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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>I’ll ask the question before I start any serious disassembly. My near daily driver, 1964 MGB, is still on the road although the next few months I will likely drive it a lot less as darkness descends and roads start getting icy. A month ago, I had seal failure on my clutch master cylinder, resulting in the puddle of hydraulic fluid near my feet. Upon disassembly, I saw some pitting in the bore which caused premature seal failure (I rebuilt this unit about 5-6 years ago, not sure if I missed the pitting). So I decided to replace the master cylinder with a new Lockheed unit. Now I have a new problem – pedal motion is perfect until the car warms up and then most of the pedal resistance is lost briefly. Typically, when I drive to work (or leave work), the car starts out cold, warming up on the short city drive, and then I have 8-12 miles of highway driving. The first time I use the clutch after the highway drive, the pedal goes almost to the floor with no resistance but enough to still work. But once I do that one time, the clutch is perfect for the rest of the drive and remains good when I park the car. This will repeat itself on the drive home after the car warms up on the highway drive. Also – this motion is lost when the clutch is not used at all during the highway drive - this morning, I was halfway into the highway driving so I tested the free motion (without engaging the clutch) and sure enough, it was there shortly after the engine temperature was up to 180F. But once I did my first down-shift, going almost to the floor, pedal is now back to normal. There is no hydraulic fluid loss. Yesterday, I tried reseating the clutch line fitting on the back of the master cylinder since it looked wet but that had no effect. Still, it appears to be air getting pulled into the system, with possibly air expanding (the thermal component), or at least that is one theory of mine.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Anyway, I am at a bit of a loss. Any tips on further troubleshooting? If nothing else, I’ll do a disassembly of the whole clutch hydraulics this winter (slave, master, and hose).<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>David Councill<o:p></o:p></p><p class=MsoNormal>64 MGB<o:p></o:p></p><p class=MsoNormal>67 MGBGT<o:p></o:p></p><p class=MsoNormal>72 MGB (in process of re-installing OD transmission)<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>