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Drivetrain Tech General discussion of drivetrain for the Ford Ranger.

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Old 05-05-2014
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Piston Damage

So I recently bought a motor from a salvage yard to put into my 2002 ranger. My first motor dropped a valve at 85k miles and busted the block. The motor I bought came from an 04 ranger with 40k miles on it. They are both 3.0L v-6 engines. I installed the new motor, and upon start up I heard a knock coming from what sounded like the upper passenger side of the motor. After many failed diagnostics to pinpoint the cause, tonight I pulled off the head on the passenger side. The #1 and #3 cylinders are beat to heck...but not missing any pieces. The head in these areas are the same. I did not find any valve keepers or nuts or anything foreign in these cylinders. Anybody seen anything like this? I can't figure out what could have happened. Maybe the head was over torqued? I will try to post some pictures.
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Last edited by BlueDanger; 05-05-2014 at 11:28 PM.
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Old 05-05-2014
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Another picture
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Last edited by BlueDanger; 05-05-2014 at 11:25 PM.
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Old 05-06-2014
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Looks like it could have been caused by "pinging"(pre-detonation of fuel/air mix).

Google: images pre-detonation piston damage

Before total failure(hole in piston) the chewed up edges look similar to those of a piston that suffered from long term pinging.

3.0l was prone to pinging, if there was a vacuum leak and engine was run Lean for a long time without regard to the noise then what you see is the result.

I would pull the other head, it could have been a vacuum leak on that one side(lower intake manifold) causing a lean mix so other side might be OK.
Unfortunately it looks like a total rebuild in any case.
But you do have 5 good pistons from the other engine??

Pre-detonation comes from heat, lean fuel mix doesn't cool cylinder as much and also burns hotter, pinging itself also generates extra heat, so once it starts it is self perpetuating.
Why #2 wasn't effected as much could be it's position or injector or ??

EGR system lowers NOx emissions by cooling the cylinders, so EGR is an anti-ping device, lol, yes it is odd that adding HOT exhaust to cool fuel/air mix results in a cooler running engine, but that's what it does.

Last edited by RonD; 05-06-2014 at 12:37 PM.
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Old 05-06-2014
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Interesting. It does look similar. The damage is only where the head overlaps the piston, and none of the other surfaces (valves, plugs) show any damage at all. From what I am seeing it seems the damage is pretty uniform around the piston, and plugs and valves get damaged. Could be I just caught it prior to that much damage though I guess.

Another idea I have heard is that the motor was rebuilt with the wrong crank bearings. I didn't rebuild it, and it wasn't suppose to be rebuilt, but who knows. It'll be the last motor I buy online from out of state I'm sure of that.
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Old 05-06-2014
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Can't see it being anything else, foreign objects would cause more random marks and show on the valves, which you say are not damaged.

The "ping" noise is from the pre-ignition wavefront and spark plug ignition wavefront meeting, and that point is where it gets hottest and the damage occurs.

Shape of the head's dome and piston top would have alot to do with where you would see the damage.
From your damage description it reads like the area between piston and head was where the wavefront's were meeting, so damage could be localized to those locations.

Could be oversized connecting rod bearings, but that would be a stretch IMO, and wouldn't explain #2 with less damage, it would tend to be uniform across all cylinders.

Last edited by RonD; 05-06-2014 at 01:49 PM.
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Old 05-07-2014
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I pulled the head on the driver's side last night, and found the same piston damage on the middle cylinder. That makes it cylinders 1, 3, and 5 that are damaged. Cylinder 1 is the worst, then 3 then 5. 2, 4, and 6 show no signs of damage. Does this confirm that pre-detonation ping is the culprit? If so, what could have caused it? If I put another motor in is it going to ping too?
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Old 05-07-2014
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I would think so, can't think of anything else that would cause that piston condition.

Not sure about another motor, used is used.

I don't see a connection except for 1 and 5, these are "matched cylinders" so share the same coil, maybe coil resistance was higher and delaying spark enough for pre-detonation to start.
3 and 4 are "matched cylinders" so share the same coil, but 4 has no damage so????

I would pull the fuel injectors and number them, then inspect each one for debris in the pintle(removable plastic tip).
Ford fuel injectors should have approx. 14ohms between the two contacts.

Check the lower intake gasket for signs of an air leak at 1, 3, and 5
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Old 05-09-2014
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I checked the resistance on the injectors and they are within range. Haven't yet pulled them out for visual inspection. Intake manifold gaskets (upper and lower) were installed brand new when I put the motor in, and still look new so no obvious signs of air leak.

I have thought about several things that may be messing with the fuel/air mix ratio. I wanted to post them and get some feedback to see if they are things that could cause pre-detonation.

1. The vacuum line coming from the intake manifold to the EGR valve was dry, and when I removed it, it cracked into pieces. I replaced it with a series of fittings and random hoses with the intent of ordering the right piece to fix it once it was running. There could have been a vacuum leak here amongst the cobbled up hose.

2. The original motor dropped a valve seat. The piston pushed the valve seat into the head prior, causing coolant to fill up the cylinder. The motor was still running, with coolant coming out the exhaust pipe. There is no muffler, but it does have cat's which I did not change out. These could be restricting some exhaust flow. The truck ran great, other than the knock, so I wasn't planning to change them, but could this be causing the knock?
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Old 05-10-2014
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In the early 2000's the 3.0l's had a known issue of the valve seats getting recessed, so you were not alone, there were TSBs on that issue, basically it was to replace the heads with newer models.

I never read about a cracked head because of this but it could happen, so coolant would get into cylinder.


The EGR system was added to gas engines to lower the N0x levels, high N0x levels are caused by high ignition/combustion temperatures.
What the Exhaust Gas Recirculation(EGR) system does is to add exhaust gases to intake air but only when engine is under load, when an engine is under load the cylinder temp goes up, as odd as it sound the exhaust gases cool the cylinders, lowering the N0x emissions.
Since "pinging" is started by low octane or high temps, a non-functioning or mis-functioning EGR system would allow cylinder temps to climb too high and pinging would occur and start to cause damage.

The EGR valve often gets carbon build up in it's tube and the valve itself causing low flow, the EGR valve is controlled by the DPFE sensor and a Modulator, the EGR valve is hooked to the Modulator, the computer controls the modulator, them modulator is hooked to the intake's vacuum and to the EGR valve, as load on engine increases computer opens modulator which opens EGR valve, so EGR valve should not be connected directly to intake, unless modulator is part of the EGR valve assembly.

DPFE sensor reports pressure difference in exhaust manifold to tell computer if EGR valve is working.
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Old 05-10-2014
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The top end knock was loud enough for my wife to hear it inside the house while I was working in the driveway immediately upon me first starting the engine. This was not something that gradually came about...assuming the motor I bought was good to start with. The knock is loud upon start up, then quiets down as it idles. When I would start to drive around it would get louder as the rpm increase, but if I put some load on the engine it would get loud and stay loud, and the tempo of the knock would sometimes double. It was very weird. I idled the engine for maybe 2-3 hours total since install, and put maybe 3 miles on it. Also, If I removed #1 spark plug wire (the piston with the most damage was #1) the knock would almost go away.

I took all the valves out of the heads this morning to inspect for damage. Nothing noteworthy found. Just some carbon build up on exhaust valve stems.

Also checked fuel injectors again. All voltages read between 11.8 and 12 volts. They all look good to me. Could not find a "removable plastic tip" but they all look to be in good shape. I will attach some photos.

I mis-spoke about the EGR valve hose. The hose that I cracked and replaced with home-made parts is the PCV valve tube, not the EGR valve. Could a vacuum leak at this hose going straight into the intake manifold cause serious detonation?
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Piston Damage-img_0799%5B1%5D.jpg   Piston Damage-img_0801%5B1%5D.jpg   Piston Damage-img_0802%5B1%5D.jpg  

Last edited by BlueDanger; 05-10-2014 at 02:47 PM.
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Old 05-10-2014
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Yes, PCV valve hose is large so could/would cause a lean mix if leaking.


You have a connecting rod knocking, #1 cylinder from your report of noise lessening when cylinder wasn't firing.

When Connecting Rod bearing has loosened up, the knock "noise" comes from the cylinder firing.
What happens is the crank forces the piston up on the compression stroke this causes a gap at the loose connecting rod bearing cap(bottom), when crank/piston pass TDC(top dead center), the crank is now pulling down on the connecting rod so the gap moves to the top of the crank journal.
When cylinder fires that gap is closed instantly with the metal to metal "knock" noise.
When you stop the firing the knock goes with it, the loose bearing will still make some noise but nothing like the loud knock.

The double time knock frequency once in a while is because of the "waste spark" system Ford uses, a cylinder gets spark on the Compression stroke and the exhaust stroke both, you normally wouldn't notice the spark on the exhaust stroke, it can ignite any unburned fuel, with a bad connecting rod it would cause that second knock.

I drove a V8 out of the dessert with 7 cylinders, lol, bad connecting rod, 60 miles away from anywhere, sweating all the way, and not because of the heat, only vehicle and it was pre-cell phone days.

Reads like you got a lemon on this engine.

Last edited by RonD; 05-10-2014 at 09:43 PM.
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Old 05-13-2014
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All the bearings on the crank are tight. Definitely not .030" or more slap it would require for the piston to hit the head and cause all that damage. The knock is on the top end too, no knock in the bottom. I was thinking maybe the wrist pin has slop, but everything seems really tight when I'm spinning the motor with a socket wrench and the heads off. No hesitation or slap when changing directions of rotation or anything. Everything seems good and tight.
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Old 05-13-2014
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Turn crank so piston is being pulled down, then put wooden/rubber hammer handle on the top of the piston and hit hammer end with your hand, listen for "clunk" noise.
Repeat for each piston.

Could be a Cam bearing knock??
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