intermittent knock, Please help!

[monty509]

My 1964 CJ5 f-134 has an Intermittent knock, link to video below. I've dropped the oil pan, everything is tight and snug. No metal shavings in the pan, cylinder walls look great. I open the top and side valve cover and again everything look and feels what I would imagine is good. I have reach the limit of my knowledge and hope someone can help me diagnose were the knock is coming from. Anything helps, thanks.

https://www.youtube.com/watch?v=l0H_zQnH8OE

[TJones]

Does it knock all the time or just when you fire it up cold?
Sounds like a loose plug blowing compression until it warms up or a leaky exhaust gasket blowing exhaust until it warms up.

[bmorgil]

That sounds like you may have a load of carbon or water in the cylinder. The sound of it seems like one or two cylinders. What is the condition of the engine? A lot of hours? Does it burn any oil? Has it or does it run with the choke on a lot? Is it steaming at all out the exhaust? That is a loud knock indeed!

[monty509]

Thanks for the replies, It'll knock both hot and cold, that video was literally the first 30 seconds its ran since late November. It has a lot of hours on it but the motor is in good shape. As for the oil it's hard to tell, I get do get some blue smoke so I'm sure i does burn a little. Thought that was more likely to be because of fuel/air mixture. The knocking started last October, it knocks while at idle and under power. After I took the video yesterday it idled for about five minutes without knocking. I shut it off added oil, changed my clothes started it back up and the knock returned and hasn't gone away. I checked the spark plugs, they're snug. Perhaps the crush rings are bad? Again thank you.

[okiemark]

Well, that's a heck of a knock, but sound good when it isn't knocking. In my experience, a rod knock doesn't go away. You might get a wooden dowel a couple of feet long and place it in different spots on the engine and hold it against your ear and see if you can locate the area it is in. I had a Ford pickup once that developed a slight knock and could never find where it came from. Changed lifters, fuel pump, didn't help. Maybe look at the fuel pump arm.

[gmwillys]

Sounds almost like a wrist pin. The F134 doesn't like a lot of sustained high RPM. This will cause your intermittent knock either under load but more so at idle. With the low gear ratio, and highway speeds above 50 MPH, the engine will overspeed.

[bmorgil]

I was thinking maybe a wrist pin also gm. I just can't see it coming and going like that. I think you may have something with the RPM gm. monty509, does it always go away at higher RPM? If it is a wrist pin, I would assume it has damaged the cylinder wall by now. Compression in that cylinder would be low. The wrist pin is clamped in pretty securely with a bolt through the rod. It certainly could come loose. I wouldn't expect it to last long. It is so loud. I wouldn't run it like that. I think a compression check is in order. If a cylinder is damaged that should show, or if a cylinder has a carbon load compression will be high.

[TJones]

If you watch the video close and about the 2-3 second mark, what is the spark on #4 cylinder right where the plug seats to the head????

Could it be a dead cylinder until it fires to the electrode on the plug instead of shorting out to the block causing a dead cylinder????

[bmorgil]

TJ what an eye! I went back and looked and thought the same thing, it looks like an arc on number one. Closer inspection and I think it's a piece of paper or tape flipping around.

okiemark's suggestion (fuel pump) is also a very good thought. It sounds like it is timed with the cam. It could also be a sticking intake valve or a broken valve spring, letting the valve contact the piston. That would likely bend the valve and compression should be low on that cylinder.

[gmwillys]

From past experience, the wrist pin doesn't migrate out of the piston, so the cylinder wall is usually fine. The bearing on the rod becomes oblong, and in worst situations, the rod becomes oblong. We had a Dodge M-37 with the 236 flat head. It only had 10,000 miles on the clock after a 1976 overhaul in Denver, (great thing about overhauled military vehicles is that the depot affixes a plate to the exterior of the block giving bearing measurements of either standard or oversized- and how much) The truck was used as a brush fire truck for the local volunteer fire brigade, and had a 500 gallon tank and pump installed. The 500 gallon was cut in half when the extra weight made the truck unstable in cross country travel. Long story short, being that the truck was used for travel faster then designed, the engine developed a knock. It wouldn't do it all the time, but mainly at idle. When under a load it would quite down until you decelerated, then you could hear it.

With all that being said, it would be a good plan to check the valve train for a weak or broken spring. I highly doubt that it is on the intake side, because it is not backfiring through the carb. The exhaust valves coming up through the block will not cause extensive damage like an intake would. Since the Jeep last ran in November, it could be a possible hung valve. Then it would be as simple as working the valve to loosen it up. In your dry climate, that isn't a big probability, but worth a look.

[okiemark]

I just have never seen a serious knock that didn't keep knocking and get worse. Maybe something is slow getting oil to it.

[TJones]

TJ what an eye! I went back and looked and thought the same thing, it looks like an arc on number one. Closer inspection and I think it's a piece of paper or tape flipping around.

okiemark's suggestion (fuel pump) is also a very good thought. It sounds like it is timed with the cam. It could also be a sticking intake valve or a broken valve spring, letting the valve contact the piston. That would likely bend the valve and compression should be low on that cylinder.


I thought the same thing on number 1 and I think it is paper or paint but number 4 is definitely an arc from the plug.



59095910

[bmorgil]

My God Tim, how did you see that!? Definitely, you found it. The plug is grounding to the block. The arc is traveling down the electrode and across to ground on the block. We are hearing the fuel detonating in number 4. That plug must have a cracked center electrode. I had to put that up on the big screen to see it!

monty509, pull that plug either the center electrode is broken or the porcelain is cracked. I think TJ found it for sure.

TJones "Eagle Eye".

[TJones]

Actually I BLEW it up like you did and kept hitting the replay on my office computer and sure enough it's a arc.

[LarrBeard]

I thought the same thing on number 1 and I think it is paper or paint but number 4 is definitely an arc from the plug.



59095910

There may be several things going on, but throwing the plug in #4 as far as you can is the first and simplest fix to try.

Great eyes TJ!

[gmwillys]

Easy things first. Great catch TJ!

[TJones]

The only reason I kept looking at the video was it didn't really sound like a rod,valve,wrist pin or anything metal knocking around it was more of a muffled sound like a misfire or something.
Maybe it's not the plug but it's a lot cheaper and easier to replace a fouled/broken plug then jerking it all apart.
Believe me I have heard plenty of motors have Scrap Iron Fits and this one didn't sound to bad at all!!:confused::confused:

[LarrBeard]

The only reason I kept looking at the video was it didn't really sound like a rod,valve,wrist pin or anything metal knocking around it was more of a muffled sound like a misfire or something.
Maybe it's not the plug but it's a lot cheaper and easier to replace a fouled/broken plug then jerking it all apart.
Believe me I have heard plenty of motors have Scrap Iron Fits and this one didn't sound to bad at all!!:confused::confused:

Every so often the blind squirrel finds an acorn without a worm in it!

[monty509]

I pulled the plug no real visible damage to it besides some small chips on the very to of the insulator. The plug has quite a bit of dry fouling though, maybe that's causing the ark, insulator not being able to insulate? We will find out Sunday when my gaskets get in and I put it back together. I got some new plugs. Maybe i'll put it back in and run it in the dark and see what it does. Thanks for all the help, very kind.

Also when I pulled it out there was a very strong smell of gas.

[TJones]

You are very welcome monty509, the smell of gas makes me think it may be the plug even more but the thought of running it in the shop/garage in the dark will be the answer.

[monty509]

Ya it's some old advice I got on how to test plug wires at home. :cool:

[bmorgil]

A chip on the insulator is not good. The smell of gas, also not good. I think you have it fixed now. "Eagle Eye TJones" is the man!

Needless to say we all await in great anticipation, the results of this! That was one loud and scary sounding knock.

Could you post a picture or two of the suspect plug?

Most plugs are damaged on installation. Besides the obvious "whoops" dropped it, pressure against the insulator while installing will crack it immediately. A chip is a solid indication of damage. In any event, you shouldn't install a spark plug with ANY visible damage to the insulator.

[monty509]

Ya sure, the small black marks are the chips.

[bmorgil]

Definitely not firing very hot on that plug. Those chips in the porcelain are kind of weird. I take it this is the only plug with these chips in the porcelain? Maybe a defect? Well can't wait to see if a new plug solves it.

[TJones]

It may even have a hair line crack in the porcelain close to the steel part that is letting it jump to ground.

[monty509]

ok so I put it back together and new plugs, still knocking. I took the clutch inspection plate off to listen for anything. I cant say that its a huge difference, but there is a change. What do you all think? Just looking at all possibilities. I recorded it. :confused:

https://www.youtube.com/watch?v=srm-v2AkiaY

Edit: it still knocks when the clutch is pushed in.

[bmorgil]

Wow I thought we had it. What happens when you push in the clutch? Lets be sure it isn't the clutch. Depressing the clutch will also put a little thrust on the crank. Lets see if that changes anything. By the way what is the oil pressure?

It should at least be running better with all the plugs firing. It is so hard to tell over a YouTube video. I would eliminate okimark's suggestion on the fuel pump. Make sure it isn't coming from there. If it doesn't change with the clutch being depressed, I am thinking you should definitely run a compression test. You want to be sure the obvious things are checked off. It is sounding more and more like something internal is amiss.

[bmorgil]

monty509, I see it still knocks with the clutch depressed. I am thinking its internal. You have run the gambit on everything I can think of. Can you run a compression check? It is the last step before you need to start looking deeper.

[monty509]

Ya, I'll go rent one. What should the pressure be at? And I have no idea what the oil pressure is, a gauge has been on my "to-do list" but not really sure how to install one, never had to do it before.

[okiemark]

You can get any type of mechanical gauge and use a hose. Grease gun hose is the right size and screw it into the block where the oil sender is.

[monty509]

Ok did the test, don't know how accurate the numbers are since I didn't idle it to operating temp but it came out as follows,
1-85 2-55 3-49 4-76. Not very good i'd say.

Edit: I'm thinking I might take the timing cover off and have a look.

[TJones]

WOW, I’ve been scratching my head on this for a few hours now...
Could it be something in the bell housing????
Maybe a spring on the clutch that’s broke, a ball bearing on the throw out bearing???
It almost sounds like a bolt rubbing the flywheel as it turns.
But it may very well be internal????

[monty509]

I know, and what ever is causing it clears up and goes away whenever it wants.

[bmorgil]

monty509, before I say the numbers look bad, we need to know your process. How did you perform the test? You need to follow the service manual. On a cold engine and in general, we are looking for the following.

The service manual focuses on how well the motor compresses during the first four strokes. If compression jumps up "quickly" it indicates good pressure. If it is slow to come up and needs all four strokes to peak, it is getting "weak". If it is varying between cylinders, something is up. On these motors this is still a good way to check the general condition of the engine. It certainly has enough compression in 1 & 4 to start. Your test does not show what we want however. Cylinder 2 and 3 are to low to fire. On a cold engine cylinder 1 is what I am expecting. Does your test represent the service manual procedure? If it does I would say it is time to pull it down before it fails something, and costs much more to rebuild.

You MUST have an oil pressure gauge! I have to say monty509, don't start it again without one. If it is going away because the oil pressure is coming and going, you are causing damage that can render the engine very expensive to rebuild. These engines have very little oil pressure to begin with.

[TJones]

Your exactly right bmorgil, the oil pressure is Vital it will go into “cardiac arrest” if it’s not getting oil pressure from the get go and eventually it will be costly to repair over time.

[monty509]

Got a gauge in and it sitting at about 45-50. Trying to adjust the valves and am getting conflicting numbers Anyone know the valve adjustment specs?

edit: ive been using this as a reference. https://cj3b.info/Tech/Valves.html

[okiemark]

That's damn good oil pressure.

[monty509]

The more and more I think about it, I wanna say its probably a stuck valve. I got a mechanic stethoscope and did some listening. It definitely more of a click I'd say.

[gmwillys]

Try these videos to get a visual.

https://www.youtube.com/watch?v=9VrcG6tCQ2k

https://www.youtube.com/watch?v=zRClIFAg8W8

[bmorgil]

Excellent on the oil pressure. You are narrowing it down now. The cylinders with the low compression are probably the culprit. When the piston strikes the valve it can bend it. This usually causes a bad seal and aggravates the "sticking". You can pull the rocker shaft and exercise the intake valves. If one is sticking, it should show up when you manually open and close them. They usually stick as the valve is close to closing. The spring pressure is at its lowest.

If that's it, a valve job is a lot easier than a full tear down!

[okiemark]

That would make the intermittent nature make more sense.

[monty509]

Excellent on the oil pressure. You are narrowing it down now. The cylinders with the low compression are probably the culprit. When the piston strikes the valve it can bend it. This usually causes a bad seal and aggravates the "sticking". You can pull the rocker shaft and exercise the intake valves. If one is sticking, it should show up when you manually open and close them. They usually stick as the valve is close to closing. The spring pressure is at its lowest.

If that's it, a valve job is a lot easier than a full tear down!

How would one manually exercise the valves? Turning the harmonic balancer?

Edit: Are you saying remove the rocker shaft?

[bmorgil]

Yes, remove the rocker shaft. However before you do that you should be able to easily make this happen. Pull all the plugs to make it easy to rotate the engine. If you can rotate the engine by hand with a ratchet and a socket on the crankshaft. Remove the Intake valve cover and turn the engine over allowing it to compress and release the valve springs. Go slowly and see if you can feel it bumping a valve. As they close, watch each one to see if it suddenly "Jumps" shut like the piston is pushing it, or it doesn't close all the way. When it appears to be closed check the lash. If you suddenly have a lot of lash, rap the top of that valve and rocker shaft to see if you can get it to seat further. Use something to try to pry the valve up if you can. If the lash closes up that valve is sticking.

There are a few ways to exercise the valves. What I would try first (after removing the rocker shaft) is to simply rap the valves with a soft hammer and see if they do not fully return. To be sure, you can use a valve spring compressor like this https://www.harborfreight.com/universal-overhead-valve-spring-compressor-60335.html to remove the springs. Then you can easily move the valves to see if you have a valve sticking. You need to be careful when doing this. You do not want to drop a valve into the cylinder. The piston must be at TDC when you remove the valve spring.

[monty509]

Okay a little update, haven't forgot about you guys. So removed the covers and rotated the crank and inspected the valves, nothing unusual, put back together to take it to my fathers shop. The thing wouldn't start, rechecked the points, plugs, wire ect. Seemed like some of the wires going into the cap hoods had moved making bad contacts from wire to cap. Bought some new wires and bingo started, with a very slight knock. Let it idle for about 10 minutes which was rough. Once it smoothed out a little bit I started to mess with the carb settings as I adjusted them and the idle smoothed out and slowly the knock got quieter and quieter. Now the idle isn't set perfect cause I'm no expert at It. I got it to idle pretty well on its own with a little sputter for about 10 minutes and decided to take it for a small trip around the block, I backed it out of garage and went over a little bump and it shut off and wouldn't start again. Smelled a little rich so I think I'm still a little off on the right settings. If anyone has any tips/tricks on setting them I believe this carb to be a solex replacement, not 100% sure though. I don't think I'm out of the woods yet though but one more thing off the list. I gotta wait for the battery to charge as I ran it dead trying to start the thing. So tomorrow I'll post a video of how it sounds. I also got a mechanics stethoscope and probed everywhere. I don't hear anything that doesn't sound like a mechanical sound, just maybe, fingers crossed here some very light detonation. Lets hear your thoughts, open to any suggestions. Anyway hope everyone is well and enjoying their weekend, mine just got a whole lot better.

[okiemark]

All you can really adjust is idle mixture and idle speed. Screw the idle mixture in until it tries to die, then back out and leave it at the spot where the engine is the highest RPM. On idle speed you just put it where it sounds right for you. Might have a loose electrical connection making it shut down.