Checking out bottom end, need some advice

[staticpat]

Well I had a low tapping noise, and I assumed it was rodknock so I'm looking at the bottom end to check my clearances and whatnot. I want to see if it's fixable or if I might as well get a new engine. I've never done this before, so I need a little help. I have been taking pictures of everything but I don't have the right cable for my camera :icon_conf , so I'm going to try and describe things the best I can. On the other two rodknock engines I've seen, the problem was clearly identifiable (ie. rod broken, or had tons of play) but all my rods are solid in place, so I'm doing my best.

Here are my questions/concerns.

-First thing that stood out to me was there was some scoring on the bottom of the back 4 rodcaps. The sides of the caps and rods are perfect. The oil pan and block look perfect, doesn't look like they have been hit at all. (EDIT: the rods are hitting the pan, read next post for clarification) I don't see what the caps could be hitting. This is a picture where I tried to describe the scoring. This is not my engine of course.

3 of the rodcaps have 3 score marks, and 1 of them has 4, all equally spaced out. They are not deep, but I can feel them with my fingernail. Will this throw the engine out of balance? Should I replace the rodcaps? or is this a sign of a bigger problem.

-I checked out the rearmost rod so far (this one had the 4 score marks so I assumed it was the worst). The crank looks great, no scoring or pitting. Bright and clean. So hopefully replacing the bearings will be sufficient. The bearings look a little worn and some pits, but to a beginner's eye I don't know if they are bad or not. I plastigaged this rod and it came back within spec (between the .038 and .025 marks, about .021). This is obviously on the low side, but the TSRM only says to worry if its over .07. What do I do if its lower than specs?

-When I order new bearings the TSRM says to use the number matching system if I can't read the number off the bearing. My first bearing says 3A 0.25 c696 AM. Is this enough information to bring to Toyota, or do I need to still match up the crank #, rod #, and bearing #?

-Another thing I noticed is my harmonic balancer has a chip in it. This is recent, as last time I was under the car it was perfect. Could this be enough to cause my noise and the damage to the rod caps?

-Some of the rods are obviously high up. Can I turn the crankshaft with no oil to get them reachable or is this a no-no? Also I remember reading that its best to check clearances when the rod is at its lowest point.

Thanks much. If my questions seem retarded, remember you all had to start somewhere too.

 

[Facime]

Im not a real expert but I can answer at least a few of your questions.


Here are my questions/concerns.

-Another thing I noticed is my harmonic balancer has a chip in it. This is recent, as last time I was under the car it was perfect. Could this be enough to cause my noise and the damage to the rod caps?

The Balancer is intended to remove torsional vibration from the crankshaft. In real simple terms it is kinda like a shock absorber for your crankshaft. It is not like a wheel weight for balancing tires. While anything that is weighted improperly on the engine can cause vibration, I seriously doubt that the chip you describe is alone the direct cause of your ticking. However, if what caused the chip, damaged the rubber connection inside the dampner then it could be a cause, and should definately be replaced. Its really hard to say from here. As to whether or not that could cause the scoring on the bottom of the rod caps...I really dont know for sure, but my guess would be no.

-Some of the rods are obviously high up. Can I turn the crankshaft with no oil to get them reachable or is this a no-no? Also I remember reading that its best to check clearances when the rod is at its lowest point.

Yes, you can turn the engine by hand. The engine isnt entirely without oil between the surfaces, and you are obviously not generating any heat. Turning it by hand is fine. and yes you should check your clearences when the crank is at a "neutral" stress location, where the rod is essentially perpendicular to the crank.

 

[staticpat]

Thanks Weezl.

I went back and re-checked some things. The damage on the bottom of the rod caps is 4 marks on 3 of them, and 6 on the rearest one (one i removed). The oil pan does show signs of being hit upon re-inspection. It has some slight scoring for 2 of the rods. The other 2 rods are most likely hitting the oil pump pickups, I haven't verified yet.

Here's a 7m cap, the red marks show the 6 marks on the one cap, and the blue marks roughly show the 4 marks on the other 3 caps. The wear only happened on one side of each cap (side to front of car).

So the rods are defintely smacking the oil pan, but not the block. And I assume that's the noise I was hearing. Could 1 spun bearing cause all this? Or could it be a dampening problem? I could go ahead and pull the harmonic balancer and check the rubber that Weezl mentioned.

 

[Facime]

Ive never looked closely at a toyota balancer, but I dont believe you can visually inspect it. Someone else with a bit more experience should be able to answer that correctly.

Here is what my question is though: If the marks on the rod caps are perpendicular to the direction of travel that seems odd to me. In your picture it looks like the way you drew it the scoring cuts across the cap and not in line with it. That tells me the damage did not occur from rotational contact.

I have also never looked inside a 7M (the only motors I ever rebuilt were SBC's) but is it possible that what you are seeing on the caps is machine marks made during their manufacturing? Im racking my brain trying to think of a way you get horizontal scores on the rod caps and I cant think of any.

Can you please find some way to upload an actual picture of the marks in question?

 

[GrimJack]

The bearings that you pulled out - are they silver or copper colored? The rule of thumb is that silver bearings are fine, copper colored ones are toast.

The scratches on the rod caps sound like marks to keep them in order... when you pull them out, you're supposed to mark them so that you can put them back in the right spots. Sounds an awful lot like someone has pulled that bottom end apart in the past.

By low, I assume you meant low on the engine, not low in the RPM band, or low in volume, or something? Is you are 5speed or automatic? Automatics can break their flexplate, and that sounds awfully similar to rod knock. So do loose flywheel bolts or loose harmonic dampeners.

 

[Facime]

Ohh snap! Grim I think you nailed it. ...last cylinder has 6 marks on it...Ding! we have a winner.

Of course that doesnt solve your issue but it rules that out.

One other diagnostic question that wasnt asked, When did you first notice this sound, did it come on all of a sudden? did it come on slowly until you noticed it?

Another thing that can cause a tick sound possibly like you describe is the balancer being loose. It wallows out the keyway and will get bad enough over time that you end up having to replace the crank. Since you are concerned about the nick in the balancer, pull it off and check the keyway and key for signs of deformation.

 

[staticpat]

-Matchmarks confirmed, 6-5-4-3-2-1. Wow some are deep though. Now I need to find out what scratched my pan, because it does have some scoring as well. Thanks guys.

-The bearings are silver, no copper visible anywhere.

-Low as in low volume, but yes, also low on the engine. Now that I see the scoring on the oil pan/rod caps I'm sure that's the noise I was hearing. I have a 5speed, but recently put in a new clutch so loose flywheel bolts may be the noise. The noise is in the band people associate with rodknock though (3500-4000ish?).

I was running about 18psi on an upgraded CT-26 (I dynoed 360rwtq at 12psi) before this happened. I know the stock bottom end is supposed to be stout, but is it possibly crankflex/crankwalk?

I just re-plastigaged the oil clearance(double checking can't hurt) and it comes between .038-.051mm, I'd say 49mm. This is defintely in spec. And as stated previously the crank looks great, and the bearings do show wear but nothing that looks drastic to me.

I'll continue on checking clearances, and see if one is out of whack. Thanks for help.

EDIT:matchmarks confirmed, many statements changed.

 

[Facime]

hmmm, you see corresponding marks on the oil pan....well that could certainly be a cause for noise. But Im still having a hard time visualizing just how the marks would cut across the caps and not go in the direction of rotation.


if your crank is rotating this way: <----------->

and the cap contacts the pan, your scarring should also go this way <------>

and not this way:
^
|
|
|
V


Right, I see the matchmark edit. but if you see scoring in the inside of the pan that may be a problem. Is it possible that damage came before a prior rebuild? or does it look fresh?
I also still think you need to check the balancer and the flex plate.

 

[GrimJack]

I'll bet one of the bearings is fried - one is more than enough to cause this noise...

 

[staticpat]

OK 3 down, 3 to go. I was hoping one would look really bad, so I would have something to compare too. So far all crank journals look great, and all bearings have similar, but not severe, wear. All are within spec so far (the last one was really close to the max, so I may replace it).

I have a new concern, as stated above I'm not sure how to order new bearings. All of the bearings so far have the same markings: 3A .25 0696 AM. I guess since this has been rebuilt, they probably aren't Toyota bearings either. How am I supposed to order new ones if they are all the same?

 

[staticpat]

Good news I found my one trashed bearing. Obviously different than normal wear as on the others. The crank journal looks in good shape too. Thanks for help guys.

 

[GrimJack]

I thought that would be the case... it's usually pretty easy to pick out the trashed bearing. As to bearing sizes, I've always gotten my machinist to order them... I'm sure they have some system for measuring the crank and rod, but I'm not familiar with the exact procedure.

BTW - stock sizes that originally shipped with your engine are usually stamped on the sealing surface of the block where the oilpan sits. Bearing sizes on one side and something else on the other side.

 

[staticpat]

Okay I think I got this all figured out. They are King bearings (I can tell by the logo), all the same part number. In King's catalog it shows these are all .25. So I assume whoever did the rebuild reground the crank to fit all same-sized bearings instead of messing with Toyota's numbering system. So now I either need to order a few more of the Kings, or get all new ones. I suppose I could get a whole new set of Clevites as long as they are .25. I'll go by the machine shop Monday and ask them and order something.

Thanks again for the help guys, I'm still baffled that my matchmarks were cut in with an angle grinder and my oil pan seems to have scarring. Still can't figure out what hit the pan, must have been pre-rebuild.

 

[Facime]

The prior owner probably dropped a rod and that banged around in there. Probably why he rebuilt it.