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So last week I took my 06 Commander Limited with a 4.7L in to program my TPMS sensors programed, sway bar bushings replaced and a broken head stud replaced. I noted to the mechanic I could hear a tap in the engine when the engine was cold but as the engine warmed it quieted down. I stated I thought it may be a valve or a lifter. His first response was it is probably nothing as it quiets down as the engine warms. He stated the broken stud is the issue, when the metals cool the gap in the manifold expands and contracts when the metal heats up. Agreed that is why I gets quitter. But I still thought I heard a tap that wasn't quiet right.

Today I get a call that they had the vehicle on the lift and they feel the tap is the main bearings and that the vehicle needs an engine. I questioned why not a bottom end rebuild, why did it need an engine? The guy I spoke to stated I needed to talk to the mechanic who looked at it. I will be going tomorrow.

First it seems odd to me that a main bearing(s) going bad wouldn't necessarily tap?

Second why would it need a complete engine?

Any thoughts info would be appreciated.
 

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1st, if you truly need a new engine, then what's the damage in continuing to drive the current engine till it blows, other than needing to call a tow truck when you're left stuck. So, I wouldn't let them talk you into agreeing to an engine replacement because of a ticking noise.

Honestly, Labor is so expensive today, pulling an engine having someone do a rebuild or a partial rebuild, is probably more expensive than buying a rebuilt engine and swapping it in. And the precision of modern engines, the typical independent shop and many dealerships would probably screw up a partial rebuild anyway.

A tick during warm up could be a lot of things, sure a spun bearing could be the cause, so could other things.

The 4.7L has a lower girdle (correct me if I'm wrong, I'm NOT positive), which makes changing out a main bearing or crank more difficult than older designed engines, but NOT impossible. A spun rod bearing would be no more difficult than any other engine. Often, I hear the advice, which makes sense, if a bearing spins, it will extremely likely damage the crank, and blending rarely remedies the damage, that you should just replace the crank with the bearings, or you're at risk of the new bearing spinning again.

Honestly, I would tell them to finish the work you authorized and you'll get a 2nd opinion. The engine could blow up and you're still no worse off than what they are suggesting as a fix, well other than the cost of a tow.

I also would want to see an oil pressure reading, if you had a bad main bearing, oil pressure should be low. Does the low oil pressure light ever come on with the engine running? At hot idle? Have you had any oil system problems with the engine? Have you neglected doing regular oil changes?

Have you've been using conventional oil or synthetic oil? What oil filter do you use?
 
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