07 grand caravan sounds like a rod knocking, but look at them & no sign of worn out bearing.

Well a low tone knocking noise at startup is usually a worn engine bearing.
You should be able to have someone listen to the engine to tell if it is coming from the top or bottom.

You need a trained technician to listen to this, but it sounds like a connecting rod and or a crankshaft main bearing noise. I lean more towards the rod knock form a worn out bearing.

Hi...I responded to your earlier post.
I asked if you had plasti-gaged the crank journals before putting it back together. Sometime s one or more journals are more worn than the others and require a slightly over-sized bearing. If one journal is undersize it will cause a knock. Additionally I mentioned that the wrist-pin may be worn (the pivot pin that connects the piston to the connecting rod) An experienced tech can hear the difference...it is a slightly different, double knock. Less likely, but can happen, a piston skirt may be worn. That can sound like a knock. Older 4.0 engines were famous for that but haven't seen one recently. (usually noise subsides a bit as the engine gets hotter) What does your oil pressure look like? sometimes the camshaft bearings can wear enough to lower the crank pressure and cause knocking as well. (unusual but if engine was starved for oil before replacing the crank bearings it is a possibility.)

If your engine has a rod knock the engine has to be rebuilt or replaced rebuilt is about $2000 to $3000 dollars and a new motor even more.It is unusal for a rod to be out around 60,000 miles unless it was ran real hard or run out of oil or way low on oil.

sounds like you have failed rod or crank bearing, this is causing the loss of oil pressure.

How many miles on it? Could be the oil pump if the oil level is full.

not good. u should check with a mechanic. might be a rod knock, if your lucky just a lifter. If it was ran real low on oil its probably very serious and should get checked asap.

big end or main bearing.

A loud low knock? And it sounds like a disel now, sounds like one of your rod bearings is going bad. Basically, unless you want to put a new motor in it or have the one in it rebuilt, the only thing you can do is drive it till it blows. Sorry to be the one to give you bad news like this, but your motor is old. Parts are worn out. You either have to freshen it up or let it die.

Hi Bill 609!

Definitely sound like a rod insert to me. With my practiced ear, I cna tell the difference between a main bearing knock (deeper sound, more of a thudding noise), rod bearing knock (not so deep, gets louder as the engine revs, kind of a rat-tat-tat-tapping noise), and a wrist-pin knock (not quite as loud or deep and gets louder with decelerating RPM).

You can tell which cylinder the knock is on by removing the spark wires to each cylinder one at a time while the engine is still cold enough to knock. (Don't get shocked!)... when you hit the right one, the knock will noticeably quieten or possibly quit altogether!

The 300 Six is a tough old motor and I have seen them survive for years with rod knocks... Just allow the engine ample warm-up time before driving, drive on the conservative side, and keep an eye on oil level and pressure.

An oil and filter change to a higher viscosity oil with a can of STP Oil Treatment (Or something similar) is a good band-aid fix for now, I would recommend Castrol GTX 20/50w... in my opinion, Castrol is the best brand out there, I use it religiously - - - I have a customer with a Chevy Suburban who has followed my advice and adhered to good maintenance discipline that has racked up over 300,000 miles on the original small block and no consumption or engine issues, and is still running strong!

Bill, the temporary fix will work for a while, hopefully a long while --- BUT when it reaches the point that the knock doesn't go away, it is time to park it until the real repair can be done --- otherwise you risk throwing a rod and destroying your engine beyond repair!!!

Please don't hesitate to post a comment or ask if you have further questions. I hope this information answers your question and concerns and wish you well with the Ford. *** And remember to rate my assistance... Your rating is my only compensation for helping you in the free blog!!!***

Thanks!
-WildBill