Changing of connection rod bearings

[Knudsen]

Does anyone know the procedure in changing connection rod bearings?
If so, please describe it, cuz mine isnt that good after my dynotest Actually they are not good atall

[apardal]

About the connection rod bearings, it is advisable to get new ones when tuning the 4A-GE and i think it doesn't have that much trouble. You don't need to strip the whole engine, just the oil pan and crank shaft. Replace the parts and reassembly.

Best regards

[Knudsen]

How big is the risk, that the crank has been damaged too? And iv just heard that it isnt nessesary to take the crank of..?

[jamiemirror]

Remove oil pan and change all bearings (conrod and main ones).
There is a chance to scratch rod or crank due to bearing failure (I hope they are ok) - just check them for scratches and if they are ok - replace the bearings.

[Widar]

Hmm.. I can't help but i'm wondering what Connection Rod bearings are? Can't recognize this word...

Anyone wanna enlighten me?

[Ivan141]

Your crank has bearings where it runs in the engine block itself, and then there are the smaller bearings where the crankshaft connects to the connecting rods, which are in turn connected to the pistons.

All bearings on the crankshaft are of the 2 layer bearing shell type..soft metal bearings. They are basically a hard outside metal shell with very soft metal lining on the inside. When this soft metal lining is scratched or when there is a patch worn into it the bearing is faulty. The soft metal coating is so soft you can even wipe it off with a tissue. Just so people around here know that there is no such thing as "wearing in" the bearings in the engine, cause every wear on this type of bearing is a bad thing.

Anyway, back on subject, the conrod bearings are the weakest spot of most engine's, along with the conrod bolts and the conrods themselves. The conrods & bearings get the biggest loads in the engine, which is moslty due to inertia at TDC on exhaust stroke, you can then imagine that the forces of inertia are biggest at high rpm's.

Anyway: working from underneath the engine is maybe possible if you suspend the engine and then take off the crossmember, but if your going through that trouble, might as well take the entire engine out..

My advice to you: get a working 4age and swap it in, or go crazy on your original engine..while it's out you can renew all you want. Just remember NOT to re-use the conrod bolts.

[jamiemirror]

Quote:Just remember NOT to re-use the conrod bolts.

Is this so important ? I plan to check/change my bearigns too and to use the old bolts. If it is important - maybe I should use new bolts ?

[Ivan141]

It is important for a high revving engine...the bolts lose strength over time, especially after you tighten them a second time. The results from a failure of these bolts is usually catastrophic (pistons ruined, conrods punching holes in the engine block...you name it..).
On a turbo engine it might also be a good idea to change the cilinder head bolts as well.

I cant say I have any experience myself to back this up, but I have seen lots of people on club4ag with holes punched in the engine due to these bolts failing.

[KristianAE86]

apardal Wrote:About the connection rod bearings, it is advisable to get new ones when tuning the 4A-GE and i think it doesn't have that much trouble. You don't need to strip the whole engine, just the oil pan and crank shaft. Replace the parts and reassembly.

Best regards

Not entirly true.

please d NOT forget to flush the entire oilsystem /engine of all old oil.
which DOES contain microscopic parts of the old bearings.

If done seriously - I would stripp the head aswell & clean all oil channels.

K

[Knudsen]

Well, it is possible to take the oilpan of with the engine still in the bay. You just have to dismount the gearbox brackets on each side of the engine...