red4dr

Hey guys, this is going to be a little long, but I want to make sure that I get all the info out there, so sorry in advance.

So, my 90 4.0 auto with 230k on jeep and 130k on rebuilt motor has developed an engine knock. It was also overheating and suffering from being my wifes first car, so maintenance wasn't as high as a priority as it should have been. had a kid, bought her a new van (cringe) and the xj is now my play toy. it has sat for 5 years while I have whittled away at issues that I wont go into here.

While it was parked I figured I would use some tax return money to go after the engine knock, thinking it was lifters and the cam. Changed them out, fired it up, knock still there. Facepalm.

Now while going after the overheating issue I had just about everything off the block to get down to the water pump. so I figure, why now take a couple more things off and get a better look at the timing chain. I should have paid more attention to it when we did the lifters and cam, but that wasnt the issue we were looking at, so they were not looked at as closely as I would have now liked. Got everything off, chain seems to be a little loose, and there is no oil slinger. Being a 90, it should have the slinger unless the guy who did the rebuild put in a new balance and deleted it. When we did the lifters i remember having to put in a new keyway on the the crank because it was very badly worn. So now in retrospect looking back and armed with about 2 hours of crawling around with a mechanics stethoscope, I know the knock is coming from either the timing chain area or the #1 piston.

So now to the real question. Could the oil slinger not being there allow enough room for the crankshaft timing gear to move around causing the keyway to wear down also causing the knock? Due to money issues, I haven't gotten the new timing set to see if the gear fits better on the crankshaft. There is no damage to the crank that would show slop, but the gear was loose on there when i took it off. I know it is sandwiched by the balance to not have play when it is all buttoned up, but could there be a small void there that the slinger should be occupying?

Sorry again for such a long post, but I feel that all the info is helpfull. I did not think about these issues when I was removing the balance to see if the crank and balance had a void or were touching before using the puller to remove the balance. id like to put it all back together without the timing cover so i can see whats up, but I do not have the balance install tool. That might actually answer a lot of my question here to go get the tool from autozone and check that out.

red4dr

wow, it is really long thanks to anyone that reads it through all the way!

Turbo X_J

The "badly worn keyway" will probably lead you to the problem.

red4dr

just an update. I did a lot of poking around today. The crankshaft timing gear is wallowed out a bit in the exact shape of the keyway. It took the edge off of the grove for the keyway. there is matching wear on the crankshaft right next to the keyway. When jiggling the gear around on the crankshaft, the keyway would unseat at times and let the gear move about a tenth of the way around. I am pretty sure now that this is the cause of my knock.
There was also a wear mark on the washer that holds on the harmonic balance that shows the washer was bottomed out on the crankshaft.
This leads me to believe that the missing oil slingger caused not enough pressure to be placed on the camshaft timing gear. This allowed it to eventually wear down the previous keyway and provided just enough slop to cause the knock.
Any thoughts?

red4dr

my plan as of right now to fix this issue is to replace the timing set, order a new oil slingger and to put a little jb weld to fill the void behind the keyway. I was a little apprehensive about the jb weld, but it will just be filling a small void and will have nowhere to go if it does break down due to the oil slingger and harmonic balance closing off any escape route.
Thought?

red4dr

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