Motor Running - Knocking like hell

[Cowracer]

Just as review, remember that I had a coolant leak in the drivers head, that hydro-locked the engine during starting.I checked deck heights on the 4 pistons, and as far as I can measure with my lashed-up rig, they were all within 3/10,000ths of a an inch. I figure that nothing is bent or broken.

I got the replacement head on the truck, and it runs. But it knocks on the #1 hole.

This is what happens..

When I start the truck cold, it has a miss and spews white smoke (unburned diesel). After a minute or two, the truck warms up the miss goes away, and is replaced by a bad knock. The miss and knock are definatly on cyl #1 which is where my motor hydro-locked with the coolant leak in the head. If a crack the injector line, the knock goes away.

I first thought it was a bad injector. I relaced it with a new one, with no results, I put the original #1 into #3 and the knock remained in #1. Other than the knock, the motor runs good, has good oil pressure, and everthing else seems ok.

In reading some other posts, I got to thinking that maybe I had the #1 and #3 injector lines crossed. I pulled the intake last night and no luck, all injector lines are in the proper order.

I am 99.9% confident that it is NOT a rod knock or other mechanical thing. To me, it seems like a combustion knock. Like the timing is way out on #1.

My question is...

Could hydro-locking the #1 hole have affected my injection pump? I am sure that the cyl P.S.I when it was locked was pretty high, could that pressure bleed back into the I.P. and hurt something? Or could trying to inject fuel into the high P.S.I. of a hydro-locked cyl damaged something.

I've spoken with Jamie, and he is checking with his pump expert, but I thought maybe one of you pump guys might chime in here.

Thanks!
tim

[rjschoolcraft]

Probably not what you want to hear, but I would bet wrist pin with resultant piston slap.

[john8662]

Any chance you have a bent push rod?

Perhaps the head gasket that was on the engine originally was the .010 thicker gasket and now the gasket is the standard thickness gasket?

I've been told that you can lose one cylinder via a poppet valve with the DS4, but since you can loosen the injector and the knock quits, I suspect you're getting fuel. Want to give us an audio recording?

[More Power]

Hydrolocking or ingesting a glow plug tip can produce a bent or even broken piston skirt. This then results in excessive rocking motion of the piston while traveling up/down the bore, and is more pronounced when firing on the cyl.

Was that cyl the one that hydrolocked?

Jim

[tom.mcinerney]

J.B.:
>>The miss and knock are definatly on cyl #1 which is where my motor hydro-locked with the coolant leak in the head. If a crack the injector line, the knock goes away.

Tim--My first read of your post , I'm thinking, 'ahhh, lost his mind, the hydrolock would've done it to mine too'.
Now thinking probably as suggested by Ron or Jim, but possibly a valve train issue, as John mentions. This valve train possibility didn't 'jump out' at me....However the hydrolock would massivly multiply the effort required to open the exhaust valve if it cranked through the full compression-to -power stroke. Further, the resultant--lower compression and retarded combustion, matches the symptoms. Not sure what would happen to the intake if the crank flexes and rebounds??

[Ignoring your protestations against mechanical problems],if one cylinder is missing at startup , it probably has lower compression, or some water in the cylinder. A compression test of neighboring cylinders may show something useful. Water might be present if the hydrolock cracked the cylinder. The 'steamy start, then run' deal is characteristic of a leaky head gasket, cracked block or head. The gear-reduction starters on these engines should be able to do some damage....

Your combustion knock theory is interesting. I've never bought the line of thinking, but hydrolock conditions might be just the thing to make the exception . I don't know how to test short of swapping in a known 'good' pump.

Other unmentioned possibilities: cracked piston ring/land , or a cracked crankshaft(causing low compression , and slightly retarded timing).

John's suggestion of an audio might help, but {as i've whined previously} an oscilloscope trace would be much nicer...easy to see that all the rattling is equally spaced (or not) and similarly shaped (or not) and of comparable amplitude (or no).

Godspeed in your troubleshooting , and thank god we don't have to negotiate IEDs here.

[Kennedy]

Did you let the coolant sit in the ring grooves?

I'd "glass plate" the pushrods as mentioned above along with checking the rocker shaft for breakage/bending. The shafts can crack at the bolt hole. Testing the injector or swapping to a different hole would also be a good idea. A compression check or better yet leakdown test would also be a good place to start.

[tom.mcinerney]

Good thinking, John.
Tim the rocker shaft check needs to be thorough (magnaflux) if it seems only to be valve train problems.

Your (Bennie's??!) engine really is a candidate for a thorough leak-down test. Dr Lee said they're the definitive deal.

Good Luck.

[autocrosser]

I you loosen the injector line does the knock change in sound? That would indicate a problem associated with combustion pressures in the cylinder. If it's a wrist pin you may hear a double knock as in a gas engine but the engine combustion noise might drown it out. If the skirt is broken as More Power suggested it may get a little quieter due to non combustion but there will still be compression so that won't totally eliminate it. Removing a injector and cranking it is another option but again the noise mite confuse the issue. I'm not sure what backing off on the rocker nuts would result in.

[patrick m.]

my vote is broken piston skirt, unless the 18:1 pistons you have are skirtless, as many new piston designs are.
really doubt they are skirtless, except for the inboard skirt on number one :mad:

[5.7L oldsdiesel]

It's my understanding that if you loosen the injector line fitting and the knock goes away,its a rod bearing knock.If the knock still exists after killing the fuel to that cylinder,then its a wrist pin knock,because its piston interia which causes the noise,which is why the noise does not go away when the fitting is loosened.I read this information in a textbook from an automotive college,so i thought i would throw this information along.Interesting though on how coolant got in there.