Learn me (more) rod knock

This time it's not my car, but I'm dealing with a 2005 PT Cruiser - NGC 2.4 N/A motor, 140k - that has developed a knock.  I assume it's a rod, but haven't done any teardown yet.  How this happened, I do not yet know but I feel responsible for it.  The oil pressure sender was leaking real bad a while back so I swapped it out with a fresh one.  After a week, the oil light started coming on intermittently so I replaced it with another fresh one.  Everything was fine for a while.  I don't possess an oil pressure gauge, so I couldn't test it, but it started flickering on and off again recently apparently and my plan was to swap it out for a Mopar sender as soon as I got back from Daytona next week.  When I was examining it, there was no top end noise and the flickering didn't correspond to changes in RPM or load on the motor.  It did correspond to tapping on the sender and its wires.  Last night, she said she heard clattering and pulled off the highway to add oil and put a quart in.  When she started it, there was a distinct knock.  When I got there, I still wasn't showing anything on the dipstick so I put in another quart but I find that particular dipstick to be really hard to read so not sure what's up.  I had her baby the thing home and park it until we can figure out a plan of action.  Another weird thing, may or may not be related, is that the battery is about a year old and it starts every time, but it almost seems to hesitate on the first rotation of the engine as it starts.  Like just an almost imperceptible pause in the rotation.  Instead of whomp, whomp, whomp, purrrr it's more of a wh...omp, whomp, whomp, purrrr.  Just weird.

Anyway, the first thing I need to do is get a mechanical oil pressure gauge and actually test the oil pressure to see what's going on with that.

Is there any chance of success to dropping the pan, splitting the rods, hitting the journals with a little emery cloth, and putting new bearings in or is that just a fool's errand?  Getting motors in and out of PT Cruisers is not the most enjoyable task in the world, so if there's a reasonable chance that the journal is okay and I can swap bearings then I suppose it's worth the attempt.  Obviously, if there is a pressure issue that's a bigger deal and all the bearing in the world doesn't help that.

In reply to wae :

What do you want to do?  Nurse it to the dealership and flog it off? OK , might last that long.  Drive it for a short while? Then flog it off?  Better use a really good synthetic like Mobile 1, cross your fingers, get every lucky charm you have, and pray.  ( in other words not very likely) 

Once  you run a motor out of oil it’s pretty well shot.

Either time for a good used junkyard motor ( and not everyone is worthy ) or some other solution.   

No way to know without dropping the pan.  You'll probably get the first indication of how bad it is just by draining the oil.  Start with a really clean catch pan so you can see how much glitter is in there.  Oil from engines with severe bearing damage has a distinct smell...smells like burning money.  If that's not too bad, then proceed from there.  

Hopefully the reluctance to turn over isn't because the rod bearing shell halves are overlapping and seizing up.  

Good luck and post pics.

She added a quart and there was still nothing on the dipstick .. I don't think it's your fault in any way! Unless you forgot to check the oil when diagnosing it? Whoops!

Are you trying to diagnose the noise?  Rod knock is low in tone, but steady and pronounced.  It generally is not a "clatter."

I am not sure I would even drop the pan or spend money on bearings; just add some STP--thick oil--and definitely not synthetic (that is a waste of money) and continue driving it.

What is the worse that can happen?  It is already on its way out.

wae said:

... it's more of a wh...omp, whomp, whomp, purrrr. 

 

My daughter's Accent is acting that way too.  I'm assuming the starter is getting close to the end of its life.  In your case, that's the least of your worries. 

By the time you can hear the noise driving, it's spun a rod.  It's junk.

I have slapped bearing in a couple neons/PT cruisers in my day. I had one go another 60k doing that. 

It it for sure a bottom in noise, It could also be piston slap (super common) or even lifter noise (even more common).

As for the oil light flickering, make sure it has oil in it..... Thats where I would start. 

I am pretty sure it's a rod knock.  I've heard top end noise and got plenty of piston slap in my Ford vans and this is that lower, coming from the pan, knocking noise that you almost feel rather than hear.

Sounds like throwing bearings at it is a crapshoot at best.  If it was mine, I'd probably try it just in case.  But since I don't have to live with my decisions, sounds like trying to source a used engine would be the better bet.

The motors are pretty easy to pull. If you do buy a used motor Id be interested in the motor out of it if the "core" is cheap. 

In reply to Professor_Brap :

In a PT?  What's the trick to it?  I seem to recall that when we pulled the turbo motor out of a PT in the junkyard it was a real PITA.

I pull them from the top, the trick is to remove all the accessories (ps, ac, alt, and crank pully). You should come out with ease then. 

Don't tell anyone but I once slapped fresh bearings on the bottom of an S14 BMW motor, then proceeded to thrash it for another 10 thousand miles before selling it.  I was honest with the new owner.

My first indication that something was not right was a slight lack of acceleration, like it was running on 87 octane.  No it was a slight rod knock causing the pulled timing.

No shame, if it works it works. 

Yyjoeg1982 said:

Are you trying to diagnose the noise?  Rod knock is low in tone, but steady and pronounced.  It generally is not a "clatter."

I am not sure I would even drop the pan or spend money on bearings; just add some STP--thick oil--and definitely not synthetic (that is a waste of money) and continue driving it.

 

What is the worse that can happen?  It is already on its way out.

 

Synthetics give a little more protection than regular oil.  Is it more expensive? Yes!  But if you want a little more life without a proper rebuild it might give you enough. STP isn’t a lubricant. It’s an oil modifier and thicker oil will just take longer to circulate. On dry start up that might be the kiss of death.  

No oil in it = not your fault.  Operator error is the problem.

I finally got a chance to pull the old girl into the shop.  There's good oil pressure from start up through to normal operating temp at idle, so I'm going with another faulty oil pressure sender.  It appears that the sender was also leaking, causing the low oil condition.  Right after the noise started, about 2 quarts of oil were added and I think I drained maybe three quarts back out.

When I drained the oil, I ran it through a coffee filter and I got some little metal bits and a little shimmer to the oil.  The inside of the oil filter had a little metal in it as well, but there wasn't a ton of material floating around.  I cleaned off my magnetic pickup tool and dredged it through the drained oil and the remains in the oil pan after I dropped that and it came out completely clean every time so the metal bits were probably not rod, block, or crankshaft since those are all steel.

The noise was most prominent from the #4 cylinder and I didn't need to drop the balance shaft carrier to investigate so I went ahead and cracked that rod and pulled the bearing:

Some pitting and scoring for sure.  The rod looks fine:

Other than a little paper towel lint, the crank doesn't look discolored or scored:

I told my friend that this is a total crapshoot.  If she was willing to gamble on bearings, rod bolts, a gasket, oil, and a filter I'm willing to put in the time to try it.  Best case, we'll buy some time for her to save some more cash to buy a new car, but I'm giving it about a 20% chance of success.  Not finding any steel in the oil and not seeing any damage to the crank journals gives me a little bit of hope, but without dropping the bedplate, I can't see what the main bearings look like.  New rod bolts should arrive on Tuesday so we shall see.

In reply to wae :

Are the rod bolts one time use in these?

I have raced worse looking bearings than the one pictured!

Bad news is you took it apart you own it now.  :^)

You should keep looking for what has cast off the metal in the oil. It's not the #4 bearing making noise.

If a bearing has actually failed, chances are you can't fix it in the car. Putting new rod bearings in a motor that has a bad main bearing is a total waste.

Did you check the end play on the crank before opening it up? Often if the mains have failed the end play opens up and offers a clue.

Did you check for a cracked flex plate?

I never replaced rod or head bolts on any of the motors I raced.....

Never broke any and never took it out of first gear (auto) 30 laps 16 seconds per lap on the rev limiter twice each lap.

The rod bolts are TTY so one-time use, apparently.  I would consider just reusing them, but for only $30 I decided to go all out with my one-cheek job.

It isn't really picking it up in that picture, but running your fingernail across the surface you can feel how rough it is. Plus there are some fairly decent pits in the bearing.  I used a small prybar and didn't get any perceptible movement of the crank but the rods are all kind of sloppy.   I'm not expecting miracles but if we can get another couple months out of the thing, it'll be a major win.

Never done a PT, but for what it’s worth with Neons it’s actually easier to unbolt everything and then lift the car off the engine rather than vice versa. 

In reply to Duke :

If I had a lift or some other non-death-defying way to lift the car up over the engine, I would agree wholeheartedly with that statement.  But I need to turn more old cars into dollars before I can afford that.  What the Professor was saying makes a lot of sense, though:  When we were extracting the lump from a PT in the junkyard for the rallycross car, the biggest problem we had was that it kept getting hung up on the crank pulley and we didn't have a puller with us in the yard.  Dropping the engine down, popping that pulley off, and then lifting it back up looks like it would work fairly easily if it comes to that.

In other news, I forgot to take pictures, but actually the #3 bearings looked much worse than the others, but they all had some degree of wear on them.  I'll agree that none of them looked super awful, but they're definitely damaged.  The crank journal on #3 doesn't give me warm fuzzies to be honest, but there's not much to do about it at this point.  It is smooth enough that I can't catch a nail on it, or find the questionable spot by touch, but when the light is shone on it, it reflects a little funny in one spot.  I'm guessing that if everything else works out, the best case is that I've started a timer on that bearing.  Don't know how long that timer will run for, but eventually that spot is going to wear that bearing.  But again, this whole project is known to be a relatively short-term crapshoot, so the owner is okay with it.

When I first opened it up, I was getting about 1-2mm of side play on each of the rods but I couldn't perceive any endplay on the crank at all.  Last night the balance shaft carrier came out and I got all four new bearings installed and torqued/stretched.  Zero side play on the rods now.  The balance shaft carrier is re-installed but I need to get the tensioner set properly before I put the cover on it and finish closing things up.

As an aside, I complain about this every single time I use it, but how can something that is designed to be so slippery -- assembly lube -- simultaneously be so damned sticky!?  Ugh.

That bearing wasn't knocking.  That bearing looks great.

If it were knocking, it would look half melted and beat all to heck.

In reply to wae :

Where did you get your bolts and other parts from? I'm particularly the rod bolts. I'm cracking open the 2.4 tomorrow night and will need them sooner rather than later

In reply to Knurled. :

The #3 was definitely more beat to heck.  I wouldn't put it up there with half-melted.  But it definitely looked worse.  And the side play was way out of spec according to the chart in the FSM.

But I absolutely am not 100% sure that this was the source of the knocking yet.  Just keeping the fingers crossed that I can get away with something here.