Superman_20

I am driving a 2005 Mustang GT with 148,000 miles and just a couple of days ago the car was fine. Suddenly I started the car and now I am hearing a LOUD engine knock upon starting the car and on acceleration. I don't hear the knock when I take my foot off the gas, or when driving downhill. The best way to describe the noise is like the sound that baseball cards would make in the spokes of a bicycle. It is not a mild knock, I mean this is one LOUD knock.

I changed the oil, the filter and added Lucas oil treatment and the sound has not improved. I drove it quiet a bit to give the oil a chance to lubricated but the knock is still there. I had not had any knocks on the engine or any indication that anything was about to go wrong and all of a sudden it just started. Does anyone have any ideas about what could be causing this and so suddenly? I don't have low oil pressure problems, or check engine lights, etc. just this loud knock that has be worried. Help please? Thank you!

Dino Dino Bambino

Sounds like you might have a spun rod bearing, which probably means all of the other rod bearings will be worn down to the copper as well.
You could try pulling each plug lead in turn while the engine's idling. When you reach the offending cylinder, disabling the spark and preventing combustion will reduce rod knock.
Don't drive the car anymore until you've diagnosed the problem 'cause if it IS the rod bearings, you risk scoring the crank journals (if they aren't already) or worse, having a rod/piston assembly make a window in the block.

Superman_20

Is there any other possible explanation for it? If it is a spun rod bearing I would more than likely be looking at a rebuild or having to drop in another engine correct?

roegs

Two links below. First is the sound of a spun rod bearing. Second is a good description.

BlindGUYnAR

Your description is classic spun bearing sorry.

Dino Dino Bambino

If you had an automatic, you could get a similar noise from loose torque converter to flexplate bolts. However, the balance of probabilities is in favor of a major engine problem and a spun rod bearing is no.1 on the list.
Pull the oil pan and inspect the bottom end. Only after assessing the extent of the problem will you be able to decide if a rebuild is feasible or complete engine replacement be necessary. If it's the latter, you could consider a stroker short block.

cruisin5268d

Welcome to the forum. I'm afraid that you may have a very sick engine and I would encourage you to not drive it unless necessary.

Superman_20

I am thinking that it is a spun rod bearing after seeing the videos. I don't think that I will put the work into it for a 05 with that much mileage on it. I might just try and sell it as is on AutoTrader or give someone who is interested a good price on it and go for the 15 GT. It is sad because the interior is red leather like new, built in navigation system, shaker system, etc. It is a beautiful car. It is really a shame but considering the amount of miles on it and the year, I think I have to say good bye to it.

2005Redfire6

Just pick up a take out motor from another GT and swap them, it is pretty simple if you have the space, tools, and time.