Brake Bleeding Advice

[ralph92ZR1]

I bought my '92 ZR-1 in March '05 with 12,000 miles and have since added 3500 -fun miles. I traded a '69 that I had completely rebuilt the calipers and brake system, i.e. I saw the damage done by not changing brake fluid. I am looking for advice because when I checked with my dealer they said "with the new calipers " fluid does not really need changing. That may be the same as "if not broke-let it alone". Must a pressure bleeder be used?? Any issues with the modulator if no air has entered the system??
Thanks for advice given...:)

[cwmoss]

Ralph,
It is a VERY good idea to regularly change the brake fluid. I had a 2001 Z06, that had only 2900 miles on it when I bought it, but it was about 4 years old. I bought one of the Mini Vacs. You can get them at Harbor Freight and other places for about $40.00. What you do is first get a turkey baster and suck most, not all, of the fluid out of the reservoir, fill it with new fluid. Then go to the CLOSEST caliper, attach the flex line to the bleed screw, then pull a vacum with the mini vac, and crack the bleed screw and it will suck the disgusto fluid out. Do this until all you see is good clean fluid. Remember to check the reservoir so you don't get too low. Then go to the next closest caliper and repeat( 1.Left-front, 2. right-front, 3. left-rear, 4. right-rear.) It's a one man job. After I bought my ZR1 a few months ago, that was the first thing I did after changing the oil. It was a snap the second time around. The moisture in the system will rust the lines from the inside out. I had a '67 big block car that I bought back in 1983 and it had brake problems. So I bought a SS kit from one of the vendors and when I started taking the original stuff off, the lines just came apart. Good Luck !!!!
:thumbsup:

[WB9MCW]

DOT #5 my mech. swears by it and upgrades it for all of his rides incld his 98 vert. All the exotics use it...must be a reason why ya think!!!!

[Tom]

Bleeding the fronts is very easy and quick since you don't have to remove the wheels, just raise the hood and you have access to the bleeders. Jacking up the back end, removing, and reinstalling the rear wheels takes most of the time to complete the job.

[Bill]

DOT #5 my mech. swears by it and upgrades it for all of his rides incld his 98 vert. All the exotics use it...must be a reason why ya think!!!!

I had read that Dot 5.0 brake fluid was silicone based and as such is not compatible with our ABS equipment. I know that silicone based brake fluid is more moisture resistant. Higher numbers (5.1 & 5.2) were ok. Has any one else heard this, any comments? The most frequently recommended fluid is (no flames please) Ford Blue brake fluid. :blahblah:

[ralph92ZR1]

Thanks...makes sense and I appreciate the help.

[cwmoss]

I agree, Dot 5 is Silicone and for the earlier "NON ABS" cars.:thumbsup:

[WB9MCW]

well that raises a ? then. is 5.1 and above really that much different than 5.0

[Bill]

well that raises a ? then. is 5.1 and above really that much different than 5.0
Brian, now your making me work. I was not sure either so I found this:

Stolen from the Airheads BMW Club newsletter - July 1995
Battle of the DOTs
DOT 3-4 Verses DOT 5. Which brake fluid should I use?

From Oak Okleshen #35 "With regards to the DOT 3-4 verses DOT 5 brake fluid controversy, here is an article sent to me by Mr. Steve Wall. It is one of the most professional treatments I have seen on the subject".

[I had to condense this article from 6 pages to 1 due to space limitations -ed]

Brake Fluid Facts
by Steve Wall

As a former materials engineering supervisor at a major automotive brake system supplier, I feel both qualified and obligated to inject some material science facts into the murky debate about DOT 5 verses DOT 3-4 brake fluids. The important technical issues governing the use of a particular specification brake fluid are as follows:

1. Fluid compatibility with the brake system rubber, plastic and metal components.
2. Water absorption and corrosion.
3. Fluid boiling point and other physical characteristics.
4. Brake system contamination and sludging.

Additionally, some technical comments will be made about the new brake fluid formulations appearing on the scene.

First of all, it's important to understand the chemical nature of brake fluid. DOT 3 brake fluids are mixtures of glycols and glycol ethers. DOT 4 contains borate esters in addition to what is contained in DOT 3. These brake fluids are somewhat similar to automotive anti-freeze (ethylene glycol) and are not, as Dr. Curve implies, a petroleum fluid. DOT 5 is silicone chemistry.
Fluid Compatibility

Brake system materials must be compatible with the system fluid. Compatibility is determined by chemistry, and no amount of advertising, wishful thinking or rationalizing can change the science of chemical compatibility. Both DOT 3-4 and DOT 5 fluids are compatible with most brake system materials except in the case some silicone rubber external components such as caliper piston boots, which are attacked by silicon fluids and greases.
Water absorption and corrosion

The big bugaboo with DOT 3-4 fluids always cited by silicone fluid advocates is water absorption. DOT 3-4 glycol based fluids, just like ethylene glycol antifreezes, are readily miscible with water. Long term brake system water content tends to reach a maximum of about 3%, which is readily handled by the corrosion inhibitors in the brake fluid formulation. Since the inhibitors are gradually depleted as they do their job, glycol brake fluid, just like anti-freeze, needs to be changed periodically. Follow BMW's recommendations. DOT 5 fluids, not being water miscible, must rely on the silicone (with some corrosion inhibitors) as a barrier film to control corrosion. Water is not absorbed by silicone as in the case of DOT 3-4 fluids, and will remain as a separate globule sinking to the lowest point in the brake system, since it is more dense.
Fluid boiling point

DOT 4 glycol based fluid has a higher boiling point (446F) than DOT 3 (401F), and both fluids will exhibit a reduced boiling point as water content increases. DOT 5 in its pure state offers a higher boiling point (500F) however if water got into the system, and a big globule found its way into a caliper, the water would start to boil at 212F causing a vapor lock condition [possible brake failure -ed.]. By contrast, DOT 3 fluid with 3% water content would still exhibit a boiling point of 300F. Silicone fluids also exhibit a 3 times greater propensity to dissolve air and other gasses which can lead to a "spongy pedal" and reduced braking at high altitudes.

DOT 3 and DOT 4 fluids are mutually compatible, the major disadvantage of such a mix being a lowered boiling point. In an emergency, it'll do. Silicone fluid will not mix, but will float on top. From a lubricity standpoint, neither fluids are outstanding, though silicones will exhibit a more stable viscosity index in extreme temperatures, which is why the US Army likes silicone fluids. Since few of us ride at temperatures very much below freezing, let alone at 40 below zero, silicone's low temperature advantage won't be apparent. Neither fluids will reduce stopping distances.

With the advent of ABS systems, the limitations of existing brake fluids have been recognized and the brake fluid manufacturers have been working on formulations with enhanced properties. However, the chosen direction has not been silicone. The only major user of silicone is the US Army. It has recently asked the SAE about a procedure for converting from silicon back to DOT 3-4. If they ever decide to switch, silicone brake fluid will go the way of leaded gas.
Brake system contamination

The single most common brake system failure caused by a contaminant is swelling of the rubber components (piston seals etc.) due to the introduction of petroleum based products (motor oil, power steering fluid, mineral oil etc.) A small amount is enough to do major damage. Flushing with mineral spirits is enough to cause a complete system failure in a short time. I suspect this is what has happened when some BMW owners changed to DOT 5 (and then assumed that silicone caused the problem). Flushing with alcohol also causes problems. BMW brake systems should be flushed only with DOT 3 or 4.

If silicone is introduced into an older brake system, the silicone will latch unto the sludge generated by gradual component deterioration and create a gelatin like goop which will attract more crud and eventually plug up metering orifices or cause pistons to stick. If you have already changed to DOT 5, don't compound your initial mistake and change back. Silicone is very tenacious stuff and you will never get it all out of your system. Just change the fluid regularly. For those who race using silicone fluid, I recommend that you crack the bleed screws before each racing session to insure that there is no water in the calipers.
New developments

Since DOT 4 fluids were developed, it was recognized that borate ester based fluids offered the potential for boiling points beyond the 446F requirement, thus came the Super DOT 4 fluids - some covered by the DOT 5.1 designation - which exhibit a minimum dry boiling point of 500F (same as silicone, but different chemistry).

Additionally, a new fluid type based on silicon ester chemistry (not the same as silicon) has been developed that exhibits a minimum dry boiling point of 590F. It is miscible with DOT 3-4 fluids but has yet to see commercial usage.

here is the link where I found it
http://www.xs11.com/tips/maintenance/maint1.shtml

We all know about the reliability in web info, so I'll keep looking. :)

[WB9MCW]

GREAT POST BILL!!!! Looks like my best friend/mech of mine WILL NOT BE PUTTING DOT 5 IN MY ZR-1!!!! I too did a search of the zr-1 list serve and a recent post by KIM L. that she went with the super dot4 new ones and was happy....Jeeeze why does it always have to be so complex???? ok guys this this the time to chime in and let us know what is workin out there in the real zr-1 world......WE WANNA KNOW WHAT DOT UR USING ON YOUR ZR-1!!!!! AND WHY AND HOW HAVE YOUR RESULTS BEEN!!!

[Tom]

DOT 5.1 is a synthetic non-silicone brake fluid. I use DOT 3 brake fluid and change it once a year. Some track day events require you to have changed the brake fluid within so many days before the event, for example within 30 days of the event, to ensure the fluid has not had time to absorb moisture and reduce the boiling temperatures. You can look up most brake fluids at the manufacturers website and see what the new boiling point is. Different DOT 3's and 4's will have different boiling points, they just have to meet the minimum boiling point.

MINIMAL boiling points for these specifications are as follows:
Boiling Point Ranges
Dry Boiling Point Wet Boiling Point
DOT 3 205°C (401°F) 140°C (284°F)
DOT 4 230°C (446°F) 155°C (311°F)
DOT 5 260°C (500°F) 180°C (356°F)
DOT 5.1 270°C (518°F) 191°C (375°F)

[WB9MCW]

but now the big question is will dot 5.1 swell up the rubber parts??? if not then it would be a good fit 4 the ZR-1!! right??? posib. the dot 4's could work as well as no silicone too. But have not the Germans used reg dot5 in cars with ABS??? If so they why would the chev./gm say no go to dot 5.0 in the ZR-1 i wonder??? my mech still thinks the dot 5 is the way to go but he did admit to me he had never done an abs and was gonna check with his peer group guys on this and let me know!!!

[Tom]

The temperatures I posted above are minimums, if you look at premium DOT 3 and DOT 4 manufacturers data you will find they have dry boiling temperatures in the 500 deg range like DOT 5. If you use one of these premium fluids and change it regularly to keep the moisture content down you should get performance equivalent to the DOT 5. In addition since DOT 5 is not hygroscopic, any moisture that gets into the brake system will be free water with a boiling point of 212 deg.

I believe some DOT 5 containers have the statement "Not for use in ABS systems".

Converting to DOT 5 properly is a major job. You have to completely disassemble the brake system and replace every rubber component, all seals and rubber hoses, and completely flush all remnants of the DOT 3 or 4 fluid from all components including the brake lines or your boiling point will be whatever it was with the old fluid. Simply flushing the system with DOT 5 will not remove all of the old fluid since the seals and rubber hoses absorb quite a bit of the brake fluid. The old brake fluid will come out of the rubber parts until equilibrium is reached.

If you are concerned about seal swell you should use the fluid from the Chevy dealer that is listed in the owners manual since this is the fluid used in the certification tests for compatibility with the rubber components. ASTM D6546 gives the standard test method for performing swell tests when determing fluid/rubber compatibility. For a typical brake seal test you would weigh the seal in air, weigh the seal in water, immerse the seal in the brake fluid that would be installed in the vehicle, put the immersed seal in a 250 deg oven for a specified time, remove the seal from the fluid, rinse it off, and reweigh it in air and water, and then calculate the seal swell. Once this test is done you can place the seal on a sheet of white paper and see a large amount of fluid come out of the seal and form a ring on the paper and small drops on the seal surfaces.

[bobbyhi]

Way too technical for this old goat.............When I change mine I will probably go with the GM product recommend.

[Hotrod]

Becareful when using the vaccuum method for bleeding the brakes.. when the vaccuum is applied and the bleeder screw loosened, air can be sucked in around the threads of the bleeder screw and end up in the system!

[WB9MCW]

Thnx for the nice detailed post Tom! I think I will just stay with OEM fill, because as you point out, it is indeed and big ordeal to switch. Perhaps for the Auto-X-er it is worth the upgrade, just like most of em are upgrading the brakes anyway, so to go the extra yard on the fluids is no biggie! Sometimes the General knows best!!! LOL

[tomtom72]

Becareful when using the vaccuum method for bleeding the brakes.. when the vaccuum is applied and the bleeder screw loosened, air can be sucked in around the threads of the bleeder screw and end up in the system!

Yes be careful of that. It is difficult to get the hang of not letting the air in around the threads of the bleeder screw. Next time I do it I'm going to have it done by a shop with the proper pres bleeder. I wasted too much time getting it air free to be worth the trouble. I finally used teflon pipe dope on the threads, carefully, to get a good seal.

Tom

[Tom]

I have been using the vacuum method of changing the fluid on my ZR-1 for almost 15 years. After the first time I changed the fluid I put teflon tape on the bleeder screws since I thought I was less likely to get the teflon tape where it shouldn't be than if I had used the teflon dope. The teflon also helps keep the bleeder screw from seizing in the caliper. I also put the teflon tape on the bleeder screws of my 1999 Firebird Formula the first time I changed it's brake fluid.

[ralph92ZR1]

Thanks for all the advice; certainly learned alot about brake fluids. Am also now concerned about the "vacuum" method and potential of air intrusion at the bleeder valves; actually my friend has a C-4 and uses a vacuum pump but always had trouble with air.

Hate to beat a dead-horse but have you any recommendations on a pressure system. I tried Motive products but they are no certain on a ZR-1. Any advice in this area??? Its winter and I'm bored and really want to drain the fluid without hassles. :iamwithst

[WB9MCW]

RALPH if u a re a member of the zr-1 net/reg. in the (i think) fall newsletter Mark H.(who runs a specialty zr-1 shop in the western chicago sub's) had a very nice article on the special way he does the zr-1 cooling system including the 3 out of ten hard to do air entraped ones. He details a specific method to employ for the tough ones. It is restricted to the paid members only so I cant copy paste it here or give u a link(you need the pass word to get in the members section). So it is such: membership has it privilages!!! lo...l yes no doubt air entrapment is a PITA and any good mech. willl tell you they have their little secrets as to how to conquor the tough ones!!! Mark H. tell us his in the newsletter!

9-1-10 I see Ralph was asking about the "pressure brake bleeding system" not the cooling system... LOL silly me.

Well the info on the Marc H. cooling fluid replacement is well worth the read for you members Issue #4 Oct 2005

[Tom]

Here are a couple of links to universal pressure bleeders sold by snap-on; http://buy1.snapon.com/catalog/item.asp?P65=&tool=all&item_ID=56237&group_ID=1671&store=snapon-store&dir=catalog

http://buy1.snapon.com/catalog/item.asp?P65=&tool=all&item_ID=12342&group_ID=1670&store=snapon-store&dir=catalog

I have used this style before that looked more like a round sphere but I don't remember the manufacturer. This style forces fluid through the system from the master cylinder. Even using this method you will still sometimes have difficulty getting all of the air out of the brake system when dealing with anti-lock brake systems. I have also seen literature on a system that forces the fluid into the system at the bleeder screws but I have never used this style.

Of the three choices, pumping the brake pedal while somebody opens and closes the bleeder screw, pressure bleeding from the master cylinder, and vacuum bleeding at the bleeder screws, I prefer vacuum bleeding at the bleeder screws.

For a lot of vehicles during vehicle manufacturing the entire brake and clutch hydraulic systems are filled using vacuum. When the system is completely assembled but dry, a vaccum is pulled on the entire system at the bleeder screw farthest from the master cylinder, a valve is shuttled that ports brake fluid to the bleeder screw instead of the vacuum, and the vacuum in the system sucks the brake fluid into the system filling it completely. Some hydraulic clutch systems are completely assembled and bled using this method on a bleeding fixture and then installed into the vehicle as a complete assembly.