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ide noise??? im stumped...


Joined
Aug 7, 2007
Messages
18
City
Ohio
Vehicle Year
1991
Transmission
Automatic
The truck is a 98 4.0 5 spd 4x4 with 96,000 When started and idles down to 700-800 roughtly i get a rattle/clunking noise from the passenger side of the truck, anything above that rpm the noise stops. i looked at the catalytic conver cover and seems ok, clutch has no effect on noise and truck runs great except for the noise... any thoughts on what it could be?? im stumped and want it gone
 
I know what you mean about getting the noise gone. You seem to be looking around the exhaust for your noise. On 93-94's all heat shields on the exhaust begin to shed under 100k mi in my experience and don't know if they improved in 98. Even in one instance the upper heat shield on the muffler came loose on one side and flipped onto the driveshaft. If it is exhaust it could be a piece of debris or a rock in between the shield and pipe resonating at the idle speed, tapping a hammer gently along the system will usually find the issue. Hope you just find a rock in the shields.

Good luck
 
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no it isnt anyhting with the exhaust i already checked all of it, it seems to be coming from the passenger side of motor/tranny above exhaust
 
Some questions:

1. Is the coolant full? 4.0Ls often make occasional knocking sounds after the engine is turned off if it's a little low. If it's really low, it's obvious in the radiator. Low coolant can cause preignition, and it's very serious.

2. Is timing sensible on all cylinders? Note that 4.0Ls use waste spark ignition and it's normal for them to fire every crank revolution (instead of every other one). You're not looking for just a little off. You're looking for it WAY off, or for extra sparks.

3. When the clutch is down, is the transmission in gear? If not, try it that way and see if the sound goes away (this would isolate it to the transmission if it did).

4. With the engine cold, try running it briefly without the serpentine belt. This will test whether an engine accessory is at issue. Don't let it warm up.
 
Also check where previous mechanics have been if you have had them work on your vehicle. In 02 the Ford dealership dispatched their mechanics to my home to finish what should have been completed at the shop. The crossover had not been completely attached at the frame after a radius arm bushings had been installed. (similar low rpm noise) Hopefully you will not be looking at anything in the drivetrain but be prepared.

Good luck
 
clutch/gear makes no difference, already eliminated all accesories with out belt, and only does it when running at idle... and it runs perfect, just has the noise... when it recieves a load it goes away...
 
That sounds almost exactly like the cat heat shields loosing one of their welds. (Also on the 93-94 there is a steel ID plate spot welded to the cat that will come off and rattle loudly against the bottom shield)

Good luck
 
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I agree with the rest. Problems as you describe are almost always exhaust related, and that heat shield is tricky. They are hard to pinpoint because its a long frikkin piece of metal from the back to the engine so of course it can sound like its coming from anywhere. My bonneville, I coulda swore its engine was going because it made a weird noise that sounded like it was coming from the engine at certain RPMs. Turns out heat shield I had bent down was smacking the exhaust at certain idle rpms.
good luck and please post back.
 
i had the same problem with my 91...but after i put a American Thunder cat-back on...it disappeard!! was it a coinidence or did it fix the problem.
 
you guys are talking about the heat shield on the cat correct??? i have been reading about ford's marbling issue with ohv 4.0 on rps and ford-trucks.com and it describes the problem exactly... can anyone tell me anything more about this marbling problem ford had with these engines besides the basics and is there anyway to fix it from being noisy(granted i look at the exhaust again and it is fine)
 

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