I have researched this and haven't found any real solutions. While driving from a cold start after about 3-5 minutes my jeep starts making a high pitch whistle. The noise has been getting worse. It appears to be coming from my power brake booster. When I press on the brake pedal it completely goes away. When I put my foot on the brake from a cold start and start the jeep the pedal does move down. Is this something I can fix or should I replace the power brake assist unit?

Erik
1989 XJ

 

Sorry buddy I cant give you much info other than to research Bendix 9 ABS system and you"ll see the biggest problem. Hope the guys who know more troubleshooting can help you. I share your pain.

 

sounds like booster going south to me time to upgrade...http://www.jpmagazine.com/techarticl...des/index.html

 

Sounds like a plan. I'll hit the salvage yards looking for a 1995 non abs XJ. Thanks!

Erik

 

Before you run out and buy a new brake booster. Check out the check valve that is on the booster that goes to the intake manifold to see if it is cracked or even disconnected. Also check the hose that goes to it.

 

I checked both the vacuum line and the valve. Both are working okay. I think it's the booster.