Thys Posted March 30, 2008 Share Posted March 30, 2008 The latest on the blown head gasket. I had the head skimmed, and gave the engineering works the valve head stand down specifications of: Inlet valve: 0,81 - 1.09 mm. Exhaust valve: 0,86 - 1,14 mm. Knowing the engineer personally, and having used his services for all my vehicles, I collected the head, and re-installed, painstakingly going through all the preparations, and torque sequinces...... Guess what, she started and idled like new, but after idling for 3 minutes a faint metallic knock became audible, increasing as the time went on. I nearly lost it, it took one week of my valuable leave, and an extremely patient wife, and now this. I re-checked the valve clearances, the operation of the injectors, but in the end removed the head again, this time not draining the coolant properly, ending up with coolant spillage in the oil system, all my expensive Caltex Delo 400 messed up. I looked at the piston tops, no 4 piston had a faint circular imprint of the exhaust valve. I then measured the valve head stand down of each of the eight valves, all were within the specified range except No's 7 & 8 valves, both exceeded the stand down by 0,02 mm. So, as usual, my desperate questions: 1. Can I compensate for the 0,02 mm stand down by replacing the current 3-hole head gasket with the one with 0 holes? 2. If not, can one try to cut back on the valve seating faces? 3. Or do I bite the dust, and buy a new head? Cheers Quote Link to comment Share on other sites More sharing options...
BogMonster Posted March 31, 2008 Share Posted March 31, 2008 I don't have the figures to hand but the thicker head gasket might do the trick, however it will also reduce compression ratio a small amount - I don't know if this makes any difference in practice or not. Head gasket selection is to do with piston protrusion IIRC, rather than to avoid the valves I would think cutting the exhaust valve seat back a bit might work but others might know more about it. Quote Link to comment Share on other sites More sharing options...
Les Henson Posted March 31, 2008 Share Posted March 31, 2008 The next size up (no holes) is .1mm thicker than what you have now, so as long as the stand down is .02 and not .2mm - you should be ok. Otherwise you can restore the original head thickness with a shim steel insert, which goes with your old gasket. Les. Quote Link to comment Share on other sites More sharing options...
Thys Posted March 31, 2008 Author Share Posted March 31, 2008 The next size up (no holes) is .1mm thicker than what you have now, so as long as the stand down is .02 and not .2mm - you should be ok. Otherwise you can restore the original head thickness with a shim steel insert, which goes with your old gasket.Les. Thanks Les and Bogmonster. I took the head back to the engineering works this morning, and we noted that the valve seat still had a lot of "meat". We deepened the no 3, 7 & 8 valves. No 8 was the culprit, 3 & 7 were on the limit. It is now 19:33, and I am busy changing the oil, top up with new oil, coolant filling, and then we will see. One advantage of removing the head again, this time it was easier, and re-assembling went like a dream. After the first re-installation, I found the tappet adjusters and nuts very stiff, and stuck. This time I cleaned the lock nuts with a no 3 tap, and the adjusters with a thread cutter, what a pleasure to set the valve clearances after that exercise! I will report back once she is running. Quote Link to comment Share on other sites More sharing options...
Les Henson Posted March 31, 2008 Share Posted March 31, 2008 It is now 1933 That's a coincidence - Bogmonster was born in that same year Les Quote Link to comment Share on other sites More sharing options...
BogMonster Posted March 31, 2008 Share Posted March 31, 2008 Several years younger than you Henson Quote Link to comment Share on other sites More sharing options...
JimAttrill Posted March 31, 2008 Share Posted March 31, 2008 So I guess you have learnt not to trust the average engineering shop when it comes to things like stand down of the valves. It is very simple, and they should have known better. I always check the stand-down after getting a head back from the engineers. Now I see why I do it! We often replace the valve adjusters as they do go a bit funny and stick after a few adjustments. They are pretty cheap from CCA. Quote Link to comment Share on other sites More sharing options...
Thys Posted March 31, 2008 Author Share Posted March 31, 2008 That's a coincidence - Bogmonster was born in that same year Les Now this is not a April Fool's prank, I started my Disco, and the knock is still there. I utter desperation, I drained the new Caltex Delo 400, thinking that the lubricant may be the cause of the knocking. I replaced the Caltex with Shell Helix Super Diesel.; no change. I took her for a long drive, highway with speeds up to 120 km/h. No problem with acceleration, or power, just this sharp knocking. I replaced the head gasket, water pump, and timing belt front cover. Is it a big end bearing on it's way out? But how, I only worked on the head? At this point in time I've decided to drive her, and see what happens. I will get experts to listen to this high pitch metallic knock. Quote Link to comment Share on other sites More sharing options...
JimAttrill Posted April 2, 2008 Share Posted April 2, 2008 Your 'ignition' timing could be too advanced. It should be 10 deg BTDC. Unfortunately the only way to check it is with a piezo thingy which attaches to the diesel injection pipe. We have one at the workshop. Otherwise, remove the aircon adjuster, slacken the 3 10mm bolts on the injector pump sprocket and move the central bolt back slightly anti-clockwise. This will retard the timing slightly. If the knocking goes away, it was the timing too advanced. If it doesn't go away then the fault is something else. Quote Link to comment Share on other sites More sharing options...
Les Henson Posted April 2, 2008 Share Posted April 2, 2008 I suppose the piston striking the head of the valve repeatedly might knock a big end shell or small end bearing out, bit unlikely though as the pushrod would be the weakest point and it would just flex or bend in extreme cases. Les. Quote Link to comment Share on other sites More sharing options...
Thys Posted April 4, 2008 Author Share Posted April 4, 2008 I suppose the piston striking the head of the valve repeatedly might knock a big end shell or small end bearing out, bit unlikely though as the pushrod would be the weakest point and it would just flex or bend in extreme cases.Les. I found the knock! On the back of the crankshaft pulley, facing the engine there is a steel cap, protecting the dust seal and pulley shaft entry into the timing belt cavity. When I removed the pulley on my first removal, I dropped the pulley, on the third removal of the pulley I started the engine, and the sharp knocking was gone. Closer inspection revealed a small "dent on the cap side. I tried to press it out, but the cap was now "out-of-round". Re-installed the pulley, sharp knock was back. It was now 03:00 in the early hours of Thursday morning, in utter desperation I cut the dished end with a sheet metal cutter, and bent the cap flat against the pulley, no more knocking. If I have to remove the pulley again, I will replace it. Obviously, to the experts, the clearances between the pulley cap and the cover plate are minute. I am now a very happy Discovery owner again. Quote Link to comment Share on other sites More sharing options...
oddballrovers Posted April 4, 2008 Share Posted April 4, 2008 Hi Thys. I just stumbled over this thread and have read is now. I am happy to hear that you got it right this early morning, gosh I do know how you have felt during this (despair might be an understatement I guess) I have been there, done that, I have learned from life that very seldom Landrover tech problems are as bad as one think at the first moment I do not know if it is because we sometimes look at at life in a not so positive way, but anyway congratulations have a nice weekend. Regards Ole. I found the knock!On the back of the crankshaft pulley, facing the engine there is a steel cap, protecting the dust seal and pulley shaft entry into the timing belt cavity. When I removed the pulley on my first removal, I dropped the pulley, on the third removal of the pulley I started the engine, and the sharp knocking was gone. Closer inspection revealed a small "dent on the cap side. I tried to press it out, but the cap was now "out-of-round". Re-installed the pulley, sharp knock was back. It was now 03:00 in the early hours of Thursday morning, in utter desperation I cut the dished end with a sheet metal cutter, and bent the cap flat against the pulley, no more knocking. If I have to remove the pulley again, I will replace it. Obviously, to the experts, the clearances between the pulley cap and the cover plate are minute. I am now a very happy Discovery owner again. Quote Link to comment Share on other sites More sharing options...
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