knock knock knock...

[bjowett]

I'm sure at least a couple of folks here have blown an engine, so maybe you can tell me what goes wrong with these big sixes and why. I started my truck up today and itsa knockin'... :-[ goes away in roughly five minutes, or as the temp gauge starts read/climb. Normally I would think a rod that knocks would get worse as the engine heats up. Soooo.... Piston slap? I did run a couple of bottles of injector cleaner through it in one tank recently.

Have at it.... should I start building my 4.? from the spare engine?

 

[landtank]

I'd start with a compression test. Pay particular attention to #6. The HG seems to fail there and as the engine heats up maybe it's compensating for it.

 

[Junk]

bjowett, is it worse under load? I could hear the piston slap with mine really bad if in D as I would start to depress the go pedal.

 

[cruiserman]

I'm guessing piston slap, but get a definitive diagnosis before tearing into the motor. At least find out where the noise is located.

Robbie's got some experience with piston slap. I would talk to him about it.

 

[IdahoDoug]

What's the status of your oil? Honestly, if it were my vehicle and something like that cropped up I would IMMEDIATELY change the oil, and save the filter to be cut open if needed to help me diagnose it. There have been a lot of strange oil gelling issues lately and if this happens it will cook your engine even if the dipstick says full.

Also, you have omitted some key information here in addition to the oil's condition. What's the oil pressure guage doing (details)?

DougM

 

[landtank]

Piston slap? I didn't think that was all that common. I was thinking along a detonation problem. My gasket's #6 cylinder sealing ring was deformed and carbon covered and thought a similar condition might give a knock.

 

[bjowett]

Will do the compression check, amongst other things.

The noise is much lighter during RPM increase and load. To reiterate, Gone after 5 minutes from a cold start.

The super duper hi-tech screwdriver listening device places the noise towards the rear of the engine, down in the block.

The oil has about 500 miles on it, 5W40 Rotella Synthetic, still clean and golden. FYI, filter is a large Motorcraft/Purolator FL1A, it has the proper bypass pressure and drainback valve along with an excellent filter media.

Oil pressure is excellent via the gauge, always has been.

My thoughts lead towards the double dose of injector cleaner breaking some carbon off of the the hot #6 piston rings lands and skirt. I'll probably pull the number 6 plug wire to verify. Also, no skips, misses, roughness... nice and smooth. All the coolant is where it belongs.

 

[robbie]

Hello Brain:
I would pull the oil filter and replace it and see what is inside when you open it up. If you have both Iron (attracted by a magnette) and non ferrous material then my guess is piston slap. What may cause this, the injector cleaner may of but my first guess is the fuel pump not keeping up with demand. The pump may be working but not keeping the pressure up when the engine needs it the most. Either the two speed relay is screw up or the pump is bad. You may need to hook a fuel pressure guage in line on the pressure side and see what pressure is. I did control lite piston slap for a couple of years with 5w50 castrol syntec and allowing the engine to warm fully all the time.
Have you done a head gasket recently? If so this may be from that, It happens.
Back to the fuel system, Plug injectors will also cause this expecially if the fuel pump is not up to the job. I have seen this happen on all piston bores (1-6) no one cylinder is exclesive to this, but I have seen #5 occur more.
Just as a side note I just worked on a 93 engine with 175kmiles on it with slight piston slap on #3, the HG needed to be done and coolant was inside the engine, very slight, but had coolant/ moisture stains on the pistons bores. That also can cause improper lubraction on the sides of the cylinders thus leading to scratches and removal of piston skirt creating piston slap.
Some more infromation is needed from you. Like others said, cut the filter open and see what material you have inside. Did this happen suddenly? How were you driveing the day before? How many miles on your truck?
Sorry to hear this. later robbie

 

[e9999]

BJ,
mine is making all sorts of noises. Sound normal to me, but curious, how loud is this knock of yours?
E

 

[IdahoDoug]

Couple things to think about:

It's recommended that you do the cleaner just prior to oil changes as it's highly corrosive and also loosens highly abrasive carbon deposits - some of which end up in your oil via normal blowby. If, and I say if, you have an injector that's leaky after shutdown and you double dosed it as you say, you may have ended up with significant amounts of this substance in the oil via normal leaking past rings after shutdown. This may have significantly deteriorated the oil's properties - especially when cold - and result in localized oil starvation.

Could it be more of a wrist pin sound from a cylinder that's not firing properly when cold, perhaps due to a piece of carbon getting loosened and whanging the injector tip enough to mildly distort it? At higher RPMs the increase in FI pressure masks it, but at idle the cylinder's not getting much/threshold fuel level and the normal slack in a wrist pin is now banging from a semi-dead cylinder? With normal combustion pressure on it, you'd not hear the movement. This same theory would apply to the main bearing on that cylinder.

What injector cleaner did you use?

The reason I suggested (and still do) an immediate oil change is that a friend bought a used Camry. He drove it for 2 years with faithful oil changes. One day he called me from out of town to say it was making banging noises. I recommended an immediate change. he checked it and it was full and elected to drive home. A total rebuild was the result. Turned out the PO wasn't as faithful on oil changes and thickened oil was getting loosened and accumulating here and there by his freeway trip. Starved a couple areas (banging) despite full oil and voila' - $3000 cost vs an oil change.

DougM

 

[bjowett]

I will check the FP, had no idea on the dual stage pump... Will also pull the filter and inspect.

The cleaner was run through just before the last change, Chevron Techron was used.

The truck sat for a good 6 weeks, during that time the gears/lift/tires were installed. I've only been driving it for a few days, been very easy on it to break the gears in properly and such.

The knock is pretty loud... not easy to miss.

I did not consider the wrist pin, very possible

I'll be happy if I can get this summer season out of it. The spare engine I have will get torn down and rebuilt.... MMMmmmmmm, over bore, ported head..... See, not all knocks are bad news.

 

[Pskhaat]

[quote author=IdahoDoug link=board=2;threadid=16423;start=msg157937#msg157937 date=1084694833]
What's the oil pressure guage doing (details)?
[/quote]

IdahoDoug, in this context what changes would you expect the oil pressure gauge to be doing differently?