This is such a basic engine that I'm really hopeful that someone can help me. I have, or had, 275,000 miles on this 300 4.9L. It has had a bottom end knock since I bought it with 198,000. It does not burn oil at all. The valves do not tick at all.

Today on the interstate I noticed the knocking getting worse and then I lost power. No loud bangs at all. It stills turns over and is not leaking any fluids. The temp was fine and the oil is not contaminated.

Issues to note: 1.) when you turn it over it has a lop-sided kind of sound that is otherwise somewhat normal, 2.) it does not knock while turning over.

I am so busy that if I don't come up with ideas to give the shop that towed it for me that I will have to give it away. It is in too good of shape for me to be OK with this.

Should I be able to find the problem just by having them look at the bottom end with the oil pan off? Could an engine that is healthy other than the bottom end be fixed without a major rebuild possibly?

Thanks so much in advance. I'm panicking.

 

Hello Ed and welcome to the board.

I do not know enough to help you with your problem. We have some great mechanics that are members here, but you may need to wait until they find your post and respond to it. This place tends to get more traffic in the evening, so stick around, or come back in a couple hours to see if anyone has responded.

Good luck!

 

Hey Ed, I have the same motor in a '91 Lariat, I had a problem with mine turning over but not holding any power, it made a strange clanking sound when tried to turn over and it turned out to be the cam was screwed up, you might wanna have a look at the lower end and make sure everything is ok. Also you might wanna check compression and head gaskets. Sorry if I'm not much help but I hope ya get it figured out, if your like me I know you love your truck and would hate to lose it. Best of luck to ya.

 

Check for spark and check the fuel pressure. Also check the computer for codes. The knock may have been louder when this happened because the truck was stalling out. Sometimes when the engine isn't under power a knock will sound louder because the combustion isn't keeping force against the worn rod bearing.

 

with the amount of miles on the motor, first thing i would do is a compr3ession check. It's possible it broke a rod, but didn't throw it through the block. Also you may have broken a ring, or even a valve. A simple compression check and 30 minutes of your time will tell all this. With the mileage, you're bound to have variation between cylinders, but it shouldn't be alot. 20 psi max.

The other thing here I'd be concerned about, is why would you have to offer suggestions to a repair shop for your truck? Wouldn't that be why it's there and not in your driveway?

 

Well, I have to offer suggestions because they claim that it has to be destroyed and needs to be replaced. I know better than to assume that. Secondly, the truck is over an hour from my home stranded in a town where I know absolutely no mechanics. Thirdly, it's not coming to my house because I do not have time for any wrench turning at all right now due to work. If I had the time and the space it would be the ultimate playtime, but I can't right now. This makes it all so much more frustrating. I will tell them that I want to know the compression of all of the cylinders before making another move.

I have thought all along that it sounded like play where the rod connects to the crank. It's funny what you can learn by listening. At idle, it knocked pretty well. At a speed where it's not coasting or accelerating, it barely knocked. Under acceleration, no knocking. I know that someone who really knows engines can explain what this is. My guess was that the pistons had enough inertia to keep play where the rod(s) connect to the crank from knocking. I should note that it did not knock at all as the engine wound down, further contributing to my guess of connecting rod play at the crank. Oh well, I've never broken an engine down at all so I really have no good, educated guess at all. I would love to look through the oil pan at the crank area though.

 

This sounds the the big end on one of your connecting rods. Or it could be a bad head gasket. If you are getting coolant into one of your cylinders it will knock, and will cause a loss of power. Either way stop driving it as you don't want to pop a connecting rod through the side of your engine block.

The 300 6 is a very easy engine to rebuilt. If you don;t want to rebuild what you have The 300 Ford 6 was made for a lot of years so you should be able to find a good used engine. It is puzzling what would cause a 300 to fail like this with what for this engine is low mileage. I have driven Fords with the 300 with well over 250,000 miles on them and they ran fine and and did not use oil.

 

The truck is stranded in another town, with a ruined engine from what I can tell, so there certainly isn't an issue with driving it like it is. That said, there is also no coolant leak, etcetera. Plus, the engine has 275,000 miles on it so it's no spring chicken. I'm having them check the compression and take the oil pan off and have a look up into the bottom end.

 

Sounds like a spun rod bearing that eventually just let go. Spun rod bearings can be quiet when they're being turned by the starter and then start clanking around once things are running. Also, the symptoms you listed are part of what a dying bearing sounds/feels like (loss of power that just gets worse and worse). At this mileage, could be anything though.

Yes, our engines are built like tanks, but that tan like quality is what may have kept this alive with a bad bearing for almost 100K miles.

Between the shop guys are opening up the bottom end and doing a compression check (maybe a leak down test while they're at it?) you should be able to identify or eliminate bearings, valve train, rings and head gasket.

Reman 4.9 engines are about as cheap as they come in terms of engines...but it's still more than these trucks cost sometimes. Ball park figure of $1,800 to get a long block on your door step. About $400 for a rebuild kit if you want to do it yourself.

 

Oh 275,000 miles, yes It will be a bad connecting rod or an bad main bearing, or both. what often happens with high mileage failures is the big end rod bearing will come appart and plug up the oil drillings on the mains causing a failure there, or a main bearing will start to come appart and plug the oil drillings causing a nearby connecting rod to fail.

Again I will tell you a 300 is not a tough engine to rebuild really the only tough thing about it is it's weight, a good engine stand is worth it's weight in gold.

I was looking through the net and I found this outfit that has rebuilt 300's $1090, plus shipping with a 300 dollar core charge.
http://remanufactured.com/Ford_6_Cylinder_Engines.htm

If you want to have some fun with a 300 6 go here:
http://fordsix.com/

If the truck is otherwise in good condition I would consider the above or if not install a used 300 in it. If the truck is self is not in that good a shape there are loads of F150, 250's for sale so you can get yourself another truck.