Engine rattle with higher rpms or no load

[rmarshusa1]

Most of the postings I have read talk about engine rattles coming from the valve train or timing gear. I am not so sure that is my problem

I bought a 91 scout 4x4 4.0 with 67,000 on the odometer - I am sure it is a least 164K or maybe even 264K.

Anyway - when I start it there is a rattle that goes away instantly - the engine doesn't smoke at all and doesn't use oil except for some leaking around the valve covers.

When I am driving, it rattles at shift points - like 2000 to 3000 rpms, rattles if I over-rev it 4000 rpms, and rattles when I may just be cruising around around or over 2000rpms. The rattle will stop when I put a load on it - like going up hill or just pressing on the gas pedal.

What do you guys think???

 

[majorboot]

wouldn't hurt to have a mechanic have a listen.....
The timing chain noise makes the Exploders sound like a diesel engine. If it sounds like that, you might need to have some-one take a look sooner rather than later.
I just bought a 97 Limited with a timing chain problem (bought it for next to nothing knowing the problem) now attempting to buy the parts from the USA cos the parts are obsolete in Australia.
Good luck with your truck mate.

 

[rmarshusa1]

thanks, it doesn't seem to be getting any better I've tried a heavier oil and I seafoamed the engine.

 

[MrShorty]

The OHV doesn't have much if any trouble from timing gear/chain rattles. From the situations when yours rattles, I would suspect the valve train.

 

[ragajungle]

wouldn't hurt to have a mechanic have a listen.....
The timing chain noise makes the Exploders sound like a diesel engine. If it sounds like that, you might need to have some-one take a look sooner rather than later.
I just bought a 97 Limited with a timing chain problem (bought it for next to nothing knowing the problem) now attempting to buy the parts from the USA cos the parts are obsolete in Australia.
Good luck with your truck mate.

Majorboot is right a "rattle" could be as serious as a bad main bearing (usually clatters on decel/shift points) or could be as simple as a broken/sheared off harmonic balancer pulley bolt...

 

[rhauf]

load dependant rattle. could just be something rattling against the engine or exhaust, and when the engine is under load (torquing very slightly to the side via the engine mounts rubber play) it moves such that the rattling surfaces don't meet.

i'd guess it's proboably something external and not a concern at all. i'd start by checking the exhaust for rattles. a loose heat shield could be you're problem.

the 91-94 4.0's dont have valve train/timing chain issues (they are not overhead cam)

bearing rattles (serious bottom end stuff) would usually rattle louder under load, and would be more of a deep metal knock. (like a hammer tapping in the block)

if you took a video of it and posted it on youtube we could probably take a way better guess at the problem here.

 

[rmarshusa1]

Thanks a lot - I'll try to get it on youtube.