Jeep cherokee with a 4.0 6 cyl when a start the motor cold it sounds like a diesel engine, lots of clanking. last a couple of seconds then goes away. replaced oil pump. no help there.
Lots of clanking when first started sounds like a worn rod bearing. Check the engine compartment and rev engine to listen for knocking. It will get progressively worse as time goes by. Nothing to do except buy/install new crankshaft kit from autozone, about $300+.
In the mean time, just change oil and put in some oil additive to lessen the knocking. High speeds will accelerate the wear of the rod bearing. The rod bearing is installed inside of the piston rod. This bearing goes around the crankshaft. It has very tight tolerances down to the thousands of an inch. When it gets worn, metal will flake off of the soft bearing material and contaminate your oil more. If you catch it early enough, you can replace the bearing without too much trouble. Here is what you need to do.
Find the bad bearing. If you hear the knocking with the engine on and under the hood, disconnect a sparkplug. If the knocking goes away, that is the bad bearing. Do this disconnecting/reconnecting until you identify the bad bearings. Now disconnect battery. Next loosen drive belt- done from steering pump. Loosen 2-13mm bolts on back, one on top and one on bracket on bottom. On bottom right-hand side of pump will be a long adjusting bolt. Loosen turn this bolt counter clockwise to loosen drive belt. Now jack vehicle from the frame, vehicle will raise but tires will remain on ground. keep going as high as your jack will go. Install jack stands on frame. This extends your suspension and keep body raised. Drain oil, remove steering damper. It's the shock absorber looking thing connected to your tie rods/center link. The easiest way to remove the oil pan is to get a 3/8 inch socket adapter for a cordless drill. The bolts will come out in a hurry if you do this. Keep track of where the double sided bolts are, they secure the fuel line brackets. After all are removed, wiggle, tug, and pull pan out. Now you will see the large main caps and the rod caps. The mains are bolted to the block and the rods will rotate up and down with the spinning of the crankshaft. Spin the crankshaft to see. Each bearing cap needs to be marked. Use a center punch and hammer to mark from front to rear. 1 mark for rod cap 1 and so forth. You should end up with 6 marks on rod cap #6. Do the marking on the front side of the cap so you know how it fits back. Remove the rod caps that corresponded to the bad bearing identified earlier. Remove nut on cap. Wiggle cap back and forth until it comes loose. It will eventually come out. Inside the cap, you will see the bearing. It is basically a liner for the cap that rides on the crankshaft. there is one on the top of the rod too. Remove it by pushing rod up into cylinder and pulling it out with your hand. Ensure you remember the orientation of the bearings. One side has a notch, the other has a key that fits into a hole on the rod. Now you have the bearing in hand, check for scoring, or wearing on the face. Check the web for a nice color picture. Feel the crankshaft bearing area with your finger nail. It should be smooth and not ridged. Purchase some plastigage along with a standard .000 bearing. Clean rod surface, install new bearing and plastigage. Tighten to torque. Remove cap and measure plastigage for your oil clearance. Now you can purchase the correct bearing to match your oil clearance. If you don't have a repair manual, now's a good time to get it. It has bearing tolerances for you to get the correct bearing. After you have the correct bearings, use oil additive to grease up the new bearing/crank surfaces. Put everything back together, put some quality magnets inside of your oil pan near the drain hole and cross your fingers.
Nov 20, 2008 |
Jeep Cherokee Cars & Trucks