Engine/Transmission (1994 - 1998) Got a new 12v truck and has a knock??

[MLee]

your streatch

I stretched the overflow spring (it was a little less than 1/2"). Truck does seem to run a lil better but have the same noise. It has not got any worse or better stays about the same. Any lift pump better than the other? I would rather get a good one the first time then have to buy another next year. Any sponsors want to sell me one? PM ME!

The proper length of stretch on the over flow spring is-. 05. 5", just a hair over the 1/2" mark.

Geno's has the best price on the transfer pump. [lift pump] As stated, these pumps are bullet proof.



Unless you decide to do a Fass set up.

 

[JCurry]

The noise is the same in any gear that i am in. Thanks for the rubber hose suggestion i will try that tomorrow afternoon. I have an airdog on my other truck but wanted to keep my 12er close to stock as i can. Thanks for all the suggestions!!!!

 

[CodySanders]

i disagree with the knock getting worse real quick. i burnt a piston on my 06 and towed a trailer home (26k) almost a 1000 miles. the knock stayed the same and i had to pull the motor anyway and fix it all better to do at home. if it is a steady knock and gets louder with higher rpm it is probablly a burnt piston. i burnt a hole in number 1 but that was due to a stuck open injector. number 5 or 6 usually is the one that gets melted. please let us know what you found. i was hoping for the same thing you are something easy but it usually is not that way.

 

[JCurry]

What are other symptoms of a burnt piston? Did you have any loss of power? How can i check to see if it is infact a burnt piston without pulling the head?

 

[MMiller]

Excessive blow by, blowing out the dipstick from too much blowby, cutting open the oil filter and finding aluminum schrapnel.



Michael

 

[tgordon]

At the risk of sounding stupid (whoops I already opened my mouth) do you have a more noticable smell of diesel fuel in the oil with a burnt piston?

 

[kenny61]

I would think so. no compression fuel aint burning should have a miss too. probaby could adapt an airhose to the injector port and see if it holds pressure or its blowing out the breather bar engine till both valves are closed

 

[MMiller]

You could also get extra fuel in the oil if the lift pump is bad.



Is this truck turned up real hot? Is it bone stock? I can see a scored hole or piston if its a real hot rod, or if its been worked within an inch of its life.



I'm just saying its far easier and cheaper to throw a lift pump at it to see if thats the noise you are hearing. Do you have an old school stethiscope for working on engines? You can let the engine run and listen around until you locate the area the noise is exactly coming from. You could also put a long screwdriver up to your ear and put the tip on the engine, but its not as easy.



Michael

 

[JCurry]

The truck is stock but it could have been turned up before i had it. When i got it, it didnt even have a hitch on it and had a hole in the bed probably from a stack. I have no idea if they hot rodded it or not. I will check for blow by and ordering my lift pump on monday when i get paid. The dipstick does not blow out but i will check @ the fill cap and see if its bad. Im takin the truck on a 350 mile trip in the mountains this weekend so it better hold up LOL.

 

[JCurry]

Just took a load with the truck. It has very little blowby cold or hot. I compared it to my 24 valve and it seems the 24v has more blowby than the 12 does! The 24 has about 40k more than the 12v does so maybe thats why. I guess that is a good thing? When i checked my filters last oil change there were no metal shavings in it at all. Does a bad piston ALWAYS have blowby or could i still have a bad piston even though i dont have any? Wish i had the lift pump already... I CANT SLEEP AT NIGHT haha
Thanks for all the help!!!

 

[kenny61]

You could have anything. a holed piston will cause all of the above plus a miss because the truck will be down a cylinder. From what I gather the truck is running good but you have a noise. This could be a bunch of things up to a rod bearing which will eventually let go and will probably blow a hole in your block. I. m not a parts changer but with the long distance diagnostics it hard to tell what is wrong . Get the new fuel pump in the truck and let us know what happens. I would not recommend driving the truck until you find the problem, at best you can get stuck at worse your engine will become a very large paperwieght

 

[JCurry]

Well just got back and i made it. I hate to risk it but i have to use it for work. It never got worse after driving another 500 miles this weekend. One thing i did notice was that going down a hill where there is no load on the engine, it gets quieter, if i let off the throttle completely, you cant hear the knock/tap at all. It gets louder the more load on the engine. Does this sound like a lift pump or does it sound more like a rod bearing? I have put 2778 miles on the truck since i bought it, i would think if it was a burnt piston i would atleast have some blowby by now? I have got a hose and it seems the noise is coming from the driver side bottom of the block between #5 and 6 cylinders.

 

[tp0d]

I think you need to find someone else with a 12v and go for a ride...

Also think your lift pump is fine, if you have good power. The lift pump will tick, not knock. A waste of money changing it in my opinion. These things dont fail like the 24v's pump

If you had piston damage, you would have some pretty good blowby.

Find another truck local, and compare.

good luck

-j

 

[ata]

I'll still bet on a hurt piston. What happened is somebody got that engine real hot. (water temp) The piston expanded and SCORED the skirt. Now it drags on the cylinder wall tipping the piston making a knocking noise. The more load on it the harder it tips the louder the knock. There will be no metal in the filter. no blow-by, no miss, and no loss of of power. It will run like that for ever as long as you DON'T OVER HEAT IT AGAIN. Like I said before CRACK the injector lines at the injectors one at a time. The noise will almost go away when you open the right one and you'll atleast know which cylinder to look at. My 0. 02 cents.

 

[JCurry]

ATA: Thanks for the tip, i will try cracking injector lines in the morning. If that is what is happening, why would it not do it when coasting down a hill with no throttle? I am not doubting you, i just think it would do that running all the time, load or not? I am no expert just trying to get all the advise i can. When i do find what cylinder is causing my problems, is there any way to find exactly what it is that is causing the "knock"?

 

[ata]

When coasting you are not loading the piston. So the piston is floating in the cylinder. No heavy load on it to make it drag and rock in the cylinder. There will still be a knock but it will light when you crack the injector line. It will be better to warm the engine up and then test it. Other then pulling the head and or piston there is really no way to tell the exact cause. But I would bet something is wrong with the piston skirt. It takes vary little damage to the skirt to make a piston knock.

 

[KnightR]

What price all this glory. I remember when I put used pistons in my flathead engine on Saturdays for something to do. Held the record in West by GOD Virgina for out and in by myself including removing the hoods. My 70 Blazer (I bought new) over 250K miles and still does'nt use oil. Got to be a happy medium for all this Diesel glory. Just have a hard time figuring it all out. Of course I could complain about the wifes new VW I opened the hood and ... ..... ? Just closed it when I seen they had put the engine in the wrong way.

 

[JCurry]

Been working alot and havent got to try cracking the injectors yet. When i leave for work its too cold to crack them and by the time i get off work its too late. I did change the fuel filter just to see if it would help, AND IT DID. I can barley hear the knock now! It is about 1/4 of what it used to sound like. Only problem now is that after changing the filter it seems to be low on power and the idle wants to go drop to 400 rpm and then it goes back up to 500 rpm. It didnt do that before the change, it used to idle fine at 500 rpm. I ordered an overflow valve just to keep on hand. Do you guys know if this could be an overflow issue? I have friday off so im gonna try cracking injectors then and see what i come up with. Does anyone sell a tapped banjo bolt for the 12v trucks for putting in a permanent fuel pressure gauge? Thanks for all the help guys!

 

[Diesel Fever]

I believe this is what you're looking for as far as the banjo bolt goes.



BANJO BOLT - TAPPED ('98. 5-'09, 5. 9L & 6. 7L 24V) DODGE-Dodge Cummins Diesel Truck Accessories - Geno's Garage





It will work on the 12v's so don't let the 98. 5 scare you. I believe the reason why they post 98. 5 is because it is more crucial to have a permanent FP gauge on a 24v, than a 12v. Just remember the replacement gaskets and replace the CLEAN fuel line banjo bolt with this one. Good luck.



Best Regards.

 

[ata]

For one thing your idle RPM is way to low. Bring it up to 800, 850. Being low on power after changing the fuel filter sounds like you might be sucking in air. Check your Geno's catalog they use to have a Bango Bolt that was drilled and taped.