chevy p-30 brakes
Had to replace my front rotors and pads and master cylinder. Bled all wheels and all working fine. Then they started dropping again to the floor. I noticed last trip after a hard climb through the nevada mountains at the top of the pass that the rear brakes were non existant and the fronts were grabbing hard at the bottom of the pedal travel. I had to stop and let the moho cool down so I boondocked at the top of the pass. Next day going down the hill all was good again. As the engine heated up my brake function started to reduce effectiveness, especially the rear disc pads.
When I got home I pulled the wheels and the rear pads and calipers were working correctly. Traced the brake lines and found that they run parallel to the exhaust manifold for about 6 inches where they connect to the master cylinder. The brake lines for the 6 inches are only 1 7/8 inches from exhaust manifold. The fluid was boiling before it was even entering the ABS system. Of course the DOT3 was boiling and then cooling causing water vapor to form in the brake lines and mastercylinder.
This a very serious manufacturing defect that Chevy refuses to address. To repair, I made a heat shield from some light steel to protect the brake lines and master cylinder. I bolted it on to the main frame channel. Then I've replaced the brake fluid with DOT5.1 rather than DOT3 as the shop manuel states. The boiling point of DOT5.1 is much higher than the DOT3. Don't bother with DOT4.
In order to correct this engineering mistake, you must do both, heat shield and upgrade to DOT5.1, just changing to the more expensive fluid will not solve the problem, it will just put off failure for a little longer. Do not use DOT5, it will not mix with the DOT3 or DOT4.
In searching the net I found very little solutions for this very dangerous and common problem. Apparently chevy was aware of this problem when they sold to workhorse. No recalls have been made at this time to correct this problem. Failed front rotors are a common symptom of the boiling brake fluid problem due to the fact that the rear brakes are disabled by the hot gas in the rear line so all the stopping responsibility is thrown on the front rotors and pads. Then the over heated boiling brake fluid freezes the front rotors and "wallah" no brakes at all!!!
When I got home I pulled the wheels and the rear pads and calipers were working correctly. Traced the brake lines and found that they run parallel to the exhaust manifold for about 6 inches where they connect to the master cylinder. The brake lines for the 6 inches are only 1 7/8 inches from exhaust manifold. The fluid was boiling before it was even entering the ABS system. Of course the DOT3 was boiling and then cooling causing water vapor to form in the brake lines and mastercylinder.
This a very serious manufacturing defect that Chevy refuses to address. To repair, I made a heat shield from some light steel to protect the brake lines and master cylinder. I bolted it on to the main frame channel. Then I've replaced the brake fluid with DOT5.1 rather than DOT3 as the shop manuel states. The boiling point of DOT5.1 is much higher than the DOT3. Don't bother with DOT4.
In order to correct this engineering mistake, you must do both, heat shield and upgrade to DOT5.1, just changing to the more expensive fluid will not solve the problem, it will just put off failure for a little longer. Do not use DOT5, it will not mix with the DOT3 or DOT4.
In searching the net I found very little solutions for this very dangerous and common problem. Apparently chevy was aware of this problem when they sold to workhorse. No recalls have been made at this time to correct this problem. Failed front rotors are a common symptom of the boiling brake fluid problem due to the fact that the rear brakes are disabled by the hot gas in the rear line so all the stopping responsibility is thrown on the front rotors and pads. Then the over heated boiling brake fluid freezes the front rotors and "wallah" no brakes at all!!!
