Hello All,
I have a 1990 LS400 and it recently had the following brake work done.
Front rotors resurfaced, new oem brake pads, and the two front brake hoses replaced (due to small leak in the hose).
The work was done at an indy, and while replacing the hoses, apparently enough fluid had leaked causing the master cylinder reservoir to be nearly emply which could have induced air in the system.
The LS has traction control.
The car has had very very mushy / spongy pedal ever since.
The brakes to work and stops the car, but there's never a point in the brake pedal where it would actually stop and not travel any further towards the firewall.
with sligh pressure the pedal goes all the way to the floor with engine running.
With engine off, the pedal does not sink at all. But with pressure on the brake pedal while engine is off, once the engine is turned on, as soon as the hydraulic booster kicks in, the pedal goes all the way to the floor with the pressure that was already on it...

The bleeding done by the indy's has been just opening the 4 valves at the 4 ends and bleeding conventional way.
I have read the service manual and there's description of the bleeding of traction system however I am not sure how to have the TRAC pump operated as it is described in the service manual to be able to bleed the air out.
Any ideas would be greatly appreciated.

P.S. There are many many threads on how to bleed the brake system and references to the manual as well where it says that the master cylinder should be bled along with the traction system .
However nowhere in the posts does it mention how to run the traction pump so that the bleeder valve can be opened while the pump is running.
Could someone kindly post the method to bleed the traction system on the first gen LS400.
thnx.

 

I understand that the Toyota/Lexus diagnostic computer is needed to control the brake pump and it's valves during brake bleeding. Brake bleeding may be one of the few jobs I'll take to a dealer...

 

ya i looked that up today and u need to use the lexus game boy aka scanner

 

I hope you can read my scan. I have to downsizing to be able to attacht image.

Or you can pm me for a 1.2 MB version of the original scan.

 

thnx for the manual snap shot. I actually have access to the pages describing the method, however my questions is : In the traction bleeding section the manual states to activate the traction pump so that the actuator and the accumulator can be bled.
How do we activate the traction pump ? just starting the engine doesnt do the trick and when the bleeder valves are opened nothing comes out of it. air or brake fluid...

 

bump for some more input

 

I just read in the manual that said " If no fluid comes out at the bleeder plug, loosen the flexible hose union bolt on the accumulator. This will make if easier for fluid to come out of the bleeder plug".

We never use the scan tool or any jumper wire to bleed the brake system on the 1LS. I'm sorry that I can't help much.

 

thnx for the update. however I wanted to know, the manual page states to run the trac motor by starting the engine.
The trac motor doesnt run everytime we start the engine, and because of that the bleeder valves aren't throwing any fluid out either.
How do we engage the Trac pump/motor in order to bleed the system ?

 

update:
I opened up the bleeder valve with the car off and the fluid did come out. Once the pressure dropped and no more fluid came out of the Trac Actuator valve, I then closed the valve and started the engine to try to get more fluid to come out as per the manual pages.
But nothing... so I closed the valve. drove the car a bit and tried to bleed with the engine off and got more fluid through the valve.
what's strange is that there's no fluid coming out when the engine is running and the Trac motor never turns on either as per the manual.
Has anyone ever tried doing this on their LS ? The dealers are mostly not aware of the traciton bleeding either. Most dont even know that there are bleeder valves on the traction system. !

 

To the top:

Has anyone figured out how to run the traction control pump?

 

I had lifted the rear of the car and pushed on the gas pedal. That activated traction. and I bled the rest. But I'm sure there's an easier way to do it.

 

Did this resolve your "very mushy/spongy pedal feel". How are the brakes engaging; correctly without side pull? No more pedal to the floor while engine is running?

 

Anyone bleed Trac correctly?

 

2 ways to activate the trac pump for bleeding:

1) lift the rear of the car, start the car, stomp on the accelerator. this will artificially fool the system into thinking there is a loss of traction and activate the trac pump

2) disconnect the electrical plug on the trac pump and briefly connect it directly to the battery.

 

trac pump
Could someone tell me how they applied power to the pump to bleed. I'm not ready to put the back wheels off the ground and run. I tried at the plug. I see the ground then the 2 blu/yellow wires. could someone post the exact steps?
Thank you very much.
Darren
darren.evans@comcast.net