Franko6
Vendor , w/Business number
Yesterday I pulled a marathon for a poor guy that followed all the rules for an ALH, did a decent Timing Belt changout using one of the popular vendors timing belt kits. He followed all the instructions on the Timing Belt Replacement instructions in the TDIClub "Articles" section. The Bentley Torque specifications were followed and the work done accurately.
The car went 15 miles and the timing belt circuit failed, breaking two lifters and bending multiple valves. Cause of the failure: the camshaft sprocket came loose from the camshaft.
The 'correct' torque setting of 45Nm or 33 ft lbs was applied. That torque specification is the point of failure for the engine I worked on yesterday and many other timing belt jobs.
What I discovered when disassembling the vehicle was galling inside the camshaft sprocket. This is not an uncommon occurrance. I've seen several repetitions of the event. It certainly is not an isolated event. The low torque value was not enough to keep the two pieces firmly together.
I have stated my case before in the TDIClub and I will say it again. If I stop one person from crashing their cylinder head, then it's worth the time to say it again and again.
DO NOT USE The 45Nm (33 ft lbs) torque setting for the camshaft sprocket bolts in either 1Z, AHU or ALH engines. USE 45 ft lbs.
No damage will occur from the additional torque. It is the setting I have always used. The 12mm bolt can certainly handle the additional load. The increased torque doen't make the camshaft sprocket any more difficult to remove and does not force it further onto the camshaft.
Some could make a case that poor workmanship could cause the sprocket to slip when using the Bentley prescribed torque setting. Grease, dirt, damage to the mating surfaces, or an out-of-adjustment torque wrench could affect the mating of the cam and sprocket and cause the cam sprocket to slip.
My feeling: when there is so much to gain and nothing to risk, the higher torque setting of 45 ft. lbs (80Nm) will do much to eliminate failures due to the sprocket slipping.
The car went 15 miles and the timing belt circuit failed, breaking two lifters and bending multiple valves. Cause of the failure: the camshaft sprocket came loose from the camshaft.
The 'correct' torque setting of 45Nm or 33 ft lbs was applied. That torque specification is the point of failure for the engine I worked on yesterday and many other timing belt jobs.
What I discovered when disassembling the vehicle was galling inside the camshaft sprocket. This is not an uncommon occurrance. I've seen several repetitions of the event. It certainly is not an isolated event. The low torque value was not enough to keep the two pieces firmly together.
I have stated my case before in the TDIClub and I will say it again. If I stop one person from crashing their cylinder head, then it's worth the time to say it again and again.
DO NOT USE The 45Nm (33 ft lbs) torque setting for the camshaft sprocket bolts in either 1Z, AHU or ALH engines. USE 45 ft lbs.
No damage will occur from the additional torque. It is the setting I have always used. The 12mm bolt can certainly handle the additional load. The increased torque doen't make the camshaft sprocket any more difficult to remove and does not force it further onto the camshaft.
Some could make a case that poor workmanship could cause the sprocket to slip when using the Bentley prescribed torque setting. Grease, dirt, damage to the mating surfaces, or an out-of-adjustment torque wrench could affect the mating of the cam and sprocket and cause the cam sprocket to slip.
My feeling: when there is so much to gain and nothing to risk, the higher torque setting of 45 ft. lbs (80Nm) will do much to eliminate failures due to the sprocket slipping.
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