Auto Service Professional

APR 2016

Magazine for the auto service professional

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47 | April 2016 The Tech Bench Tech tips From brake system fuid to break-in oil KEEP BRAKE FLUID FRESH The condition of a vehicle's brake fuid is all too often ignored. Too frequently, brake fuid is only topped off when low or fushed and flled only when the system has been serviced, as with master cylinder, caliper or brake line replacement. DOT 3, DOT 4 and DOT 5.1 fuids are hygroscopic, which means that the fuid absorbs airborne moisture. The system doesn't need to be left open for days on end in humid conditions for this to occur. Atmo- spheric moisture will eventually migrate into the system over time. As moisture enters the system, the wet boiling point of the fuid is reduced. When the system is hot (during hard braking), water boils and turns to steam. Water in the fuid reduces the ability of the brake fuid to provide a solid pedal. Also, the rust inhibitors that are in brake fuids tend to break down over time. If ignored, the moisture contamination leads to gunk deposits in the lines and hydraulic components, resulting in sticking cali- pers and wheel cylinders and seal damage. Generally speaking, a brake system's fuid should be changed (and that means fush- ing out all of the old fuid and reflling with new fuid) at least every two years or so. Flushing, reflling and bleeding needs to become part of a vehicle's routine preven- tive maintenance. FORD DIESEL WOES If you have a Ford F-350 Super Duty in your shop equipped with the 7.3L Navistar diesel engine and the customer complains about an intermittent surge issue along with DTC P0470, take a look at the EBP (exhaust backpressure sensor). This is located at the front of the engine, on the passenger side near the top. The sensor is connected to a tube that feeds from the exhaust. The sensor and/or feed tube may be clogged with carbon deposits. Remove the sensor and the tube. Replace the sensor and either clean out the tube, or if it's rotted, replace it. A clogged exhaust pressure sensor and tube can cause the surge issue. Even if this does not cure the driveability complaint, chances are that the sensor and tube need to be cleaned anyway. AFTERMARKET ENGINE PROGRAMMERS You may run into a diesel-powered truck that exhibits driveability issues such as surges, stumbling, hard starts, etc. If you've chased DTCs and are still scratching your head because you can't locate the problem, check to see if the owner had a performance programmer installed. This can sometimes interfere with the OEM ECU. Try de-wiring the aftermarket programmer (take it completely out of the system) and then see if the driveability problems disap- peared. Later models of these programmers can often be re-fashed with a software update to cure a problem, while older ver- sions may not have that capability. BREAK-IN OIL NOT FOR FLAT TAPPET ONLY Since many conventional engine oils have reduced levels of high-pressure zinc phos- phate ingredients, a special "break-in" oil that contains higher levels of ZDDP is rec- ommended when breaking in and running an engine that's equipped with a fat-tappet camshaft. However, even with hydraulic lift- ers, this break-in oil or break-in additives (offered now by Joe Gibbs, Royal Purple, Comp Cams and others) is also a good idea when running high-pressure valve springs and/or higher-ratio rocker arms, to elimi- nate premature wear on valve tips, even with roller rockers. ●

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