# piston slap on 4.9?



## juggernaut (Jan 14, 2004)

I have been asking alot of questions lately but its such a great site with great info I cant help it. Anyway is anyone familiar with the infamous 4.9l piston slap (knocking sound at idle goes away when warmed up)? I only have 114,500 mi on it, runs great. I can hold 60-70mph on the highway easily on grades of Pennsylvania depending on head wind. It runs smooth as a swiss watch, you can hardly tell its running at idle, when its warm its whisper quiet, different story when cold though. Oil pressure is 25-30lbs Hot using castrol 10w30 ("Hot" as in driving 20 miles minimum on the highway, not going by thermostat thats not an indicator of hot oil). Additionally the problem is worse after changing the oil, it gets better sounding after you put roughly 700 miles on the new oil, then you hardly hear it all. 

Also the engine seems to vibrate more at 1500 to 1800 rpm (tell me these sixes vibrate more than v-6s right?) engine oil pressure is fine as mentioned above. I might also mention that the top of the engine is spotless no deposits, and it uses maybe a 1/4 qt of oil or less over 3000 miles. Im debating as to whether or not to send in an oil sample, Is it worth it? Any insight would be very helpful its driving me crazy.


----------



## 85F150 (Mar 13, 2003)

I have had three of these trucks and you have to love the durabiltiy. Yea everyone i have owned has a slight kncok at startup. What is your oil pressure while it is doin this. HAs it come up yet? Mine won't have any pressure for a sec or two, is the only time it makes the noise but the best filter i found te rsolve that prob is the Motorcraft one or Hastings. Stay away from the purolater because the six hates that filter. Not really sure of the term piston slap? It is either the rockers/lifters not having oil up to them or the bearings not having oil up to them.


edit: dunno about the vibrations, could be a slight miss at those rpm's. I wouldn't waste time/money on oil test. You can determine the prob without that


----------



## juggernaut (Jan 14, 2004)

Yes the oil pressure comes right up at startup to 50 psi when cold, it doesnt make a lifter tap from bleed down, I am familiar with that noise. It makes a deep knocking noise, that seems to be inconsistant with rpm or pressure and quiets down after I drive down the road a bit and warms up, its not the "post overnight startup knock." 

The vibration isnt like a miss it seems more like the engine is noisy and loud like a diesel. Im comparing it to a 94 explorer 4.0. so im not sure what to expect. I checked the exhaust though its not that.

Im just worried about these slight noises that will likely get worse from plowing and eventually be the death of the motor.


----------



## juggernaut (Jan 14, 2004)

I might also mention the engine only makes the knock at cold idle, or after it has sat for a while. It pretty much goes away when warm. Should I be worrying? What is funny is that is gets worse with new oil and decreases as oil is more used.


----------



## 85F150 (Mar 13, 2003)

that is weird about the oil used and old, to mee it sounds like it could be the oil pump just because it would have a harder time picking up the oil freah then th older stuf....or the screen could be gettin clogged...not sure though....mine has an exhaust leak at the manifold so i can't tell ya about noises goin donw the highway, good thing i have a great stereo.... If it was me and i worry about my stuff to much i would drop the pan and replace the oip pump an dpickup tube and check the pump drive shaft to see if it moves around it the distributor....but that is just me and i sweat the little stuff...may not be a prob..my last straight six has 240,000 on it and i jsut replaced the lower bearings because it was knocking. The truck i drive right now i put 50,000 on in last year so i am at 151000 right now and it still runs awesome, so i have a hard time the old six is just gonna puke on ya.


----------



## crashz (Jan 12, 2004)

Had a similar problem with my V6 Ford. Thought I spun a bearing. Turned out to be a faulty anti-drain back valve. Put a new filter on from Napa and she runs smooth when cold. Oh- this was also with Castrol Syntec 0w-30 (German stuff).

You said the top end looked clean. Did you pull the valve cover? I'm wondering if a little AutoRX would clean up your oil passages. Check out bobistheoilguy.com for more info on AutoRX.


----------



## juggernaut (Jan 14, 2004)

How hard is it to drop the the pan on a 4x4 straight six. Doin that seems to make the most sense to me although the looking down the oil fill neck with a light the engine looks spotless but it cant hurt to try.


----------



## juggernaut (Jan 14, 2004)

Also would the old "quart of tranny fluid in the oil" before and oil change help?


----------



## juggernaut (Jan 14, 2004)

I agree 85F150, the I6 is supposed to be one of the greatest engines ever, thats what everyone has told me at least, but this noise sounds serious. It hasnt gotten any worse in the last 12000 mi though. I have tried a new oil and filter. I am changing my oil every 2000 to 2500 miles using castrol and Motorcraft filter, and the "noise cycle" if you will, starts all over with each oil change meaning the noise lessens as oil ages, noisy when cold quiter when warm. If it were the pump being clogged wouldn't the oil pressure be much lower? This truck has to last until at least 250,000 miles, and I really cant afford an engine rebuild any time soon either (time or money). 

Anyways if it doesnt get any worse its not really a big deal I guess, but this really pisses me off though. I payed $7,300 for a black, reg cab, 5spd, pwr everything 95 f150, more or less mint condition truck, for plowing so it "might help my image" ya know (the 85 was a moving pile of iron oxide). I took the truck to a mechanic even before I bought it, he said "good truck, he'd buy it for the price", so I buy it. I get it home, change the oil in it, and find out the damn engine is knocking. The dealer ship sees no reason to tear it apart, but Im sorry engines do not normally make this noise. %^&#! Oh well, as you can see it frustrates me.


----------



## crashz (Jan 12, 2004)

1st - the tranny fluid won't help. Very little detergents in modern tranny fluid. That trick worked 30 yrs ago. Could help to thin out the oil, but you're better going with a good, lighter weight engine oil. 

Changing the oil every 2000 miles has to help the cleanliness inside the engine, but what oil are you using? Try moving to a lighter weight and see what happens. What do you use in it? I think for 95 you should be using 5w-30. As dino oil ages, it sheers down a grade, which could be allowing more flow to the bottom end of the motor. Also as the motor warms up, the oil thins out. 

What I'd do is get some motorcraft 5w20 and run it on the hwy for a few hundred miles. See if you can see any difference. Keep a close eye on this oil and see if its cleaning anything out. Don't run it too long, because i'm not sure if the 4.9 is on the list of vehicles that Ford approved for 5w-20.

Seriously look into AutoRX. It is an ester based cleaner that safely cleans sludge build up out of an engine. Much safer than using solvent type flushes. I've used it in my Ford and a VW with great results.


----------



## juggernaut (Jan 14, 2004)

Interesting you mention a thinner oil that was exactly what I was thinking, but to be honest with you Im not too keen on 5w30 in a good ole 300 six but hell Ill try anything seems like a good Idea. By the way Im using castrol 10w30 winter/10w40 summer, are these decent oils I heard some stories about Pennzoil/Quakerstate but I have no experience with them first hand Thanks. Appreciate your time.


----------



## juggernaut (Jan 14, 2004)

Also the thing about the noise is it starts after the high idle cycle, ie you start it up the rpms go to 1000-1100 then they come down after a few seconds then the knocking begins (until it warms up). Im just trying to give you every detail I know about the noise to help anyone better identify the problem. You can figure the "Knocking noise" itself sounds like a loose rod but IM not sure about it.


----------



## Dan S. (Jul 29, 2002)

I have an 89 that does the same thing, also had a 76 van with the same motor, one thing about them is they do make some noise, I think it is just normal for the motor, that long crank and cam (gear driven) just make more noise when everything is spinning around. I would suggest using a heavier weight oil and see if that helps reduce the noise, as oil breaks down it gets thicker, that would make sense as to why the noise gets quieter as more miles are put on the oil, I run straight 30w in winter and 40w in summer in mine, the big six is not a high revving motor, it is more like a diesel, low RPM's and lots of torque. The manufacturer's like that lightweight oil because it improves drive-ability when cold and shortens warm-up time.
I would not worry to much about the noise unless it sounds really bad and does not go away.


----------



## juggernaut (Jan 14, 2004)

I thought oil gets thinner as it breaks down?


----------



## streetsurfin' (Jan 22, 2004)

Have you tried using a synthetic oil in the recommended weight?


----------



## 85F150 (Mar 13, 2003)

i would stick with castrol, i have had the best luck with it and thermal breakdown and all that crap.....I ran 10w40 in my trucks but run 20w50 in my 220000 miler because it had a slight knock at idle all the time and i needed to replace the bearings....try the synthetic but it will find any spot to leak if there is one.....

yeah oil gets thinner as it gets warmer...after rereading this again, i would possibly suggest maybe a lifter problem. not enought oil getting to it or it's internals aren't working properly and it is jumping open real quick later then it should, possibilty? Does it run any different when it is cold, like maybe a little pinging or somethin....still scratchn my head on this though.


----------



## juggernaut (Jan 14, 2004)

Yeah thats kind of what Im thinking, it seems to be a frequent suggestion will that hurt anything? To answer your questions, it runs fine the knock goes away if you bump the throttle and raise rpms, and also yes it does seem to ping occasionally before completely warmed up (ie oil is hot then goes away). Thanks, appreciate your input.


----------



## Dan S. (Jul 29, 2002)

Did you mean oil breakdown as in old dirty contaminated oil? or oil getting thinner with temperature? As far as your noise being a lifter or bearing or piston pin, if these parts were damaged or worn out the noise would not go away with a change in RPM's it would be there constantly and get worse as the wear increased. Sometimes a lifter will bleed down overnight and when you first statrt up the motor you will hear a clacking sound until the oil gets to the lifter and reduces the valve adjustment back to zero.


----------



## juggernaut (Jan 14, 2004)

Yeah it goes right away when you up the rpms (hell I had good luck for a while from raising the idle speed 50-100 goes right away). Dan S that is exactly what I mean, with older contaminated oil it appears to run slightly better, I know sounds rediculous. I am very aware of valve noise on startup there is none (ohhh trust me on that having owned two 2.9L in the old Bronco II's I was quite familiar with that noise, those damn things came of the assembly line ticking & clacking on startup). I was talking with someone from Fordsix.com (great site if your into the best engines ford ever made) he said this:

had a similar problem on my EFI '94. Turned out that when I removed the Thermactor valves I left a hose unplugged. This hose runs into the exhaust ports through a manifold for air injection at low temp. The sound was the one way check valve slapping open and shut. Felt pretty stupid as I discovered this just before I was about to pull the engine and replace it with a 5.0. So I plugged the hose, no more noise. 

Is anyone familiar with this? Also don't know if I mentioned this before but could it be the piston rattling around in the bores 
when cold (expands, fits tighter when warm no noise?) Thanks.


----------



## Dan S. (Jul 29, 2002)

Hey juggernaut, thats what I was trying to say in my other post it makes sense that when the oil starts getting contaminated it thickens up, I think the bix six runs better when you use a heavier weight oil. On the subject of the thermactor valve I think that is the valve that controls the flow from the air pump into the air injection manifold, this is an emission controls system, it could make some noise if the exhaust is leaking back through the control valve towards the air pump, try plugging the hose between the pump and the valve and see if that helps.
On the subject of piston slap its possible but it usually does not sound real loud or like something heavy like a rod bearing, let me know if you have any luck finding out what is causing it, like I said my 89 makes the same noise for the first few minutes of driving when cold then goes away.
Thanks


----------



## streetsurfin' (Jan 22, 2004)

A few checks you could do....
with it running short out each cylinder, 1 at a time and see if the noise goes away while the plug is not firing.Is your vacuum at idle steady and between like 15 and 22? Compression test on each cylinder. Check out a manual from the library to do these. I wouldn't want to recommend something like the plug shorting test if it might harm the electronics on a certain vehicle.
Thermactor valve was a good call to check that. Do you have a manifold heat control valve in the exhaust manifold. Mine clatters on my dodge till its warmed up aand opens all the way. This is controlled by vacuum via coolant temperature, and I think ambient temperature.


----------



## juggernaut (Jan 14, 2004)

What exactly on the manifold would I be looking at In order to find the manifold heat control valve Im not familiar with all the emmissions junk on this vehicle, I thought this might be a promising lead but then I realized that the noise is affected by oil mileage so Im thinking it might be the noisey lifter route.


----------



## streetsurfin' (Jan 22, 2004)

My bad, the oil wouldn't effect that. It's like a choke butterfly valve at the exit of the manifold just ahead of the Y-pipe. I don't even know if your ford has that like my dodge. Has anyone mentioned a worn cam lobe? ( can I go to the first page w/o losing my post?) I dont recall if you were losing power, but I believe a worn cam lobe would do that.

I have a chart for driveline noises from ford and can give you 34 reasons for oil consumption, can't help you much on thiis one I guess. I went back and saw you said it ran fine. Good luck though, I hate not knowing what a noise is, it's worrysome.


----------

