91 Explorer Knocking noise | Ford Explorer Forums - Serious Explorations

  • Register Today It's free!

91 Explorer Knocking noise

Ajbeck_88

New Member
Joined
February 20, 2017
Messages
3
Reaction score
0
Year, Model & Trim Level
1991 Ford explorer XLT
Hello, this is my first post here. I had a quick question about my 91 explorer. The other day I noticed it was leaking coolant from the lower intake gasket. I took it all apart, replaced the gasket and valve cover gaskets as well. I filler her back up and started it, I started to hear a rather loud knocking noise from the passenger side valve cover. I shut it off. I wondered if I had left something in there so I took the valve cover and upper intake back off. I couldn't find anything. Put it all back together, started it, the knocking was still there, I let it run and warm up, and the knocking noise went away. I put 70 miles on it and it ran fine. I can't still hear it very faintly, and it does effect the rpm, very little though, maybe 100 rpm. Could this be a vacuum leak? That's the only thing I think it could be.
 



Join the Elite Explorers for $20 each year.
Elite Explorer members see no advertisements, no banner ads, no double underlined links,.
Add an avatar, upload photo attachments, and more!
.

















Check your rocker arms, they are known to wear
 






Its hard to diagnose an issue from the web. If it sounds like a knock, it could be a stuck valve, a rocker, a piston, etc. Lots of these older 4.0's develop a "tick" that goes away after the engine warms up. Mine has that, but I found out it was a exhaust manifold leak that is not worth fixing as it goes away after about 30 seconds. If it sounds like a vacuum leak, that's a totally different kind of noise. If you got through that intake seal job, it sounds like you know your way around a engine. I am in the process of that now and its a job. Biggest issue for me is getting all the wiring and vacuum lines in the right places.
 






Ya getting the passenger side valve cover off was no easy task. I had to pull the alternator and idler pulley off.
 






Back
Top