I currently have a 1994 Mazda B4000 4.0 (same as Ford Ranger) with 120,000 miles on it. I bought it last year as a winter vehicle and to tow my 18' boat. I bought it for $1,100.00 but it needed a ton of work. (tires, wheel bearings, waterpump, radiator, shocks, hubs, brakes, electrical, tow hitch, etc.) I spent @$3,500.00 getting it up to snuff! It is now a very reliable 4wd truck . The only problem is it can barely tow the boat. I have a hard time staying with the flow of traffic on the highway. Especially on long hills!

I only tow the boat on the highway about 10-15 times per year. So I could live with it but I wish I had a more powerful truck.

With all that said, let me get to my dilema.

I work for a Honda dealership. We recently took a 1999 Ford F-150 4x4 XLT supercab with 150,000 miles on it in trade. It has the 5.4 triton V8. The truck is in great shape and would be perfect for what I need. The transfer case and valve covers are leaking but those should be easy to fix. The big problem is a "knock" in the motor. It seems to be coming from the lower end. It is very noticeable at idle but not when you rev it up. It almost sounds like a diesel while idiling although not as loud. There are times when the knock isn't as noticeable. It seems to be inconsistent with temperature. Sometimes it is barely noticeable when it is cold and gets louder as it warms up. Other times its just the opposite. It could be my imagination but that is what I've observed so far.

I've read the topic on "piston slap." After reading almost every post I am thinking the noise I am hearing is not piston slap. Most people described that the piston slap noise usually only happens when it is very cold out and it goes away as the truck warms up. My noise doesn't seem to go completely away.

The reason why I am even considering buying this truck is because I can buy it for less than $4,000.00! Besides the knocking the truck is in great shape.

Now for my questions.
What should I be listening for? Also, how/when should I listen?

Assuming the worse, how much should I expect to pay to have the motor rebuilt? I could probably do it myself but time and specialty tools become the problem.

I would like to thank anyone who actually read this whole post. Any help you may have I greatly appreciate.

 

If it's truly a knock and not a piston slap, could it just have some bad gas in it? These like 87 octane, but you might want to see what happens if you dump some higher octane fuel in it. Otherwise, you may just be hearing the infamous piston slap. If the valve covers are leaking this may contribute to the problem...
Have you checked the engine oil level?

 

I checked the oil tonight when I got home. It was down about 1/2 a quart so I topped it off. The person who owned the truck before said that he used Mobil 1 since 10,000 miles. He bought the truck new and he was the only owner. I am going to change the oil next week and I will use Mobil 1. I have used Mobil 1 in all my vehicles and I will continue to use it. Is 5w30 the best weight considering the mileage and New England winter weather coming?

The knock was much less pronounced after the 30 minute ride home. In fact it was barely noticeable. If I wasn't listening for a knock I wouldn't have been able to hear it at all.

I don't think it's because of low octane gas but once the tank is low I will fill it with 93 octane just to make sure. It doesn't seem like spark knock to me.

The passenger side valve cover is leaking. It isn't pouring out but it is leaking/seaping. If I buy the truck that is one of the first things I plan on fixing.

What I've noticed is that if I rev the motor the knock doesn't increase. In fact it seems to go away above 1000 rpms. If I rev it to 2000 rpms then release the gas the knock seems to come back as the motor returns to idle.

Is there anything else I should try or listen for to better help explain the problem?

 

I'd be concerned about a "knock" in the bottom end. All the symptoms that you describe go in the "negative" column.

150,000 miles
knock sounds like bottom end
doesn't go away

 

Im thinking that perhaps you got a bad rod or crank bearing. If thats true you might be money ahead of the game to put in a reman longblock. How often did the previous owner change the oil?

 

The prior owner bragged about how well he took care of it. He said he only used Mobil 1 since 10,000 miles.

I just noticed now that when I put the car into gear the knock goes away. When I put it back into park or neutral it returns. The knock is there while driving slow and I am off the gas. I can hear the knock as the revs drop and I am off the gas. When I accelerate and stay on the gas I can't hear it.

Assuming the knock is in the lower end, lets assume crank or rod bearings, how much would it cost to buy a remand lower end?

Is it possible that the motor could last a long time with this problem?

 

I have a 98, 4.2L, 150,000, same knocking, change the rod bearings, noise went out for a litttle bit and came right back, I am driving it until it dies...a dj in a radio show told me to start thinking about another engine, so I just live with the noise.

 

Beekermartin,
Maybe you ought to think about cutting this one loose? I'd bet you come across another good deal soon enough...

He may have taken really good care of it. He also may have been trading in his truck because he knew the knocking was a bad thing.

 

Keep in mind, I am only paying $3,600.00 for this truck! Besides the knock, a few minor leaks, and some brake work the truck is all there. I am figuring that it will cost about $500.00 - $700.00 to fix the leaks, change the fluids and replace the rotors and pads. If I'm into the truck for less than $4,500.00 and the motor goes I think I am still ok.

I guess the question is how much should I expect to pay to have the long block replaced?

If I decide to do the work myself where is a good place to order the longblock from? About how much does one cost? Is there anything else I will need besides the longblock and gaskets?

 

Have you checked for a broken or loose motor mount? Better to do a new longblock cause new parts sometimes make old parts fail. dont know what it will cost.

 

Sometimes the exhaust manifold bolts crack and emit a ticking knocking sound on these motors that sounds similar to a rod or crank bearing. There was a thread about this in the 5.4 forum somewhere.. Also it does not always emit a leak from the gasket that is easily heard. Take the truck down the road and drive it near a wall with good resonance. If you hear a slight chugging sound it may be those cracked manifolf bolts. You might wanna try that before putting a new motor into it. Good luck.

 

After driving it all weekend I've noticed a few more things.

After driving it for a little while the knock almost completely disappears.

I can't hear it resonating off walls. While accelerating there is no knock at all. I don't think this problem is exhaust related. It definately sounds like it is in the lower end of the motor.

This morning it was in the mid 40's. I had to move the truck to take my car out of the garage. When I first started it it was knocking worse than I've heard so far. I backed it up and reved it to 1500 rpms for 30 seconds. It was knocking the entire time. After that 30 seconds the knock reduced a lot but was still there.

The more I drive it the more I think it is the famous piston slap noise I've read about. But since the knock doesn't go completely away I am not sure it is piston slap.

I am going to change the oil and filter this week. Should I use 5W30?
Also, should I go to a Ford dealer to get a Motorcraft filter or is there an aftermarket filter that will work just as well?
Should I try some kind of an additive like Slick 50, lucas, engine restore, etc???

 

The symptoms you explain sound like rod or main bearings. You should always change/polish The crank shaft when changing bearings. If the bearings are bad the crank will have rough places. Rule of the auto world ALWAYS CHANGE OR POLISH THE CRANKSHAFT......

Just my advice

Jason

 

I just changed the oil and filter. What a pain in the *** it is to get at the filter! When you take the filter off oil drips down the entire motor. I am going to look into a filter relocation kit. I also had to make a quick trip to Autozone to pick up a new drain plug. The one that was in there was covered in some kind of sealant and half the threads were extremely sharp. Whoever maintained this truck before decided it was better to use a sealant on the threads instead of spending three dollars on a new plug!

Anyway, I used 6 quarts of Mobil 1 5w30, a Motorcraft filter and a bottle of Slick 50 high mileage additive.

While it was in the air I listened closely to the knock. It seems to be coming out of the tranny bell housing. That's where it is the loudest.

 

Thats rough. Mine has "piston slap" when it first starts in the cold. It sounds like it comes from the transmission also. Hasn't broken anything yet. Had a 94 5.0 that had a wierd knock at high rpms sounded just like a lifter tick. after checking the lifter and rocker arms we were stumped. Eventually pulled the motor and found a broken connecting rod. at certain rpm it would swing around and beat up the block. the engine was junk.