Motor Knock FZJ80 (1 Viewer)

[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!

 

[Addi]

So in preparation for rebuilding the motor finally, I was cleaning the valve cover with some purple power and I noticed some hard black pieces floating around. It looks like it’s maybe a sealer for that plate that’s on the underside of the cover aa it’s around some of the rivets and all along the outside edge of that plate. I was hoping that it was just dried oil gunk but I’m not sure that’s the case. Does anyone know anything about this? Should I be worried about it breaking off inside the engine if it’s so brittle?

 

[Addi]

Also, in my nonstop cleaning I think I found the source of the oil leak that killed the engine in the first place. I assumed it was originally a bad gasket but there's a small crack on the inside of the upper oil pan that connects to a bolt housing. Perhaps a mix of the two are what caused so much oil loss, I'm told the previous owner would put in a quart every tank. I think this might be cause for a replacement oil pan which I'm not super pumped about.

 

[lexustruck]

I thought the brittle sealer was also oil and snapped most of it out with a pick before giving it any second thought. 7k on my rebuild and the baffle hasn’t dropped onto the cams yet but

I’m also curious about what people do with this. I don’t know how to tag users but hopefully the rebuilder in Oregon can comment.

Not seeing it on any valve cover pics on google. Is that really buildup from the oil?

 

[Malleus]

So in preparation for rebuilding the motor finally, I was cleaning the valve cover with some purple power and I noticed some hard black pieces floating around. It looks like it’s maybe a sealer for that plate that’s on the underside of the cover aa it’s around some of the rivets and all along the outside edge of that plate. I was hoping that it was just dried oil gunk but I’m not sure that’s the case. Does anyone know anything about this? Should I be worried about it breaking off inside the engine if it’s so brittle?

View attachment 3715186

Looks like either the PCV valve or plug seal detritus. I'd bet on the PCV valve. I've seen them rock hard.

 

[AussieHJCruza]

I thought the brittle sealer was also oil and snapped most of it out with a pick before giving it any second thought. 7k on my rebuild and the baffle hasn’t dropped onto the cams yet but

I’m also curious about what people do with this. I don’t know how to tag users but hopefully the rebuilder in Oregon can comment.

Not seeing it on any valve cover pics on google. Is that really buildup from the oil?

@Fj80oregon is who you're after I think

 

[Kernal]

"looks like it’s maybe a sealer for that plate"

Exactly what it is IMO: the thin brown brittle pieces found in the valve cover are old sealant which was originally applied to seal the oil baffle plate when it was riveted into place during manufacture of the valve cover. The original sealant gets brittle with heat/age and crumbles off. More will flush out from inside the baffle box along with any sludge build up (if you aggressively clean out the oil baffle box), a can of Brake cleaner is not enough. I use a degreasing soap/detergent and a garden/water hose to flush it from every direction/orifice on the valve cover and baffle. Any small pieces remaining, if they ever move, would eventually flow down to the oil pan and be stopped by the oil pick up screen or the oil filter.

The upper pan is no longer available but a welder with experience working with aluminum might be able to fix it (weld or braze?). Soaking/cleaning/heating (repeat) of the pan would be required to get the oil out of the cracks and pores in the casting. Due to the size of the upper pan a machine shop engine block washer (using a cleaner that's safe for aluminum) might help.

 

[Fj80oregon]

I thought the brittle sealer was also oil and snapped most of it out with a pick before giving it any second thought. 7k on my rebuild and the baffle hasn’t dropped onto the cams yet but

I’m also curious about what people do with this. I don’t know how to tag users but hopefully the rebuilder in Oregon can comment.

Not seeing it on any valve cover pics on google. Is that really buildup from the oil?

I’m your huckleberry!
What are you asking if the sealer from the manufacturer on the valve cover is an issue? I have never had an issue with it and I hot tank all my covers. I do as posted below and flush them out real good after the tank because it breaks up lots of old oil buildup. You can still buy a new cover on partsouq for $240ish. As far as you oil pan I have a bunch if you need one. I also have a welder, older fella in his 80’s that welds my turbo oil return bungs onto the cast aluminum pans that could probable fix your pan.

 

[lexustruck]

I’m your huckleberry!
What are you asking if the sealer from the manufacturer on the valve cover is an issue? I have never had an issue with it and I hot tank all my covers. I do as posted below and flush them out real good after the tank because it breaks up lots of old oil buildup. You can still buy a new cover on partsouq for $240ish.

I was curious if you make an effort to remove the stuff, but obviously the 1FZ guy has access to a hot tank lol you tear them down and ship them out about as quickly as I can hand clean my valve cover.

Clean all the sealer out once it looks like that, right?
And then run some FIPG in the name of mud OCD?

 

[Fj80oregon]

I was curious if you make an effort to remove the stuff, but obviously the 1FZ guy has access to a hot tank lol you tear them down and ship them out about as quickly as I can hand clean my valve cover.

Clean all the sealer out once it looks like that, right?
And then run some FIPG in the name of mud OCD?

Any thing that loose clean it up with a wire brush, I don’t go picking all the stuff loose around the rivets. Don’t try to seal anything from the outside it will be just fine. What’s going with your pan that’s cracked? The photo you posted is hard to tell what’s going on?

 

[lexustruck]

Any thing that loose clean it up with a wire brush, I don’t go picking all the stuff loose around the rivets. Don’t try to seal anything from the outside it will be just fine. What’s going with your pan that’s cracked? The photo you posted is hard to tell what’s going on?

Makes sense! Also I’m not the one with the cracked pan. Wasn’t sure if you mixed that up in the last reply so I didn’t say anything but yeah this isn’t my thread, just nosy

 

[Addi]

I’m your huckleberry!
What are you asking if the sealer from the manufacturer on the valve cover is an issue? I have never had an issue with it and I hot tank all my covers. I do as posted below and flush them out real good after the tank because it breaks up lots of old oil buildup. You can still buy a new cover on partsouq for $240ish. As far as you oil pan I have a bunch if you need one. I also have a welder, older fella in his 80’s that welds my turbo oil return bungs onto the cast aluminum pans that could probable fix your pan.

Ok great! This is all good information. I'll see how well I can clean that valve cover on my own, I paused once I thought I might be degrading that sealer with the degreaser or something. It's nice to know that even if some bits do come off they won't do anything besides fall to the bottom. It's funny, it seems like every new area of the engine I start on I find some new question or problems that I have to wait and figure out. This is before any rebuilding even starts, since I'm still waiting on the bearings to come in.

Regarding the oil pan, it's a bolt housing that connects the upper and lower oil pans so it's on the very bottom. I knew that the leak originated from this area based on the tons of caked oil on the bottom of the engine, so it makes sense. I sprayed some brake cleaner in the hole to see if it would drip through, but nothing. I assume once it's rattling around that's another story. I'll ask my machine shop if they can handle a repair like this, and since I'm in Abq now there's a lot more options for this kind of thing thankfully. Here's another slightly wider pic but you can't see the crack as well. Also I may have to pm you about getting one of your spares haha.

 

[Addi]

Motor is painted, the main bearings all gauged out perfect, now I'm on to checking piston to sidewall clearances. I'm not very happy with the work that my previous machine shop did, and I wish I had double checked all of this a year ago when I got the parts back. I'm getting numbers all over the place for the clearances. The FSM states standard clearances are between .0016 - .0024, and I'm getting anywhere between .0005 and .0026. My new shop says that the .0026 isn't anything to worry about and I'm inclined to believe them because I'm running out of money. The .0005 can be blamed on one abnormally large piston, measuring in at 3.9581, whereas the smallest is 3.9563. I did send in all the pistons with the block for the original work, so I feel like it shouldn't have been an issue.

So question is how much should I be worried about this tight fit? Would it be crazy for me to order a cylinder hone off amazon and try it myself to knock a few 1/10's off? I can take it in to be professionally done, but that's more money and at least a few weeks till I get it back.

Here's some more photos because why not.