4.0 engine rattle

[cp2295]

So I've posted on this before got some replies and just kinda figured screw it I'll replace the engine with a sohc eventually.

Anyways the issue is a rattle around 2k+ rpms under light load (when in gear and barely on the throttle) sounds like loose metal like gears or something. A loud rattle. No it's not a deep knock and no it ain't valve train it's very weird sounding. The oil psi is pretty dang low 8 psi at idle with 15/40 diesel oil.

So I figured I'd have to rebuild the motor or swap a sohc in like I've wanted to. However I just had an idea, could it be the oil pump is loose (gears ground a little or something weird) and rattling since it's not tight anymore and now I have low oil pressure and that nice is because of the the oil pump being screwed.

I have no bearing material in the filter, the motor pulls 20" hg at idle so it's a strong running motor that noise just bugs the hell out of me. I just don't know what else would rattle like that, thrust plates? Idk even know what those look like anyways haha

 

[bf750]

check timeing chain. 4.0 is bad for that

 

[Angie]

just wondering if it is a cat rattle or from the exhaust? doubt it's timing chain slap because of the tightening system in a ford 4L, and if the tightener was broken, you would know it because the chain would be flopping bad throwing the valve train out of time.

any more info where the sound comes from under throttle?

 

[cp2295]

It doesn't under hard throttle or idle or no throttle just that light throttle at 2k+. It doesn't sound like an exhaust rattle either. Definitely engine sounds like the back but if I put a stethoscope on the block I can hear good. I can get it to do it in neutral if I bring the rpms up and give it light throttle.

 

[Angie]

sorry i can't think of anything else that would do that. the oil pressure sounds fairly normal though. no rpm to spin the oil pump = lower oil pressure on the gauge.

if you are at 1500 rpm at 8 psi you have problems.

hope you can get a answer on this one.

 

[cp2295]

I don't think it's anything in the tranny either because it'll do it even with the clutch pushed in. Very weird I'll post a video of the noise if I can get It to pick up the noise

 

[AllanD]

the usual source for a "Rattle" on a 4.0 pushrod engine is galled pushrod tips and the pushrod socket in the underside of the rocker arm.

timing chain? on an OHV engine? No.

timing chains are a major issue on the 4.0SOHC engine

 

[cp2295]

It's not ticky like the rods and rockers, should I look into the tranny what kind of things would exhibit a rattly noise in the tranny at a certain engine rpm/load. Pilot bearing possible? It didn't look screwed up when I had the tranny down a week or so ago. The noise was made before I dropped the tranny btw

 

[Dune Runner]

I agree with AllanD. OHV engines suffer from worn pushrods. They don't have the timing chain issues that the sohc engines have. Some of the ohv engines had a rattle from the factory. Google it and you will find many conversations on the subject.


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[cp2295]

I have a 98 4.0 engine so it has the marbling but it's a very weird noise would I be better off looking at the tranny being my source of noise ?

 

[Dune Runner]

Can you post a video?

 

[FloridaGrown]

Thrust plates are metal that are in the rear and in front of the crankshaft they take damage when the crankshaft thrusts forward and backward. If it where thrust plates your engine would have hand grenaded by now and you would be out of a block and crank and everything else. So no I doubt it's your thrust plates. I didn't even know gas engines had those I thought it was just diesels. huh. the more you know. I second a timing chain or loose gear. A chain and gear can be tightened up by centrifugal force. But again your engine would be locked up. A chain more then likely.

 

[cp2295]

When I had the engine apart the chain was tight, and everything looked good so I didn't replace it, and sorry guys I'll post a video by the end of the night once I get off work, thanks for the replies!

 

[AllanD]

The marbles rsttliong noise in the late '97 early '98 4.0 engines was due to a factory error in the cam grind of the piston skirts.

Remember than in that late 1997 transition period ford switched to a lighter weight rotating assembly in the 4.0 engine. That required some weight changes in the pistons for engine balance and someone screwed up the cam-grind of the piston skirts which in turn resulted in some inadvertently designed-in piston slap which resembles the noise of castinets (BIG heavy ones)

 

[Dune Runner]

AllenD. Didn't that problem extend through the 99 model year? I know mine has it.


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