Serious Rod Bearing problems... please help

[Alvin77]

Before I get started; yes, I've searched and yes, I've read, alot.

With that said I'm so disheartened about this problem I've resorted to making a thread and seeing if I can get some help on my specific issue.

Anyways... Initally my problem started as a light knock at high RPMs. The knock would continue down to about 2,500rpms and then stop. It got to the point where the engine would knock the entire time is was ignited. This is at 120,000 miles, so I decided to pull the engine out and just rebuild the entire thing. Upon opening up the engine, I found just what I expected, 2 shot rod bearings. One was broken in half and the other was cracked and well on its way to breaking.

So I ordered 2 new rods (mistake, I know), a new crankshaft and bearings etc etc etc.

Put the whole thing back together along with new gaskets, followed the service manual down to the T. It ran great for about 2 weeks untill....


On the way home from work one day it started knocking REALLY bad, A LOT worse than it had before... so I pulled over and had it towed home the next day, it was that bad.

This time I decided to just drop the oil pan off and try and replace just the rod bearings.... Not happening. The suckers were MELTED to the rods on #1 and #4, it was terrible. However, the 2 new pistons (#2 and #3) were fine. So I pulled the entire engine out AGAIN. This time I replace everything, new crankshaft, 2 new rods, and a complete bearing set.

I took the rods, bearings, and crank to a machine shop and had them check the oil clearances for me. He said that I had bearings too large (.5) and gave me smaller ones (.25).

Put it all back together and yet again......... (yes for the 3rd time) I've got a very slight knocking....


Am I missing something??? I'm incredibly disheartened by the entire thing, I love my car and really hate not being able to fix a problem... from my reading the only thing I might have done wrong is touch face of the bearings, which may repel the oil?

I just can't possibly understand what I'm doing wrong... Please help me


Cliffs:
Engine was knocking, found 2 bad bearings and rods
Replaced 2 rods and all bearings (2 new rods, 2 old rods, new crank, new bearings)
Combination of old rods and new bearings completely melted
Combination of new rods and new bearings were 100% clean
Replaced 2 rods and all bearings (2 new rods, 2 semi-new unharmed rods, new crank, new bearing)
Engine knocking again at high RPMs

 

[Locke]

What is your oil pressure looking like?

 

[Shadow98]

Did you prime the oil pump at start up and/or are you sure your oil pump is working correctly.

 

[BigRand]

OIL PUMP +1, might as well do the water pump while your there too.

 

[Alvin77]

What is your oil pressure looking like?

Sorry I forgot to include this in my first post.

But yes, I did buy a brand new oil pump at the time of the first rebuilding and I do prime the oil pump and fill the filter before putting them back on the car.

I do appreciate the replies though.


As for the actual pressure, I have no idea, my car is an RS so my gauges don't include oil pressure and I am unsure about how to measure this without one.

 

[bucknasty88]

When you install new bearings you should always have them plasti gauged. Your chiltons manual will have the tolerances and specs your bearing should be at. Get new bearings and take them to a shop along with the engine and have them install them and plasti guage them, or you can do it yourself if you have the means. Good luck!

 

[Alvin77]

When you install new bearings you should always have them plasti gauged. Your chiltons manual will have the tolerances and specs your bearing should be at. Get new bearings and take them to a shop along with the engine and have them install them and plasti guage them, or you can do it yourself if you have the means. Good luck!

I took the rods, bearings, and crank to a machine shop and had them check the oil clearances for me. He said that I had bearings too large (.5) and gave me smaller ones (.25).

Thanks

 

[bucknasty88]

Let us know if that fixed your problem.

 

[miklaver]

did you clean the crank with some kind of solvent before you put it together? did you use assembly lube when putting together?

 

[VelocitàPaola]

Your methodologies don't sound too off-kilter, but there's something not quite right...

For one, if you hear knocking, you've already passed a point of no return. You can't just slap on new bearings, or oversized bearings and call it a day. The crank has already sustained damage at that point. Some people try getting away with "polishing" the crank with an emory cloth, but I would take it to a machine shop and have it belt polished, or turned for the next up oversized bearings.

Second, when putting together a rotating assembly, always make sure of the following:

1. All bearing surfaces are absolutely spotless before assembly. Clean with WD-40 if necessary.
2. Apply copious amounts of assembly lube to all bearing surfaces, including thrust bearing.
3. Only use brand new TTY (stock) rod and main bolts, or torque your ARP rod and main studs to the recommended torque given any stretch.
4. Prime the oil pump by packing the input (where the oil pickup tube goes) with petroleum jelly. Fill the oil filter with oil. Some go as far as removing the bolt on the oil pump and adding oil... I don't, but you can.
5. Don't forget the small, but important details, such as the bedplate O-ring or the oil pickup tube O-ring.

My advice... tear it all down and try again.