1998 f150 4.6 V8 150K

I bought this truck about a year ago with 2 bad pistons. Replaced those and has run well since pulling lawn trailer and taking 1000mile pleasure trips. Has always had valve train noise since I purchased the truck. On a trip from FL to NC about 2 months ago towing a popup and a big bike rack the truck (upon startup after sitting overnight) sounded like there was a marble rolling around inside a tin cup for a second or two. I also noticed a slight increase in valve train noise on the interstate. Sooooo I've been assuming that one of the lash adjusters was bleeding down overnight and causing the noise. I replaced every one of those little b@stards last night.... broke them in as to manual specs. Seems quieter on the road but still makes crazy startup noise. any suggestions ???

Thanks
Adam

 

Are you using 5W20 oil? Were the old lash adjusters actually bleeding down? Did you inspect the cam followers for damage? Are you sure that it is not the timing chain tensioners allowing the chain to slap the front cover? Is the noise RPM related?

JMC

 

piston slap...

 

I am curious about the two bad pistons you had. One question is did you ever determine why they were bad and the other question is. When they were replaced are you sure they were installed the correct way? If a piston is installed backwards it will make noise upon startup until the piston gets hot and its dimension changes. Not sure what brand oil filter you are using but I would recommend a Motorcraft. Some different brands tend to bleed down when the vehicle is off and the lag time it takes to refill the filter upon startup can generate a momentary noise concern. As mentioned above the chains ( and valve train) can make noise if they are not getting sufficent oil pressure or supply ( sludge buildup). May want to check the oil pressure at the oil sending unit or at the cyl heads with a manual gauge. Good luck.

 

ok hopefully i can answer all the questions so that i can get more help.

Oil- running 5w 30 with a napa gold oil filter. Fresh oil with new lash adjusters. I have been running 5w 30 since i got it with motorcraft filters from Wal-mart. Oil pressure on the gauges is usually between 1/2 and 3/4.

As far as the pistons: The guy i bought the truck from owned it since new. All services were completed at regular intervals. He's been a good friend for quite sometime. Never towed or hauled anything. When i pulled the head on the passenger side you could see where # 4 had been blowing by the rings. #3 was bad as well but not anything like 4. Being cheap I honed both cylinders and replaced both pistons. I have no idea what caused those two pistons to fail. I also replaced the valve guide seals since it would smoke on startup. I'm not sure if a leaking valve seal would cause a cylinder to fail over time but that's the best i can come up with. I did all the work myself and i'm 100% that the pistons were installed in the correct direction. For 15000 miles since the new pistons there hasn't been any noise on startup.

The noise ONLY lasts at most 2 secs. It sounds like a marble in a tin can. Then i never hear the noise again until the truck is turned off and allowed to sit for a couple hrs. I still have valve train noise on the interstate as well.

The adjusters that i took out seemed to be in good shape. The followers looked fine with no discoloration, pitting or any signs of excessive wear.

I'm kinda leaning on the timing chain tensioner but i still don't know.

thanks for all the help so far, any new thoughts?

 

once again... piston slap

 

HI!... Does it still make the noise after the truck is up to operating temp? If not, it's piston slap.

 

Ok, so if it is piston slap how is the problem fixed?

 

The only time it makes noise is after the truck has sat for a couple hours. The noise will only last AT MOST 2 seconds.

 

Pull the cam covers off before starting it up in the morning. Inspect the valve train. Do not turn the camshafts. Use the crankshaft bolt and a breaker bar to turn the crankshaft to uncover the lash adjusters.

JMC

 

that is in fact piston slap, a lot of new engines do it, most rebuilt engines do it. Mine does not. Not much you can do about it.

 

well that totally sucks. It's freaking embarrassing to start the damn thing up with people around. Sounds like it's gonna shoot something out

 

Uncovering the lash adjusters? meaning rotate the crack until the heel of the cam lobes are on the rollers? then check how much play each adj. has?

 

I'm leaning the same way as my 99 makes the same noise, I believe. Please, by all means if you change the tensioners, report back and let us know if it fixed anything. I've heard piston slap and its not the same sound mine makes. I'd throw the money at mine to see if new tensioners fix it, but I can't afford to any time before summer.

I don't have other noise after the first few seconds, luckily. The startup sound is embarassing enough.

 

Yup. The cam has to have the lobe pointing away from the follower so there is the least amount of tension. While there is no spec on the lash in the book the lash adjuster should take up the slack. Silly question; Did you put the lash adjusters back in their original positions?

JMC

PS running the engine with the cam cover off, while messy, will allow you to see if there is any slop. Be advised that oil from the followers squirts everywhere so if you do this do one side at a time.