I am in the middle of a 91Q (89,000 miles) chain guide replacement job. The actual guide work went smoothly and the cover is now back on. There was no obvious chain jump while I was changing the guides. But... when I turn the crankshaft pulley I can hear a slight click noise from one valve cover, then the other one at a certain few points in the rotation. Should there be silence, or is a tiny noise with manual rotation ok? Am I just being paranoid?
What does pistons contacting valves feel and sound like?
The engine ran smoothly, with plenty of power, and quietly (except for chain ratttle at start-up) before I started the work.
The lower cam chain guide near the oil pump was in pieces and the chain had worn a small groove in the oil pump housing. There were some grooves in the finger which protrudes from the back of the front engine cover.
Thanks for all the help from people who made previous postings on the chain guides issue!
Q45 timing question
The clicking is the cams snapping forward when the cam lobes pass their apex on the lifter. The valve spring is forcing the camshafts to rotate ahead of the crankshaft. Depending on which cam is rolling forward, you'll develop slack at different points along the chain. I think the noisiest clicking comes from taking out the slack that develops between the camshafts, when the driver's side cam snaps forward. If the pistons and valves were hitting, the crankshaft would come to a dead stop as you turned it (slowly and carefully of course). Not much noise though.
Wow, if you were wearing into the "finger" on the front cover, your chain was pretty loose! I assume you replaced the tensioners.
Wow, if you were wearing into the "finger" on the front cover, your chain was pretty loose! I assume you replaced the tensioners.
The clicks could also be the tension guides (the curved metal guides which the tensioners pressure) slapping against the timing covers.
The tensioners are oil driven and unless you precharged them with oil, they won't work right until engine oil fills them. When they are empty they tension guides have no resistance and can flap freely. The camshaft run-ahead action that David mentioned causes the chain to suddenly tighten on the slack side (tensioner side) of the chain and throw the tension guide against the timing cover.
When you start the car, the tension guides will make ALOT of noise for a few minutes as the tensioners fill with oil.
Both david and I experienced this when we did our guides. His stopped after he cleaned oil passages in the LH upper timing cover. I had to pull the LH tensioner and fill it with oil to quiet my engine.
dan
The tensioners are oil driven and unless you precharged them with oil, they won't work right until engine oil fills them. When they are empty they tension guides have no resistance and can flap freely. The camshaft run-ahead action that David mentioned causes the chain to suddenly tighten on the slack side (tensioner side) of the chain and throw the tension guide against the timing cover.
When you start the car, the tension guides will make ALOT of noise for a few minutes as the tensioners fill with oil.
Both david and I experienced this when we did our guides. His stopped after he cleaned oil passages in the LH upper timing cover. I had to pull the LH tensioner and fill it with oil to quiet my engine.
dan
The pan has a baffle in it. I could hardly see into the pan very far, and poking around with a piece of stiff wire, and with a flexible "pickle grabber" did not reveal anything. I even tried a vacuum but could not get a hose far enough past the obstructions to be useful.
Most of the broken guide fell out when I took the front cover off, but not enough pieces to reconstruct it. I am guessing 2 to 3 pieces of 3/8 to 1/2 in size are not accounted for.
Most of the broken guide fell out when I took the front cover off, but not enough pieces to reconstruct it. I am guessing 2 to 3 pieces of 3/8 to 1/2 in size are not accounted for.
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maxnix
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1995 Infiniti Q45t
2000 Infiniti Q45
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Thus the need for the pan drop. You are performing the service correctly. Don't stop now.srpim wrote:Most of the broken guide fell out when I took the front cover off, but not enough pieces to reconstruct it. I am guessing 2 to 3 pieces of 3/8 to 1/2 in size are not accounted for.