Can crankshaft bearing and crankshft be changed from bottom end

First, I have to ask...Why do you have to replace the conrod bearings? I am assuming they are "rattly" but why? Did you run out of oil? Anyway, conrod bearings can be changed after removing the sump. After removing the sump, rotate the crank so that the conrod is at BDC. Remove the conrod cap. Slide the bearing around and out of the conrod, lubricate the journal and replace the bearing in the reverse manner. Remove the old bearing from the conrod cap, fit the new bearing, lubricate and refit the cap and tension to correct specs. Do this for each conrod individually. There are some things that you MUST be aware of if you are going to attempt this work. It is extremely important to measure the crankshaft journal and check for roundness BEFORE fitting a new bearing. Bearings are made in undersize status to compensate for the instances where an engine has been reconditioned before and the crankshaft has been reground to a minus size. Make sure you line up the "locating lug" on the new bearing shell with the corresponding groove in the conrod and cap. Make sure that the two "locating lugs" are on the same side when putting back together. If the crankshaft is not perfectly round, DO NOT fit the new bearings! A crankshaft grind is necessary and will require engine removal to do that work.

If the knocking is from the bottom of the engine, it may be the big end bearings have worn.
Replace them or not? Difficult question.

Replacing the big end (crankshaft/piston rod) bearings may stop the knocking/rumble noise. It depends on the crankshaft..

If the crankshaft has worn oval on its journals, fitting new bearings is unlikely to achieve anything as the bearings may break up due to the oval of the crankshaft. Removing the crankshaft and checking the journals for ovality/regrinding if necessary isn't a 5 minute job.

You say you have good oil pressure. That's a positive.

Personally, in your situation, I would try an engine oil additive that's designed to eliminate knock provided the main bearings haven't worn down to base metal. It's the cheapest option.

Failing that - and again, personally - I would remove the oil pan and fit new big end bearings in the hope that it would work.

The next step, if that doesn't work - would be to remove the crankshaft and have it reground and fit oversize bearings. Or get a 2nd hand engine...

You say the car was given to you for free .. you have nothing to lose. Try an additive first.. molyslip/molybdenum or whatever...

Good luck ...

Hi there
Big end bearings are set when you get them as they are set to the crankshaft grinding so you buy bearings with the crankshaft OR stamped on the bearing shell is the o/s [like 020u/s or 020 o/s
but if the crankshaft is worn at all then dont put any bearings on it untill its been ground.

The crankshft is at the heart of your engine. It is what the pistons are connected to. It is what drives the transmisson. It is a big heavy peice of machined steel.
If it's broken you have a MAJOR problem.
Here is a picture.. http://www.google.com/imgres?imgurl=http://datsun-240z-blog.viczcar.com/wp-content/uploads/2006/06/LD28-Crankshaft-240z.jpg&imgrefurl=http://datsun-240z-blog.viczcar.com/ld28-crankshaft-the-heart-and-soul-of-the-stroker.html&h=331&w=600&sz=29&tbnid=Du8REx363DzfOM:&tbnh=74&tbnw=135&prev=/images%3Fq%3Dcrankshaft&zoom=1&q=crankshaft&hl=en&usg=__eAW8ZOyBXXLq-FEoSuSytYjWYxU=&sa=X&ei=t-lqTeOPO5TegQft4KTPCg&sqi=2&ved=0CE8Q9QEwBg

Using a air impact gun would be quick and simple. Check the pulley, sometimes the rubber seperates from the actual pulley. Crankshft pulleys usually don`t walk off. I think it seperated. Have your service shop take alook..

Crankshaft torque settings for 2002 Audi TT 225 BHP:

1. Main bearings: Renew bolts = Yes
2. Main bearings: Stage 1 = 65 Nm
3. Main bearings: Stage 2 = 90 degrees
4. Big end bearings: Renew bolts / nuts = Yes
5. Big end bearings: Stage 1 = 30 Nm
6. Big end bearings: Stage 2 = 90 degrees
7. Flywheel / driveplate = 60 Nm + 90 degrees (use new bolts / nuts)
8. Crankshaft pulley / damper centre bolt = 90 Nm + 90 degrees (use new bolts)

the little dot on the crankshaft sprocket has to be aiming staight up and you will also need to remove the #1 spark plug to make sure the piston is at top dead center.you can check if it is all the way up by using a long,thin screwdriver and putting it in the spark plug hole.if the piston is not all the way up.you will need to turn the crankshaft 1 whole turn clockwise and stop when the dot on the sprocket is aiming up agin.the piston should now be at top dead center.i hope this information helps.take care and good luck, manny

the oil pump on any car is rarely the cause of low oil pressure. if you remove the oil pressure sending unit and install an oil pressure gauge,even the type you can buy as an add on,and the reading you get is low.the problem is genrally worn out main crankshaft bearings.to avoid unneseary replacement of these,you should buy some plasti-gauge from an auto part store remove the bearing caps one at a time and measure the clearance this way.there is a risk here because the smallest grain off dirt that getts into the bearing, crankshft will ruin the bearing when you restart it.if these are worn out you probabably shoul consider replacing the engine because the other bearings are probably also worn out by this time.

Knocking sounds in the lower engine area usually are from loose/damaged connecting rod bearings. Repairs are centered around resurfacing or replacing the crankshaft and the associated bearings. (many penny!)

if your rocker shaft was busted and the valves were not opening, alot of the unburned fuel in those cylinders will end up in the crankcase. the problem is that fuel dries things out and hinders lubrication, the crankshft and camshaft bearing and journals can become damaged. fix your rocker, put fresh oil in, then change it a second time after about an hour of running, use a quality oil additive like MOA or Lucas stabilizer in the second change. low oil pressure can indicate worn crank and cam bearings and or journals.