CUCV Detonation? - Knocking Noise

[Castle Bravo]

The vehicle is a 1986 M1028 that is mostly stock. I have done the Doghead mod and I have bypassed the resistor and taken 12v directly off the bus above the glow plug relay. I have AC60G glow plugs.

I recently was stranded by dead glow plugs. I got the truck home and began to work on it. Each glow plug had no continuity and I could not get a reading of the resistance through them. (OL on the multimeter)

Deciding those glow plugs were dead, I got some AC Delco AC60G glow plugs and some 1/4" spade connectors. I removed 4 of the old glow plugs without any problems. The remaining 4 were swollen and would not come out by hand. I borrowed the JJ And A Racing glow plug remover tool from a buddy and used it to remove the others. I squirted a bit of WD40 onto the thread area of the glow plug hole to lubricate it so the swollen glow plugs might come out easier. I didn't have to put a socket or wrench on the tool to get the swollen glow plugs out, they came out with finger strength. No bits of pieces seemed to be missing from any of the swollen glow plugs. Thinking maybe WD40 wasn't the best thing to use, I left the glow plug holes open overnight so maybe it would evaporate out.

The next day, I put the new glow plugs in, installed the new spade connectors and fired the truck up. It started great, but now has a tapping/knocking sound. I shut it off and started it again and it has the same noise. I feathered the throttle a bit and the noise followed the RPMs. I took the glow plugs out and they are undamaged. I disconnected the pink wire and cranked the truck for about 30 seconds to see if I could "blow out" anything. I put the plugs back in and started it again with the same tapping/knocking noise. I tried to listen to see if I could figure out where it is coming from, but I can't locate it specifically.

---

Did I detonate the WD40 in the pre-combustion chamber and bend a rod? Did I hurt an injector? What is my next step?

 

[BIG_RED]

Did you get 8 entire glow plugs out of the engine, or is there a chance a part of one is still in there?

 

[uscgmatt]

I would think your alright as to the wd40. The propellant is what has the best chance of going boom. And overnight it should have cleared enough.

 

[jeffhuey1n]

Odd, WD-40 never messed up my engine and I use the daylights out of it. Couldit have caused damage? I can't answer that, diesel engines are not my area of expertise. I'm more of a turbin engine kind of guy. Try this: pull all the plugs again. Insert a small magnet (the kind that looks like a pen...sometimes the little inspection mirrors have one) into the open chamber; it may catch whatever is in there (assuming something is in there). Check all the chambers. A scribe with the 90 degreebend is good at finding stuff too, just takes patience. If none of that works and nothing is found, go to the next step. Get a long metal tube, wood works too. It needs to be thin enough to reach most of the engine and long enough as well. Basically your making a stethascope (sp?) for engines. Put one end on each cylinder location and poke around until you find the noise. Don't check the fan using this method unless you need saw dust. by the way, wood works best just for that reason and you can't get electrocuted by it either. That's all i can advise with what you've provided. hope it helps.

 

[M1008driver]

I thought they always rattled until they warm up...most of them anyway.

 

[Castle Bravo]

Did you get 8 entire glow plugs out of the engine, or is there a chance a part of one is still in there?

I am 99% certain I got all of all 8 glow plugs. 4 came out without any problems and appear the same size as a new one. The other 4 have very small bumps on them, but don't appear to be missing any material.

Odd, WD-40 never messed up my engine and I use the daylights out of it. Couldit have caused damage? I can't answer that, diesel engines are not my area of expertise. I'm more of a turbin engine kind of guy. Try this: pull all the plugs again. Insert a small magnet (the kind that looks like a pen...sometimes the little inspection mirrors have one) into the open chamber; it may catch whatever is in there (assuming something is in there). Check all the chambers. A scribe with the 90 degreebend is good at finding stuff too, just takes patience. If none of that works and nothing is found, go to the next step. Get a long metal tube, wood works too. It needs to be thin enough to reach most of the engine and long enough as well. Basically your making a stethascope (sp?) for engines. Put one end on each cylinder location and poke around until you find the noise. Don't check the fan using this method unless you need saw dust. by the way, wood works best just for that reason and you can't get electrocuted by it either. That's all i can advise with what you've provided. hope it helps.

To me, this doesn't sound like something is on top of one of the pistons, but this is the first time I've encountered this. I'll see if I can localize the sound.

I thought they always rattled until they warm up...most of them anyway.

This is definitely a new noise.

 

[that1028guy]

I had the same thing happen to me, a glow plug let go while driving the truck and bounced around in the cylinder before disappearing out the exhaust, I suppose I was lucky enough everything was hot and maluable. It mushroomed the top of the piston just enough to make contact with the head. (Something to remember about a pre combustion chamber diesel is all of the compression takes place in the pre chamber. So the head to piston clearance is nil.) I had a nice little metallic clack that was rpm related after that.

 

[mistaken1]

Harbor freight has mechanic stethoscopes cheap/

 

[sandcobra164]

Mine used to do that from time to time. I feel like you have an injector sticking open. An older gentlemen advised me to pour about 2 gallons of fresh 15W40 in a tank of fuel. Between that, some 2 stroke oil, and some PS Diesel Kleen, it doesn't do it any longer. I've got AC 60G's installed and resistor bypassed as well but those changes aren't relevant to the issue if all the old swollen ones came out without breaking.

 

[Castle Bravo]

Harbor freight has mechanic stethoscopes cheap/

I have one, I'll listen to hear what I can find out.

Mine used to do that from time to time. I feel like you have an injector sticking open. An older gentlemen advised me to pour about 2 gallons of fresh 15W40 in a tank of fuel. Between that, some 2 stroke oil, and some PS Diesel Kleen, it doesn't do it any longer. I've got AC 60G's installed and resistor bypassed as well but those changes aren't relevant to the issue if all the old swollen ones came out without breaking.

I will try that. Its something I've meant to do (Put some oil in occasionally) but haven't yet.

 

[Goose2448]

Check your oil level. I have a leak on my work truck, and when it gets a little low she starts knocking like there is something in the cylinder and its about 2 quarts low. Also run 1 oz per gallon (of diesel fuel) of auto trans fluid (injector cleaner), 2 stroke marine oil (lube), and DieselKleen (all that and a bag of chips).

 

[Blue2actual]

It sounds like most of the advice should/will cover what the problem is. Have you checked the operator level stuff the TM says to do? i.e check exhaust system, alternator mounts/brackets/belts, motor mounts? I looked in the TM for your symptoms and the troubleshooting it lists doesn't sound like it would fix your problem, but it is worth a shot I guess to try and eliminate stupid first. I Hope you find the source. I'm interested in finding out what it winds up being.

 

[Castle Bravo]

Check your oil level. I have a leak on my work truck, and when it gets a little low she starts knocking like there is something in the cylinder and its about 2 quarts low. Also run 1 oz per gallon (of diesel fuel) of auto trans fluid (injector cleaner), 2 stroke marine oil (lube), and DieselKleen (all that and a bag of chips).

Will check.

It sounds like most of the advice should/will cover what the problem is. Have you checked the operator level stuff the TM says to do? i.e check exhaust system, alternator mounts/brackets/belts, motor mounts? I looked in the TM for your symptoms and the troubleshooting it lists doesn't sound like it would fix your problem, but it is worth a shot I guess to try and eliminate stupid first. I Hope you find the source. I'm interested in finding out what it winds up being.

The -34 TM has a few things I am going to try.

 

[rickf]

Couple of ideas, I have seen a lot of 6.2 and 6.5 lifter problems. Mine has one that will tap like **** sometimes. Very seldom it will lose power on the one cylinder. I have just been too lazy to change it, I do not drive the truck that much any more but it has been that way for many thousand miles. The other problem I had which caused a knock that sounded so much like a rod knock that I changed the rod bearings right after I got the engine. One of the injector lines had gotten bent and that caused enough change in timing to knock like a rod. New line, no knock. Are all of your vibration dampers on the lines?

Rick

 

[Castle Bravo]

Couple of ideas, I have seen a lot of 6.2 and 6.5 lifter problems. Mine has one that will tap like **** sometimes. Very seldom it will lose power on the one cylinder. I have just been too lazy to change it, I do not drive the truck that much any more but it has been that way for many thousand miles. The other problem I had which caused a knock that sounded so much like a rod knock that I changed the rod bearings right after I got the engine. One of the injector lines had gotten bent and that caused enough change in timing to knock like a rod. New line, no knock. Are all of your vibration dampers on the lines?

Rick

I'll check that stuff out.

I turned the truck on, let it idle for about 10 minutes. After about 5, the noise went away. I went and fueled it up and it never made the noise again during the trip. I will see if the noise comes back tomorrow when the motor is cold.

 

[1 Patriot-of-many]

There's a reason a mechanic called my truck a rattler just asking for a quote on service. It's normal. In fact I'm thinking of getting some stencils and painting "Rattler" on mine as a name.

 

[M1008driver]

I turned the truck on, let it idle for about 10 minutes. After about 5, the noise went away. I went and fueled it up and it never made the noise again during the trip. I will see if the noise comes back tomorrow when the motor is cold.

I still believe this is normal. Tonight I started my truck cold and it sounded like a lifter rattling. As soon as the truck warms up it goes away. I've seen many trucks do this in my day and none of them blew up on me.

EDIT- It is a Chevy.

 

[rockspider]

I believe the noise is due to the hydraulic lifters being old and worn, and thick cold oil doesn't help either. In winter the engine is much more rattling and knocking in the first minutes of idling than it is on warmer months.

 

[rickf]

You are aware that the timing is advanced along with the idle raised during warmup aren't you? The advanced timing will cause a louder than normal rattle but only during warmup. If it is after this time period then there is a mechanical issue and if it is intermittent I would lean towards the lifters. They are roller lifters so you can interchange from another motor if need be. They are not like flat tappets that wear into the cam and have to be kept matched to that lobe.

Rick

 

[Hasdrubal]

I didn't know 6.2's had roller lifters. Is this accurate info?