of the way and is firm... And doesn't sink.

Suspected booster so swapped in spare booster.
Booster # 2
Booster works well when first pushed. After holding assist seems to fade. Pump the brake and assist comes back.

So... First off, I've got 4wheel discs which have been working well for 15+ years, so it's not going to be fixed by a brake adjustment.

What next? Another booster? Replace Booster and master? Fix one of the 1977 Fj40/45 boosters... If so, how?

Any thoughts or theories?

 

[Fast Eddy]

Problem 1 sounds like a broken piston in the master.

Problem 2?? Maybe a bad booster?

I'd say you should take apart the whole shebang, inspect the master and pull a vacuum on each booster and see if it holds.

OTOH, just order a new FZJ80 master and pick up a used 4Runner booster and have it fixed in an hour or two.

 

[bikersmurf]

Used the same master. By hard, I mean firm and unassisted... Will still lock up all 4 wheels if the brakes are hammered on damp pavement at 10 mph.

Both boosters hold vacuum when engine is off. There are no audible leaks from either booster. The outside seal at the front looks fine on both. The engine pulls 16-20 of vac at idle.

What year of Forrunner? Would a 60 booster work (years)?
Which boosters provide the most assist (space isn't restricted)?

 

[bikersmurf]

Would an 80 series booster work?

 

[RWBeringer4x4]

Would an 80 series booster work?

My understanding is that virtually any booster with the correct bolt pattern will work, and that about 80% of toyota boosters have the right bolt pattern. Vae Victus started a thread discussing booster compatibility a while back.

The issue is that most of then will be wider than the stock one, and as a result, cover the closest bolt on the clutch master cylinder. The result is having to disconnect the booster to replace the slave. Not really a huge deal - my truck currently has this type of setup.

 

[RWBeringer4x4]

https://forum.ih8mud.com/40-55-series-tech/731418-1976-1980-fj40-brake-booster-replacement-list.html

There ya go.

And, just realized you commented on that thread and are therefore probably aware...sorry!

 

[bikersmurf]

From what I've read, it looks like 80 booster will bolt into a 60... Likely a 40.

Does the fjz80 non-abs master have the same bolt pattern?

 

[Fast Eddy]

The issue is that most of then will be wider than the stock one, and as a result, cover the closest bolt on the clutch master cylinder. The result is having to disconnect the booster to replace the slave. Not really a huge deal - my truck currently has this type of setup.

Mine too. I have '90-ish 4runner boosters in both my rigs. You don't actually have to disconnect anything. You have to remove the two firewall mounting nuts closest to the clutch and loosen the other two. It kinds sucks, but it's not the end of the world. It's good motivation to buy a quality clutch master.

I will replace my 2nd Napa rebuilt clutch master in a year with a new Toyota unit soon.

 

[bikersmurf]

I've recently rebuilt my clutch master for the 2nd time in 22 years. I've never removed it to rebuild is, so I'm really not worried about it.

I'd like to just replace the booster first, and mess around with the hydraulics when I can get it into the shop. I'm getting to old to crawl around on the ground when it's cold & wet out. Done too much of that in the last 22 years of 40 ownership.

 

[JohnnyC]

Biker... please update us when you get one... mine has recently developed a hiss when steping on the brake... I will be needing to do something kinda quickly

I have a spare that is good...but... one of the studs that holds the master broke off... bummer!

 

[bikersmurf]

Biker... please update us when you get one... mine has recently developed a hiss when steping on the brake... I will be needing to do something kinda quickly

I have a spare that is good...but... one of the studs that holds the master broke off... bummer!

You can likely mix and match parts to fix your spare... the housings are likely interchangeable.

 

[Chachie]

You need to talk to Kevin Desert Tool he will know the answer.

 

[bikersmurf]

You need to talk to Kevin Desert Tool he will know the answer.

How do I contact him?

 

[DSRTRDR]

his username is "Tools R Us"

 

[bikersmurf]

Looks like the next thing I'll need is a, "spacer from a 1978 minitruck"

The firewall is thicker on the 80, and hence the input pushrod is about 1" longer.

Initial comparison: looks like the 1992ish booster will fit, and the old master would bolt on, but I've not done it yet.

 

[Vae Victus]

https://forum.ih8mud.com/40-55-series-tech/731418-1976-1980-fj40-brake-booster-replacement-list.html There ya go. And, just realized you commented on that thread and are therefore probably aware...sorry!

I updated that thread just now with the exact model I purchased.

 

[bikersmurf]

Any recommendations for an inline check valve to work with the 80 series vacuum booster?

 

[bikersmurf]

Cnclusion...project for another day will beoth boosters have issues. The 80 booster works awesome.

After trimming the input rod 1/2" shorter and adjusting it to it's shortist, the 1991 S-HDJ81V-RNPEX (80 Series) Boster fits. It did need to be rotated 180 degrees because the offset is different. I adjusted the output rod to match the 1974 Drum Brake master cylinder and bolted it on. I did need to mive a couple if the brake lines a bit so they wouldnt be pinched behind the edge if the booster. The booster will likely need to come out to remove the clutch master (or at least be loostened off),

Swapping in the 80 series Master will be a project for another day.


Now all I need is a tidy check valve to finish it off. Anyone have a source for an inline one?

 

[bikersmurf]

Found a check valve. VW wreckers had one for $10. Made by 'ATE' for 1970s VW vans etc. Also used in Volvos from what I've seen on eBay.

The local Toyota dealer was helpful and tried to find me one... But a $70 special orders with no returns wasn't so appealing.

 

[bikersmurf]

Installed the 80 master. Omg does it ever have breaking power. One finger, pushing the brake pedal, can just about lock them up on dry pavement!

If you're looking for more power, an 80 booster and master is excellent.

It's also a lot shorter to clear the carb... To all of you running 2Fs in earily 40s with carb clearance issues.