chris71 Posted September 29, 2016 Share Posted September 29, 2016 so here the problem i've changed over to a dual diaphragm brake booster . and since the change over my climate control doors for defrost floor and vent don't work now . just blows through the defrost vents ? i still have the small round vacuum canister , so far i've checked it for leaks using a vac brake bleeder tool . it holds vac and i've replaced the vac line from it to the manifold , is there a way to fix this or do i just need to go to the jy and get the larger vac can ? or would an inline vac pump work like whats on the newer jeeps ? thanks in advance Link to comment Share on other sites More sharing options...
cruiser54 Posted September 30, 2016 Share Posted September 30, 2016 How about from the vacuum ball to the firewall? Have vacuum there? Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 30, 2016 Share Posted September 30, 2016 You don't need a larger vac can for the new booster. If the vac system and HVAC doors were working fine before you changed the brake booster, therein must be the problem? Check the booster vacuum check valve. If okay, try the below procedure: Test Power Brake Booster If the pedal feels "hard" while the engine is running, the booster isn't operating correctly. If you suspect the booster is defective, do not attempt to disassemble or repair the power booster. Doing so is unsafe and will void your warranty. Test 1 With the engine off, pump the brake pedal to remove any residual vacuum in the booster. Hold pressure on the pedal while you start the engine. When the engine starts, the pedal should drop about a 1/4", this indicates that the booster is working properly. Test 2 Run the engine a couple of minutes. Turn the engine off and press the pedal several times slowly. The first pump should be fairly low. The second and third should become slightly firmer. This indicates an airtight booster. Test 3 Start the engine and press the brake pedal, then stop the engine with the pedal still pressed. If the pedal does not drop after holding the pressure on the pedal for 30 seconds, the booster is airtight. Inspect the Check Valve Disconnect the vacuum hose where it connects to the intake manifold. Do not disconnect the vacuum line from the booster. Air should not flow when pressure is applied, but should flow when suction is applied. If air flows in both directions or there is no air flow, the valve needs to be replaced. Verify Enough Vacuum Check the operating vacuum pressure when the engine is at normal operating temperature. There should be a minimum of 18 in. of vacuum. Vacuum may be increased by properly tuning the engine, checking for vacuum leaks and blockages in vacuum lines. Link to comment Share on other sites More sharing options...
chris71 Posted September 30, 2016 Author Share Posted September 30, 2016 cruiser54 no i have not checked that vac line to the firewall , hornbrod the booster seems to be working ok but i didn't know about the testing , or even think to check the check valve on it . i'll check both suggestions after work today when i get home . i'll update what i find thanks Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 30, 2016 Share Posted September 30, 2016 If you haven't checked the vac line to the firewall yet, that's probably the problem. Look around the battery where it passes through the firewall. Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted September 30, 2016 Share Posted September 30, 2016 Just throwing this out there .... You didn't happen to disconnect the vacuum hoses on the servos / diaphrams on the drivers side of the HVAC box ? Link to comment Share on other sites More sharing options...
chris71 Posted September 30, 2016 Author Share Posted September 30, 2016 i did disconnect some vacuum lines on the drivers side but only the ones that went to the factory air box that is no longer in the truck but that's been gone for over a year . and this just started after installing the 95 cherokee booster . i'll look at that vacuum line running up by the battery also . Link to comment Share on other sites More sharing options...
ComancheKid45 Posted October 1, 2016 Share Posted October 1, 2016 Just throwing this out there .... You didn't happen to disconnect the vacuum hoses on the servos / diaphrams on the drivers side of the HVAC box ? This^^^ check under the driver's side of the dash and look for the colored vacuum lines and make sure they are still connected. Link to comment Share on other sites More sharing options...
chris71 Posted October 1, 2016 Author Share Posted October 1, 2016 thats a good idea i was under the dash installing the brake booster i might have unplugged some vacuum lines . Link to comment Share on other sites More sharing options...
chris71 Posted October 4, 2016 Author Share Posted October 4, 2016 so after checking all of the suggestions this weekend i found the vacuum leak . it was the line going into the firewall . somehow it got a hole rubbed in it fixed the hole and secured the line from rubbing on anything . thanks for the help Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 4, 2016 Share Posted October 4, 2016 Common problem. An easy solution is to move the vacuum canister into the engine bay where it belongs. I did mine like like this. There are more examples in the DIY forum. Link to comment Share on other sites More sharing options...
chris71 Posted October 6, 2016 Author Share Posted October 6, 2016 that a great idea , gets it out of the right front inner fender area . Link to comment Share on other sites More sharing options...
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