Just turned over 66K on the truck. Drove it this week and noticed the brake pedal seems a little mushy. Looking at the pads/rotors, seems like it might be time. Has anyone trying these before?

http://cgi.ebay.com/ebaymotors/ws/eB...DME:B:EF:US:11

 

Have any fellow gx470 owners experienced a soft brake pedal? Lexus of Rockville (MD) replaced the fluid, pads, rotors, and power booster but the pedal still doesn't grab like the loaner RX brake pedal did. Wondering if anyone has had and fixed this problem.

Drew

 

How funny is this; I have the same truck and just posted a thread on a soft brake pedal.

So far the dealer has replaced: the rotors, pads, fluid and brake booster. The pedal is better, but doesn't grab right away.

I purchased a set of EBC green stuff pads from www.ajusa.com even though the dealer put new pads on. They are great pads, low wear, no dust, and great performance.

I am thinking my problem has something to do with air in the system; either abs unit or brake lines.

Drew

 

I've merged the threads for easier reading and responses.

 

Usually a spongy brake pedal=air in the system. I'd find it hard to believe the booster to be leaking so soon. How old were your boosters? The one on my old 4runner (classic vacuum type) is 21 yrs old and doesn't leak! The electronic one on my LX is 4 yrs old, no leaks. If you're sure you have no air in the system, the booster isn't leaking, then you could always install stainless braided brake hoses to firm up the feel.

 

That's a good point. I said that to the guy in the shop, but they insisted on replacing every component including the booster. Can I blead this system on my own; or do I have to get them to do it for warranty purposes?

Steel braided lines on my wife's SUV, I never imagined going that route

 

According to the Lexus service manual, it says the scan tool the dealer has is needed to bleed the brake system.

 

Thank you; it's going back in when they receive the necessary parts to repair my clunk. I'll have them check it again.

 

I'll probably change the pads and rotors, then have the brake fluid flushed at the local Toyota shop. I noticed a major difference in braking response between the GX and LS. I don't think it's air or a booster issue. Probably the 40K miles difference between them. Lack of response to the eBay link tells me no one has tried this supplier, so I might as well be the first.

 

I've yet to bleed the electronic booster, only the traditional vacuum booster, but have asked a couple of techs on how to bleed the electronic booster. For the rear, if you depress the brake pedal and crack open the bleeder w/ the key in the "on" position, the electric pump will continuously pump fluid out. The toyota tech suggested pulsing the pedal, like a couple seconds on, couple seconds off, to let the motor rest. Be careful the master doesn't go dry as the pump can pump fluid fast. For the fronts, I'm told you can use the lexus tester, Toyota ABS SST, or pump the traditional way. This makes sense to me since if the booster fails, the failsafe mode is ZERO pressure to the rear and reduced pressure to the front brakes, at least for the LX/LC. This implies the rear brakes are completely powered by the electric booster while the front is an assist. For the time being, I've been having the dealer bleed the brakes on the LX every 1-2 yrs while I do it on the toyota 4x4 and honda to cut costs. I bring in my own brake fluid (Valvoline dot 4 synthetic), as the dealer uses the cheapie Pyroil (made by Valvoline) low end dot 3 fluid. Make sure they don't use a pneumatic brake bleeder (toyota dealer does this)...not good on the seals, IMHO, as it forces the fluid through the seals purely by pressure.

 

Thanks for the input; I will make sure to have them go thru the procedures you listed above.

KBach,

If you read my post, they replaced all of that stuff.

--Drew

 

As others have said, it's most likely air in the system, especially since they replaced so many parts and had the system open in so many places. In my experience, there's usually a benefit to bleeding a second time, and be SURE to do it in the correct sequence.

Regarding stainless braided lines, in and of themselves, they will not change the pedal feel. Stainless armored lines are more rugged and resistant to being torn away by flying debris (hence they are so common on race cars, etc.), but it's a common misconception that they flex less than standard lines that simply have rubber armor on the outside instead of stainless. (People seem to be under the impression that the stainless braid portion of the lines somehow give them more resistance to bulging, but that's not the case.) The reason that people change to stainless lines and then feel a firmer brake pedal is that they ALSO do a good bleeding at the time. If they put on new 'rubber' lines and did the thorough bleeding, they'd get exactly the same brake pedal feel.

source: personal experience on numerous vehicles with both conventional rubber-armored lines and with 'stainless' lines, along with extensive input from the technical director of Performance Friction while working on a project with them a few years ago

 

whoah...i didn't think soft pedals were a problem on the GX. My wife keeps complaining about the brakes not grabbing enough. I even just had pads replaced and rotors turned just two weeks ago. still, it is soft...

what do you guys think? should I go and have the brake lines bled?

please advice

 

If the pedal really is soft, a thorough bleeding might be needed. As you probably know, 'soft' is a matter of opinion, to some extent. For example, if you compare perfectly-working GX brakes (or just about any brakes) to some of the Honda Accord brakes, the non-Accord brakes will seem like they are mushy and require too much pressure because the Accord brakes can practically go into ABS mode with the slightest bit of pedal pressure (waaaay too sensitive, IMO). My point is that the brakes might have a problem, or they might just be the way GX brakes are designed to operate -- just need to identify which, and fix the problem if there is one.