So working on a 2005 F150 with a 5.4. Started off as a phaser replacement. Turn out the passenger side timing chain guide was badly damaged.

Front timing chain cover came off and replaced the guide and phaser. Got everything back together and it ran rough. Pulled the front timing cover off and the passenger side was off a tooth. Retimed that passenger side and also replaced the tensioner because the seal on the old tensioner wasn't the best. Now rotating the engine, i noticed the tensioner pushes then retracts. Seems like a vaccum is created pulling the plunger in, but not entirely sure. Only the passenger side does this, not the drivers side.

Worried about putting the front cover and valve covers on, buttoning everything together and having it skip another tooth because of slack in the chain. Anyone come across this? Any fix for it or reason why it does it?<!-- google_ad_section_end -->

 

Out of the HUNDREDS of these engines I've had apart, I don't think I've ever run into the issue you describe that wasn't caused by installer error. And YES, I plead guilty to have done this myself. Twice actually, once was also on a 5.4L 3-valve engine like the one you have, and the other time on a 4.6L 32-valve Aviator engine. FWIW, timing the passenger side cam is always the toughest on these modular engines, due to the fact that with the crank timing mark at exactly the six o'clock position, there seems to be A LOT of tension on the passenger side cam, when held in the position it needs to be, to enable chain installation. This is why I find it's a very good idea to have an assistant up top holding the cam in position as you finesse the chain on, while installing the tensioner.

 

Thanks mchan. We have two sets of hands on this. We think the timing is correct. Our worry is that when the we rotate the crank over by hand (just checking everything), the tensioner piston retracts and causes slack in the chain. I am worried that if were were to run the engine that slack is enough to skip a tooth. When we continue rotating the crank, the piston extends. The Tensioner is new so not sure if we have a bad part or what. We almost here a suction sound coming. Not sure if that is what is pulling the piston in.

 

The timing chain tensioners on these engines use engine oil pressure to maintain tension. Remember, with the front cover removed, and spinning the engine over by hand, you have no oil pressure going through. The reason the piston on the new tensioner is retracting as you've described is because it hasn't been primed up with oil pressure yet. Did you happen to notice what happened as you compressed the old tensioner piston into the released position? You would've seen residual oil exiting the tensioner as you were doing this.

 

I suspected it was oil pressure that did but wasn't sure. Next step Is to button every thing up. Hopefully everything will run right. Thanks for your help.

 

Did you ever figure out what the problem was ? I just replaced my tensioners/guides on my 4.6 OHV Expedition and the same thing is happening to me. If I spin by hand, the pass. side chain loosens alot, then tightens up again in about 1/2 turn of the crank.

It's so lose, at one point the chain can touch itself then tightens back up as I turn the crank. I'm pretty sure I timed it right, but am nervous to button everything up and come to find out I have to take it all apart again.

 

I am pretty sure that it's normal that there is slack. We ended up buttoning up and started the truck up. It ran like crap so we got nervous. Ended up frying a COP in the process which caused that. Once that was swapped out it ran fine. We think we steamed a COP when coolant splashed into the plug well.