loud tapping/knocking

[RangerJ]

It's me again the money pit still has issues. 1989 4x4 xlt 2.9 auto trans. Today after a steady drive on the highway I noticed a loud knock that sounded like it was on the left side of the engine. The oil pressure gauge shows it is in the normal range. After it sat for a few minutes the noise was gone It doesn't do this driving around town .I didn't notice any power change/ The only thing is poor gas milage which I posted earlier Any ideas thanks

 

[UnderMedikated]

My 88 does this. I changed to synthetic, flushed the oil and it helped for awhile.
I have a cracked head so it's sitting at the moment. I'm going to replace the heads and lifters and clean everything I can while it's apart. 2.9's really suck from an engineering standpoint. If I had the time and money a 5.0 or a Toyota engine would be going in-LOL! Check your oil cap for a chocolate milky substance as well as your oil for any antifreeze. My truck is paid for and it's clean so I'll dump 700-800 into the upper end and cross my fingers the knocking/tapping isn't the crank bearings. Good luck!

P.S. Clean you oil pan screen if you can get it without lifting the engine?

 

[UnderMedikated]

Check this page;
http://www.forbes.com/2004/01/23/cx_dl_0126featslide_5.html?thisSpeed=20000

 

[IMenriched]

It's me again the money pit still has issues. 1989 4x4 xlt 2.9 auto trans. Today after a steady drive on the highway I noticed a loud knock that sounded like it was on the left side of the engine. The oil pressure gauge shows it is in the normal range. After it sat for a few minutes the noise was gone It doesn't do this driving around town .I didn't notice any power change/ The only thing is poor gas milage which I posted earlier Any ideas thanks

It might be the oil filter getting plugged. exspecially if its a Fram. but that is on the other side.

wouldn't trust the factory gauge, if yours is still equipt.

I think that these later models also had an anti-knock sensor on the block too, just above the starter??? might want to check that out.

might want to do a compression check

might also be a U joint going bad on the front end, only showing up at higher speeds..or a buldge in a tire??

 

[dgndngrngr]

http://www.therangerstation.com/forums/showthread.php?t=34229

one theory is that the oil gets stuck on the top of the engine and doesnt flow down as easily as it did up. the knock and the 2.9L go hand in hand. just like imenriched said, adding an aftermarket oil pressure gauge is the way to go. the one on the dash says you either have good pressure or you dont. good pressure is around 40ish. mine drops to 20ish after its warmed up for awhile. just means i have to not let it drop to idle long at stoplights and while parked. if it drops to around 5, you have engine trouble.