I have been diagnosed with a bad connecting rod. My question is would a rod knock last for 12000 miles without blowing. The knocking starts after warmed up oil pressure is where it should be. Noise accelerates with rpm and stops from time to time. I did an atf flush today in hopes it is just a lifter? The noise has been consistent for the year I have been driving it.. so more like 16000 miles.... any thoughts?

 

I seriously doubt an engine with rod knock would last 16,000 miles. It would blow itself to bits. If its a tap that starts when the engine gets hot and goes away above ~3,000 rpm it might be a slipped sleeve, which is more of a tapping noise.

Knocking from a rod knock literally shakes the entire engine and car.

 

You certainly wouldn't get 12-16K miles with a big end knock as it would normally grenade shortly after it starts. Unlikely to be a small end death rattle so I reckon it's either a rogue tappet or more likely a slipped bore liner. Whatever it is it certainly won't improve only get worse so best to address the problem sooner rather than later.

What is an "atf flush" ? as atf is 'automatic transmission fluid' which is totally incompatible with engine oil.

 

If it is a slipped sleeve how long do I have before it's toast... is it worth maintaining as usual and replacing gaskets or should I be looking towards a new motor?

 

If it's a slipped sleeve, it is not worth maintaining, and you do not necessarily need a new motor, per se. You would either invest a small amount into a used engine that will very likely have the same problem OR not far from developing the Rover-afflicted condition of a slipped sleeve or bore liner. Your best option is to disassemble the top end, and verify that a liner has/is moving. Then, you would rebuild your original block with new bearings and upgraded top-flanged liners. Once liner has loosened, you can't put a timeline or guarantee on it severely defaulting. Sometimes you can get the operating temp of coolant low enough that it doesn't move again, it keeps randomly moving and making noise forever, or the scenario which the block cracks behind the liner and it continuously fills up with coolant and/or combustion gas, rendering the engine useless.

 

Well, if it is not overheating or losing coolant, then it could last a very long time, years even. It will eventually become a problem, but there are some that have run with the slipped sleeve for probably the life of the truck.

One of the trucks I own had a slipped sleeve, but it was only noticeable when the engine got warm. If I kept the temp below about 190, it wouldn't tick. If the temps got up to 200 or so it would start ticking. It ran good like that for a while until it blew a head gasket.

You could look into pinning the sleeves, but I wouldn't bother. At that point you just need to get a new engine.

I'd just keep it running until it blows a head gasket and then get a new engine. There's not really any point in trying to dump money into fixing it.

 

Thanks for all the input... if I ever find a mechanic willing to look at it I'll let you know!

 

I friend of mine is a car broker, he brings DiscoII's by house as he finds them... I am looking for one for my daughter. The last two 4.6 liter DII's I have looked at both had a lot of rod knock at low miles.. so I passed. I think this is inherent in the 4.6 liter engine.

I found out a lot of the noise at idle is coming from the fuel injectors, I believe they pulsate until a certain RPM to control fuel injection.

 

After I flushed and changed oil again, the ticking stopped at idle after a 30 minute drive...
What would you recommend for fuel injectors. Sea foam? Looking for inexpensive ideas for trial and error since I am starting to give up... seems to run a lot better now and hopefully ticking will go away

 

That's good to hear. Might be a lifter / valve train related. As for an injector cleaning, Sea Foam works really good. You can dump a can it in the fuel, but the best way is to let it suck it up through the vacuum line over 30 seconds and then give it a hard drive. Smokes out the neighbors though...

If it is a slipped liner though, nothing short of replacing the engine is going to fix the tick. Glad to hear it is a tick and not a knock. My parts car had a spun bearing and it sounded like this: