Ford & Mercury 2.5L V6 Rattle at Start-up

If you have a Ford product 2.5L V6 that makes a rattling noise on start-up, you may have a loose timing chain. It's not a problem you want to ignore. The rattling is the chain flapping around. It can rub on the oil pump. It can break off the plastic timing chain guides. Then the timing chain can wear into the aluminum guide. The chain can also skip a tooth or more and get out of time.

Here's where the timing chain rubbed on the oil pump. (I took out the chain guide.)

Here's a picture of a tensioner against a timing chain guide (not in the engine). The piston is actuated by oil pressure. But the ratcheting rod keeps tension when there isn't enough oil pressure.

If that ratcheting rod fails, then it will rattle pretty badly on start-up. That happened in my case. Here's a picture of the original tensioner on the right, and the failed one on the left. The ratcheting mechanism totally failed and allowed the rod to go back into the tensioner.

This allowed the chain to get loose because the tensioner's piston was allowed to retract.

That allowed the chain to slap against the chain guide, breaking the plastic off and rub into the aluminum chain guide.

Then the plastic parts got chewed up by the timing chain and spit into the oil pan where they clogged the oil pickup tube.

I had put RTV black between the plastic and aluminum parts of the chain guide when I replaced it the first time in this blog entry. So when it came off, the RTV did too and helped clog the oil pickup. The oil light was flickering at idle. Then it came on steady on the highway and stalled in the right lane in heavy traffic. It took five minutes before some nice guy pushed her off to the side of the road so she wasn't blocking traffic anymore. I was on my way and found her safe on the side of the road. The Cougar actually started again and we drove it off the freeway.

Loading it onto the dolly to tow it home was an interesting experience. Let's just say we got it on the dolly with maybe 10 guys lifting the front end back into its proper place on the dolly. I wish I had video of that, but I didn't think about it at the time.

Update 3 June 2017

I just put a new chain guide in. To make sure the tensioner wasn't too loose, I pried gently on the tensioner guide to take up all the slack, then released the pry bar and made sure there was no slack on the ratcheting rod. After I put it all back together, it actually still runs. I drove it around the block and it seemed fine. Miracles still do happen! Maybe the Prolong I added a long time ago helped.

The entire job took maybe 16 hours, basically two Saturdays. I had to take off the upper intake, the valve covers, the exhaust Y pipe, the oil pan, the passenger side engine mount, coolant overflow, power steering pump, and the alternator bracket to get the timing cover off. The alternator is crammed in there pretty tightly with not much room to get at the bolts.

Update 7 June 2017

Well, it lasted less than 10 miles before the engine started making a squealy tapping knocking sound. I took the drive belt off, so it's not that. But you probably figured that would happen when I told you about the oil light coming on.