Hi everyone, wondering if I could get any insight into the issue that I've been experiencing on my 99 GS400. Anyway, story time!!!

About 8-10 weeks ago I noticed that my car had started pulling to one side during normal driving. I did all the usual checks, tire pressure/wear checks, suspension component checks (most of the front suspension is less than two years old), and decided it was worth getting an alignment. The shop showed me the alignment was good and my suspension was in great shape overall, so no issue there - however the car still pulled to the right after leaving the shop.

The next step I took was to check my brake calipers and lines to see if there was any dragging. I easily noticed that my right front wheel was dragging excessively on the brake rotor (right front wheel way warmer after normal driving, and harder to spin when on the lift). Easy fix right?! Old 185,000 mile front calipers are bound to wear out, so I changed both front calipers and upgraded to the braided Stoptech lines, bled the brakes fine, took it for a drive... Damn thing is still pulling like nothing changed -_-

Now I'm a little stuck as with every car with a dragging brake caliper I've worked on, rebuilding or replacing the calipers or changing brake lines usually fixes the problem instantly. I put the car back on the lift and noticed that even with my new calipers and lines, the resistance to move the right front wheel is still higher than the left side, as well as the right wheel is much hotter after driving, almost like the pads are being forced against the rotor more on one side. One last detail is that I changed the BMC late last year as my old one was failing. I replaced it with the later model 2GS BMC and it's worked great ever since. My brakes and suspension overall feel great, its just this stupid pull that makes the car a chore to drive. Is it my new (to me) master cylinder secretly failing? A proportioning valve I don't know about?

Thanks for reading!

 

Most I can think of off the top of my head is either 1: a hub or 2: a warped rotor. First of all, a bad hub will have effects on the alignment, so thats pretty unlikely that it's the case.
A warped rotor is more of a possibility. You might also have a point about the BMC, but that would be something in the ABS unit so I can't say much about that. Also, there is no proportioning valve. All of the brake pressure adjustments are preformed by the ABS/EBD unit.

 

Its been a while since I’ve worked on a GS but how are the caliper guide pins? On my GS3 I had to replace one that was making the caliper stick. Are the pads wearing evenly on the inside and out? Lastly are you sure it’s not the bearings? Take of the caliper and see if the wheel still drags when turning.

 

Thanks for the info on the ABS unit. When I was replacing the calipers I checked for play in the hubs but couldn't find anything abnormal. I'm curious about a warped rotor though, especially since my front rotors are only about a 18 months old. Maybe I can temporarily switch them side to side and see if that makes a difference; I don't necessarily do any hard braking.

 

Thanks, I think I will test wheel bearing resistance side to side again next time I take another look at the brakes, just to rule that out. The guide pins on my new calipers seemed to have the same amount of resistance on both sides, so I'm curious as to why the brakes feel more "clamped down" on one side and not the other. The pads are relatively new but seem to be wearing evenly, though they are definitely being overworked compared to the left side of the car. I found quite a lot of buildup on the trailing edge of the brake pad chamfers on the right side.

 

What do you mean by they feel like the same resistance on both sides? Did you buy the entire caliper assembly, including caliper bracket, or just the caliper itself? On my car, the caliper guide pins were seized all the way, no movement at all. This caused the pads to compress harshly even without brake pressure and it was a lot worse on the right side. It made my rotors dang hot, glad they didn't warp. The guide pins are supposed to be able to move in and out without much resistance at all. (you have to take the caliper off to test the resistance)

The caliper pins are highlighted in red in case you didn't know where they are.

 

I bought 2 remanufactured calipers with brackets and new slide pins, fittings, etc. What I mean by resistance is moving the slide pins in and out by hand to make sure they travel smoothly, which they did. Even though the new slide pins came pre-lubricated, I may clean them and grease them myself again just for peace of mind. Once I get some time, I'm going to take a look at rotor clearance and how everything sits on the hub to see if anything's warped or misaligned. I'll report back if I find anything, but thank you for the help so far!

 

In this instance, your pins are probably fine. If it makes you feel safe, regrease them. Since those are fine I suspect the rotor is probably warped. Like I stated earlier, a bad hub would most likely cause an off alignment (most often the case). Wish you the best of luck!

 

I recently changed out my front brake calipers with some larger LS400 calipers. At the same time I rebuilt my rear calipers. Through all of this, I lost enough fluid that I felt like I got air in the lines that I just could purge out. I tried all the manual methods, watched the youtube videos, etc. I just couldn't get the brake pedal to feel as good as I felt it should. So I took the car to Lexus - the only service I've ever had done in the 5+ years I've had it - to have them bleed the master cylinder with their Techstream tool. It cost some money, but when I got the car back, the pedal felt great and the car's brakes inspire confidence. The point I'm making, albeit a bit long-winded, is I am suspicious that you could have some air somewhere in the airline on one of your front wheels. So when you mash the brake pedal, the front corner that does NOT have the air in the line responds quicker, and causes a pull toward that side. Might be worth forking over a few bucks to take it to the dealer and have it properly bled. Good luck!

 

Hey KyleH,
What's funny is that when I installed my replacement BMC I had the same issues you had after bleeding. When I would first begin braking, the car would pull to one side for a split second before straightening out. It turns out I had a little bit of air left in one side which I managed to get out; after that, all was good. The issue I'm having now is a constant drag on the right front brake rotor whether I'm braking or not. I have to hold the wheel straight with some force on the highway, otherwise it wants to immediately turn right as if the pistons or slide pins are stuck. New calipers and lines didn't solve the problem so I'm going to swap the rotors side to side this week as my next troubleshooting step. If that doesn't work, I may have to call a local Lexus specialist for advice - strange as I've also never had anyone work on or troubleshoot this car other than myself... Thanks for your input!

 

My apologies for not recognizing the symptom was a constant pull. Hmm... I can understand how this is frustrating. I'm assuming you've taken a micrometer to the rotor - swapping sides should be the same - assuming these are not cross-drilled & slotted, as I believe those rotors are side-specific. I really don't think you'd be able to get the caliper with new pads over the rotor if it were wider than spec - assuming you didn't have to hammer or otherwise force the caliper & pads into place. Granted I'm just grasping at possibilities here, but do you think it's possible the heat is coming from a cooked wheel bearing? There should be some other symptoms such as noise and play found in that case too. And frankly for all the wheel bearings I've had fail, I never noticed enough resistance to cause the vehicle to pull in one direction. I'm not near as well versed on the master cylinder functionality, but could it be possibly it's "failing" in some way, thereby, applying constant pressure to that particular brake line? As theoretical test, might pull the caliper off the rotor and have someone hit the key and see if any pressure is being applied when the pump runs - maybe put a block of wood or something between the pads just in case.

 

So it has been a hectic few weeks and I couldn't find much time to work on this issue until this past weekend. I'll admit here that in the interest of time I changed multiple variables at once (not the best for troubleshooting but oh well). I actually redid the full bleeding procedure for the BMC and bled the front calipers again for good measure. Additionally I swapped the rotors side to side to see if that changed the behavior of the brakes at all. I think the bleeding of the BMC made a slight difference in how the brakes behave. They feel a bit more solid and there is less pulling to the right but it is not completely gone. KyleH, in regards to what you suggested in seeing if there was any pressure applied when the pump runs, it didn't seem to change much with the key on or off. What I did notice when removing the calipers off the rotors after bleeding was that both sides' brake pads were clamped pretty hard onto the rotors without any pedal pressure, though they eased up once I'd driven the car a bit.

To be honest, with the general reduction in brake dragging and the less aggressive pulling, I may just be try to work on the wheel alignment to get me the rest of the way. The right side brakes are still a bit warmer than the left after driving, but not nearly as bad as before. It's not the most ideal solution to the problem, but there's a limit to what I can change at this point, and the issue may really be a combination of factors outside of just brakes. If I somehow manage to find a full fix or any revelations, I'll be sure to share.

 

Did your brake pads have the little chatter clips installed on both sides? I haven’t had my pads off in a while, so I don’t remember the exact setup. I haven’t seen these cause a car to literally pull to one side, but they are designed to push the pad off the rotor when the pedal is released. Sometimes they get lost or aren’t reinstalled when brake pads are installed and that comes to mind when you said the pads felt like they were clamped to the rotor when you tried removing them. Also, what is the status on the rear brakes? I sticky e brake on the opposite side would cause it to pull, and they are frequently forgotten about? Just a couple things that came to mind while reading your post

 

Wrong posta