Remember the post a week or two ago about all the other forums and their shortcomings? Well, I posted the following this morning on the '97-'07 forum and still have no replies...18 views with not 1 single reply.

Hi folks!

I spend most of my time on the '48-'60 forum, but I have a question about my '98 F150 XLT 4X2 with the Triton 4.6L V8. It has 112970 miles on it and has been (and still is) a great daily driver. I've noticed lately when I step on it a little, I hear a slight knock. This also happens sometimes when I first crank it up. A friend told me it may be the timing chain, but I want to see what you folks think. I change the oil religiously with synthetic, and tune it up on a regular basis. This truck is bone stock, so the problem isn't something I've added on. First off, is this serious, and if so, any ideas what it may be? Thanks for the help...


Like I said, I know this is the wrong forum, but I thought maybe someone here could give me some words of wisdom. Thanks!

 

This is the wrong forum but if it was posted in the 79/07 we can see what happens here. Hope you find an answer.
Try reposting it back in the 97/07.

 

My guess is that the folks there are not really mechanics - they do not work on their trucks. And it is very hard to guess about a "slight knock" - it could be anything. If it were my truck I would be all over it pulling and twisting everything to see if something is loose - like a motor mount, muffler clamp, air box, about anything engine related.

It could also be something inside the engine, but that does not seem likely to me - but that is just a guess. Mostly with old fords it is better to be a bit hard of hearing - slight knocks tend to get louder when they really need to be fixed.

It is a lot easier to find a loud knock, or even a slight one if it happens all the time.

 

As ***** said check everything you can for it being loose. It could be anything from that description.

I have even seen the fuel rail on the older "ranger type" 40 degree V6s knock. One guy wrapped insulation around his so he wouldn't have to hear it any more. LOL

 

Thanks for the advice guys. I went all through that engine bay this past weekend and found nothing. I was thinking it was something loose too. If that's the problem, I didn't find it...

 

sounds like a bad tensioner. not that hard to replace. the knock shoud be on either the right, or left bank, half way between the valve cover and the pan. the tensioner for the right bank(pass side) is located under the belt tensioner, and the left bank is located just to the right of the center water pump bolt. the tensioner guides have a tendency to break, if the tenisoner fails. last one i repaired was $379.00 in parts, and 12 hours of labor.

 

cabby daddy, you are talking about the spring-loaded roller device that presses against the fan belt, right? How could one of those failing cause so much damage?

I don't doubt you, just surprised - my last engine overhaul was less money than that.

 

I think that if you talk to your local Ford dealer, you may find that some of the 4.6L and 5.4L have had some problem with carbon build-up in the combustion chamber causing a knock. I'm not sure if it is in the form of a TSB, but there is a recommended procedure using a chemical to solve the problem. I'm of course not sure if that is your problem, but I have overheard my dealer talking about it.

Talk to them and see

 

Earlier Ford EFI ('89) had an 'anti-knock' sensor under the hood, to regulate engine timing, to prevent engine knock. I don't know if the newer systems still use it.

 

Scroll down to our "Modular V8 (4.6-5.4)"....those guys know everything about Mod motors.

 

Good info folks; thanks!

 

Have you ever replaced the injectors in it? I have had a sound in my daily driver, that is similar to the one that you have mentioned, and it turned out to be the injector.
Might want to look at that. You will probably have to take it in to your local Ford dealer for the diagnostic check, on their scope to tell for sure.

 

Code, as its been said, I ahve heard tales of the belt tensioners making a light knocking noise, and carbon build up causing a slight knocking noise. Now-a-days with fuel injected engines, carbon build up is not as prevalent as it was with carburated engines. Back in the day I used to get this one little old lady about every 2 to 3 months complaining about poor performance and wanting a tune up. When I pulled the file on her car I noticed that she had had several tune-ups, each one with less than 500 miles from the last one. The car also has some light knocking in the engine. I would take her car out, put it in first gear and drive it until it shifted on its own(this was a 78 Buick Electra) The car would chug out massive brown clouds of smoke for awhile and then slowly clear up and run like brand new with no noise. I never charged her a thing.

Probably not a big help to your situation though.

Take a long screwdriver or prybar and place it against the engine and put your ear on it. Move it around to different area and see if you can isolate it that way.

Good luck
Bobby

 

Bobbytnm

Thats a great thing to use to pin point the noise. I myself use the wooden broom handle cut off to about 3 feet, or a yard stick. Surprising what you can hear with one of these.

Another good inexpensive tool for pin pointing dash rattles, or squeaks is a piece of heater hose. Anyway hope you find the noise in your trucks engine, nothing more agrevating than that.

 

Thanks guys. The weird thing is that's it's only when I romp on it, or sometimes when I first start. I'll do the poor man's stethoscope thing this weekend.