Question about 1990 Volvo 740
Your vehicle has what is called a brake booster on it. It is mounted on the firewall under the hood and your brake master cylinder is mounted to that. The brake booster works off of vacum pressure that your engine builds. When the booster goes bad the vacum pressure escapes and it sounds like a hiss at your pedal. This problem will get worse and can cause your pedal to go to the floor. This could be a dangerous situation for you. I recommend that you get this checked out for safety reasons. Hope this helps. If for some reason this goes out on you and you are on the road you can find the big vacum hose that goes into the booster, take the hose off and plug it with something. Please note if you do this you will not have power brakes after that you will be on manual brakes and it takes a lot more pressure to stop your vehicle so drive slowly and not to close until you get it fixed. If the booster goes all the way out your engine will run rough or die at idle. If you do have to block the vacum line your engine will run smooth again but it may set off the check engine light. Take care, Roger
Posted on Feb 07, 2010
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Posted on Jan 02, 2017
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