Car knocks real loud


#1

I WAS TOLD A ROD BLEW IN MY 99 BUICK PK AVE ULTRA, STILL RUNS NO OIL LEAKS, SHUTS OFF AFTER 30 MINUTES OF DRIVING, ENGINE HAS LESS THAN 88,000 MI, I WAS TOLD TO PUT A USED ENGINE IN BUT MILES ARE 40,000 - 50,000 HIGHER THIS ROUTE I WOULD RATHER HAVE ROD AND BEARINGS FIXED OR WHATEVER IT NEEDED AND KEEP THE LOW MILE ENGINE I HAVE I WAS QUOTED A PRICE OF APPROX 1400-1500, IS IT POSSIBLE TO FIX A BLOWN ROD AND WOULD IT COST LESS THE SAME OR MORE THAN REPLACING THE ENGINE DON’T KNOW WHICH ROUTE TO TAKE…


#2

If the rest of the car is in great shape and you like it, and if the diagniosis has been confirmed by a second shop, a remanufactuered engine may be the way to go.

I don’t know if that car has an in block cam or not. If it’s an overhead cam, then a busted rod can only mean a connecting rod. That connects the crankshaft to the piston inside the cylinder, and if that’s banging around in there the cylinder is trash. Even if the cylinder damage were minimal, it would require a total engine rebuild. A remanufactured would be the best option, or a boneyard engine if the rest of the vehicle is getting old.

If it’s an in-block cam, then a broken rod could mean a broken pushrod. That would be the rod that the camshaft pushes that then pushes the rocker arm to open the valve. If that’s the case, then the engine may be repairable.


#3

I am assuming that the knocking is because of afailed rod bearing. If the rod itself has broken, it may have done irreparable damage to the block if it hasn’t put a hole in the block. The problem with having just the rod and bearing replaced is that you have to remove, disassemble, reasssemble, and reinstall the engine. The broken rod would have to be replaced, the crankshaft reground, and new rod and crank bearings installed. If the rod is knocking because of a bearing failure, it is likely all other plane bearings have been getting poor lubrication causing accelerated wear. Unless all of this is looked at you will not know how much longer the engine will last. About the only thing you will save by the rebuild of this engine is that the cylinders, pistons, rings, cam, lifters, and heads can probably be reused. Otherwise, the work is equivalent to installation of a rebuilt engine. You will have to decide for the economical approach or the reliable approach.


#4

how do u tell if it is a in cam or overhead cam the car is a 99 buick park ave ultra w/supercharger


#5

A rod does not blow, but a rod bearing may knock or a rod may break or be thrown.
It’s possible to do a crankshaft/rod bearing repair only if the crankshaft is still in decent shape and IF there is no other internal damage.
If a rod has been thrown then it’s debateable whether the engine is even repairable as often the engine block will suffer damage. When this happens it’s not cost effective to repair it.

You do not have a low mileage engine anymore; you have a boat anchor.
JMHO, but you’re better off buying a complete reman engine for it.


#6

In truth I was being way overly optimistic with that last statement. I was including the very small possibility that the engine “may” possibly be savable, but in truth it couldn’t be saved even under the best conditions without putting in more cash than the car is probably worth. Even a busted pushrod would probably mean a valvetrain problem…they don’t bust without a reason.

Another poster also pointed out, and I agree, that it could also be a bad bearing. That’d mean a total rebuild. I was taking my clue that it was a rod (connecting or push) from your post and extrapolating from the descriptio that the engine was still operating that it might have been a pushrod.

Anyway, get a second opinion, but I think you’re looking at a boneyard engine replacement.


#7

I’d get a second opinion first to be sure its the engine. A lot of things can make a loud knocking sound besides a rod or main bearing. A loose timing gear sounds exactly like a spun rod bearing. Some accessories could also make a loud knocking. A broken flex plate can make a loud noise too. You need to isolate exactly where the sound is coming from.

BTW you have a cam in block engine. The 3.8l is the only engine available for this car.


#8

Assuming; it’s a 3.8L, if it is still running it hasn’t ‘thrown a rod’ and may be worth pulling the pan and inspecting the damage. I have installed .001 under rod bearings on those engines with a great deal of success.


#9

my buick has a supercharger in it what if i can’t find a boneyard with one in it does it really make a difference


#10

Since it is still running . . . and has no major oil leaks, I’d say pull the pan and inspect the damage. Although the general feeling here is that the engine is shot, the “blown rod” doesn’t make complete sense as a “broken” rod would flail around and do major damage. I would hope for a breakage which would disable the piston and “only” result in pieces in the oil. Any further running will only hurt, but pulling the pan to inspect/determine the cause of the noise iss first, in my opinion. Good luck! Rocketman