bearing questions

['70 521 L16]

So it was almost time for an oil change last week  when the truck started making a weird noise. I drove it to school (probably about 20 miles round trip) that morning, and when I got in about 3 hours later to go to work it made this scraping scratching noise upon startup. My initial thought was the new alternator I'd put in a few days earlier, or maybe the water pump that was on the list of things to do... but before I could find the noise, it stopped. It came back a few times on the 4 mile drive to work, but always went away after a few seconds. Then when I was leaving work, it started again on the way out of the parking lot. It didn't go away, and I pulled over when the oil light came on less than a mile later and shut it off. Checked the oil and found nothing on the dipstick. This is odd because I've checked pretty often over the past few months that this thing has been my daily driver. I filled it up and babied it home. It made the noise the whole way back, and the tach seemed to flutter around 2k, but as long as I was careful, I could keep the light off. I checked the oil while it was still running, and once again, there was nothing on the dipstick, thought there was still oil in it. There it has sat until today when I tore into it.

 

Since it was time for an oil change any way, I went ahead and dropped the pan (and the rest of the junk that was in the way.) I'm hoping it's not a spun bearing, but I'm a little bit lost on low end stuff. I bought this block from a guy who had put a freshened crank and .40 over pistons in for his truck until he decided to put a z in it. Now that I'm looking at it though, things don't seem quite right...

 

u60 crankshaft?

 

 

This is right behind the front end cap thing. On the first counterweight? Looks like a funny machining mark of some kind. Is this normal?

 

 

Its tough to get a good angle under there in the dark, but the end cap as well as the bearing cap are labeled "2". Maaaaybe that's not a big deal?

 

 

But then, the second one is labeled 1...

 

 

...The third bearing cap is labeled "7"...

 

 

...and number 4 is labeled "2".

 

Also, I can wiggle all of the rod ends maybe 2 mm back and forth in place. I turned it over with a big wrench on the pulley and watched everything and I dont hear any unusual noises. There's this hissing that's always been there, but nothing out of the ordinary. I did notice coolant leaking down from 2 and 3, which got me a bit worried, but I've never seen any water in the oil before...? Why would that happen? Am I even right in suspecting something low end? Does this seem reasonable? Would you like fries with that?

['70 521 L16]

Also.......

 

 

[TheBirdistheWord]

The numbers are supposed to correlate with the cylinder that rod is attached to, from what I understand its recommended to keep those matched up.  However, I suppose if the bearings were replaced the number and the crank at the very least polished, that may not be an issue.  As far as it saying 7 on one of them, I think the l20B mains and the L24, L26, and L28 share the same main bearing/crank journal size.  Someone could have used a bearing cap from a Z motor.  I know that some wiggle with the rods is standard, there is a measurement you can use to verify, but I can not think of it at the moment.  The hissing is compression from the cylinder reaching TDC, I think you can mitigate that by removing the spark plugs.  Dont have a clue about the machine mark, U60 is one of the two or three standard cranks that came in a L20B. Have you checked fuel pump or timing chain? make sure the nut that secures the of center nut spacer thing that drives the pump is tight. Also, make sure your fan belt is tight.

 

with that said.... not much else you can tell without pulling off those caps to see if there was damage to the crank when the oil pressure dropped, did it over heat when that happened?

['70 521 L16]

Nope. Temp seemed fine.

[Stoffregen Motorsports]

It seems you have a steep learning curve ahead of you.

 

The main caps have cast numbers as well as stamped numbers in them. The forward main cap has a "F" which means it is the front cap. The center and rear main caps are self explanitory as to where they need to be as the center main has the thrust bearing built into it and the rear has the gasket surface and seal surface maichined into it. The #2 and #4 mains are different widths, but they can be interchanged. From the pics, it seems as though your main caps all seem to be in order, but I'm also relying on your description.

 

That funny machining mark is actually an oil galley plug that is hammered in from the factory.

 

U60 is a L20B crank.

 

If you pull the #3 rod cap you will more than likely be able to tell if your engine is hurt or not. The #3 rod gets oil last and is most likely to come up short in an oil starvation situation. You can check your crank thrust or endplay by measuring the for and aft movement of the crank to find out if your thrust bearing is trashed or not. Use a large screwdriver and torque the crank forward against a main cap, then use the screwdriver to torque the crank backwards. Measure the amount of movement and if it's more than .010", it's likely your thrust is trashed and possibly your crank too. This can be caused by a misadjusted clutch putting constant pressure on the back of the crank. If you want to remove a rod cap or bearing cap, pay close attention to how it came off so you dont' get it back in the wrong spot or in the wrong direction.

 

Another possibility is a broken crank. They can make lots of noise. But none of these account for the oil consumption. It's likely that an oil leak developed and brought you to this state as opposed to the other way around.

[EricJB]

Looks like the crank got hot. It's purple.

 

[datzenmike]

Yeah, that's from a spun bearing, maybe previously fixed. I would drop that rod cap and take a look.

 

My concern is filling with oil and driving home only to fill again???? So where's the oil going?

 

Oil light cam on? They are set for 5-8 PSI or less. Not good to run out.

['70 521 L16]

There was oil in it when I got home. I drained out plenty of normal looking used oil, with no shavings... nothing unusual. I'm wondering if something is blocking the oil before the pressure sender and keeping it from falling back into the pan or something. It's strange that the problem would show up after months of daily driving though, with no warning. Is it not? I wasn't seeing any problems with oil pressure until this noise started up out of nowhere. Maybe things weren't torqued down properly? I'll take the rod caps off and take a look and a few more pictures when I get a chance. What exactly should I be looking for aside from obvious score marks? Does anyone have that oil flow sequence diagram handy?

[datzenmike]

Well to be clear... the nosie started about the time the oil had run out and the red warning light came on, right? That is understandable. Lack of oil = strange noises.

 

How much oil did you put in in the parking lot? Because one qt. isn't going to do much if it was empty and the light on. Did you read to the full line in the parking lot??? If not when you got home it would still not read on the dip stick.

['70 521 L16]

The noise started before the oil problems. I wouldn't have driven it after that had the noise been constant, but it went away. The light didn't come on until I left work, 4ish miles after the noise started. I filled it to the full mark in the parking lot. Just happened to have my 5 qt jug in anticipation of the oil change. I used a little over 2 qts if I recall correctly.

[Stoffregen Motorsports]

That blue color near the rod journals of the crank is not an indication of a bad bearing. That color is from the machining and heat treating process. A crank that has spun a bearing will be more black looking than blue.

[datzenmike]

The noise started before the oil problems. I wouldn't have driven it after that had the noise been constant, but it went away. The light didn't come on until I left work, 4ish miles after the noise started. I filled it to the full mark in the parking lot. Just happened to have my 5 qt jug in anticipation of the oil change. I used a little over 2 qts if I recall correctly.

Has to be leaking... two miles to the quart and you'd know something was burning. The oil light will stay off above 5-8 PSI... you could have been running as little as 6 psi on the way to work. 

 

Well find your leak and fix it. As long as the pan is off take a look at those bearings and if they look ok, button it up and go on.

[TFM1066]

is it just me or in pic # 3 and 5 are those drops of coolant hanging off the crank?

[Stoffregen Motorsports]

Looks like coolant to me.

['70 521 L16]

It is coolant. See first post. No water in the oil. This is the first hint I got that something might be awry. What up with that?

[datzenmike]

Noise could be the water pump bearing going. Look on the under side of the pump just behind the pulley. There is a weeping hole to drain coolant that has gotten past a failed bearing seal.