Need opinion on brake issues Land Cruiser 80 LS swap, second posting.

[Desslok]

Still need help. I wrote before about this issue, here is the original post: "Took possession of an 80 series that was my brothers from a shop in Wisconsin. He had them swap an LS 6.2 L92 with a 6L80 out of an 2007 Escalade into a triple locked 1996. My brother passed away serving in the Middle East last year and I am trying to sell it for my sister in law and her kids. Drove it 1000 from Wisconsin to Colorado Springs, it ran strong but the brakes started to crap out in Omaha. The Toyota booster is working as it should. The brakes are intermittent, working, then very soft, going to the floor to get any engagement, the brake assist doesn't engage. An OEM Toyota valve was placed in the vacuum line from the engine to the master cylinder, still no improvement. Any thoughts? Thanks in advance."
After weeks checking the master cylinder, booster, bleeding the lines, checking out the wheel bearings, the shop is now saying the brakes failing will be fixed with an after market vacuum pump because we are at 5000 feet in Colorado Springs. The brakes failed after working and being driven hundreds of miles from Wisconsin to Nebraska. They failed in Omaha at 1000 ft altitude. I am at a loss on this, it doesn't make sense to me that the vacuum pump is the issue. Am I wrong? I just need it fixed soI can sell it and help my sister in law get the best price. Thanks in advance.

 

[jpoole]

brakes are intermittent, working, then very soft, going to the floor to get any engagement

That's pretty relevant. A few things that I've seen cause this, intermittent soft pedal scenario:

• internally failing master cylinder
  • A failing MC can cause different symptoms/feel and sometimes can intermittently feel good/bad
• loose wheels/rotors
  • if a rotor or wheel is loose it can push the brake pads out and away from the rotor so that initial pedal push(es) take more pedal travel before the brakes engage
  • if this is the issue then the pedal should feel better after it's been pressed a few times to push the pads back against the rotor which makes this a pretty easy cause to test for and rule out
  • Sticky slide pins on the calipers can make this scenario worse by holding a pad, or pads, away from the rotor thus reducing braking power and making the pedal feel bad.
• brake booster
  • I know you say it's good but in the situation you are in, if you are at all unsure and start putting parts into it I'd consider a new booster or thoroughly testing the one you have per the FSM.

Spongy brakes can of course be caused by failing brake hoses (the rubber can balloon out), air in the lines, leaky/failing calipers, etc. but those causes are not going to be intermittent so I wouldn't assume they are relevant in your case.

Since this is a swap there may be relevant alterations to the stock system. I don't know if you are still running ABS, if the system is stock or altered, etc. so there could be other causes for what you are experiencing. Someone may have simply taken some things apart and failed to torque them back properly which lead to components loosening on the trip, etc. If it were mine I'd be doing a thorough inspection before taking further steps or buying parts.

If you really can't figure it out, everything is stock and checks out in a visual inspection then I'd consider a new MC and full flush/bleed as worth the relatively minimal cost. The following MC is oe equivalent, as I understand it, and very reasonably priced:

ADVICS BMT-046​

The OE equiv Seikens booster is more expensive but if you just want to spend some money on it to try to get it to sale I'd consider the booster as well. Of course, I'm cheap and don't fire the parts cannon until I've figured out what the problem is typically so I'd test thoroughly first...

Good luck getting it sorted and sold.

 

[Desslok]

That's pretty relevant. A few things that I've seen cause this, intermittent soft pedal scenario:

• internally failing master cylinder
  • A failing MC can cause different symptoms/feel and sometimes can intermittently feel good/bad
• loose wheels/rotors
  • if a rotor or wheel is loose it can push the brake pads out and away from the rotor so that initial pedal push(es) take more pedal travel before the brakes engage
  • if this is the issue then the pedal should feel better after it's been pressed a few times to push the pads back against the rotor which makes this a pretty easy cause to test for and rule out
  • Sticky slide pins on the calipers can make this scenario worse by holding a pad, or pads, away from the rotor thus reducing braking power and making the pedal feel bad.
• brake booster
  • I know you say it's good but in the situation you are in, if you are at all unsure and start putting parts into it I'd consider a new booster or thoroughly testing the one you have per the FSM.

Spongy brakes can of course be caused by failing brake hoses (the rubber can balloon out), air in the lines, leaky/failing calipers, etc. but those causes are not going to be intermittent so I wouldn't assume they are relevant in your case.

Since this is a swap there may be relevant alterations to the stock system. I don't know if you are still running ABS, if the system is stock or altered, etc. so there could be other causes for what you are experiencing. Someone may have simply taken some things apart and failed to torque them back properly which lead to components loosening on the trip, etc. If it were mine I'd be doing a thorough inspection before taking further steps or buying parts.

If you really can't figure it out, everything is stock and checks out in a visual inspection then I'd consider a new MC and full flush/bleed as worth the relatively minimal cost. The following MC is oe equivalent, as I understand it, and very reasonably priced:

ADVICS BMT-046​

The OE equiv Seikens booster is more expensive but if you just want to spend some money on it to try to get it to sale I'd consider the booster as well. Of course, I'm cheap and don't fire the parts cannon until I've figured out what the problem is typically so I'd test thoroughly first...

Good luck getting it sorted and sold.

Thanks for that extensive reply, I appreciate the time you put into it. The shop has looked at the MC, booster, lines wheel bearings, LSPV, flushed, bled. Now they are saying vacuum pump and to me it doesn't make sense because the brakes failed at 1000 ft altitude. No sure.

 

[ajax1]

Thanks for that extensive reply, I appreciate the time you put into it. The shop has looked at the MC, booster, lines wheel bearings, LSPV, flushed, bled. Now they are saying vacuum pump and to me it doesn't make sense because the brakes failed at 1000 ft altitude. No sure.

What cruiser shop is working this for you?

 

[mudgudgeon]

Original thread here

Thread 'LS swap brake issues' LS swap brake issues - https://forum.ih8mud.com/threads/ls-swap-brake-issues.1341597/

Had some to and fro with @Desslok by PM tonight.
He's being told by the shop the 6.2 LS isn't making enough vacuum to operate the brake booster because of the altitude.

Makes no sense to me.

Any club members in Colorado Springs area that may be able to help?

 

[Desslok]

What cruiser shop is working this for you?

I brought it to a standard highly rated shop in Colorado Springs. I figured that the brakes would be pretty straight forward. Slee and Redline were backed up 6-8 weeks.

 

[ajax1]

I’m just asking as I would take it to shop that knows Toyotas, specifically cruisers, and Ls swaps. Did you try Japanese auto in Denver?

What vacuum pump and valve for master cylinder are you talking about? If it is all Toyota all you have is brake booster and master, with valve in the brake booster. Does it still have the lspv for the rear brakes? How old are your lines? What does the fluid look like? Post some pics of everything

 

[AussieHJCruza]

Does the LS have a fairly stock cam? If there's no significant lope to the idle it should make sufficient vacuum. Easy way to rule out would be tee a vacuum gauge into the brake booster line.

I'd lean more towards faulty master, and/or improperly bled ABS pump if it's still there.

Quick check on the booster, if you pump the pedal a few times with engine off until it feels quite hard, then whilst keeping the brake pedal depressed, start the engine. What happens? If the pedal falls a few inches once the booster has vacuum on it, IMHO it's got enough vacuum to at least do something.

 

[ToyosRUs]

Does the LS have a fairly stock cam? If there's no significant lope to the idle it should make sufficient vacuum. Easy way to rule out would be tee a vacuum gauge into the brake booster line.

I'd lean more towards faulty master, and/or improperly bled ABS pump if it's still there.

Quick check on the booster, if you pump the pedal a few times with engine off until it feels quite hard, then whilst keeping the brake pedal depressed, start the engine. What happens? If the pedal falls a few inches once the booster has vacuum on it, IMHO it's got enough vacuum to at least do something.

It has an aggressive cam with noticeable lope. No fall from the brake pedal after trying your suggestion...so just manual brakes. I was able to use a vacuum gauge and identify the engine pull only surpasses 15in/Hg at 3500RPM, generally idling around 10in/Hg. I heard of a little experiment to double check the brake booster/MC function: get to a decent rolling speed then shift into neutral, press brake and accelerator simultaneously to get the RPMs up and increase the engine vacuum -- boom, brake booster engaged at 3500RPM, even ABS kicked on, so I knew the rest of the brake system was functional. I blocked off the vacuum port and installed an electric vacuum pump. Gotta love JEGS. Now has full braking power independent of the engine.