4.0 Top End Knock

[Douginator]

I’ve recently picked up my 2003 FX4 for $700 with a broken timing chain on the left head. When I pulled the motor to do the chains I found the usual broken guides and related debris in the oil pan which was thoroughly cleaned before installation. All valves were replaced while the motor was out. After I put everything back together the truck ran phenomenally for 14.2 miles, when my left hand timing chain broke. I had made the mistake of purchasing a cheap timing chain set, and ended up pulling the left head again and replacing the chain. Fortunately none of my valves had bent, so I put the engine back together with the only new parts being the left head gasket and timing chains on the front of the motor. I had doubts about the cheap timing chain set before I installed the motor, so I had purchased a cloyes cassette for the rear chain. All timing components besides the rear cassette were replaced with Melling parts. The job went back together without a hitch and the truck drove great for 300 miles when I started heading a ticking noise on the highway. I continued driving but for the next 15 miles the ticking got louder and louder until I lost oil pressure and I was forced to pull over. I checked the oil and found it to be clean and full. I would be able to drive the truck for a minute or so until it lost oil pressure, so I limped it nearby to a friends house. I did an oil change (with filter) and have not had an oil pressure issue since. At the same time I pulled both of valve covers in hopes I would find something in the top end to explain the knocking noise. Other than irregular wear on #6 exhaust cam lobe everything checked out. The irregular wear could be described as looking like graphite powder on the cam love. It didn’t seem likely that this would cause such a deep knock. To diagnose the noise as rod knock I pulled each spark plug wire until the noise got quieter. It seemed at the time that the noise almost disappeared when spark plug wire #6 was pulled. To confirm my theory I pulled the pan and found that no bottom end bearings had spun on their journal. There was more wear on the bearings than I would like, but not enough to explain oil pressure loss or bearing knock. The pickup tube however was almost completely plugged by metal debris. I cleaned the pickup screen out and thoroughly cleaned the pan for a second time. The knock still remained when I put the pan back on. I was not able to make the noise change by pulling any spark plug wire at this point. Which indicated to me that the problem is getting worse. I’ve been driving the truck with the noise for the past couple of days, but the noise is becoming more constant now, so I pulled the valve covers tonight. The noise was louder than I’ve ever heard it, and when using a mechanics stethoscope on each cam cap with the engine running the noise can very noticeably be heard coming from the cam cap between #6 intake and exhaust. I don’t know what I am dealing with here, so I’ve decided to source a used head instead of trying to fix this mess. I suspect the oil passages in the head may be plugged or perhaps that valve is sticking in the head. The rocker arms were removed from that cylinder and were in pristine shape. No flat spots and no hard spots in the roller. Whatever it is seems to be unique to my motor as I cannot find anyone describing a similar situation. I’m curious to hear what others think of my situation and if there’s any ideas out there

 

[600$04Ranger]

I went down a similar path and ended up pulling my motor 4 times before I did what I should have done the first time I pulled it. I tried replacing only the most obvious parts that were toast instead of doing a thorough teardown, cleaning, and inspection. Would have saved myself a lot of time, money, and frustration. Like you I paid nearly nothing for the truck but also knew nothing about it's history and took a friend's bad advice to replace broken timing and see how it ran after that. A detailed inspection would have revealed other significant wear without crossing fingers and turning the key. Seems like you have some good clues and have been able to look closely at the critical areas and by your description of debris in oil I would want to make sure oil pressure was good and think about pulling that thing apart, replacing bearings and anything else that might lead to disappointment in the near future. Since my rebuild about a year ago I have put 20,000 trouble free miles on it. Hopefully you pinpoint the issue and correct it while keeping your expenses low but be careful not to miss something that causes major damage in a short time period. Like low oil pressure. I'll be interested to hear what you find though. Best of luck!

 

[Douginator]

Thank you for the insight. While it’s tempting to replace the one head right now, I agree that it would be best to pull the engine and do a partial rebuild. I have not taken an oil pressure measurement since cleaning the pickup screen. It was originally my plan to convert the truck to a 1.9 TDI with the tdconversions adapter. I was just trying to make this motor last for a year so I could save up for the swap. I just need reliable transportation right now so I need to fix the motor I have before I even attempt that project. I’ll be back with an update hopefully by the end of the month

 

[09fx4guy]

Seeing as you have the skills to do the work, I would do as you said and do a partial rebuild. If the pickup screen was that plugged, chances are many components were starved for oil at some point. It might not be a bad idea to find a motor you can rebuild while it is out of the car, if the motor currently in the truck ends up being toast.

 

[Douginator]

It has been a busy month. Since my last post I have pulled the motor out and installed a remanufactured left head and replaced all lower end bearings. I installed a Melling high pressure/volume oil pump and primed the oil system with zinc additive before installing the motor. The only thing that was really weird is that my brand new connecting rod bearing with 60 miles on it had very irregular wear as pictured. I replaced with the rest of the bearings and put it back in the truck. Upon startup I immediately heard the knocking noise; so I decided to park it until I could figure out what went wrong. As I looked more into it I became convinced that I in fact had wrist pin knock - and the only reason I hadn’t found is because I hadn’t pulled the piston out. Now it seemed like removing spark from #6 caused the noise to almost completely go away, where before it didn’t make much different. So I went ahead and ordered a used piston and I finally received it in the mail this last week. So I pulled my pan and my head after work last night with the intention of replacing my #6 piston. As can be seen in the pictures it was very apparent that the noise was caused by piston slap. So I went ahead and bought a 3 stone hone and honed my cylinder wall and re-used my new bearing on the new piston. I did not re-use my rings however; instead opting the use the rings on the new piston because I had no way of knowing if my pistons rings were damaged by the irregular motion. After putting it all back together I was very relieved to hear my engine run like the first time I put it together. Other than smoking for a few minutes my engine now runs quietly. I’ve put 30 miles on the odometer today so we will see how it goes. My plan is to pull the lower pan at 1000 miles and make sure my pickup is clear and free, and also put a magnet in the bottom preventatively. Fingers crossed I won’t have another stroke of bad luck with this thing