I have noticed a knock in the engine on my M4500DT. This is my first tractor which I havent had for long and not used to its sounds. I have a small diesel tipper and Kubota excavator which are quieter but have the usual diesel tappet sound. The tractor has a noisy valve train sound which I thought was normal being open and from what I read about this old model. However this sound I notice is different like "Rod Knock". I have heard this type of knock in gasoline cars during my lifetime, so this worries me that its the same. I am not familiar with any injector knock timing sounds and doesnt sound like piston slap because it doesnt go away. It only blows a tiny bit of white smoke on reving and the knock is not any louder with revs, but you can hear it more clearly on idle and cold or warm is the same. There is some blow back. I realize no one can diagnose sounds over the internet. I will get a mechanic in to diagnose but does anyone know if this model can be checked with the injectors removed and putting a rod down and hand turning crank past TDC and feel for downward piston play? I see on gas cars they remove spark plugs to check with this method. I also thought an oil pressure guage but it may not give the correct diagnosis. If it were a car or truck I could drop the pan and check the journals but on the tractor this doesnt seem possible. The tractor is built around the engine and appears to be a huge job just to check the bottom end. I can take the head off but once i start it may as well be a rebuild which I dont want to do. Any advice to positively identify the knock is appreciated?
Engine Knock M4500DT
- Thread starter Fishfarmer
- Start date
I have an M4500 with the same engine S-2600A and it has 2400 hrs on it. I have had it for several years and put on about 200 trouble free hours. When did you notice this "knock"?
If the rod is knocking, its frequency will increase with rpm. Is that the case?
The puff of smoke when you rev the engine is just excess fuel that isn't burned as the engine speeds up.
Can you tell what cylinder the knock is on? If you can, then switch the injector from that cylinder to the farthest one away from it and see if the knock follows the injector. If it does, you have found your problem.
Your tractor was made in model years 1978 - 1985.
Diesel engines of that era are much noisier than ones 30+ years younger.
JerryMT gives you good advice.
Dave
Diesel engines of that era are much noisier than ones 30+ years younger.
JerryMT gives you good advice.
Dave
I recently did some work on a D600 and found that by cracking the fuel fitting at the top of an injector slighty, it would reduce fuel to that injector and cause a rod-knock-like sound. This is how I could tell if a cylinder was running right: at idle, crack each injector one at a time and see if the knock comes, then tighten to remove the knock. (it is like pulling a plug wire to that cylinder).
In your case, you may find that one cylinder makes no difference...that would be the knocking culprit. If so, then swap injectors with another cylinder and see if the knock moves...if the knock moves then you have a clogged or failed injector.
btw a paint flake caused one of my injectors to clog at top and cause knock.... I used the above procedure to find the problem...... grrrr that stupid grey-blue flakey paint....beware if you do work on the engine!
In your case, you may find that one cylinder makes no difference...that would be the knocking culprit. If so, then swap injectors with another cylinder and see if the knock moves...if the knock moves then you have a clogged or failed injector.
btw a paint flake caused one of my injectors to clog at top and cause knock.... I used the above procedure to find the problem...... grrrr that stupid grey-blue flakey paint....beware if you do work on the engine!
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Thanks guys I will try moving the injectors around. i have had a fuel leak at injector on number 6. So its possible it is this.
I thought i fixed it because it looked like only the return line was leaking. I also have a leak at the fuel to injection pump bleeder which i thought I had also fixed. Turns out either could still be leaking, the side of the tractor has diesel over it again so I am not sure if I have fixed one, or no leaks yet. The knock became a primary concern for me instead. It does seem to come from number 6 ( the one been leaking) I will try the screwdriver stethoscope and swap 1 and 6 injector to see if the sound moves. I notice the welsh plug has been changed once before on 6. Its usually the hottest cylinder on anything but the tractor runs cold, which is probably a bad thing, I am guessing the thermostat has been taken out. ( cooling system runs perfect otherwise) Jerry the frequency increases with revs but the sound doesn't get any louder if that makes sense, rev it and the tappets drown it out but it is still there. It could have had a knock from the beginning when I bought it. Only getting used to the sounds now. Oil was black in the transmission so gave it the oil changes and after that it had hydraulic linkage problem which I addressed in my first post. I did realize the white puff is unburnt fuel thanks, just putting info I had out there for diagnosis. Maybe this is caused by the bad injector. I hope it is only that that is the problem. Can they really sound like a rod knock ? Its not a loud knock but its there, loudest at idle, but maybe I should say clearer sound of it when the valve train is running slower and not as loud. The rail is very clackity clack.
I thought i fixed it because it looked like only the return line was leaking. I also have a leak at the fuel to injection pump bleeder which i thought I had also fixed. Turns out either could still be leaking, the side of the tractor has diesel over it again so I am not sure if I have fixed one, or no leaks yet. The knock became a primary concern for me instead. It does seem to come from number 6 ( the one been leaking) I will try the screwdriver stethoscope and swap 1 and 6 injector to see if the sound moves. I notice the welsh plug has been changed once before on 6. Its usually the hottest cylinder on anything but the tractor runs cold, which is probably a bad thing, I am guessing the thermostat has been taken out. ( cooling system runs perfect otherwise) Jerry the frequency increases with revs but the sound doesn't get any louder if that makes sense, rev it and the tappets drown it out but it is still there. It could have had a knock from the beginning when I bought it. Only getting used to the sounds now. Oil was black in the transmission so gave it the oil changes and after that it had hydraulic linkage problem which I addressed in my first post. I did realize the white puff is unburnt fuel thanks, just putting info I had out there for diagnosis. Maybe this is caused by the bad injector. I hope it is only that that is the problem. Can they really sound like a rod knock ? Its not a loud knock but its there, loudest at idle, but maybe I should say clearer sound of it when the valve train is running slower and not as loud. The rail is very clackity clack.
M4500 with a 6 cylinder engine should be quieter than a 3 or 4 cylinder engine & if it operates any where near as quiet as the 5 cylinder engine that the M4900 I'll bet it was quiet before the "knock'. I suggest to check for a faulty fuel injector. I would 1st utilize some fuel conditioner labeled as inj cleaner.
Thanks Jim, I have looked at the injector cleaner products. I bought some already but it was only standard injector cleaner to be added to the fuel in small amounts. I put some in my truck tractor and excavator. I see the diesel purge product is designed to be used instead of fuel. One we have here is liqui moly. It is to be used directly and bypass the fuel line. Apparently it quietens things down after about 15 mins while it is purging. Is this what your talking about ? If the noise goes away while purging it cant be rod knock and must be the injector.
I'm not familiar with the product referred to as Purge. Have you considered having suspected injector "pop tested"? Leaking return line should have no affect on how engine sounds when operating. Another alternative to screwdriver as a substitute for a stethoscope for noise detection location is a wooden dowel rod
…. “of EQUAL displacement and in similar installation and service.”…. is implied in that statement, I’m sure.
You cannot compare a 6 cyl diesel in industrial service with a 3 or 4 cyl diesel in a compact tractor, for example.
Diesel purge is supposed to clean injectors and the fuel system with great reviews, but I have my doubts about it. You mentioned fuel cleaner so I thought this is what you meant by Inj cleaner ? It may be okay in some circumstances but my tractor starts perfectly and runs without missing, I don't think its miss firing at all. The valve train is very clackity and the purge is supposed to quieten it when you run it through. If the knock dies down it isn't rod knock. I have just listened to some you tube of injector nailing and it is possible it is that. It does sound top end but when I move around listening I cant be sure. Thanks for the tip about the dowel. Its probably a better stethoscope than the large screwdriver. If I can locate the sound more closely which I think is number 6 and I swap injector with number 1 it should tell me if the sound definitely changes. Otherwise I am possibly looking at rod knock and I will try to feel for piston movement test if I can get to the top of the pistons with the injectors removed. That's is if all other methods fail to eliminate if its rod knock.
GeoHorn
M4500 has 49 pto HP & a 6 cylinder engine. Tractor manufacturers make 4 cyl engines with a lot more HP than 49 PTO. So please explain your statement because I wasn't comparing a 6 cylinder engine in industrial service to an engine in a compact tractor.
replied most of your question next post next post but answer to return line I fixed it but it may not be leaking from there, diesel is over the RH side of the tractor again which could be the fuel bleed still leaking or it may be leaking at the injector itself. Its not leaking at the injector pump line connection. I have not looked at pop testing. Will look at that thanks
That’s what I SAID, Jim…. My statement is self-explanatory…and only clarifies the one you implied.
kubotafreak
Well-known member
Equipment
GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
My thoughts are like TX-JIM.
If you don't have metal shavings in the oil, then more than likely you have an injector hitting at the wrong time. The older diesel poppet style injectors can absolutely make knocking noises themselves, and cause piston slap/rod knock ping due to popping off at the wrong time. The injectors have a spring and shim, that determines seat pressure. This seat pressure(supposed to be equal) will affect overall injection timing of that cylinder.
If you don't have metal shavings in the oil, then more than likely you have an injector hitting at the wrong time. The older diesel poppet style injectors can absolutely make knocking noises themselves, and cause piston slap/rod knock ping due to popping off at the wrong time. The injectors have a spring and shim, that determines seat pressure. This seat pressure(supposed to be equal) will affect overall injection timing of that cylinder.
6 cylinder is inherently smother than 8, 4. or 3 due to geometry. 3 cyl is worst of the lot. This causes parts to vibrate and rattle.
Valve train noise per cyl is same for all (if same technology compared i.e push rod or OHC or 4 valves or 2 valves).
Valve train noise per cyl is same for all (if same technology compared i.e push rod or OHC or 4 valves or 2 valves).
When I first bought the tractor I did complete oil changes. I noticed metal shavings in the transmission oil (probably never been changed which was black) filter which I read to be normal. I read it was almost impossible for engine oil to be in the transmission. Shavings couldn't be from engine bearing or would have blown up already. Did not check engine oil for shavings when I changed it. Would this be in the sump or filter or both? Will change it again and check. If it is bad timing like you say, can I crack the feed line to injector causing the problem would the noise go away or is it best to change them around as JerryMT stated and follow the knock ?
kubotafreak
Well-known member
Equipment
GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
Haven't worked on many tractors with black hydraulic/trans fluid. Most are clear fluids with cloudy being water ingress. Maybe some poor farmer put used engine oil in it. Metal shavings on the trans filter magnet are somewhat expected(no chunks). The engine oil will have a glitter to flake type metal particles if the lower end is knocking. But as we assume the lower end is more than likely fine, and you have an injection problem.
You mentioned white smoke. That could mean low compression/bent rod/piston/water in fuel issues. A compression test would eliminate this. Might try removing the lines from the engine. Crank the engine, and check that the injection pump delivery valves all appear to jet the same amount of fuel. If this checks out, I would suspect injectors. White smoke on a warm diesel isn't good to see. I always suspect compression when I see this...I know this is many options, but something on this list will stand out, and you can interrogate that once you eliminate some things.
Russell King
Well-known member
Lifetime Member
Equipment
L185F, Modern Ag Competitor 4’ shredder, Rhino tiller, rear dirt scoop
Have you verified the valve clearances or not. I think you mentioned tappet noise and knocking noise. Valve clearance adjustment may reduce the tappet noise but would do nothing for the knocking (as far as I understand the operation of a diesel).
You could be right about compression, the engine turns over easy. It fires up easy as well. At first it didn't want to start, white smoke billowing and eventually it would start on the second battery. I thought some glow plugs were gone. It turns out there was no power to any of them. I thought some must have been working to start at all ! As soon as I got power to them it starts easy. Maybe too easy, it doesn't seem to have the resistance which my 4 cylinder excavator feels like when turning it over, you can hear the compression on it as the battery takes up, before it starts. The tractor seems to turn over too easy, yet it seems to have enough torque when doing work. Maybe because its a 6 cylinder Vs 4 cylinder excavator with same HP. I only want to slash 5 acres every 4 months so I wont be doing anything hard for it if the engine is tired anyway. The white smoke is only a small amount just noticeable when I hit the revs.
I was going to buy a cheap compression tester anyway. ( not the ebay cheap that don't work) I am told to make sure it has a Schrader valve and then it should give a good readout. Thanks I will do oil change and report back on any metal in it. Need another week my daughter and grandson visiting for school holidays.
Thanks Russell i haven't done the valves yet, I will be taking the rocker cover off anyway because I can't see the valve decompressor which its supposed to have. Maybe someone has taken it off, I don't want a runaway engine. You are correct, it will quieten down the engine but wont satisfy a knock. Other are saying its the injectors. I hope so, common sense place to start.