br99

I have a 99 gt and when i start it i get a knocking sound from the driver side bottom of the motor it only last about 15 20 seconds then stops and only does it the first time i start it for the day after that i can cut it on and off all day and it wont do it. Any help is appreciated, could it be crappy oil or something i just got the car a few weeks ago but i never drive it.

Dan04COBRA

Piston slap isn't all that uncommon up until 02. Have a compression test done to start. Get a mechanics Stethoscope and listen, that knock may not be going away like you think.

mustangman03

The tensioners might be leaking down mine does that also if i let it sit for a while. I know a guy that has a 5.4 that rattles real bad for about 30 mins. and its been doing that for 50,000 miles just have it looked at b/c it is hard to diagnose noises over the internet.

br99

I am gone try changing the oil 2mrw, bc the only time i hear it is on the first start a the day and only for a couple minutes, it doesnt seem to be running any different, doesnt idle bad or miss or anything else, i have a steeda timing adj it only set at 12* and i always use 93 oct and use seafoam in ev other full tank

br99

anyone esle any thoughts

99BlackPonyGT

sure its at the bottom? mine does it...its just a stuck lifter, no big deal

or it could be your timing chain tensioners going bad...theres a sticky about that

Tazzy

Make sure you are using the stock motorcraft oil filter or a k&n oil filter, these have the anti-drainback valve installed. What happens is all the oil drains out of the oil filter after sitting for a couple hours and when you first start the car you have no oil pressure until the filter fills back up. But this should only take around 3-5 seconds. If you are getting 20 seconds worth of rattle than it is probably piston slap. I can't beleive ford put the filter horizontal on these motors, vertical would have been much better.

br99

well i just changed the oil there was no metal on the drain plug and the oil lookd fine, now it seems to do it worse than b4, but the car still runs fine, i have no clue what now.

99BlackPonyGT

it doesnt sound like piston slap at all!!! dont listen to that garbage...piston slap doesnt just suddenly disappear

timing chain tensioner or valve tick is the most likely reason

br99

deff not valve tick it is metal to metal, an now appears to do it all the time, it sucks bc i have put maybe 500 miles on the car since i bought it, and it is n excellent shape has new everything. but i startin to get mad now bc i cant drive it bc i dont know what gone happen