I'm getting ready to flush and replace the brake fluid on a 1998 Corvette that I recently acquired. But I'm getting some conflicting information.

I've succesfully flushed the brake system on my 1979 Corvette numerous times using a hand vacuum pump attached at the caliper bleeder, maintaining the master cylinder full of fresh fluid, and using a vacuum to pull the new fluid through the system and thus force the old brake fluid out ahead of it. But my 1979 does not have computers or ABS brakes.

Initially I was told that the above procedure used on the 1979 would work fine on the 1998 Corvette.

Then someone told me that I should not use the vacuum pump, that only a master cylinder pressure bleeder should be used. Something about damaging the ABS controller???

Then someone else told me that I needed to disconnect the battery before flushing the fluid to avoid setting off ABS diagnostic trouble codes???

Someone else told me that the fluid replacement was a dealer-only job due to the potential for messing up the ABS controller???

NEED SOME HELPFUL CLARIFICATION IF POSSIBLE!
(I've searched the previous posted threads but can't find the asnwers.)

Is there someone that has actually performed a brake fluid replacement on a similiar year C5 Corvette that can describe the appropriate DIY procedure/steps? Hopefully utilizing a hand vacuum pump (which I have).

Unfortunately in my rural area I don't have a local Chevy dealer that I would trust working on my Corvette.

THANKS MUCH,
Craig W

 

Anybody Help!

 

I looked in the shop manual, and found only 2 methods: pressure and manual, I am copying them below. I would not use vacuum.

Note to other people: This is for a 1998 C5, later years (not sure on the cutoff year) use a different sequence due to location of the ABS Unit. If your ABS unit is in the engine compartment DO NOT USE THIS SEQUENCE.

Document ID# 319650
1998 Chevrolet/Geo Corvette

Hydraulic Brake System Flushing
The entire hydraulic brake system should be thoroughly flushed with clean brake fluid if there is any doubt as to the grade of the fluid in the system or if the fluid used contains the slightest trace of mineral oil.
All rubber parts which have been subjected to contaminated fluid must be replaced before flushing the system.
Flushing is performed at each wheel similarly to bleeding. The new fluid must be forced through the system until it emerges clear in color. Approximately one quart of new fluid is needed to flush the system.
After completing the flushing operation at all of the bleeder valves check that the master cylinder is filled to the correct level.
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Hydraulic Brake System Bleeding Pressure
Tools Required
J 35589 Pressure Bleeding Adapter



1. Remove the master cylinder reservoir cap. Replace it with J 35589 .
2. Charge the bleeder to 140-172 kPa (20-25 psi).
3. Connect the hose to J 35589 .
4. Raise the vehicle and support. Refer to Lifting and Jacking the Vehicle in General Information.


5. If it is necessary to bleed all of the brake calipers, the following sequence should be used:
A. Right rear
B. Left rear
C. Right front
D. Left front
6. Place the proper size box end wrench, or equivalent, over the brake caliper bleed screw. Attach a clear tube over the screw and allow the tube to hang submerged in a clear container partially filled with brake fluid.
7. Open the brake caliper bleed screw at least ¾ of a turn and allow the brake fluid flow to continue until no air is seen in the brake fluid. Apply intermittent pressure to the brake pedal while pressure bleeding.
Notice
Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
8. Close the brake caliper bleed screw. Tighten
Tighten the brake caliper bleed screw to 12 N•m (106 lb in).
9. Repeat steps 6 through 8 until all of the calipers have been bled.
10. Lower the vehicle.
11. Check the brake pedal for sponginess. Auto bleed the modulator and repeat the entire bleeding procedure to correct this condition. Refer to ABS Automated Bleed Procedure in ABS.
12. Remove the brake bleeding equipment from the master cylinder.
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Hydraulic Brake System Bleeding Manual
The time required to bleed the hydraulic system can be reduced if the master cylinder reservoir is filled with brake fluid and as much air as possible is expelled before the master cylinder is installed on the vehicle. Pumping the piston can evacuate the air from the piston cavities.
Power brakes require the vacuum reserve be depleted by applying the brakes several items with the engine off. Care must be taken to prevent brake fluid from contacting any painted surface. Use rags to catch the excess fluid.



1. Fill the master cylinder reservoir with brake fluid and keep the reservoir at least half full of fluid during the bleeding operation.
Notice
Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
2. If the master cylinder is known or suspected to have air in the bore, then it must be bled in the following manner, before bleeding any caliper:
A. Disconnect the forward (blind end) brake pipe connection at the master cylinder.
B. Allow the brake fluid to fill the master cylinder piston bore until it begins to flow from the forward pipe connector port.
C. Connect the forward brake pipe to the master cylinder and tighten.
D. Depress the brake pedal slowly one time and hold. Loosen the forward brake pipe connection at the master cylinder to purge air from the bore. Tighten the connection and then release the brake pedal slowly. Wait 15 seconds. Repeat the sequence, including the 15 second wait, until all air is removed from the bore. Tighten
Tighten the brake pipe tube nut to 18 N•m (13 lb ft).
E. When clear fluid flows from the forward connection, repeat steps 1 and 2 to bleed the master cylinder at the rear (cowl) connection.



3. Individual brake calipers are bled only after all air is removed from the master cylinder. If it is known that the brake calipers do not contain any air, then it will not be necessary to bleed them.
. Place a proper size box end wrench, or equivalent, over the brake caliper bleed screw. Attach a clear tube over the screw. Submerge the other end of the tube in a clear container partially filled with brake fluid.
A. Depress the brake pedal slowly one time and hold. Loosen the brake caliper bleed screw to purge the air from the cylinder. Tighten the brake caliper bleed screw and slowly release the pedal. Wait 15 seconds. Repeat the sequence, including the 15 second wait, until all air is removed. It may be necessary to repeat the sequence 10 or more times to remove all the air. Rapid pumping of the brake pedal pushes the master cylinder secondary piston down the bore in a way that makes it difficult to bleed the system. Tighten
Tighten the brake caliper bleed screws to 12 N•m (106 lb in).
B. If it is necessary to bleed all of the brake calipers, the following sequence should be used:
i. Right rear
ii. Left rear
iii. Right front
iv. Left front
C. Check the brake pedal for sponginess.
D. Auto bleed the modulator and repeat the manual bleeding procedure to correct this condition. Refer to ABS Automated Bleed Procedure in ABS.

 

I've used vacuum on my 2001, and 1989 neither had a problem and worked prefectly before and after the procedure. Ron B.

 

I used a vacuum. Took most of the brake fluid out of the master cylinder and poured in new fluid. I was going to Super Blue racing fluid - which is really blue.

I started at the right rear and started sucking brake fluid until it was all new fluid (make sure MC stays full). Go to left rear, then right front, then left front. Followed same procedure.

No problem. Great brake pedal. Did 2 days at HPDE in July with 100+* air temps. The brakes performed great. So I guess my method worked ok.

 

I have done both vacuum and pressure bleeding on my 97 and my 03Z. Actually they are both pressure bleeding since the principle is the same. A higher pressure at the master cylinder Vs a lower pressure at the brake caliper bleeder screw. The only difference is how the pressure differential is achieved. The biggest problem with using the hand vacuum pump is the amount of pumping you need to do. My vacuum bleeder is powered by my air compressor and can suck the master cylinder dry in about 3 minutes if I open the bleeder screw all the way. The advantage of the pressure bleeder is the fact that I put a certain amount of fluid in the unit and I can monitor the fluid level in it easier than I can the master cylinder especially when I am on the other side of the car.

However, all that crap you listed in your post that various people told you their was only one that was truthful. You can do it with a vacuum bleeder so have at it.

Bill

 

I purchased a Hand Vacuum Bleeder at Griot's last month and bled the brakes on my 2001 about 3 weeks ago with no problems. There seems to be some confusion about whether or not the ABS unit is cleaned out using this procedure? I am have been told that you need a Tech II to cycle the valves to get a "complete" system flush which is probably true, but I am pretty sure I got over 90% of the old fluid out. I did turn the ignition key to the ON position and placed the car in gear with the parking brake on which is what the Griot's Vacuum Bleeder instructions directed for ABS systems (in general) - don't know if that helped? I got very few air bubbles, but the fluid removed was dark and the clean fluid came out of all four calipers at the end.

 

Thanks much for all the responses.

From those of you that has actually done the job - sounds like the hand vacuum pump procedure that I'm used to will work fine on the 1998.

Any furthr comments on the issue of disconecting the battery? Turning the ignition key on or off?

Thanks again for all that responded.

 

i installed ss lines about a month ago on my 03' Z, and did the have-the-neighbor-pump-the-pedal routine. got a really good pedal amd no abs lights or codes.

 

Vacum bleeding is without question the most effective, neatest and quickest method of bleeding any conventional hydraulic brake system. If you consider the physics, all you are doing is causing a less then atmospheric pressure point at the wheel (bleeder screw) and allowing the same atmospheric pressure (14+ psi/sq in) at the master cylinder to force the fluid, internal rust and potential air out of the hydraulic system. Pressure bleeding (old fashioned bleeder ball) can cause cavitation and if bled with too much pressure can activate certain hydraulic valves which will impede the process. If you have lot's of time and I mean lot's of time, the old gravity bleed method works well. Open all the bleeders and walk away returning periodically to keep the master cylinder from running dry. If you're concerned with the ABS assembly, remember it is not activated during this process so you will never enter the ABS section of the brake system in order to flush it. Frankly it's not necessary to bleed it unless you've had to replace a component related to the ABS. In any case, it's a good idea to flush the fluid on a periodic basis. If you want to upgrade, use DOT 4 which is esentially a "high test" version of DOT 3 glycol based hydraulic brake fluid. In case someone suggests it, you should avoid the use of DOT silicone fluid. Although it has a much higher wet boiling temperature, it does not like to be "hammered" as will happen if the ABS feature is activated. Hope this helps.
IZZY