The Stovebolt Site Forums The Shop Area Engine Shop Clunk in newly remanufatured 235

After being accused by Denny Graham of running out of stuff to do in this thread I thought I would post this where it belongs.

My newly remanufactured 235, which now has about 400 miles on it, has a suspicious clunk, clunk, clunk sound in it. This sound is not in the valve train and seems to be emanating towards the front end of the engine. Also, the noise becomes more noticeable at idle as the engine warms up. I've done the rod to ear listening thing but can't isolate the culprit.

Right now I'm thinking about dropping the pan for a look see but will more than likely call the reman shop for their input. I'm also thinking of putting the truck on a trailer and driving over to Orlando and let them listen to it.

Nothing would make me happier at this point. My problem is that the last time I heard my 'bolt run was in 1996. At that time it had a 216 in it that had seen far better days. It sounded something like a clickedy clickedy clackedy, clunk, du-wop, pah-thump, clickedy, clickedy, clack. I wish I had something local to compare sounds with, or remembered what a newly rebuilt 235 sounds like. I've heard the term "nothing purrs like a six in heat" but this is more like a beast ready to pounce.

This is one of those tricky issues where you may be damned if you don't and surely damned if you do (pulling the engine). Anyway and ideas, moral support, etc. is appreciated.

Don

Don,

Deep clunks are usually associated with main bearing knocks. There have been some threads lately dealing with "clunks" and the vibration dampener has been an item of interest.

If you have a mechanics stethoscope, you can attempt to isolate this noise further which might solve the mystery. Don't overlook silly things like a generator or even a waterpump.

Stuart

Can you lessen the noise by pushing in the clutch? This would load the crank to one side of the thrust bearing keeping it from floating back and forth if the bearing was the problem,
Scott

As others mentioned, deep clunks are normally associated with main bearing. If that is the source, it is usually accompanied with a drop in oil pressure.

but other clunk sources would be a loose flywheel or a crank pulley with an oversized hole or either not properly installed. also consider any bolt on accessory drives with loose bolts.

Try clutch in or out, air (if you have it) on or off, different engine speeds and loads. Check back with your findings and maybe we can be of more help.

All input is more than welcome. Unfortunately, the clutch idea is not going to help as the clutch assembly has it's own issues. Clankity clankity as the clutch fork rattles around. This is not a throw-out bearing and is more than likely related to not enough pressure being applied to the pressure plate as there is no adjustment left in the linkage. It's also a 9" clutch assembly installed in the 235.

As I proceed through this issue I will update this posting so that others can learn from my mishaps.

Don

A piston installed backwards on the connecting rod, or the entire rod/piston assembly reversed on the crank journal will cause some oddball noises due the the wrist pin offset being turned the wrong direction. The piston is "floating" in the cylinder as the spark plug fires, causing the piston skirt to slap against the cylinder wall.

A main bearing knock generally is loudest as the engine is accelerating, and tends to diminish or disappear as the load comes off the crank just before the transmission is shifted to the next higher gear. Then the knock begins again as the load comes back on. Connecting rod knocks tend to get more noisy as speed increases. Yours sounds most like a main bearing, with a possible piston slap and a rod knock following, in that order.
Jerry

I've been exactly where you are as my truck had a very deep thuinking sound after it was rebuilt. You can follow along with my nightmare here by my message #148631 - August 10, 2007 . It was the crankshaft that didn't get enough oil and I had to pull and rebuild the motor a second time. I'm no expert but I recommend you stop driving it until you can determine what is making the noise. Drop the oil pan and look for metal filings. I found alot in mine. It ran great until it warmed up and started thunking... good luck.

Don, don't make any snap decisions and think this thing through. As you suggested I would trailer it to the reman shop and let them listen to it. With only 400 miles on it I would hope you have a warrantee of some kind? Don't take any chances by continuing to drive it.
I also give you lots of moral support because I too know what it is like to have a clunkedy clunk and wonder "now how much is THIS gonna cost". Good luck pal and we all wait to hear what you find.

Dang it!

I found that using a piece of 3/8" plastic hose to listen with was very helpful. I put one end to my ear and pointed the other end at the area I wanted to listen to. I would bring it within an inch of the area. I found this to be extremely directional in nature.

Pull spark plug leads while engine running to find if noise goes away.... if it does, it's a conrod knock on the cylinder # that you pulled the wire off of.....

Thanks guys. truckernix - I forgot that I did use a piece of 1/2" PVC pipe in addition to a "listening" rod. I'll be talking to the reman folks tomorrow.

I'll also take all of the advice and not drive it anymore until I get something done. It is a bummer for sure. Fortunately, the rebuild came with a 36,000 mile warranty. Of course that doesn't include the yank and reinstall. We'll see just how good of a warranty I was provided.

Don

Hey Don....check your mail.

Dave

A 36,000 mile warranty should help you alot! My first motor rebuilder died six months after he rebuilt the motor. With his untimely death, went his company and my warranty. He was a very nice old man but I still have to laugh about the "Lifetime Warranty" that only lasted six months... :-)

That's an interesting view of a "Life-Time" warranty. I have actually asked, on occasion, who's life are we talking about here. The usual answer was "the original purchaser's, or something to that effect. I never thought to ask... "what happens if you croak?" SOL, I'm sure as you have unfortunately found out.

Too funny, but so true. I'll let you guys know how I make out. I just hope someone else wasn't running a odometer on my rebuild.

Don

Good luck!