Anemic brakes in '91 with LS3 engine swap (2 Viewers)

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Joined
Jun 11, 2025
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Location
Boone, NC
As stated, super soft braking power - I'm the new owner of a '91 FJ80 the PO dropped in a 5.3L LS3 engine among many other upgrades.

But the brakes totally suck - local Toyota mechanics (great reputation in Wilkesboro, NC) -- we had evidence the LSPV valve was bad, replaced that - bled the system and ensured we were finally getting fluid to all 4 corners. But the master cylinder indicated it was bad - so they replaced the master then the booster. Bottom line, we're sitting with a little better braking power but still pretty anemic.

Suspicious of the vacuum setup off the LS engine - does anyone have some specs we could measure against to chase if we're getting too much / not enough vacuum pull? The master and booster are OEM spec to the FJ80. Next would be swapping out front calipers. Just trying to gather some info to pass along to the shop - any help / experience is greatly appreciated!

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Have you checked all of the rubber brake lines. One or more of the rubber lines could be breaking down and ballooning reducing pressure and also feel spongy.
 
really nice looking 80 !!

Have the rotors & calipers been upgraded to the later FZJ80 type or still 1991 fj80 spec?
theres a big difference in braking power with the later equipment predominantly the rotor diameter / size
 
Have you measured the actual stopping distances from various speeds and can you post them?
 
Wow - everyone always says how awesome the IH8Mud forum is... but my first posting, it's overwhelming!

Short version of where things are now - replaced the LSPV valve, redid the brake lines connecting (due to damage in the swap from rust issues); everything properly bled and flushed. New master cylinder and booster installed and dialed in to the best of the mechanic's abilities. Compared to 'before' the stopping power is MUCH better - but still not optimal according to the mechanics. They plan to order / replace the front rotors - I believe OEM spec, not the FZJ80 version.

Once I know, I'll update - and I'll try to post some stopping distance metrics. The speedo is off a variable amount because of the larger tire size (35") and lift - which I just pace based on traffic and feel. But apparently you guys want scientific accuracy and methods ;-)
 
My question of measuring stopping distance was a bit tounge in cheek, but was meant to highlight that your question was a bit subjective :)

With that being said, I would recommend the 93-97 rotors/calipers (use OEM Toyota) which will be a bolt-on to your vehicle. You have the large rims to accomodate them. If your front brakes are new, and your master cylinder, booster, and hoses are all new OEM Toyota parts, assembled and bled properly, your brakes should work well with your 35" tires.

How was your intake manifold adapted to your brake booster? I sell a nice inexpensive kit for that which is super clean and requires no adapter fittings or multiple hoses.
 
Not to throw another wrench in the works here...but it is somewhat common to have poor pedal feel and difficulty bleeding these old systems due to failing old ABS actuators. While I am trying everything I can to retain mine, I've driven vehicles with the LSPV and ABS actuator deleted and they have a MUCH better pedal feel and braking performance. You may consider that if you don't find fault anywhere else in your setup. I stress that you must rule out all other components of your setup before deleting stuff. I made leaps of improvement on mine replacing the master and booster with new factory parts. I've had varying degrees of bad luck with aftermarket parts FWIW.

Also, for your speedo- if you're still running the H2FA transfer with the electric speed sensor in the tail shaft, @Lutz Auto makes a great bit of kit to sort that out. Worth a look....
 
Not to throw another wrench in the works here...but it is somewhat common to have poor pedal feel and difficulty bleeding these old systems due to failing old ABS actuators. While I am trying everything I can to retain mine, I've driven vehicles with the LSPV and ABS actuator deleted and they have a MUCH better pedal feel and braking performance. You may consider that if you don't find fault anywhere else in your setup. I stress that you must rule out all other components of your setup before deleting stuff. I made leaps of improvement on mine replacing the master and booster with new factory parts. I've had varying degrees of bad luck with aftermarket parts FWIW.

Also, for your speedo- if you're still running the H2FA transfer with the electric speed sensor in the tail shaft, @Lutz Auto makes a great bit of kit to sort that out. Worth a look....

His 91/92 should not have ABS
 
Delta's Big brake kit (OEM).
I saw that Delta is now selling their big brake kit.

Not of fan of them redrilling 200 series 5 lug rotors because I think they are no longer balanced but I could be mistaken.

It is too bad that they couldn't find an off the shelf solution (4runner rotors?).

I think the wheel mounting surface has also moved outward, but hard to tell since they also machined a new hub.

I am looking at CEIKA because they offer front and rear, and I have 18" rims.
 
My question is, Have you compared it to another like cruiser?

Your vehicle has a simple brake system and you replaced everything. How do you know for a fact, its actually broken? There's a bunch of threads here where people modify their brake systems to change the pedal feel and decrease the stopping distance.

Bigger tires and more weight mean longer stopping distance. My cruiser has a perfect brake system but due to the design, the booster makes the pedal softer than my more modern vehicles and my mods made the stopping distance longer. I'm planning on a slightly larger master cyl to stiffen the pedal some. I have upgraded the brake pads to a harder biting compound and the rotors to a better grade to bring my stopping distance down. Also any tech worth a dam would have taken a vacuum reading at the booster and seen if it was correct. They have the numbers at the shop. Not enough vacuum means stiffer pedal not softer.

Also, longer flex lines have more expansion. If the PO replaced the soft lines with longer, that can cause a softer pedal especially if their aftermarket. All flex lines expand slightly, some more than others.

Diagnostics on a vehicle should start with a hydraulic test and a booster test. You would be surprised how many "professionals" I've worked with over the last several decades that don't actually understand brake systems. The one's who truly understand tend to be the ones who own and have modified their vehicles. A tech is trained to fix broken vehicles and put them back into factory spec. A good tech doesn't necessarily mean good at a modified vehicle. At the dealer, I had access to new and used cars. Sometimes you had to go fetch another like vehicle and compare. Does the shop have another lifted 25 year old cruiser to compare to and how many of them has the tech regularly driven? Also, add in cheap aftermarket and everything goes out the window.

This is where you end up either going to a Cruiser specialty shop or learning the system yourself. If your going to learn it yourself, this place is a good resource. Just remember, outside of basic diagnostics, a good tech cant diagnose a problem without having the vehicle in front of him. Especially when its something vague like "It doesn't seem correct".
 

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