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FCP Euro Service Kits

FCP Euro Kits

Back in the day, servicing your own car was a labor of love. On air-cooled Volkswagens, there were millions of things that needed to be checked during a service. Points needed to be adjusted, zerk fittings needed grease, and valves needed to be adjusted. On newer cars, even the humble dipstick has been deleted, and almost everything is electronically controlled. Have you had to use a timing light on a car made this millennium?

One major pain, for me, was adjusting valves. On an overhead cam engine, it's tedious, dirty, and not very rewarding in my opinion. Measurements had to be made, shims had to be fitted, and the camshaft had to be removed and installed repeatedly, rinse, repeat. In the early days of water-cooled Volkswagens, they switched to hydraulic lifters, which don't require adjustment. They are still using the same design today, because in the world of Volkswagen, if it ain't broke, don't fix it.

Diagram showing hydraulic lifter in action. As the lifter moves down, the oil galley on the left is no longer in alignment, sealing the oil in. Diagram showing a hydraulic lifter in action. As the lifter moves down, the oil galley on the left is no longer in alignment, sealing the oil in.

 

IMG_20141124_100051_716 Three different hydraulic lifters, from an 85 Golf, 97 Jetta, and 04 Passat. Note the striking similarities.

Valve adjustment is important to the correct operation of an engine. If there's too much space between the camshaft and the lifter, it can cause noise, wear, and poor running due to incomplete opening of the valve. If there's too little room, the valves can stick open slightly, causing a loss of compression and rough running. Hydraulic lifters maintain contact with the camshaft, and don't require the use of shims to ensure proper clearance, the way that solid lifters do.

A hydraulic lifter works by using oil pressure to keep the lifter touching the cam and the valve spring. If you look inside one, you'll see a cavity in which oil collects. Oil enters through a hole on the side, and fills the little cups inside. The oil pressure isn't enough to open the valve though, just enough to expand the lifter to zero tolerance between the cam and the valve.

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As the cam lobe hits the lifter, it pushes it down and out of alignment with the oil supply galley, blocking oil from exiting the lifter. This effectively creates a solid pocket of oil, which can't be compressed. A check valve is installed in the upper section, which creates a high pressure pocket of oil in the lower section of the lifter. As the cam rotation continues, the oil galley lines up again, the check valve opens, and the oil pressure is relieved inside the lifter, back to that of the engine oil pressure.

IMG_20141124_100325_854 Further teardown of the check valve, showing the oil passage and cage which holds the ball bearing in place

Hydraulic lifters are nearly silent compared to solid lifters, due to their contact with the cam at all times. There are a few disadvantages, however. A loss of oil pressure can create low compression, as the lifters can't get oil to stiffen up. At much higher engine speeds, hydraulic lifters can cause valve float, where the valves don't fully close each time, causing low compression. Hydraulic lifters can also be alarmingly noisy on a cold start or a first start after an oil change, because there's not enough oil in the valvetrain yet. This is pretty normal, and the noise goes away after a few seconds without causing any engine damage.

Hydraulic lifters simply haven't changed in thirty years. The same lifters in a Mark 2 Golf are in the B5 Passat – though the sizes are slightly different. I for one am grateful that I haven't had to adjust valves in years, and I hope that I never have to again.

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About the Author: Chris Stovall

IMG_20140324_173718_051Chris is a journeyman mechanic from Berkeley, California, specializing in late model Volkswagens and Audis. A glutton for punishment, his spare time is spent rebuilding every component of his '83 Rabbit GTI.


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Written by :
Chris Stovall

Chris is a journeyman mechanic from Berkeley, California, specializing in late model Volkswagens and Audis. A glutton for punishment, his spare time is spent rebuilding every component of his ’83 Rabbit GTI.


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