91 LS400 All Four Brakes Sticking, Master Cylinder?
01-15-19, 08:14 AM
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91 LS400 All Four Brakes Sticking, Master Cylinder?
Hey everyone! Just picked up a beautiful 91 LS400 w/trac with a few issues but is definitely worth pouring some love into.
First things first, all 4 brake calipers begin seizing up after a few minutes of driving; after half a mile or so all 4 wheels won’t spin freely when I jack the car up and stick it in neutral.
I’m gonna start with replacing the master cylinder, but it’s been a pain in the @$$ AND the wallet finding a replacement MC -let alone a repair kit- for a traction control equipped 91 LS.
I purchased and am waiting for a used unit from a junked 91 w/trac to mess around with, but are the differences between a w/o trac and w/trac that significant? There doesn’t seem to be a lot of people running into this issue on the forum, so any insight’d be greatly appreciated guys!
First things first, all 4 brake calipers begin seizing up after a few minutes of driving; after half a mile or so all 4 wheels won’t spin freely when I jack the car up and stick it in neutral.
I’m gonna start with replacing the master cylinder, but it’s been a pain in the @$$ AND the wallet finding a replacement MC -let alone a repair kit- for a traction control equipped 91 LS.
I purchased and am waiting for a used unit from a junked 91 w/trac to mess around with, but are the differences between a w/o trac and w/trac that significant? There doesn’t seem to be a lot of people running into this issue on the forum, so any insight’d be greatly appreciated guys!
01-15-19, 01:11 PM
#2
I'd definitely consider the MC as the first suspect, given that the problem appears on all 4 wheels.
It's very easy to rebuild. Not much more than just R+R'ing with a new one. I did that on my '91. PN for the Lexus kit is 04493-22220.
But rather than just the rebuild, which will replace the rubber seals, etc., a MC that has a mis-adjusted rod can cause the problem you're seeing. Once you start driving and using the brakes, the brake fluid in all the lines will expand slightly due to the heat out at the calipers. The expansion ***should*** force a little fluid all the way back up through the system, through the MC, and into the brake fluid reservoir. But if the MC rod is mis-adjusted, the pathway for that fluid to move may be blocked, and the expanding fluid instead will cause the calipers to clamp onto the rotors, just getting worse as time goes on and the temperature increases.
So if you've recently done anything with the MC that may have let it become misadjusted (I don't know if simply bleeding the brakes with a little too much brake pedal could do this), you might want to look into that first.
It's very easy to rebuild. Not much more than just R+R'ing with a new one. I did that on my '91. PN for the Lexus kit is 04493-22220.
But rather than just the rebuild, which will replace the rubber seals, etc., a MC that has a mis-adjusted rod can cause the problem you're seeing. Once you start driving and using the brakes, the brake fluid in all the lines will expand slightly due to the heat out at the calipers. The expansion ***should*** force a little fluid all the way back up through the system, through the MC, and into the brake fluid reservoir. But if the MC rod is mis-adjusted, the pathway for that fluid to move may be blocked, and the expanding fluid instead will cause the calipers to clamp onto the rotors, just getting worse as time goes on and the temperature increases.
So if you've recently done anything with the MC that may have let it become misadjusted (I don't know if simply bleeding the brakes with a little too much brake pedal could do this), you might want to look into that first.
01-15-19, 03:13 PM
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Thanks for the advice Oldskewel, will definitely look into those internal components over the weekend, hopefully it’s something relatively easy.
Are there functional differences between MCs for trac and non-trac LS400s? Seems pretty easy to order the wrong one so given the lack of barking online I’m wondering if it’s not really an issue?
thanks again
Are there functional differences between MCs for trac and non-trac LS400s? Seems pretty easy to order the wrong one so given the lack of barking online I’m wondering if it’s not really an issue?
thanks again
02-17-19, 01:53 PM
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Just wanted to follow up on this issue and how I -fingers crossed- solved it ..
Purchased a used MC for TRAC-equipped LS400 on eBay, took it apart, cleaned out a ton of gunk, greased it up, and reinstalled.
The biggest problem I ran into was bleeding the TRAC system as I couldn’t get any pressure in the brake system and the pedal offered very little resistance. No fluid or air was coming out of the bleeder valves of the TRAC accumulator, actuator, or the calipers themselves when following bleeding procedures.
I’m probably an idiot, but later deduced bleeding the TRAC system requires the fluid in the MC reservoir remain well above the “min” level to ensure fluid gets to the accumulator/actuator, unlike the calipers which allowed levels to fall below the “min” line.
Car stops perfectly now, no more seizing calipers although I’ve only driven it a few miles.
Anyone think I messed anything up?
Hope my experience can add some clarity to the mysteries of TRAC equipped 90-91 LS4s
Purchased a used MC for TRAC-equipped LS400 on eBay, took it apart, cleaned out a ton of gunk, greased it up, and reinstalled.
The biggest problem I ran into was bleeding the TRAC system as I couldn’t get any pressure in the brake system and the pedal offered very little resistance. No fluid or air was coming out of the bleeder valves of the TRAC accumulator, actuator, or the calipers themselves when following bleeding procedures.
I’m probably an idiot, but later deduced bleeding the TRAC system requires the fluid in the MC reservoir remain well above the “min” level to ensure fluid gets to the accumulator/actuator, unlike the calipers which allowed levels to fall below the “min” line.
Car stops perfectly now, no more seizing calipers although I’ve only driven it a few miles.
Anyone think I messed anything up?
Hope my experience can add some clarity to the mysteries of TRAC equipped 90-91 LS4s
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