whats next? Piston Slap or worse?

snakepit · 07-15-2004

I stumbled on some info in another forum, I basically responded to a common problem associated with a rattle at startup in a new Mach 1. The noise described, the sound of rattleing when the engine is cold - almost sounds like a diesel engine but not as raspy. Since I changed over to synthetic (mobil 1) I experienced that same sound. I now use AMSOIL 20W50 and have the same thing occur but usually 2000 miles after the oil change. It could all be related to the oil filter stop valve (rubber flap inside the filter) and or the grade of oil used. At first I was told it was associated with the hydrollic timming chaine tensioner which made sense at the time.

Now I discovered that there are issues with the 4.6L motors regarding incorrect piston size. I am not sure what years are affected, but some of the threads noted that it dates back prior to 99. The issue is piston slap associated with the forged pistons. It is a big issue with the 03 Cobras and with the MACH 1. The information also links the problem to the mystery oil consumption with the 4.6 L motor.

I am not sure what if any concerns I should have if my problem is piston slap. (Some how I think it is something different since the noise I hear does not occur every time the motor is started cold.)

Ouch. Does anybody have any start up issues when cold? At first I thought this was all B.S. Apparently it is not. It would be nice to find out what vehicles are affected, what years, and how to correct the problem.

Here is one of the links I book marked: It pertains to F150's, There are many more relating to mustangs out there too.

http://www.f150online.com/forums/sho...&threadid=8747

Mana4Real · 07-16-2004

Piston slap is a known problem. But you also should not be filling your car with 20w-50 oil. It's too thick.

Defyant · 07-17-2004

Could that just be bad or low octane gas?

snakepit · 07-17-2004

you may think that the AMSOIL 20w-50 oil is too thick, to my amazement, it is very thin and flows rather well. In fact I did not experience any change in pressure either. I have used it in my ford explorer over winter and did not have any problems with it. As for conventional motor oil, 20w-50 is extremely thick.

For one thing, I changed over to 0w-30 AMSOIL series 2000. The only difference I noticed is that has a shorter cling time. The only issue I had with the 20w-50 is that it would cling for a long time after shutting the motor off. It would take at least 1/2 hour for the oil level on the dip stick to reveal how much oil is in the pan. I had the tapping noise prior to the use of the 20w-50. The second time I used Mobil 1 is when I had the problems with the noise, which is the reason I changed to AMSOIL. I did some research on the subject and found that many users of Mobil 1 and AMSOIL have reported engine noise which sounds like piston slap. I only rarely heard the tapping noise with the 20W-50 oil, which made me think twice about using it any further. I have run only 5k miles on Mobil 1, and over 14k miles on 20w-50 AMSOIL series 2000.

One thing to safe guard your motor is to let it warm up a bit before driving. That will allow for the piston to expand in the cylinder before putting it under load.

BAD GAS, you get that everywhere. It only took one summer to carbon up a motor with mobil fuels. I can no longer drive the Cobra with mobil gas otherwise it pings like hell. I only use 93 octane fuel, and for some reason, I think Mobil, Texaco, and Exxon are reducing the additives that they put in their fuels. (the brands listed are the ones that detonate in my 01 Cobra, mobil is the worse) Unfortunately there is no means to regualte the additives since it is added to the fuel at the time it is put into the tanker truck or at delivery at the gas station. The carbon buildup was prior to changing over to synthetic oils, but remained a problem until I cleaned out the engine this spring by using water injection mixed with isopropal alcohol.

Actually I was unaware of piston slap. This old dog can learn new tricks. At least with than knowledge I can minimize any excessive wear and tear by letting it warm up. I am more convinced that what I have experienced is associated with the timming chain tensioners rather than piston slap since it is not noticed on every cold start. Perhaps about 5% of the cold starts do I experience any ticking noise and usually under load at 2500 RPM to 4500 RPM and becomes less noticable above. I only notice it in second gear, never had any problems in idle, or 1st gear. At first I thought it may be the transmission, but the noise is comming from the engine. However, I was told by someone it could be piston slap. It could very well be something else. However, since the aluminum alloy pistons expand at a different rate than the iron sleeves, piston slap is probable.