Closed Circuit / Self Bleeding (Recirculating) Brake System

[94shodriver]

Anyone ever used/installed these?

I'm having overheating issues with my brakes. I'm running the 12" PBR set-up under slicers. My car is full weight and I track it a bit. This season I've taken it to the track three times. Before the season I did a complete flush with Motul 600. The first track day finished off half a set of HP+ in the rain. The track was very wet and there was a lot of ABS activation, so I bled the brakes healthily after that session. The second session was dry, no issues other than a lot of micro rotor cracking and cooking through a half set of brand new Hawk Blues. Again after that session I bled the tops off of the brakes. The last session was dry, with a little bit longer session times. Halfway through the third session, I boiled the fluid and when I pulled in I had complete cracks in both rotors and the pads were to the brackets in the front. I was prepared for this and had new rotors and street pads with me. I bleed the brakes as much as I was comfortable with at the track and when I check the master-cylinder, it had brown fluid in it just like the boiled stuff in the calipers. I don't recall any ABS activation between the second and third days, so I'm inclined to think that my issues are heat related and not equipment related.

That said and knowing that slicers do not offer the best cooling, I'm looking for ways to combat the heat build up and retain my current set up. I still drive the car on the street and I have a set of track tires on a second set of slicers. I'm trying to avoid 17" wheels for many other reasons too; cost, weight, diameter, etc. I would rather not go to cooling ducts because I actually use the fog lamps and I don't want to have to instal and remove them every time I go to the track, or risk shooting gravel at my rotors.

I did some research, and found a little information about closed circuit brake systems, where the fluid is circulated and cooled instead of sitting in the calipers. It could help with the pad and rotor issues too. Nothing I found stated weather or not this would work with ABS or not. Looking through the Taurus manual and at the info on Wilwoods web page, it appears that if I place the first check valve below the ABS module and the second very near the t at the front of the master cylinder, I would retain ABS functionality.

Before I hack my brake lines up and spend some money I thought I would inquire if anyone has used these on a SHO or any other ABS equipped car.

Thoughts?

 

[LJRuddy]

Not to be an ass but with the brake set up you are running, over heating should not be an issue. Some people on here track their cars with stock gen 3 brakes and solid lines and have no issues with them.

What are your braking habits like?

 

[94shodriver]

I'm braking deep, but not out of line with other, well set up cars. The thing is I even backed of my brake points by about 50ft on the last day, just to try to save them a little. I have SS lines too.

I don't know how Portland International Raceway compares to other tracks with regard to brakes. All the other SHOs that I know of running there have 13" brakes or are gutted, though some of them are supercharged.

 

[gmorrell]

I run the Baer 12.5" PBR 2-piston brakes on a full weight supercharged car on the track without any fluid boiling issues, I also run 16 X 8 track wheels (ROH Snypers). I looked into the fluid recirculation systems many years ago, but never though it necessary, and disliked the additional complication of extra flex lines to the calipers.

Have you looked into some effective brake cooling ducts and proper baffling to make sure the air makes it to the centers of the rotors, and also washes over the caliper body? You might also consider using some 3" 12 Volt bilge blowers in the brake ducting to increase the airflow on slower parts of the track. Bilge blowers are available at marine supplies, and stupid ricers think they're electric superchargers.

I would try brake cooling long before I resorted to a fluid recirculation system.

 

[shopartsnw]

I am wondering if you have either a bad master cylinder (dragging) or maybe a bad batch of brake fluid. I am really baffled because you have done everything correctly as far as I can tell.

As a reference, the GI SHO team beats on the car hard, and rotors/pads can last a 24 hour race. I know that car has been stripped of a lot of weight, but I don't think it would account for such a significant difference, especially since Karen runs the S/C car at more than full weight and the brake pads last for a long time.

The more I think about it, the more I wonder if it is not a master cylinder issue. With the engine running, do you have a firm pedal? Does it engage at the correct point and not drop away if you hold pressure on it?

Other experts please chime in.

Mike

 

[shopartsnw]

Gary,

Thanks for the input. I did not see your response until after I posted. I am working on custom brake ducts to get cooling into the rotor eye, but time constraints are pushing it out into summer development.

In this case, I think Ian is doing everything right, but obviously something is still wrong and I am missing it too.

Thanks

Mike

 

[SHOtime2511]

If its not a dragging issue Im also thinking there is a fluid issue.
Is it possible you didn't get a complete flush and fill with the new stuff?

Killing pads that fast makes me think the slides may be stuck?

 

[94shodriver]

Gary- I am considering any sort of cooling system. It just seems for my purposes and resources that a recirculation system may be the way to go. Keep in mind this is still my daily driver and will be for at least another year. That is why the issue for me is if the ABS will still function properly. Cooling ducts and fans seem to be almost as much trouble as more plumbing, especially considering that the entire system is contaminated now from pushing the fluid all the way back up into the master cylinder after changing out pads.

Mike- my caveat to the master cylinder culprit is that the brakes worked fine on the street with no apparent overheating, glazing, or abnormal pedal feel; the only difference being HPS pads. Additionally those pads are in fine shape after a thousand plus street miles.

The pad ware could have been aggravated by the condition of the rotors. I was really just trying to get one last event out of them. I think I forgot to mention that the ware was not even, with the front inboard pad having the most ware, and about a 1/8" difference across the length of the pad face.

Just to be clear, I'm not advocating the use of one cooling system over the other, just if it would be feasible for my situation. I am attracted to the idea that with a recirculation system having a higher thermal transfer rate in your braking components would be advantageous instead of spending a bunch of money down the road on titanium backing plates and stainless caliper pistons.

Thanks for everyone's input,

Ian

 

[zak]

Ian,
Run a search under my user name and the keyword "swept", you will come accross my comments regarding using the PBR setup on only a 12 inch or so rotor. Basically you are giving up considerable swept area over say the 11.6 inch/single piston caliper setup by a large margin. Swept area = heat transfer area.

Make sure the rear brake on/off valve is not stuck closed, leaving you with no or very minimal rear brakes.

zak

 

[93rev2sev]

about a 1/8" difference across the length of the pad face.
Ian

Sounds like you know your stuff. Probably a **** ton more than I do, it seems to me, though, that if you are not getting even wear (front to back on the pads), then you have a loose wheel bearing or a flexing (or bent/cracked/fatigued) bracket.

Either one of those could be causing your brake fluid to overheat, I would think.

 

[gmorrell]

Among other things, you will want to check into the following:

1. Caliper fire path is square with the rotor, if it isn't, the pads will wear unevenly. Check the piston and the passive sides, as PBR calipers have been known to spread across the bridge.

2. As others have mentioned, the vacuum boosters in this car have a failure mode that causes brake drag, at least have a look at it.

3. A brake fluid recirc system addresses the symptom, but not the cause. The cause is heat in the rotors and pads, and brake cooling ducts will help with this immensely.

4. Maybe consider pad heat shields, they are available in the PBR backing plate profile in Titanium. Ti is a really poor conductor of heat, and is frequently used as a very thin shim between the pad backing plates and the pistons to keep heat out of the fluid. One of the Camaro/Corvette performance places makes and sells these, I can't think of the name at the moment.

5. One last thing to consider: Stainless caliper pistons, and again, if I can think of the place, I believe they have a PBR piston with a thermal break in the heat path, these will also lower brake fluid temps.

 

[94shodriver]

Zak- I'm already familiar with your comments and I understand that this is a contributing factor. However, the lighter calipers, larger piston area, pad availability all contributed to my original decision to go with this set up. The 12" rotors are thicker than the 11.6" (larger thermal capacity). I would hypothesis that the combination of aluminum calipers, smaller swept area and higher friction pads all contributed to higher fluid temps than with the 11.6 type set up. I'm not just considering the heat transfer, but the destination of that transfer.

93rev2seven- I check my wheel bearings regularly and they are in good condition. Brackets as well. The rotor with the larger crack was on the drivers side which has a newer wheel bearing.

Gary- 1. I will certainly check this. I'm going to put some new seals in the calipers when I re-flush the fluid.

2. I will investigate this as well, though my comments about street performance seem to rule this out initially.

3. I believe this is debatable. Heat in the rotors and pads is the issue, but a recirculating system (in theory) acts as another type of active cooling. I don't know how effective it is versus cooling ducts, given the lower volume of fluid and lower flow rate, but higher specific heat and conductivity (I'm somewhat educatedly guessing). I doubt that it is as effective, but perhaps enough to treat my symptoms.

4 and 5. In my comments I above mentioned these items and that they could actually work against the cooling effects of a recirculating system, again, at least in theory.

If I may, I would like to redirect this thread to one of my original questions: Is it possible to install one of these systems on a SHO and retain the ABS functionality?

I'll up the ante and do a "How To" thread if I go forward with this.

Thanks again everyone,

Ian

 

[shopartsnw]

Ian,

After having multiple master cylinder and ABS pump issues, I no longer compress the fluid back into the system unless it is super clean (testing pads) or a very minimal amount. Most of the time I will connect the bleed hose and crack the bleed screw so I force the used/bad fluid out the bleeder rather than back into the system to contaminate it.

The comment on a sticking slider pin is a valid one. I put just a hint of never seize on the slider pin and the very edges of the backing plate to make sure they don't drag. Just don't over do it as never seize has a way of trashing pads.

One last option is to look at the caliper itself. I have had them get "sticky" and drag too. I pop the pistons out and make sure everything is clean. Then lightly lubricate the o-rings with silicone grease (silicone dielectric grease will work), as the silicone grease will not mix with the brake fluid, will not damage the rubber, and makes everything slide nice. Again, don't go crazy with the grease. You don't want chunks of grease breaking free and working through the system.

Definitely let us know what you find.

Mike

 

[Shoaz]

Ducting is easy, effective, cheap, and will likely solve your overheating problems. Been there, done that, on two SHOs, one of which set a bunch of track records and won some championships:

The idea is just to get the air directed at the caliper, since that's where the fluid is boiling. The setup shown moves enough air in the general direction of the caliper and rotor to keep things cool. My brake boiling problems ended after I added the ducts.

The fog lamp holes are the inlets and the inlet ducts are from Race Parts Wholesale or a host of other race supply places that carry the same rectangular-to-3" ducts.

The outlets are 3" RV sewer system elbows from Wal-Mart with the ****** cut off.

The ducts are 3" aluminum dryer vent available at most Home Depot, Lowe's, Ace Hardware, etc., stores.

 

[gmorrell]

If I may, I would like to redirect this thread to one of my original questions: Is it possible to install one of these systems on a SHO and retain the ABS functionality?

I'll look through my files at home and see if I can find the info I had about the recirc system, I think it was directed towards Winston Cup cars.

I believe it would not affect ABS function, but this was not an issue I was considering on my ABS-less '89 SHO.

IIRC, it worked using a little valve on the caliper that stayed open for a bit during initial brake application, this allowed a little bit of fluid to "burp" back to the MC reservoir through a separate set of hoses that were connected to the calipers and burp valves at the bleed fittings. After the initial burp, the valve closes, allowing normal pressure to build in the caliper.

I remember talking to the fellow on the phone about it, and he said that what you got was a little bit of extra pedal travel at initial brake application, then the burp valve closed and the pedal firmed up. The whole idea being that each time the brake pedal is pressed, a tiny bit of fluid is recirculated out of the caliper.

Truthfully Ian, I see this not as a caliper cooling method, but more just shuttling brake fluid around - keeping fresh(er) fluid on the "hot" side of the hydraulic system. For each pedal application, there can't be enough fluid leaving the caliper to effectively remove much heat. If the brake system is just too flippin' hot, eventually, all the circulated fluid is going to get overheated, so you're buying some time before all the fluid is cooked, I won't dispute that, but getting a flow of cooling air to the caliper is the KISS solution.

 

[gmorrell]

I found my notes from 1997, the company that was making the brake cooling/recirculating system was Stewart Brake Development, High Point, NC. They're now Stewart Development, and they apparently still supply a similar system to NASCAR teams.

http://www.stewartdevelopment.com/dev.html

At least back in 1997, the system was available to NASCAR teams by lease only, but I had some communications with a fellow who was running ITS in the Southwest and was using two of their burp valves mounted in the fenderwells and plumbed to the caliper bleed fittings. The system routed "used" fluid back to the master cylinder. He also commented that they were using Castrol SRF brake fluid at $70 per liter!

There was also a recirc system developed by Huntley Racing of San Diego, and it was a favorite of the Porsche racing crowd, but it seems that Huntley Racing went ****-up sometime in 2004.

I also found some references to the Wilwood Dynamic Bleed System.

"The WDBS allows small amounts of brake fluid to circulate within a closed loop system every time the brake pedal is depressed, thereby eliminating the possibility of localized fluid boiling and build‑up of gasses within the brake fluid (gases end up being vented into the master cylinder reservoir rather than being trapped within the caliper or brake lines). The result is a firmer, more consistent pedal throughout the race. The WDBS consists of two one‑way valves and a special crossover tube (which replaces the caliper bleed screws)."

Edit: Apparently, WDBS is still in the catalog: http://www.wilwood.com/PDF/DataSheets/ds213.pdf

It seems that you could purchase Wilwood's valves and do some plumbing to the PBR caliper's bleed fittings.

Good luck,

 

[94shodriver]

Mike- I think the slider pin could definitely deserve some attention too. I'll check it and **** it along with the pistons when I break everything down and inspect the firing path and so forth. Pushing the fluid back into the MC- well, sometimes you just learn the hard way. I think the UDP and the rest of the engine/transmission/suspension parts (everything) I've purchased from you are just working too well The car is only 4-5 seconds a lap behind my Exige!
BTW- Good luck this weekend.

Eric- Honestly, I was unaware that such a simple ducting system was effective with the SHO. I thought that a more direct airflow path was needed. Is that system effective without using titanium backing plates and/or stainless pistons?

Gary- I had previously found some references to Stewart components but not to that website you listed. The system that I sketched out would have to use four of the Wilwood check valves, two for each front wheel circuit. If I keep pressing forward with this, I'll post up a function block diagram for review.

Thanks everyone for your input, I know there's a lot of experience here.

Ian

 

[gmorrell]

I stumbled across this recently, DPI sells a brake fluid recirculation valve.

DPI Racing Products "Sure Stop I and II".

 

[GR8WYT]

Apparently this is not an uncommon problem. Read the article from Car & Driver about the NISMO 370Z brake problems:

http://www.caranddriver.com/features/10q2/z_meets_wall_we_investigate_why_the_nismo_z_s_brakes_failed_at_lightning_lap-feature

 

[Shoaz]

Apparently this is not an uncommon problem. Read the article from Car & Driver about the NISMO 370Z brake problems:

http://www.caranddriver.com/features/10q2/z_meets_wall_we_investigate_why_the_nismo_z_s_brakes_failed_at_lightning_lap-feature

FWIW, IMHO they sound a bit like n00bs expecting street pads to hold up on the track in a competitive environment. For a DE session, sure, but you have to drive it like it's on street pads. Early in the article they wave their hands that it wasn't a driver problem, but I'd be suspicious of any "track driver" expecting competitive performance from a car on factory pads. I'm hard pressed to think of a car where one could expect to do that.

That being said, I've been "competing" in TT with my Focus for the last several events, on the OEM Ford pads, but I ain't about to drive it like it's got anything more than that.

I think they ran out of setup talent before they ran out of brakes, strictly IMHO.