V6. Why does it make a load roaring noise when started and driven for about 5 miles?

get it fixed.
take it to any mech,.
and id have him find the noise source and cause of leak.
then work from there.
we are blind and deaf there. we can do neither,

for leaks, we clean it prefectly then drive it 10 miles
and find true source
or use the UV dye test.

It is running too lean when warm - check fuel rail fuel pressure and rail pressure regulator. This is especially if it's got a lot of miles

If the problem sounds or feels like its from the rear of the vehicle, its most likely in the differential, specifically pinion bearings.

No they don't always do that but I have found that a roaring noise could be from the tires and not the engine.

old post.zero help, so here i am, filling the hole for next person.

the V6 has no cam belt. it's a chain drive.
how many miles on v6 motor.?
the chain runs 2 times longer than a belt. easy. or more.
the hydraulic adjusters may not, when not doing oil changes on time.
the start up noise is normal (not mine) but the factory TSB covers this, on higher mileage v6,
the engine starts and the chain , or lifters can make noise
until oil pressure reaches normal. (0w oil can be and issue here)
i run 10w40 all year, and mine runs like new, all the time. 100k miles on my block.
if the noise stops , after few seconds the TSB is clear on that.
its normal.
if it makes noise full time, really any engine. its time to stop
not run it and fix it or the damage can cascade it to total engine destruction.
have an ASE mech, diagnose the noise and true source
we have tools to do that , and you dont.
we find the true source and evaluate that.
next time post how long the noise happens, hot and cold
and hot only start ups.?
most shop manuals have a chapter on noise.

here is typical translation of that.
http://www.fixkick.com/NOISE.html

is this a 4cyl or V6...how many miles??sounds like the transmission isn't shifting to lower gears....is there any warning lights lit on your dash??

3 suggestions for you, you may need to check the tire pressure, get a tire alligment done, or you have a bad wheel bearing, usally a bad wheel bearing make's a loud roaring sound going down the road. I hope I have helped you.

If the vehicle is moving I would suggest the look at the wheel bearings. they could be warned out.

check pawer steering pump belt mybe it is worn out or loose, also check the alteranator belt.

No the fan clutch doesn't need to break in. I've never heard of that and I'm a mechanic owner/operator. Our personal car is a Trooper with a 3.2L The roaring noise is normal but the timing on your Rodeo sounds like it's retarded somehow. I'd take it back to him and have him deal with it. As an owner/operator, I would definitely make sure the customer is happy with their car no matter if I was to spend a little money out of my pocket to make it right and keep the customer. He should do this for you as a shop warranty. The roar should only be heard right after start up and go away or leaving a stop light on a hot day but only for a few seconds.