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I have been unfortunately experiencing some brake issues at the track on my 1997 track car. For brakes the car is equipped with a 1" Willwood MC, a Supermiata 11" boxmount kit, SS lines, stock 1.8 none sport calipers in the back, Castrol SRF fluid. For pads I am running G-loc, R10 and R8. At the track I am unable to lock my brakes, by the time I put my foot to the floor I bottom out the MC. While I have some stopping power, I am no were close to being able to lock the wheels.
Background Knowledge
For many track days I was running this same setup except with the original Master Cylinder. The pedal felt amazing, brakes bit at the top and had fantastic modulation. Having a track day coming up and not much time I needed to bleed my brakes, I took my brakes to a shop, they bled them but after they had my car the bleeder valves on the Wilwoods were ALL bottomed out. Great job! I ignored this and put about 8 hours of track time till the fluid was cooked.
Right before another day I made the time to bleed them myself and thought it would be a good idea to change all the bleeder valve fittings on the Wilwood calipers. After I changed all of them I bled my brakes in the proper sequence using the 2 person push pedal method. Everything went well until I came to the last front caliper. I had realized that I had forgotten to tighten the bleeder valve on the brass fitting. When I went ahead to bleed this side I was getting endless small bubbles. I went back started from the same sequence with all the bleeders closed and when it got time to bleeding the last caliper I was stilling get endless bubbles. This point I gave up tested to see if the pedal was firm, nope the pedal felt spongy and only started building pressure 1/2 the way down.
Later I took it to my buddies shop and asked them to bleed the brakes, they used a vacuumed type method and the pedal felt better, but no were close to where it was. They believed I broke the MC by pumping the pedal all the way down and destroying the seals. Really not knowing what to do I tried it. I decided I may a well upgrade my MC in the process and so I went with the 1" Wilwood MC kit. I went and purchased the kit from Goodwin racing. Additionally, I decided to get bleeder assemblies for the Wilwoods because I was still getting all those bubbles when bleeding the front-driver caliper. I changed the fittings, and changed the MC. I first bled the MC from the bleed ports, something I noticed was I always got small bubbles when bleeding from the MC after the first 2-3 pumps. I called Wilwood and they said it was normal, I went ahead and bled all the calipers, no bubbles/air coming from a single corner. I took the car for a spin and I noticed that the pedal felt lower compared to the OEM MC. I thought it was a issue related to the small bubbles but it wasn't. Pumping the pedal didn't raise the pedal height either. I then realized there was lots of dead play in the pedal, so I went ahead and adjusted the spindle rod just before the rod would touch the MC. BOOM amazing pedal feel. Car felt ready to go like it used to. Pedal felt firm, wheels would fully lock.
First three track day everything seemed to feel okay but I really wasn't pushing the brakes, however, later on as the days progressed the pedal started getting lower and lower but no sensation of pressure loss. At the end I was bottoming out the pedal. Pedal has no feel until the last 20% then its stiff but wont produce enough pressure to lock the wheels. I contacted Goodwin racing and they sent me a new MC. I bench bled it, swapped it in and boom pedal feel all came back.
Second track day, I go into my first braking zone after warming my car up, bottom out the MC and I cannot lock the wheels. The pedal was stiff and throughout the day it got worse and worse till it got the to same point as the last MC, bottom 20% is the only place where there is pedal feel and it not enough to lock the brakes.
I contacted Supermiata and they got a short story and told me to adjust the pedal and give the MC more dead travel before engaging. They believed my brakes were dragging. It made sense honestly, but I never smelled my brakes. I tried this. My car felt like it had more acceleration, and rolled more when I was on a slope. I bled my brakes went to the track and same issues, no pedal till the last 20%. But the pedal feel never really came back but I had enough to lock the wheels.
My hypothesis
1. Brakes were dragging, bottoming out the MC at the track 24/7 just destroyed the MC.
- While I want to believe this I just can't because a MC shouldn't brake by pushing it all the way, plus there are no leaks, also how would it brake 2, and I never even smelled my braking fading.
2. Calipers are bad cause it happened after screwing with the bleeders. Wilwood support told me to use NPT tape to help seal the bleeder threads, dude on the phone swore by it. Worst advice ever, all that tape just got dissolved by the fluid and filled my calipers with junk. That junk clogged my bleeder valves, smh.
- Calipers broke cause of junk inside and or some kind of invisible leak, idk.
- Maybe the pistons are getting pushed back to far for some odd reason, idk.
3. My rear caliper has a point when I adjust the e-brake allen bolt. It is a little resistant and then it just keeps moving.
- I honestly cant imagine this being a issue cause its something mechanical.
4. Bad wheel bearing? They all felt fine though.
Key Points
Pedal is sponge/none existent until the last 20% of travel.
Pumping pedal does NOT build any more pressure.
Pads are new, properly bedded in.
I checked wheel bearings, with the car jacked up all wheel bearings feel solid. I cannot feel any play when nudging the wheels.
Rear calipers are set correctly for the E-brake.
Cannot see any leaks. Pedal does not feel as if it sinks.
Changing the MC once temporarily fixed the problem, then at the track the problem immediately returns.
I am at the point that I want to renew my entire brake system including the the solid lines running through the chassis. Would love to get some help getting this solved. Excuse typos.
Subscribed. Glad you posted here, lots of sharp people here. Welcome to Miataturbo.net.
Hopefully someone here has an idea other than swaptronics.
Edit: Was talking with Emilio about this more... Car is still NA right? Does the pedal feel change? lack of power locking up the brakes could be an assist issue. Unlikely if the pedal still feels spongy but.... it's an idea. If your booster diaphragm is leaking you'll lose assist/braking power. Not sure how to troubleshoot that but something you can check.
Never use a vacuum bleeder. Teflon tape is impervious to brake fluid. Op-rod needs to have some clearance when the pedal is fully retracted. You may have a leak. The fittings that came with the adjustable proportion valve that I purchased were not threaded deep enough for the tube nuts.
Car is naturally aspirated nothing done with the motor. Just a fresh and health 97 1.8.
With the engine on, the first 50% of the pedal travel is pure mush. It can effortlessly be pressed. The next quarter of the pedal is sponge and the last quarter is hard, like how the top of the pedal should feel. Once I bottom out the MC there is still not enough power to lock the wheels.
Never use a vacuum bleeder. Teflon tape is impervious to brake fluid. Op-rod needs to have some clearance when the pedal is fully retracted. You may have a leak. The fittings that came with the adjustable proportion valve that I purchased were not threaded deep enough for the tube nuts.
I did a whole general check for leaks on all the lines and calipers. Everything was dry. The adjustable prop is from SM/949. Possibly could be a leak with the stupid line I had to use to make Goodwin Racings kit fit with my portioning valve. But no visual leaks.
Is the op rod from the booster to the MC adjusted correctly? Did you remove the check ball and spring (residual valve) from the rear port of the MC?
Before it was a little to close. Now it has lots of dead play. After bleeding the brakes and adjusting brakes are still bad. The residual valve is removed.
If both rods are adjusted correctly and there is no leaks then maybe the booster is bad. I’m not sure what a bad booster would do other then increase the pedal effort.
If both rods are adjusted correctly and there is no leaks then maybe the booster is bad. I’m not sure what a bad booster would do other then increase the pedal effort.
Booster is fine, I without a doubt feel the master cylinder bottoming out(hitting the end of it). The car also only has 17,000 miles, would be pretty odd for it to break haha.
I had something happen sort of like this but nowhere near as bad. Couldn't get it to bleed properly. What ended up fixing it is doing the traditional two person brake bleed procedure but with the engine running. Person pumping the brakes does not need to stand on the brake pedal, just be firm with it. Start with the corner furthest from the master and end with the closest, also, you're going to need to bleed through a decent amount of fluid (like a quarter liter per corner) so consider maybe something less expensive than SRF for now. I think that since you're getting the added assist of the brake booster using this method, it's much better able to suddenly knock air bubbles out of places you might not have been able to by just bleeding with the engine off. Also, make sure you are closing the bleed screw before the brake pedal reaches the bottom of the throw. Short bursts.
I had something happen sort of like this but nowhere near as bad. Couldn't get it to bleed properly. What ended up fixing it is doing the traditional two person brake bleed procedure but with the engine running. Person pumping the brakes does not need to stand on the brake pedal, just be firm with it. Start with the corner furthest from the master and end with the closest, also, you're going to need to bleed through a decent amount of fluid (like a quarter liter per corner) so consider maybe something less expensive than SRF for now. I think that since you're getting the added assist of the brake booster using this method, it's much better able to suddenly knock air bubbles out of places you might not have been able to by just bleeding with the engine off. Also, make sure you are closing the bleed screw before the brake pedal reaches the bottom of the throw. Short bursts.
Love the suggestion! However, no air in the lines. We bled 2 liters of Type 200 then we put the SRF in there. No air at all in the lines. If there was air in the lines then pumping pedal would create more pressure. Sadly that's not the case. What added more pressure was changing the MC. After we changed it the pedal immediately came back then at the track it immediately left.
Love the suggestion! However, no air in the lines. We bled 2 liters of Type 200 then we put the SRF in there. No air at all in the lines. If there was air in the lines then pumping pedal would create more pressure. Sadly that's not the case. What added more pressure was changing the MC. After we changed it the pedal immediately came back then at the track it immediately left.
If both rods are adjusted correctly and there is no leaks then maybe the booster is bad. I’m not sure what a bad booster would do other then increase the pedal effort.
A bad booster would not increase stroke, it would only increase effort.
This S-bend into the prop valve looks like a huge potential air trap. Try bleeding at the connection into the valve to push all air out of that local high spot.
I had something happen sort of like this but nowhere near as bad. Couldn't get it to bleed properly. What ended up fixing it is doing the traditional two person brake bleed procedure but with the engine running. Person pumping the brakes does not need to stand on the brake pedal, just be firm with it. Start with the corner furthest from the master and end with the closest, also, you're going to need to bleed through a decent amount of fluid (like a quarter liter per corner) so consider maybe something less expensive than SRF for now. I think that since you're getting the added assist of the brake booster using this method, it's much better able to suddenly knock air bubbles out of places you might not have been able to by just bleeding with the engine off. Also, make sure you are closing the bleed screw before the brake pedal reaches the bottom of the throw. Short bursts.
Decided to give this a shot, no luck. Pedal feels exactly the same.
A bad booster would not increase stroke, it would only increase effort.
This S-bend into the prop valve looks like a huge potential air trap. Try bleeding at the connection into the valve to push all air out of that local high spot.
Agreed, I don't know why Goodwin racing didn't decide to just add an option to send 2 of the same brake lines to avoid this junction. You would think that most people with a 1" MC will also have a brake kit and will also probably have a portioning valve. I ordered SM's new kit as it will remove that point entirely. If I can find a shop that will flare some solid lines with the correct fittings Id prefer to do that but I do not even think that would make a noticeable difference in pedal feel. Anyone could chime in on that question?
I've added taking a dead blow hammer and tapping lightly on the calipers to ensure there are no stubborn bubbles trapped in the system. I was surprised to see stragglers come out.
have you thought about making your own power bleeder? How much pedal free play is reccomended for this MC setup?
From what the op has said so far it has to be the MC. Most likely if you put the previous mc back on they will work. The only causes are a bad mc, it’s not installed correctly or there is a leak. When I replace an mc regardless if it’s a factory part or aftermarket I measure from the inside of the piston to the mounting flange and compare it to the previous unit. I think last time I used a short piece of round stock, maybe 6-8mm in dia that I put a radius on one end. Then with dial calipers I compared both mc’s. There has only been a few times that I have been able to r&r an mc with out having to make an adjustment. It’s been a year since I swapped mine and I’m 2days into a dance the omicron so please excuse my writing. Just trying to help.
I've added taking a dead blow hammer and tapping lightly on the calipers to ensure there are no stubborn bubbles trapped in the system. I was surprised to see stragglers come out.
have you thought about making your own power bleeder? How much pedal free play is reccomended for this MC setup?
The mallet has always been my tool of choice for bleeding. That thing gets some suckers out after the first tap. I have thought about getting a motive power bleeder, just not sure if its compatible with the wilwood MC.
01-31-2022, 12:57 AM
No braking power!
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