91 Sport Engine "Clunking" Noise

[thomasp94]

I noticed on the drive home the other day that the engine in my 91 sport is making a very noticeable "clunking" or "knocking" noise when accelerating. It's even worse going up hills, but at idle or when going down hills you can not hear it. The noise is loud enough that I can hear it outside the truck when driving with the window down. It doesn't have any power loss at all and other than the noise the truck seems fine. It actually almost sounds like that typical sound effect you hear in movies or tv shows when a car is about to die. The truck has 190,000mi on it and it just had an oil change 1,000mi ago and the oil level checks fine. Anyone have any idea what is going on?

 

[thomasp94]

Forgot to mention that the truck does have an off and on anti-freeze leak that seems to be farther back from the radiator. It only seems to leak every now and then, and usually when it's not running. The radiator and reservoir never run dry. I did have the system pressure tested the other day at a local shop and it was fine. Not sure if the noise is related or if it is something more serious.

 

[maniac_3_2000]

Grab your exhaust pipe at different area's and see if it jiggles really easilly. I had a similar issue of it hitting the frame in the rear, but from the driver seat I swore it was coming from the engine.

 

[thomasp94]

I will check that when I get home, I was also told to see if the oil is milky.

Btw, the coolant leak I was speaking of is from the timing cover.

 

[ahodges]

If its more of a ticking or clicking noise and not so much of a clunking noise it could be the water pump going bad. The water pump mounts to the front of the timing cover so that is probably your leak anyhow. Check to see if the leak is originating from behind the pump pully or if its the gasket between the timing cover and the water pump.

Water pumps can make a ticking or clicking type noise when the bearing is going bad.
A side note is that the pumps seem to leak more when the engine is off..

 

[ledzeppelin166]

Maybe u-joints on the drive shaft?

 

[thomasp94]

An Update...

I took the truck back to my local mechanic to have him work on the coolant leak and while it was there I asked him to look into the rattle/clunk noise. Well, long story short, after sitting at his garage for 3 weeks he said he can't hear the problem. So I picked the truck up last Friday and I have drove it about 3 times of work since then. Sure enough the last time I dove it the noise started again, and it got loud enough that I could hear it over the radio and the heater blower on 3/4 fan speed.
I decided that I'm going to take my digital camera in the truck next time I drive it and take a video next time the noise starts in hopes that I will catch it in the audio. If I do I will post it here.

 

[thomasp94]

What is this noise???

Here is the video, you can hear the noise real good near the end of the clip. Like I said before there is no power loss and it doesn't always do it. For instance after I recorded this clip I drove a couple miles farther to some large hills where I thought it would make the noise even louder, instead it didn't make it at all. It seems to do it more often when the engine is warm, but not always. All fluid levels are fine, exhaust doesn't rattle when I shake the pipe. Anyone have any idea???

VIDEO --> http://www.youtube.com/watch?v=NeQ45wjFTXc

 

[burning_soul07]

Hmmmm.... My 94 ticks in the valve covers(we all know what that is) and I really couldn't make out the noise that well.... Too bad it doesn't make the noise at idle so you can search for it.

 

[ahodges]

That sounds like a really fast ticking... I would almost say spark knock if it does it under load when its warm but it should get worse with the more load you put on it. Plus, I've never heard a 4.0 spark knock.