toyboxII Posted September 17, 2014 Share Posted September 17, 2014 Hi all--switching gears on an existing thread. Posted my problem under "rough idle" and thank you all for your knowledgeable responses. Hoping this nightmare will end soon and the repairs will be completed correctly. Once it is repaired and we are back on the road, is there anything that I can do to prevent this from happening again. Two burnt valves at 99K miles--guess I should be thankful that it went that far without any major problems, but we really love this thing and want it to last forever! Wondering if there are any preventative things that I can do to make it happen? Thanks for any ideas/input. Quote Link to comment Share on other sites More sharing options...
Maineah Posted September 17, 2014 Share Posted September 17, 2014 The key to preventing burnt valves is not having them adjusted too tight. With the 4 cylinders valve adjustment is part of a proper tune up and due to the amount of moving parts they generally get loose not tight. The V6 is a bit different it is not some thing that is normally adjusted due to the intensive amount of labor. In theory they should not need to be adjusted over the life of the valve but in practice that does not all ways work out. So I would say some thing in the 80-100K range would be a good time to at least check the clearance about the same time one would replace the timing belt. They maybe fine but it also could be tighter than spec. Another way would be to check compression during each tune up and note any changes from one tune up to the next that might indicate a tight valve as the compression would drop with a valve tighter then it should be.. Quote Link to comment Share on other sites More sharing options...
zero Posted September 17, 2014 Share Posted September 17, 2014 Just seconding what Maine AH stated. Maintaining proper valve clearance in a solid-lifter engine is critical. I've owned three Toyota 4-bangers and all three tended to get too tight over time, not loose. That's what happens when valve seats wear a bit and the valves recede into the heads. When they do that the stems get closer to the cam-followers and loose clearance. It's a matter of what wears first. If the valve seats wear, the valves get tighter. If the cam followers and associated parts wear, they get looser. If they all wear a once, it's toss-up. If a valve gets so tight it's held partially open during combustion, it will burn up. Quote Link to comment Share on other sites More sharing options...
Derek up North Posted September 17, 2014 Share Posted September 17, 2014 The Service Schedule calls for both a timing belt change and valve clearance check (and adjust) at 60k miles. To me, it makes perfect sense to do both at the same time since a lot of the labor for both tasks is 'shared'. If you chose to 'stretch' the interval is entirely up to you! Quote Link to comment Share on other sites More sharing options...
toyboxII Posted September 17, 2014 Author Share Posted September 17, 2014 Thanks guy for your responses. I try to do all PM and drive conservatively. Trouble all started when I had the valves adjusted at the Toyota dealer by "the only mechanic who is qualified to do that job". Hoping you could give me suggestions as to how to keep the problem from happening again. Quote Link to comment Share on other sites More sharing options...
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