Engine knock problem solved - findings and fix

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UZJ40

OEM(ish)
Joined
Aug 8, 2011
Threads
242
Messages
2,567
Location
LV, NV
As some of you read, I purchased an LX that had an almost complete headgasket install. Within a few hours of buying it, I had it running. But there was a knock coming out of the front/lower engine.

In case anyone missed the first thread, this is the sound/video

https://www.youtube.com/watch?v=dSkE1aZw_DA

I tried different things to diagnose where exactly the noise was coming from as it was VERY difficult to pinpoint.

Unbolted PS pump- noise still there
Took off accessory belt- noise still there
Unbolted crank pulley- noise goes away

So, with the much needed help of Pin_Head, blkprj80, and allan man (for keeping me company), I determined it was the oil pump gears. Unfortunately, I had to pull the head and oil pan to get the timing cover off. Upon removal, I spun oil drive gears and there was a definite bind on one of the teeth of the crank gear, which would explain the 1 to 1 engine knocking noise. The amazing thing is that the gears actually look good, but the only way I could feel it was rotating them together.

I ordered both gears, as I figured the one damaged gear probably did a bit of damage to the other. Since I had everything off, I also installed new-

Head gasket
Thermostat
Chain dampener
Chain slipper
ALL new vacuum lines
All new seals and gaskets

After everything was back together, I fired it up, and it was quiet as new! Here are a few pics along the way...

The head looked brand new when I pulled the cover off. I was very pleased, especially for 190k

20130115_140139.jpg


The bottom end also looked great! What a pain in the ass getting the oil pan off. One of the top 5 most difficult thing's I've done on a vehicle.

20130115_173341.jpg


After getting the slipper and dampener off, I noticed both tops had small chips off of them. I wonder if one of the chips went through the gear down below.... Hmmmm

20130120_171047.jpg


And the problem gears!

20130120_171100.jpg


Thanks again for the help Mud! Going to register it tomorrow and start driving it from time to time!
 
Last edited:
Thanks for posting up what the problem was.

Congratulations and I hope that everything goes smoothly with the rest of it.

Thanks again for your help. Without your knowledge, I'd still be at square one! :beer:
 
Glad you got it all worked out. It was pretty puzzling. Any chance you can post a pic of the actual damage to the gear teeth? Just curious how much damage was causing the noise. Nice to put it all into perspective. John
 
Glad you got it all worked out. It was pretty puzzling. Any chance you can post a pic of the actual damage to the gear teeth? Just curious how much damage was causing the noise. Nice to put it all into perspective. John

John-

I honestly don't think I can take a picture of the damage, most due to the fact that I can't see the damage with my own eyes. The only way I found it was by rotating the gears together, both mounted in the car, and then just by holding them.

They rotated very smooth, but right when that certain spot on the crankshaft gear meshed, the gears didn't seat right, and they wanted to wobble.
 
No problem. I have seen a lot of damaged gears before, some like yours, where it is not obvious, but the clearance is compromised as the damage has created a high spot on the interfaces. I have spent a lot of time with a stethoscope trying to locate the sound of a damaged gear/bearing. It's always the little ones that take forever to locate. John
 
Nice followup - good catch, too!
 
Here, I took a picture. The tooth that wobbles is the '1' directly above C17. Looks like all the others, with maybe a tad more wear on it.

20130120_200843.jpg
 
Can you post up a video of the engine running (from the same viewpoint) without the knock for comparison?
 
Just bought a locked 80 today with the SAME knock at 247,000!
 
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