97 Expedition XLT Engine Knock Advice?

[SPreston2001]

Hi a buddy of mines just brought a used 97 XLT with just over 100k and after about a week she started to notice a knock coming from the engine bay. So I checked it out, and it appears to be the engine knocking. Question is should she trade the thing immediately, or hang on to it? She really likes the truck and the knock doesnt seem to have any affect on power or acceleration. Any advice? Thanks

 

[JUST4FUN]

Chamge the oil first and see what happens

 

[expeditionman]

where exactly is the "knock" coming from? Can you hear it louder from underneath by either wheel? Or is it louder from up top?

the 97, 98, and 99 are famous for the exhaust manifold gaskets crapping out. My 97 5.4 has a ticking out of the front passenger side, very loud by the tire and it gets quieter as the engine warms. check by each manifold for "burn" marks or black carbon. Thats a tell tale sign of an exhaust leak.

 

[SPreston2001]

Hi yes its definetely louder towards the bottom of the engine. Im going to change the oil to a 5w-30 full synthetic motor oil this weekend and hopefully that helps. If the problem is in the manifolds, should I replace the headers or should I just replace the gaskets? Also what synthethic motor do you guys recommend for high mileage expys?

 

[expeditionman]

For oil I use Motorcraft 5/30. I've used Quaker State full synthetic before and that stuff works good, too. Stay away from Pennzoil, though, that crap tends to rot seals and gaskets. As far as the exhaust mani's go, if they are not cracked or busted, you'll be able to get away with just replacing the gaskets. Be careful with the studs and have plenty of a penetrating oil. PB Blaster works the best IMO.

 

[GRIP]

when you change it small the oil make sure it doesn't smell light rear end fluid.here in jersey when ppl have a knock and they want to sell the car/truck they throw in read end fluid to quit it down so you can't hear it. then after the thing gets good and hot the fluid thins out and you hear it.

 

[SPreston2001]

Ok well I just got done changing her oil to Mobil 1 Full Synthethic 5w-30 and it did quiet the motor down alot but it still has a slight knock to it. I also ran some Sea Foam through the crankcase and gas tank about 3 hours before I changed the oil. Any thoughts?