 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Volvo Cars / September 200701 V70 Vacuum leak
Hi there !! My new (to me) V70 T5 has a hissing sound in the cabin, which I suspect is a vacuum leak, took it to the dealer and they said that the brake booster have to be replaced ($540 plus labor). I would like to plug the vacuum line that feeds the booster and make sure that the diagnostics is accurate/ Couple of questions: - The vacuum feed for the AC vent actuators, where is that coming from? - The vacuum hose that feeds the brake booster only feeds the brake booster, and not any other vacuum reservoirs, right? If this is a common failure, am I on the right track? Thanks Arnold > Hi there !! My new (to me) V70 T5 has a hissing sound in the cabin, which > I [quoted text clipped - 5 lines] > > - The vacuum feed for the AC vent actuators, where is that coming from? Engine vacuum. > - The vacuum hose that feeds the brake booster only feeds the brake > booster, > and not any other vacuum reservoirs, right? Again from engine vacuum. > If this is a common failure, am I on the right track? Usually the cause is some previous repair where the mechanics brakes the hose when repairing anything else. The less goings to the work shop the best. Basically you need to locate where is the hissing sound comming from. From the engine compartiment, or from the interior of the car. That's no vacuum pump, so that vacuum always comes from the engine intake manifold. Thanks for your reply, What I was asking was if the vacuum source for the AC actuators and the brake booster are coming from 2 different places on the intake manifold, so I could isolate the vacuum leak by plugging one hose at the time in the engine compartment. I could not do that if they were fed by the same point, and split with a Tee downstream, or if the actuators are fed from the brake booster. The hissing sound appears to be coming from an area under the steering wheel. I will not have access to the vehicle for another 7 to 10 days. Thanks Arnold > > Hi there !! My new (to me) V70 T5 has a hissing sound in the cabin, which > > I [quoted text clipped - 26 lines] > That's no vacuum pump, so that vacuum always comes > from the engine intake manifold. > Thanks for your reply, What I was asking was if the vacuum source for the > AC [quoted text clipped - 10 lines] > another 7 to 10 days. > Thanks Look, vacuum is changing all the time. You can have hard vacuum under heavy decceleration, and no vacuum at all when the turbo is at full pressure. So, the hissing sound must change accordingly. Hissing sounds may have many sources. You need to find the patern, when it changes sound, and so on. Brakes is hard to believe - large independent hose with an anti-return valve. The AC actuators could be, but again vacuum changes all the time inside the intake manifold. There is a small vacuum hose for the turbo indicator too. Are you sure it is a vacuum related problem? If its a gasoline car, usually vacuum problems causes the "engine failure" lamp to light (lambda sensor), due to a faulty air intake. > Arnold > [quoted text clipped - 31 lines] >> That's no vacuum pump, so that vacuum always comes >> from the engine intake manifold. Hi Mr. Albuquerque, you are correct, the hissing noise changes per driving condition, under acceleration, or when climbing a hill, it is barely perceptible, however, when the car idles, it is very noticeable. Have not had the "Check engine light on" yet, maybe the computer tries to compensate the mixture based on the O2 sensor, but I sure would like to eliminate the leak and avoid running it like this. Thanks a lot for your help. Something else I should check is if after I shut the car off, there is enough vacuum in the brake booster reservoir to apply the brake once, if I can, then I know for sure the leak is elsewhere because the check valve would hold the vacuum in the brake booster. > > Thanks for your reply, What I was asking was if the vacuum source for the > > AC [quoted text clipped - 66 lines] > >> That's no vacuum pump, so that vacuum always comes > >> from the engine intake manifold. > Hi Mr. Albuquerque, you are correct, the hissing noise changes per driving > condition, under acceleration, or when climbing a hill, it is barely > perceptible, however, when the car idles, it is very noticeable. If so, your vacuum hypotesis is quite good. At idle you get a steady situation with a good vacuum to test all the hypotesis of a leak. > Have not > had the "Check engine light on" yet, maybe the computer tries to > compensate > the mixture based on the O2 sensor, but I sure would like to eliminate the > leak and avoid running it like this. So, its a small leak. There are many small hoses hidden below the intake manifold, some go down to the turbo. The engine is very complicated to work with (very compact). Check the turbo indicator hose that shoud go up to the instruments pannel (I belive), since its a direct indicator of the vacuum and could be itself the responsible. And the AC actuators vacuum too. > Thanks a lot for your help. Something > else I should check is if after I shut the car off, there is enough vacuum > in the brake booster reservoir to apply the brake once, if I can, then I > know for sure the leak is elsewhere because the check valve would hold the > vacuum in the brake booster. Brakes system is all inside the engine compartement and most certainly a small leak cannot be heard inside the car, since those cars are very well sound isolated. >> > Thanks for your reply, What I was asking was if the vacuum source for > the [quoted text clipped - 75 lines] >> >> That's no vacuum pump, so that vacuum always comes >> >> from the engine intake manifold. > Hi there !! My new (to me) V70 T5 has a hissing sound in the cabin, which I > suspect is a vacuum leak, took it to the dealer and they said that the brake [quoted text clipped - 11 lines] > > Arnold Best chance that it is the brake booster very common complaint nothing to rebuild just replace the brake booster. The noise will get worse @ some point & the power brake's will slowly start to get harder to press Glenn  Signature" Anyone who has never made a mistake has never tried anything new" -- Albert Einstein |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.