Hello,

I am seeking some help on diagnosing a ticking sound in my 1997 F150 4.6L 4x4 with 145K miles.

I have heard this tick for some time, but knew my exhaust manifolds were leaking, so assumed that was where the ticking sound was coming from. I had the manifolds replaced with BBK Headers last week, and had a custom shop install a full stainless true dual exhaust system. I am quite happy with the increased fuel economy and performance with the new exhaust system, but the tick is still here.

Today I also checked all of the spark plugs. Four of them were a little loose. Once all were tightened, I checked, and the tick was still there.

I checked all of the header studs, and they are tight. I used a stethoscope and could not find any leaks in the exhaust.

The tick is not noticeable at start up or at idle, but only under acceleration/load, or when the accelerator is applied when in drive and the brake is applied. I can not hear it when the looking under the hood at idle. When driving the noise seems to be coming from the drivers side rear of the engine compartment. High test gas makes no difference.

I thought I picked up some ticking from one of the injectors at idle with the stethoscope, but not sure if this could be heard in the cabin or when driving.

Any ideas of what it could be? I expected a tick free truck when all the exhaust work was done. Unfortunately that is not the case (yet).

Your help is much appreciated.

Thanks.
Chris

 

Did you check the oil? when was the last oil change?

 

Sure sounds like an exhaust leak to me, but doesn't seem likely with all that you've done. My truck has a very similar tick but I can't find an exhaust leak either. My theory is that there is a resonance inside the exhaust. It only seems to do it accelerating from a stop.

 

Does the tick go up and down with engine speed? or does it get louder?
every set of headers I've ever had made odd noises, but, you would very unlucky to have the same tick with new tubing. So. I guess that I'm saying is that I'm no help what so ever. Does the truck run nice and smooth?

 

I have had that problem with the 4.6 in my old cop car.
the egr tube to manifold nut was loose.

 

Oil level is fine.

Has around 1800 miles since last changed.

I am using conventional oil (5w30) and Fram Tough Guard filter. I have read just recently that there may be a better filter for my truck. If you have any info on this, please do let me know.

 

The noise sounds like an exhaust leak to me as well.

I will get under the truck again and pay special attention to the EGR line and cylinder 7 and 8 area of the headers. The bolts are a bugger to get at due to the header tubes, so possibly it is leaking at the top of 8 for example.

Mine is only under acceleration/load, and not noticeable at idle.

Definately not a know...just tick tick tick, fluctuation with RPM.

 

It does run nice and smooth. No noticeable miss or hesitation.

The tick fluctuates with RPM's, yes, but not noticeable at idle.

 

That was where I first noticed a leak on my old stock system. I checked there now, and can't detect any leak now.

 

If you can not even hear it at idle, could it be normal for a 145K motor?
both my 4.6 and 6.8 have the very smallest tick sound.
with a stethoscope can you tell were the sound comes from?
it may be a timing chain wear noise.

 

What normal is for a F150 4.6L I can't say. It is my first. To me it is too noisy when accelerating. If I was at idle all the time, I would not care.

The only tick I detected on the top of the motor was from the injectors. One particular injector seemed noisier than the others.

I am wondering if the lash adjusters would show up with the stethoscope through the valve covers?

I will spend more time on this tomorrow. Hopefully the stethoscope will pick something up.

 

Look real close to your belt and tensioner, I had one go bad and it would tick , rattle, some times. You just about have to pull the belt off to check it. At your mileage, it shure could be time for one.

 

I checked that on my 6.8, and it is the belt!

 

Good deal! Maybe our friend has the same problem. I had a belt squeek on my 06' impala ss, and, be damned, I changed everything that rotates on that engine until I pulled the harmonic balancer and you could where the rubber dampener was slipping, I guess I'm saying, dont take anything for granted. Simple things can bite you in the butt.

 

Had a chance to look at the truck some more.

A more detailed check with the stethoscope revealed a gasket leak out of cylinder 8 header gasket at the rear, facing the cab of the truck. Likely what I was hearing. I also found leaks in the welds on both oxygen sensors on the passengers side. I have tightened up both header bolts on cylinder 8 (and all of the other bolts as well), and still have a leak. Possibly the truck was driven enough time with it leaking there that is produced a channel in the gasket material. Likely the header should come off and new gasket installed.

The only light tick I could find under the hood was coming from the injectors.

Truck will go back to the exhaust shop to have these items addressed. Hopefully then the noise will be gone!

Thanks for the help guys.