© Text and Photo: Frode H. Haaland
Adjusting valves
Vehicle: Discovery 1990, 200tdi
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© Text and Photo: Frode H. Haaland |
Adjusting valves
Vehicle: Discovery 1990, 200tdi |
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The valve clearance is an important part of the tdi engine. If the gap is to great, the engine will not produce full power - and if the gap is too small, the valves may burn out. It is a 30 minute job part of the 20.000km service schedule. |
| As you will have to turn the engine using a wrench on the
crankshaft pulley bolt, it improves access if you also remove the viscous
fan.
Remove engine breather hoses. The top hose on the cyclone engine breather was easily removed, while the lower one proved very difficult to slide off. So it was left in situ, and the cyclone breather was removed from valve cover, and tucked away. |
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The front hose entering valve cover was also difficult to remove.
Remove the three bolts (8mm heads) with its washers from the valve cover, and lift it off - tipping it and then slide the front breather hose off. |
| The valves are on the engines LH side, the pushrods being on the RH side. The job comprise in setting the clearance between the rocker arm and valve stem to 0,20mm when a certain other valve is fully open. |
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The "rule of nine" implies that you add 1 to the number of valves - the engine has 8 valves, thus adding one reads nine. When valve #1 is fully open, you check and adjust #8 (1+8=9). You will have to turn the engine around a lot if you work your way through the valves one by one from #1 to #8. To simplify the process, the table below shows the order which will require the least amount of turning the crankshaft: |
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Valve fully open | Check and adjust |
| Valve #1 | Valve #8 | |
| Valve #3 | Valve #6 | |
| Valve #5 | Valve #4 | |
| Valve #2 | Valve #7 | |
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Valve #8 |
Valve #1 | |
| Valve #6 | Valve #3 | |
| Valve #4 | Valve #5 | |
| Valve #7 | Valve #2 |
| To adjust a valve (#4 in this picture), make sure the proper
valve is fully open (#5, as seen in this picture), i.e. the spring being
fully compressed. Insert a 0,20 feeler gauge to check the clearance.
If it is to be adjusted, insert a 13mm or 1/2" spanner on the hexagonal nut, holding the adjuster threaded pin with a screwdriver. Turn the adjuster pin using the screwdriver until the feeler gauge can be inserted without nippling. Hold the adjuster while tightening the locknut. Recheck after tightening, as it is quite easy to get it wrong - the adjuster/screwdriver moves a fraction and it is all wrong again... |
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| Work your way through all the valves, turning the crankshaft slowly using the table above. |
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When you're satisfied with the valve clearances, turn your attention to
the valve cover. Check the condition of the rubber gasket. It can be
reused up to five times if a visual inspection shows it is in good
condition.
Clean the cover in and out, and refit it onto the engine - I found it easier to fit the front breather hose while tilted, and then dropping the cover down on the engine top. |
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Refit the three valve cover bolts along with its washers, tightening
evently to 5NM.
Refit and tighten the breather hoses. And please: Do not forget the spanner you left on the crankshaft! |
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Tools and parts used: |
| 0,20mm feeler gauge
Small screwdriver or similar for hoseclamps Large screwdriver 13mm spanner 32mm socket and ratchet/wrench 8mm socket Liquid gasket or proper gasket (if cyclone breather is being removed) Valve cover gasket if needed:
Job is basically the same on a 300tdi, but some details differ. |