Help!! Loud Engine knock after changing glowplugs

[banjodunn]

G'day the more i read this the more i hope i am wrong for your sake But i still think you have done a crank bearing ( big end ), don't be fooled by the sound coming from the top of the engine as this can be the piston just travelling up the bore a little more and tapping the head( I know this from experience:ashamed. By all means check your valve train but i would be draining the oil and cutting open the filter to check for metal particles, I have seen an engine do a brg and not drop considerable oil press due to the gallery being half plugged by the failed brg. Hope it works out well for you


Jon

 

[TO_Bud]

Lots of ideas here for you to digest. You've titled your post as a loud engine knock but further down you post the noise can be heard above the engine from some feet away. A rod or bearing knock will be heard some hundreds of feet away, in fact the knock might be the only thing heard from a distance. Since the tempo of the sound stays constant on accel and decel it doesn't seem to be a rod or bearing so I'm with the posters on carbon build-up. Carbon build-up on a piston or cylinder can glow red hot while the engine is running. Any fuel leakage by an injector will be ignited before the piston is at it's proper location in the stroke causing rattling or dieseling (knocking sound if you will). It also doesn't sound like a destructive condition. I would try some fuel additive for moisture and some fresh winter grade fuel first before diving into the engine.
More advice hope it helps.

 

[BeeferMan]

Now I'm no expert here, but I'm having a hard time understanding the "carbon-knock" scenario in a diesel engine. Spark plug engine, ok, that'll happen when the glowing carbon (pre) ignites the fuel before the spark normally would. But in a diesel, there is no fuel to "pre-ignite" until the injector fires - and that's when it's supposed to ignite. So how could carbon in a diesel cause a early ignition condition and the subsequent knock?

Again, I'm not saying it couldn't, but please educate me as to how it could...

 

[Jerry/MT]

Now I'm no expert here, but I'm having a hard time understanding the "carbon-knock" scenario in a diesel engine. Spark plug engine, ok, that'll happen when the glowing carbon (pre) ignites the fuel before the spark normally would. But in a diesel, there is no fuel to "pre-ignite" until the injector fires - and that's when it's supposed to ignite. So how could carbon in a diesel cause a early ignition condition and the subsequent knock?

Again, I'm not saying it couldn't, but please educate me as to how it could...

The person who posted above you said "Any fuel leakage past an injector....". That's the postulated fuel source.

 

[BeeferMan]

The person who posted above you said "Any fuel leakage past an injector....". That's the postulated fuel source.

:thumbsup:

 

[OldBulldogger]

Update on the loud engine knock/tap. First of all, thank you to everyone who replied to my post. All of the input you gave was greatly appreciated and everyone seemed to have some very valid reasons for what could be causing the loud knocking/tapping sound. That is the best thing about these forums, we all get great information and can learn from other's experience.

I have to admit, I was pretty concerned after reading what could potentially be causing all the noise and the $$$ that could be involved to fix it. I purchased a mechanics stethoscope yesterday and I will say that was well worth the $20 after using it. Long story short, when I got home last night, I went out to the shed to take another look at the tractor after reading all the great information provided.

Admittedly, I am a praying man and believe in the power of prayer so I threw up a quick one to the good Lord and then started the tractor. The loud noise was still present. So I used the stethoscope to try to isolate the sound. It did seem like one cylinder in particular was a little louder and closer to the top end. I then jumped on the tractor and revved it up and down and listened. It continued to rap loudly keeping in sync with the RPMs. The tone changed with the speed - more of a loud tapping on the faster RPMS and more knocky on the slow rpms. I revved it up and down slowly three times and then ON THE THIRD TIME REVVING IT UP - the sound disappeared completely.

The engine idled like normal - no sound. I revved it up and down several more times - no sound. I then through it in gear and drove it around the yard, using the throttle and foot throttle to work through the RPM ranges - still no sound. I live about a mile from town so by then, it was good and warmed up so I drove it into town, topped of the tank with half a tank of new diesel and drove it home - again no strange sound. Parked it for the night and fired it up again this morning in 25 degree temps. The new glowplugs did their job and it fired right up (no more ether!). And again, no more loud knocking rapping sound.

Here is my take on this so far.

First, if you are a praying man, it never hurts to ask the good Lord for a favor! I can honestly say I have been blessed many times in my life by the man upstairs, especially when on bended knee. Enough said.

Secondly, I think the post from ZZVYB6 (read above) fits. In this case, the glowplugs I changed were original and 22 years old and all had carbon build up, the center one worse than the others. And, coincidently, the loud knocking occurred AFTER changing the plugs. Sure, something else like a main bearing or rod bearing could have failed by coincidence at the same time however it would seem unlikely. (never say never though!) The one variable in the whole before and after review was pulling the plugs. It would make sense that if there is considerable carbon build up that some carbon was dislodged and floating around in the head until the point where it blew out in the exhaust after revving up the engine several times. I will admit I am surprised by how loud of a sound it made. I did talk to my local Ford/NewHolland dealer and they did say it is possible and could almost sound like someone threw a small rock into the combustion chamber. Good news is that it is gone and the tractor is running smooth as before.

I will keep this post alive with a few more updates so as not to rule out anything else and let everyone know how long term this played out. In the meantime, I love my Ford 1720 again. Okay, I never really quit loving it... I must be a tractor junkie. I have to say, they are great little tractors for their size.

If anyone has additional feedback, I would like to hear it. I learned quite a bit so thanks again. The feedback was great.

 

[Transit]

It sounds as if something loosened up, I'm thinking a valve hung up or piston slap.

 

[banjodunn]

G'day glad to hear it is ok :thumbsup: I dont mind it when i am wrong on these things

Jon

 

[Raspy]

Sounds like you got the problem resolved. Good.

If it continues, I think you should explore all options with the injection system first.

So, first off, a bad injector on a mechanical injection engine does not affect timing. Second, idling diesels do not fire prematurely from hot carbon. They can't, there is no fuel there to fire until injection occurs. However, an injector can fail by making a poor spray pattern. This means more of a jet of fuel than a fine mist. When this happens the fuel ignites with more of a bang and a knocking sound. It also makes a lot of carbon.

I suggest you crack the injector line on the carboned up cylinder, while the engine is idling and knocking. If this stops the knock and makes it run rough, you know it's an injection problem.

If it is an injection problem on that one cylinder you'll need a set of injectors, or yours rebuilt by a qualified diesel shop. And when you get that taken care of go out and work it at full throttle for a while to clean out the deposits so the corrected spray pattern is not spraying on a carbon buildup. It needs to spray cleanly into the combustion chamber and ignite while atomized.

A fuel knock can be unnerving and sound much more serious than it often is. A rod knock is more of a pounding down low in the block, and likely develops over time to become gradually louder. But all bets are off with the use of ether! I've seen broken pistons, rings, and crankshafts that resulted from ether. One man's "small" squirt is another man's flood. If you absolutely must use ether, and I mean absolutely! Just give the engine enough to smell it. That's all! No liquid! Just the scent of ether does the trick. More and you are likely causing damaged ring lands and future compression loss, or worse.

But I have to draw the line at praying for a fix. Doesn't the Lord you pray to have better things to do than take care of your tractor? And, If I was him, I'd point out that you have been deliberately hurting your engine with ether and likely caused some damage yourself.

 

[dqdave1]

I had an injector that was bad and it ran pretty smooth. It was just down on power. You may not know you are down on power since you got it with a bad injector. Ask dealer what fee is to check injector. Another way to get piece of mind for about $25.00 is to do an oil analysis. I use Blackstone Labs. They will send you the needed items for free. Warm up engine; drain oil; catch a little in supplied bottle and send it to them. They will check oil and send a report to you. If you have bearing problem , it will show up. If you have alot of "soot" in oil; it will show up and on and on.
I use my stethoscope all the time. Pinpoints noises quickly.
Glad you may have a cheap fix.