[EdLoRPI]

Hi Guys,
I'm new to the boards here, but am a member of Club3G Eclipse. Anyway, my brother has a 94 MKIV TT auto w/ around 80k miles on it. He bought it used and ever since he got it, the brake pedal feel was horrible.

Here's the deal:

When driving, and he needs to slow down, he has to press the brake pedal further a great deal before the brakes seem to engage to just slow down. It's like the pedal has 2-2.5" of give. You literally have to push it down almost to the floor for it to slow down rapidly.

Since he got it, he has had a Toyota dealership flush the brake fluid. He has bled the brakes, replaced the stock rotors (which needed resurfacing) with Stillen slotted rotors. He has replaced the brake pads (not sure if it's Toyota). The Supra now stops better than before, but still doesn't have the sensitivity of my 3G Eclipse GT. I've driven quite a few cars before - but no other Supra but his. Nevertheless, I don't believe Toyota would have been stupid enough to put brakes with this kind of weak feel on a 320hp supercar. I Auto-X, but I wouldn't feel safe Auto-X'ing with his Supra, unless the brakes had better feel. It just seems like there isn't enough pressure.

So, thanks for reading all my drivel and following me this far. What do you think it could be? Thanks in advance and apologies if this question has been answered before. I searched the board for postings with 'brake AND pressure' and 'brake' but couldn't find anything that will help.

Regards,

Ed

 

[Grant]

The 97-98 Supra have a different master brake cylinder, which gives them much more sensitive brake pedal feel. Asuming the brakes were bled properly, I can't really think of anything else that would cause this.

Nowdays many car makers put overly sensitive brakes on their cars to make it fell like they can stop better. Personally I like the older feel better, as its easier to heel and toe (and thus autocross) with. Mash the brake pedal and you will STOP. You should feel Porsche 911/996 brakes, they are even less sensitive.

 

[95SupraSE]

That's really strange. I hear people raving about the brakes on the MKIV all the time. If the TT brakes are anything like those on my NA (and they're supposed to be better), they should feel great. I've driven lots of cars, and the pedal on my MKIV feels harder than most other cars. Maybe there is something wrong woth your master cylinder.

 

[EdLoRPI]

Yeah, I'm not too sure about how the brake pedal is supposed to feel on the 94 Supra TT. I've driven a 96 Toyota RAV4, 97? and 80 Corolla (as far as Toyota's go) and all of them have great brake pedal feel - pretty sensitive. Experiencing the pressure (apparent lack thereof) of my bro's MKIV got me concerned. Since he replaced the pads and rotors, flushed? and bled the fluid, I think it might be the brake booster / brake master cylinder. He got the car used - and I could tell, the previous (2) owners didn't take care of the car...those bastards! I love the car but I seriously think the brakes should be a lot stiffer, with very firm feel. -especially since it's over 3k lbs, 320hp and has a very high capacity for getting into trouble with the law (accel & speed).

So that leads me to ask...

How would I go about checking to see if it truly is the brake master cylinder that is faulty? If it is true that the 97+ Supras have different master cylinders, perhaps it would be better to replace the current one with a 97+ cylinder. What else would need to be replaced if he were to get an updated cylinder?

Thanks for the help guys!

Regards,
Ed

 

[toypro]

How did the pads look when they came off-even wear? A "stuck" caliper can cause a soft pedal. I have never seen a booster or master cylender cause these syptoms-from what I've seen they either work or don't. I would buy caliper rebuild kits and rebuild them first-the kits are pretty cheap from toyota. Also a car with ABS is much harder to bleed the system than a non abs car. I use a vacuum type bleeder at work, but have had one(my own mk3) that I had to drive around the block, kick in the ABS and than rebleed. I would also check all the brake lines and make sure they are not "swollen" in any spots. Might be a good idea to pick up some SS lines.

 

[EdLoRPI]

Not sure how the pads looked, I'll have to ask my brother about that one. Thanks again for the help - I'm already looking into SS lines, I've heard the stock lines go at higher mileages - and this one is at 82k or so. I'll also have him check the calipers.

Q: If the master cylinder/booster failed, how would one know? Sorry if there's an obvious answer...

Regards,
Ed

 

[toypro]

Not sure how the pads looked, I'll have to ask my brother about that one. Thanks again for the help - I'm already looking into SS lines, I've heard the stock lines go at higher mileages - and this one is at 82k or so. I'll also have him check the calipers.

Q: If the master cylinder/booster failed, how would one know? Sorry if there's an obvious answer...

Regards,
Ed

When I've seen the master cylinders fail-they leak fluid-never have seen a pressure problem. The only booster I've seen fail would cause the pedal to go completly to the floor after 2 or 3 stops. None of these were on supras.Although I wouldn't 100% rule out either of these, I think you'll find your problem to be in some other part of the brake system. Toyotas in general do not have booster/master cylinder problem, but of course anything is possible. The most commen time a master cylinder is replaced is when it has been topped off with motor oil-happens more than you would think, although this is definitly not your problem. I would carefully inspect all the rubber lines and rebuild the calipers if you don't find anything in the lines.Going by what you've already done, I'd bet your problem lies in one of these two areas-Good luck

 

[red94tt]

I would carefully inspect all the rubber lines and rebuild the calipers if you don't find anything in the lines.Going by what you've already done, I'd bet your problem lies in one of these two areas-Good luck

Does Toyota offer a rebuild kit for the Supra's calipers? I am replacing pads, rotors, swapping OEM lines for the SS ones, and flushing the lines completely this winter. I was contemplating buying a rebuild kit if one is made for the calipers.

 

[toypro]

Does Toyota offer a rebuild kit for the Supra's calipers? I am replacing pads, rotors, swapping OEM lines for the SS ones, and flushing the lines completely this winter. I was contemplating buying a rebuild kit if one is made for the calipers.

I would have to assume so, I can't imaigne why not. I know they offer them for all the other cars, but I have never rebuilt a mkiv caliper before. I have never had to rebuild a twin piston/fixed caliper before, but I have seen it done. I think the kit only run about 25.00 for a pair. On my own vehicles, I rebuild the calipers every other brake job, but I'm pretty anal about brakes.

 

[red94tt]

Thats cool, I figure they would have to make them too. Every brake "expert" I have talked to suggests that it is a must to rebuild your calipers (or replace) when you do your brakes every time, or at least every other time. And rebuilding is always cheaper than replacing them 9 times out of 10! My car has 80,000 miles and the brake system is feeling tired to me, so the more things I can do, the better.

 

[EdLoRPI]

Very interesting... toypro - thank you very much for your help. Your post was very insightful - I'll have to have him look into the rebuilding as well. Though I'm not sure why the dealer and the other 2 mechanics said the brakes were fine. Argh...such a pain in the ass. If I only knew what the previous owners did to the poor car...

So here's my checklist:
calipers - check for stuck calipers, check for necessity for rebuild
stock lines - check for bulges/aging - replace with SS
check booster/master cylinder - consider replacement with 97+

The brake fluid definitely doesn't leak. Most of the system seems to check out right...which is why this problem is so puzzling to me...I originally thought it must've been something to do with pressure - which meant check lines & booster. I just hope it won't cost my bro more $$$ - he's already put quite a bit into the car, with plans on modifying it later. He's hesitant to race with it since the prior owners took crappy care of the car. Poor guy.

Thanks again for the help - this is my first experience with the board and I'm already finding it quite helpful.

Regards,
Ed