How To Quiet a Rod Knock???

[randomdude84]

Hey guys, 99 Ford Explorer XLS 4.0 OHV is experiencing some rod knocking at high rpms. Oil pressure is good. The car was ran on a cylinder 3 and 4 misfire for entirely longer than it should have been.

The car only has a 100k miles and I've been told I can use an additive to quiet it down and that the car could last a while longer.

What are your thoughts on what additive to use? I've heard Lucas has something good for this?

Also, is this something that would require a new engine?

 

[2000StreetRod]

spinning bearing?

I purchased an Aviator DOHC V8 engine that was swapped out because of rod knock. When I tore it apart I found that two rod bearings had been spinning so the crankshaft was unusable and two of the rods were unusable.

Typically, rod knock results in accelerated wear which can't be prevented by thicker oil.

 

[randomdude84]

How much would a new engine cost?

 

[MtrJunkie]

Here in Dallas I can find a used "not new" engine for $400-$500 all day long on Craig's. And guys that will swap it for another ~$500. So about $1000 on the cheap, unless u swap it yourself.

 

[randomdude84]

Here in Dallas I can find a used "not new" engine for $400-$500 all day long on Craig's. And guys that will swap it for another ~$500. So about $1000 on the cheap, unless u swap it yourself.

How is replacing one of these engines for somebody who has never done one?

Would adding any heavy weight gear oil quiet the noise down at all?

 

[Nomojeep]

Replacing an engine is really just turning wrenches. Obviously there's more to it but it's not rocket science. Nobody ever replaced one before they did it for the first time. If you're somewhat mechanically inclined and have the tools you can do it (a Haynes manual and a friend are also very valuable tools for this job).

Heavier weight/ thicker oil MAY quiet the noise a little but will do absolutely nothing to help the problem. The damage is already done and is only getting worse by running it.

Consider it this way... If you had a slipped disc in your back and an extra aspirin made it feel better, would you then go out jogging?

Sorry for the sarcasm but the fact of the matter is the crankshaft and offending rod, or rods are trash. Nothing will help except a lower end rebuild.

I meant to add that 2000streetrod said it best with pics in post #2 .

 

[randomdude84]

Replacing an engine is really just turning wrenches. Obviously there's more to it but it's not rocket science. Nobody ever replaced one before they did it for the first time. If you're somewhat mechanically inclined and have the tools you can do it (a Haynes manual and a friend are also very valuable tools for this job).

Heavier weight/ thicker oil MAY quiet the noise a little but will do absolutely nothing to help the problem. The damage is already done and is only getting worse by running it.

Consider it this way... If you had a slipped disc in your back and an extra aspirin made it feel better, would you then go out jogging?

Sorry for the sarcasm but the fact of the matter is the crankshaft and offending rod, or rods are trash. Nothing will help except a lower end rebuild.

I meant to add that 2000streetrod said it best with pics in post #2 .

What exactly am I staring at in those pics?

Is the only option a new engine or could the rod or rods that are bad be replaced?

 

[koda2000]

those pictures depict "spun bearings". once this happens you get rod knock (and other noises) and your engine is finished. your crankshaft, camshaft and connecting rods are supposed to ride on a thin film of oil and have no metal-to-metal contact. those pictures show what happens when you get metal-to-metal contact, which is usually proceeded buy a lack of oil pressure.

If you haven't worked on vehicles in the past, an engine swap is a very ambitious project. it's not "rocket science", but there's a lot involved. if you don't know what you're doing you may end up wasting time and money only to end up with a pile of junk that ends up at the salvage yard. studying a shop manual and a friend will be mandatory. IMHO, you'd be better off having someone do this job for you, or look for another vehicle.

 

[randomdude84]

those pictures depict "spun bearings". once this happens you get rod knock (and other noises) and your engine is finished. your crankshaft, camshaft and connecting rods are supposed to ride on a thin film of oil and have no metal-to-metal contact. those pictures show what happens when you get metal-to-metal contact, which is usually proceeded buy a lack of oil pressure.

If you haven't worked on vehicles in the past, an engine swap is a very ambitious project. it's not "rocket science", but there's a lot involved. if you don't know what you're doing you may end up wasting time and money only to end up with a pile of junk that ends up at the salvage yard. studying a shop manual and a friend will be mandatory. IMHO, you'd be better off having someone do this job for you, or look for another vehicle.

The engine doesn't knock while its idling. Just when the rpms start to go high. The oil pressure is good too. Do you think adding a heavy weight gear oil will quiet it down when the rpms do go high? I understand it's not fixing the problem, I'm just wondering if it will quiet the noise down?

If I had a functioning size able garage I would totally get a new engine and have that be my project. But I don't so I won't be doing that lol. Just gonna run her till she breaks. I have AAA so I'm not worried.

 

[koda2000]

try running straight 50 weight in it before you try gear oil. it might help for a while. living where you do (CHI) heavy oil will make starting near impossible when the temps are down near zero or below.

 

[SoNic67]

Don't do high on rpm's anymore. Keep it below 300rpm for now.
The "engine pressure" indicator is a poor indicator to rely on - it is a switch that just tells you if you have more than 5PSI or not, nothing in between.

My guess is that you might be starving the oil pump - typically happens when a truck is run long miles between oil changes, with regular cheap dyno oil and cheap oil filters.
Gunk gets deposited inside the small oil passages and blocks the flow. At high rpm, the oil pump sends all the oil "up" in the top of the engine, but the oil can't return fast enough - like a clogged sink. So soon, all the oil is deposited up (in the heads) but the oil sump remains without oil and the first to feel that lack of oil is the crankshaft (on lower part of the engine). The top part still has the standing oil (not good either, but still a better case).

Try changing the oil using 5 minutes before that a "motor flush" like Gunk: http://auto.howstuffworks.com/5-benefits-of-an-engine-flush.htm
After that use only full synthetic oil - has better detergents, keeps it's lubricating properties constant between oil changes.
Don't ever use cheap oil anymore. Ford recommended oil (Motorcraft) is a semi-synthetic for a reason! I know that some people think they know better than car engineers that wrote that specification, and will say "Wally oil works just fine". But believe me, on long term is not! Stupid people don't know that they are stupid. Eventually they blame the car for being ruined, have no clue that they are the ones that destroyed it.

They don't know that they don't know something. An engineer always thinks "is there something that I am missing here?"
Those engines were designed for regular oil 20W40. Then they moved to 10W30 to lower the gas mileage - but it needed to be semisynthetic because the design of the engine block didn't change. Eventually they prescribed 5W20, still semisynthetic, to comply with government CAFE requirements and then is where the things started to go bad (plus oil changes really need to be done at specified interval or even sooner).

In my tired V8 engine I have now 5W50 oil:
http://shop.advanceautoparts.com/p/...y-synthetic-motor-oil-1-quart-06250/8020612-P

Not cheap. But cheaper than a new engine.

 

[colintrax]

The engine doesn't knock while its idling. Just when the rpms start to go high. The oil pressure is good too. Do you think adding a heavy weight gear oil will quiet it down when the rpms do go high? I understand it's not fixing the problem, I'm just wondering if it will quiet the noise down?

If I had a functioning size able garage I would totally get a new engine and have that be my project. But I don't so I won't be doing that lol. Just gonna run her till she breaks. I have AAA so I'm not worried.

I'm just curious, why are you concerned with quieting it? IMO your truck is dead, plan on using AAA soon and start saving money for an engine swap or new vehicle.
And avoid driving the freeway or trying to haul a$$.

 

[2000StreetRod]

oil pressure switch

Ford did a real dis-service to its customers when it "cheaped out" and replaced the oil pressure sender with an oil pressure switch. The simulated "gauge" only displays above or below 5 psi - basically a glorified idiot light. If your rod knock only occurs after 20 minutes or so of driving at cruise then I suspect SoNic67 may have proposed an accurate diagnosis - starved oil pump. Normally, with low oil pressure the valve train is the first to get noisy. However, when the oil is trapped in the heads because of gunk preventing them from draining then the valve train will stay quiet but the bottom end loses oil pressure. If you had an oil pressure gauge you could tell if that is happening.

I agree that you should try changing the oil to synthetic but flush the engine with the old oil and Gunk just before the change. Also, make sure that you have a normal range thermostat and that it is working properly. No thermostat, a stuck open thermostat, or a low temperature thermostat will result in an excessive build up of crud in the engine.

Heavy weight non-synthetic oil will extend "dry starts" in very cold weather increasing wear due to lack of lubrication.

 

[alohamonte]

what about changing the valve cover gaskets and unclogging the oil return passages?
also +1 on synthetic oil and a high output oil pump

 

[Flash]

I'm thinking that if it doesn't knock at idle it might not be a rod, it could be in the drive train assembly.

Unless it's as SoNic67 says and is oil flow obstruction.

Try Seafoam or one of those other crankcase flush chemicals, just be aware that it will knock chunks loose that can also block up your oil galleries.

If you have a spun bearing there will be a lot of shiny metal in your crankcase and oil filter.

 

[SoNic67]

what about changing the valve cover gaskets and unclogging the oil return passages?

That's a PITA on the 5.0. Easier to try a flush first and see if anything happens - if that works, I would go further. Maybe.

However, probably the existing oil filter needs to be changed before flushing to capture all that gunk (if it is gunk). Otherwise, the old filter might go in "bypass" mode and let the crud go in the oil pan. Where it can clog the oil pump strainer.

Also I would try dunking a magnet (like the one from a broken HDD) in the used oil, to see if anything ferrous is in there. If it is, your bearings are toast - all the non-ferrous protective layer is gone.

 

[randomdude84]

You guys have given me a ton of info. I can't thank you guys enough. It's a lil past my skill level so I'm gonna have my mechanic take a look.

Thanks again guys.

By the way, changed the oil and no metal shavings anywhere, none in the filter either.