Hey guys,

Im having fun with my "reliable" rig :o

Heres the specs:

1994 F-150
302 w/ 5-speed
4x4
98k miles
Oil changed every 3k (castrol GTX) with a motorcraft filter


Just last week my engine started making a noise Ive never heard before. It started the day after a long trip, after it cooled down I assume. It was the day after I moved, so I was towing a good size trailer. All the way from CA to ID.

The noise is a tick/metalic high knock.

The noise shows up when cold, particularly during the initial start up high-idle. As far as I can tell, it is one tick/knock for every revolution. It increases with rpm.

The noise NEARLY goes away once the motor and exhaust is up to temp, but doesnt go away completely.

Once warm, I can only hear it when I put a load on the motor. Dip into the throttle at low RPMs and there it is. Let off the throttle, and it goes away.

I have a mechanics stethescope, and THOUGHT I pin-pointed the problem. Having nearly 100k on the motor, and hearing the noise strongest at the front of the motor, I had the timing chain and gears replaced. $400 later, I still have the noise. Boy do I miss my garage, Im in a rental now and cannot do any major repairs.

Today I tried pulling each plug wire, then each injector to pinpoint the cylinder. Nothing, the noise persisted. I even pulled the y-pipe, as well as replaced the exhaust manifold gaskets. Its still there.

Before I got fed up, I grabbed the stethescope again. I had checked the injectors, the valve covers, the oil pan.... but somehow I managed to avoid listening to the distributor.

Found the source. When I place the tip of the scope against the metal base of the distributor, I clearly hear that tick/knock.

Any suggestions? This is one motor Im not that familiar with (crazy I know). Does the distributor have a drive gear that wears out? What else could it be?

Thanks for ANY help. In a few weeks I have to return to CA for a few of my things (and the wife ), so Id like to get this sorted out soon.

 

Hard to diag over the internet but it kinda sounds like a rod knock. Did the mechanic that did the timing chain mention anything about it? Any experianced mechanic should be able to listen to the noise and basically tell you what it is.

-Jon

 

Thanks for the response.

All the mechanic said was "I think the noise is still there"

I clearly stated that I wanted the timing chain replaced, and to call me if something else might be worth looking at. I also told them to call me as soon as it was ready. Funny, I didnt know when it was ready until I called them, a half hour before they closed that day

I wasnt happy.

I know what a rod knock sounds like, this doesnt seem to be the case.

This noise doesnt get louder as the rpms increase, and isnt the traditional low frequency knock Im familiar with.

Ive done some more searching on the forum, could this be oil pump related?

The factory gauge (yeah, I know.... more of an ON-OFF gauge than progressive) seems to read fine. KOEO shows the needle bottomed out, and KOER shows pressure in the NORMAL.

 

This is the third time in 2 weeks I've shared this. lol. I hope it helps!

A little info on bottom end engine noises:


Main Bearing Knock:
Main bearing knock is usually apparent when the engine is pulling hard, when an engine is started, during acceleration, or at speeds above 35 mph.

Loose Flywheel or Broken Flexplate:
A loose flywheel or broken flexplate can usually be detected by this procedure:
1) Advance engine idle to 2000 rpm.
2) Turn off the ignition switch.
3) When the engine has almost stopped, turn the switch on again.
4) Repeat this procedure several times.
5) If the flywheel is loose or the flexplate is broken, a distinct knock will be heard every time the ignition switch is turned back on.

Harmonic Balancer:
A separated harmonic balancer will generally produce a heavy rattling noise that can be heard at low speed.

Rod Knock:
Excessive connecting rod bearing clearance noises are usually a light rap or clatter much less in intensity than main bearing knocks and the loudest when the engine is "floating" or running with a light load at from 25 to 35 mph. The noise will become louder as engine speed is increased. By grounding out each of the spark plugs, one at a time, you can determine from which cylinder the noise is coming. The noise may not be eliminated entirely by grounding, but it will be reduced considerably in intensity. The easiest way to ground out the cylinders is by inserting a 1.5" piece of 5/32" vacuum hose on each terminal on the distributor cap, and then placing the spark plug wires over the vacuum hose. With the alligator clip end of a non-powered 12 volt test lamp attached to ground, touch the test light tip to the vacuum hose to ground out that cylinder.

Piston Slap:
Piston slap is loudest when the engine is cold, and lessens or disappears after the engine is warm. When driving the vehicle (at from 25 to 30 mph) the noise will increase in intensity as the throttle is opened and additional load is applied. To detect piston slap, try the following procedure:
1) Pour several ounces of 40 weight engine oil into the suspected cylinder(s).
2) Crank the engine for several revolutions with the ignition turned off. This will allow for the oil to work itself down past the rings and act as a cushion.
3) Install the spark plug(s).
4) Start the engine.
5) If the noise is eliminated, the engine has a piston slap condition.

Piston Pin Noises:
Piston pin noise is usually the result of excessive piston pin clearance. This will cause a sharp, metallic, double-knock sound most noticable when the engine is idling. Sometimes the noise is more audible at car speeds of from 25 to 35 mph. To test for excessive piston pin clearance noise, use this procedure:
1) Run the engine at idle speed.
2) Retard the spark to reduce the intensity of the knock.
3) Return the spark timing to the normal setting.
4) Short out each spark plug, one at a time. The double-knock sound will become more audible at the cylinder with the loose pin.

 

Yeah, and it comes up every time I do a search.

It doesnt help, sorry.

Did you even read my post?

 

No, I just picked this thread at random hoping info on bottom end noises might be helpful.

Of course I read your post. In my 25+ years of wrenching, I've never experienced a noise like you described that was caused by the distributor gear or oil pump, but anything is possible. Pull the dizzy and have a look at the gear.

 

Thanks.

Im going to pull the distriutor and have a look see.

Im still holding out that it isnt a rod/main/wristpin knock. I cannot hear the noiser from ANYWHERE but the distributor.

Its very odd. I can put the stethescope on the base of the distributor, and hear the noise clearly. Then move it an inch away, but on the cast iron block, and cannot hear the noise.

Could a sticky lifter transmit noise thru the camshaft and up to the distributor? Wouldnt I hear a noise from the valve train?

 

Update.

I pulled the dizzy, it had a decent amount of up-down play. So I swapped in a new one for the hell of it, and fired it up. Noise persisted. So I swapped the old one back in, and returned the new dizzy.

Next up, I did a decarbonizing procedure. I used Seafoam. Afterwards. the motor seems to rev a bit smoother, and easier, but the noise was still there.

Next, I changed oil/filter. The oil in there (castrol 10w30) only had 100 miles or so, but i wnted to check for foreign metals, any obvious sign of bearing failure. Nothing, the oil, although a bit dark, was totally clear of any metals. I even ran a magnet thru it. And came up empty.

Thinking this may still be a hydrolic lifter issue, (noise goes away when the engine is warm) I fed the engine 5w30 Castrol.
The noise seems (might just imagining things) quieter, but STILL there.

The only other thing I tried was retarding the timing a bit. While this made the truck run like a dog, it seemed to help the tap, for a while. Id try driving it down the street. On the way down, the noise wasnt there, but on te return trip, it was.

Could this be piston slap? Could that just appear out of no-where? And is that a BIG problem?

Ive almost given up.
Maybe Ill just let the thing blow up.

I dunno, but I do know that next weekend the truck has to make a 1500 mile trip back to california. And the 750 mile return trip will have a 3500lb vehicle in tow.

 

There's an easy way to check for piston slap in one of my posts above, if you're interested.

Just a thought; are there any unusually shiny marks near the bottom of your dipstick? Have you tried turning your dipstick 180 degrees?

 

no, the dipstick isnt hitting anything. No obvious marks.

Ill try the piston slap tip. Thanks.

What am I in for if this is piston slap? Is this a nail in the coffin, or should it be okay for a while? Again, the noise is heard with a stethiscope strongest at the base of the dizzy.

Thanks again for the help. It i appreciated

 

The 92 has the same thing. Best I can tell is a lifter noise. Been doin it for 10k miles now and not quite enough to make me tear into it yet. Switching to 15W40 helped quiet it down.

Adrianspeeder

 

Piston slap is actually quite common in 302's. Eventually it will crack the piston skirts. I've run across it several times in 302's. Here is a picture I took of one of them (this is a TRW forged piston):




And this is after I Magnafluxed it:




BTW, the engine this piston was in had no noticeable noises, but it did have headers which may have masked them. By the time you can hear piston slap in a 302, damage is done. If you determine that is your problem, you'd be wise to do a rebuild now before any more serious damage occurs (if a piston breaks, you will likely damage the engine beyond affordable repair).



If I may, let me make a suggestion. Change the oil again, or just drain off 1 quart, and add a quart of Slick 50. I know the "scientific community" has determined that it's of no benefit, and most of the members here will echo that, but I have seen it work miracles first hand, many times. I have poured a quart into a running engine that had an unexplained ticking noise, and listened to the noise disappear in 15 seconds, with the customer watching, at least 8 or 10 times. I've never seen any adverse affects from using it, either.

I figure you've got nothing to lose, and it just might solve your problem. If your noise is in fact a valvetrain noise, odds are pretty good it will help. It's worth the $10-$15 investment, IMO.

Take care,
~Chris

 

Thanks for the insightful response.

What is your take on Auto-RX or Marvel Mystery oil? ive got both on hand already. Actually, Ive still got half a bottle of that SeaFoam as well too.

Im not TOO auwfully worried about the motor long term. I just dont want it to leave me stranded within the next few thousand miles.

Ive often considered a big block motor build, or even a diesel. The 302 doesnt cut it. The big problem being right now, is that Im in a tiny little rental apt. So that would have to wait until we find realestate here (within the year)

As far as piston slap damage, once the cracks begin, what kind of damage are we talking about? Cylinder scoring, and bearing failure once metal particles get into the oil? or would it be more catastrophic, like sending metal objects thru the pan?:o

 

reading this post make me think you have a lifter thats starting to collapse.
pull the valve covers and check the valve lash to see if one is too lose.

sounds are very hard to diagnose over the web and sound different to different people.

 

I personally am not a big fan of engine additives. I observe and make note of others experiences, but I won't recommend anything unless I have first hand experience with it.

I use Marvel Mystery Oil in my air compressor inline oil tank, for oiling my air tools, but I've never used it as an oil additive for automotive purposes, or if I have, it wasn't remarkable.

I was skeptical of SeaFoam until I used it, and now I swear by it, but my experience with it involves fuel systems and cleaning combustion chambers. I have no first hand experience with it as an oil additive.

I've never used Auto-RX at all.

I have used Slick 50, though. I'll be 40 in a couple weeks. When I was a teenager, Slick 50 was hard to find, and when you did find it, it cost upwards of $50 a quart. The old timers I learned my earliest wrenching skills from swore by it. I participated in a test at my Engines class at the local CC just over 20 years ago, in which we took two Berlinetta's, and tried to blow up their engines. We put Slick 50 in one, ran it for an hour, and drained all the oil. The other one we just drained the oil. We ran both engines with a cinder block on the gas pedal. The one w/ regular oil seized in less than 10 minutes. The one that had Slick 50 ran for 35 minutes, and then the car ran out of gas.

I gotta tell you, though, one of the most impressive things I've seen it do is what I mentioned before; eliminate noises within seconds of being added to a running engine.

I'm not guaranteeing you it will solve your problem, but in my personal and professional opinion, it's the cheapest and quickest thing you can do, that gives you the best odds of correcting your problem. If it was my vehicle, that's the next thing I would do.



I believe your pistons are basic cast aluminum, which tend to break apart like a coffee mug. Damage could include cylinder walls gouged to the point of needing a sleeve, or even the piston getting ****ed sideways, bending the rod, damaging the crank, and bending the valves, at least. That's a worst case scenario, which I doubt you'll have to deal with. 302 piston skirts crack. Often. But they rarely break apart. If you can hear piston slap, the damage is done, meaning you've got a few damaged pistons, but you'll tire of the noise before the damage gets worse, unless you decide to tow a 36' cabin cruiser over the rockies first.

Try the Slick 50. If that doesn't make a difference, try the routine I outlined above for determining piston slap. If it has piston slap, worry about it then. If it doesn't, at least you don't have to worry about a piston coming apart while you try and figure out where the noise is coming from.

You could knock out both before lunch on a day off.