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'84 300sd no power brakes on startup
Hi all,
It seems that sometimes on startup (particularly after not running for a few days), I have no power brakes for a minute or so. No visible fluid leaks. The brakes could probably use a bleeding, but work fine once running for a while. Is something wrong with my master cylinder, or booster? Thanks, Jack
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Jack 1984 300SD. 115k miles. |
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Answer
You have a serious vacuum issue.
The vacuum pump needs to be isolated from the brake booster to test vacuum supply pressure. My best guess. If the supply is good: * The large black plastic vacuum line has a check valve that may have failed = replace the assembly. * The O-ring, master cylinder to brake booster may have failed = replace the O-ring. * The brake booster may have failed = replace the assembly. If all of this tests good = you have one or more massive leak in the secondary vacuum system = emission, transmission or climate control. .
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ASE Master Mechanic asemastermechanic@juno.com Prototype R&D/testing: Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician. Noise Vibration and Harshness (NVH). Dynamometer. Heat exchanger durability. HV-A/C Climate Control. Vehicle build. Fleet Durability Technical Quality Auditor. Automotive Technical Writer 1985 300SD 1983 300D 1984 190D 2003 Volvo V70 2002 Honda Civic https://www.boldegoist.com/ |
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