Timing Chains | Learn from my hardship!

[04EddieBauer1203]

Sharing some wisdom for anyone about to undertake this job:

THREE TIMES I had to replace the timing chains and cassettes in my 2004 V6 4.0 SOHC. The first 2 sets failed within 24k miles. Guess why?

If you want to take away a HUGE tip from my hardships: ALWAYS replace the hydraulic tensions while you are already replacing the timing chains and cassettes.

I left the original hydraulic tensioners in every time I did the timing replacement. The right rear hydraulic tensioner had a weakened spring from years of heat. It couldn't keep enough tension on the chain at all times and all phases, which allowed the chain to rapidly damage the plastic timing cassette.

PS - If you want to know how to do the timing in this engine, I am an expert at it now! Haha

 

[mountaineer2004]

Good advice. Never cheap out on parts, unless you don't value your time/labor!

 

[2000StreetRod]

It is my understanding that the camshaft tensioner spring pressure only matters when oil pressure is low. Otherwise, the pressure is determined by the oil pressure on the hydraulic piston. Perhaps there was a piece of your broken cassette blocking oil flow to the tensioner piston. Many of the new tensioners have weaker springs than the original worn tensioners. I advise that new tensioners be manually tested before installation. Some of the cheap tensioners can seize. If they seize in the retracted position then the chain will be slack. If they seize in the extended position the cassette may break. After replacing my cassettes I installed a pre-oiler to eliminate all start up timing chain rattle.