Motor Knock FZJ80 (2 Viewers)

[Addi]

This is on my recently purchased '94 80 series. Last night while driving it home up a decently steep hill in NM, I was pushing 75 mph to test how it handles hills, and somewhere near the top I noticed an engine knock that hadn't been there before. Luckily I was close-ish to home and took it there immediately. Originally while driving it last night the knocking would occur around 3k rpm and above, in every gear. I've haven't driven it again since, but at idle there is a knocking still as well. It sounds like a high pitched knock coming from the top of the engine near the back I think, and maybe a lower pitched knock coming from the bottom of the engine. Also last night there was a ton of fresh oil around the front of the engine, which you can see in the video ( now dried up).

I've searched Mud and there's tons of info on what it could be, but does anyone know the best place to start in terms of most likely culprit to least likely?

 

[BILT4ME]

Drain and collect a sample of your oil for glitter and to send to Blackstone for confirmation. Use a clean plastic just or mason jar kind of thing.

Pull the spark plug wire on each cylinder, one at a time, then start it to see if it still makes the noise or if it's less pronounced. When it is quiet, it's THAT cylinder.

That sounds to me like rod knock, so you're looking at a complete rebuild.

Sorry for your loss.

 

[Kernal]

^^^This^^^.

Blackstone Laboratories will send out plastic collection bottles and if you prepay they will send out bottles with prepaid mailing included.

Blackstone Laboratories
416 East Pettit Avenue
Fort Wayne, IN 46806

(260) 744 - 2380 (8-5 EST)

 

[Tachycardic]

That's rod knock until proven otherwise. You'll need to prepare your finances for an engine rebuild. Sorry

 

[Addi]

Well, I tried unplugging the spark plug and listening to the engine, but there was no noticeable difference. I also tried the "placing one end of long screwdriver to engine, and one end to ear" trick and couldn't discern where it was coming from. So I bought a mechanics stethoscope to try and get a more accurate sound, but I still couldn't tell exactly where it was coming from. That's likely because I have zero experience diagnosing engines from noise alone, but I was expecting the knocking to be blaringly loud when I found the right spot.

Also, it turns out that the oil was low when I drove it home. It looks like over two quarts low. The previous owner told me that it burned a lot of oil, and I should have thought to check it before driving the long distance. Either way, I will send oil in to Blackstone and prepare to rebuild the engine. With the amount of oil that its burning and the amount that I can see caked around the engine, I think it might be a good idea either way.

 

[Addi]

Ok I'm going to try and update this as I go and keep the video up, in case anyone in the future comes across the same problem. Here's the report from Blackstone. They were spot on about the metal. There is a ton in the oil pan. See photos.

The engine is out, and seems to be in overall good condition for 250,000 miles. I honestly can't tell where all the oil was leaking that got all over the engine, but it is thoroughly caked. Lots of carbon on the pistons, and some uneven wear on the cylinder wall, but I think thats to be expected. I haven't reached the piston bearings yet, but I'm going to assume thats the culprit for all the metal.

Here's some additional photos of the engine.

 

[Addi]

Well I found the culprit. It looks like the bearings in cylinder #5 were spun, and as you can see in the photos, completely destroyed. The rod caps on that piston are difficult to get on and off and I think that maybe they have warped from the heat? This is all very new territory for me, but I think at least that piston setup is toast and will need replacing. The other bearings all have significant wear as well, but not catastrophic. I hope that the damage caused by that single piston hasn't effected the crank shaft too much. The machine shop should be able to tell soon enough. Now that the engine is almost entirely disassembled I can say that it's actually not in bad shape, and I have positive feelings towards the rebuild.

 

[Addi]

Does anyone know how much you can grind off the crankshaft before its too much? I finally got everything to the machine shop, and owner said he'd probably have to take off .5mm from the rod journals and .25mm off the mains. I was told previously that if I had to take off more than .02" then it was better to just get a new crank. Now I'm not so sure which is correct. Any advice would be appreciated!