98 Neon DOHC, 70k miles, manual tran.

car runs great engine not missing, smoking... tran shifts easily... but...

loud knock/slap

only after engine is warm
loudest 2500 - 3500 rpm
seems quiet when acceralting (noisy when constant speed)
minimal noise when no load (clutch in)
increases with RPM (not car speed), 120 beats / minutes (depending on rpm)

I changed oil to Penzoil 5w30, didn't help, changed again to synthetic 5w50 and added Lucas stabilizer, didn't help (didn't even change the sound!)

4 mechanics listened, 4 different guesses:
a) valve lash adjuster
b) timing belt bearing
c) rod knock (rod bearing)
d) piston wrist pin bearing

When I pull the plug wire for piston #1, it is quiet. Therefore c)?

Can I replace bearing by just removing oil pan?
Do I buy the bearings from Chrysler?


Thanks

 

yes you can replace bearings by removing the oil pan although it will be a bit more difficult and you can buy bearings at WWW.modernperformance.com or if you want to wait awhile you can order them from www.howellautomotive.com for the 2 most common stores. you could also shop around a bit. keep in mind that 95's are diffrent from the rest, and will also cost a bit more.

 

Rod Bearings sizes from Chrysler: "standard", .025 under, .25 under. which one?
One mechanic stated that replacing bearing without pulling crank is risky, comments?

I found this procedure (thanks Tony), valid for my engine?:
Rod Bearing Swap

1. Raise the front of the car with ramps, jack stands, or if you're real lucky, a lift.
2. Drain the oil and remove the filter.
3. Remove the oil pan bolts, lower the pan and set it out of the way.
4. Using a socket on the crank pulley bolt, turn the engine so that the #1 and #4 rods are at the bottom of their travel.
5. matchmark the #1 rod and cap so that you can be sure it goes back together the same direction it came apart.
6. Remove the nuts from the #1 rod cap and using a soft drift (I use a wooden hammer handle) tap the rod bolts to free the cap.
7. Remove the cap and inspect the bearing half and crank journal. If the crank journal isn't scored badly, you're probably in good shape to go ahead with the bearing change.
8. Place 2 short pieces of rubber fuel line or vac hose over the rod bolts to protect the crank from nicks and using your thumbs, push the rod/piston up in the cylinder until the rod bolts will clear the crank.
9. remove the old bearing halves from both the rod and cap and replace them with the new bearings making sure to line up the locks on the bearings with the coresponding notch in the rod and cap.
10. Coat both halves of the new bearing with assembly lube and pull the rod back down over the crank.
11. Remove the pieces of rubber hose from the rod bolts and reinstall the cap making sure to line up the match marks you made earlier.
12. Using a torque wrench, tighten the nuts to factory spec. (check the clearances with plasti guage)
13. Repeat steps 5-12 for the rest of the rods, reinstall the oil pan with a new gasket, install the drain plug, fill with oil, and install a new filter.
14. Disconnect the HEP wires coming from the distributer and crank the engine over until the oil pressure guage starts to come up.
15. Reconnect the HEP wires and start the engine. After checking for leaks, lower the car and take a testdrive.