Broken Rod And Bent Push Rods......

redjewel2ss · August 29, 2011

to answer one of your other questions...

you CAN raise the rev limiter with a programmer, but the companies that make those programmers only allow the rev limiter to be raised when the transmission is in gear. they do not touch the Park/Neutral rev limiter which is about 3500-4000 rpms. no where near the rpm range to cause any damage! if yours is an automatic with the stock tune, there is no way it was over-revved!

i agree with some of the others. they just replaced broken parts on your last trip, and didn't diagnose the whole problem the first time, and over looked the other parts in the valvetrain that might have been damaged by the first failure. my guess is the original push rods, rocker arms, or valve springs were over stressed when the first problem occured, and finally failed.

pm26 · August 29, 2011

Any guess as to the root cause of this failure? Which part failed first?

Doug_Scott · August 29, 2011

Any guess as to the root cause of this failure? Which part failed first?

With the added information it is even more confusing. The most recent post says they only changed two lifters on cyl 4. Not sure now if camshaft was changed as well (don't see why it would be either). To break a con rod something big failed. Dropping a valve will not break a con rod, it will normally just pound the top of the piston and combustion chamber, and end up embedded in top of piston. I guess if it happens to cause the piston to break away from the wrist pin, that would release the rod.

The only way you can bend valves is to have lost correct cam timing, or catastrophic engine failure or have the valves hang open due to broken springs, failed retainer, failed keepers, that sort of thing. Losing cam timing will bend more than a couple of valves. I think the bent valves came as a result of the rod breaking first, sending the piston to TDC and leaving it there.

We would need the complete story from beginning to end to figure out what happened. I don't think the OP has enough technical knowledge to be able to tell us the complete story. Not a slag on the OP, most people do not have the technical knowledge/background to properly relate what happened. They try to explain using their interpretation or logic, and it gets all mixed up. There is a lot of important information missing, and I do not expect the OP to be able to supply it.

kdixer · August 29, 2011

Any guess as to the root cause of this failure? Which part failed first?

With the added information it is even more confusing. The most recent post says they only changed two lifters on cyl 4. Not sure now if camshaft was changed as well (don't see why it would be either). To break a con rod something big failed. Dropping a valve will not break a con rod, it will normally just pound the top of the piston and combustion chamber, and end up embedded in top of piston. I guess if it happens to cause the piston to break away from the wrist pin, that would release the rod.

The only way you can bend valves is to have lost correct cam timing, or catastrophic engine failure or have the valves hang open due to broken springs, failed retainer, failed keepers, that sort of thing. Losing cam timing will bend more than a couple of valves. I think the bent valves came as a result of the rod breaking first, sending the piston to TDC and leaving it there.

We would need the complete story from beginning to end to figure out what happened. I don't think the OP has enough technical knowledge to be able to tell us the complete story. Not a slag on the OP, most people do not have the technical knowledge/background to properly relate what happened. They try to explain using their interpretation or logic, and it gets all mixed up. There is a lot of important information missing, and I do not expect the OP to be able to supply it.

A bent pushrod or hanging lifter can potentially hold the valves open. I would say you are spot on with the piston coming apart.

One theory would be:

Valvetrain malfunctions causing one or more valves to stick open.

Piston strikes valve and shears wrist pin.

Piston is wedged near TDC but crank continues to rotate pulling connecting rod down.

Crank continues to rotate pushing connecting rod back up, but the connecting rod flops to bottom cylinder wall and is driven into the bottom of piston

Engine begins to self destruct.

mkelly · August 29, 2011

Any guess as to the root cause of this failure? Which part failed first?

With the added information it is even more confusing. The most recent post says they only changed two lifters on cyl 4. Not sure now if camshaft was changed as well (don't see why it would be either). To break a con rod something big failed. Dropping a valve will not break a con rod, it will normally just pound the top of the piston and combustion chamber, and end up embedded in top of piston. I guess if it happens to cause the piston to break away from the wrist pin, that would release the rod.

The only way you can bend valves is to have lost correct cam timing, or catastrophic engine failure or have the valves hang open due to broken springs, failed retainer, failed keepers, that sort of thing. Losing cam timing will bend more than a couple of valves. I think the bent valves came as a result of the rod breaking first, sending the piston to TDC and leaving it there.

We would need the complete story from beginning to end to figure out what happened. I don't think the OP has enough technical knowledge to be able to tell us the complete story. Not a slag on the OP, most people do not have the technical knowledge/background to properly relate what happened. They try to explain using their interpretation or logic, and it gets all mixed up. There is a lot of important information missing, and I do not expect the OP to be able to supply it.

Valve timing would do noting to the valves......... Unless I'm mistaken the 5.3 is not an interference engine

The Chosen One · August 29, 2011

all lifters were replaced. the(2) lifters that failed were on cylinder 4, so dealership decided to replace them all. According dealership is common for lifters to make noise and even break therfore replaced all of them. They said the cam (how dont know)had been damaged as well so they replaced.

The "2lifters" thing was a typo....there were only 2 lifters damaged is what i meant to say.

I am an import guy and familiar Honda/Acura so i am not even familiar how the push rod, lifter, and valve assembly function. I do have an idea but is still foreign to me.

Now there was only1 valve bent which lead me to believe timing is not the culprit. Not sure of the firing order but my assumption would be that if timing was the case other valves would be bent as well on 1 other cylinder.

My guess is still somthing to do with the valvetrain coming apart in that cylinder. The valve was bent and still hanging out while the others were shut into place.

The good news is that they did set up an appointment with me for 9/6. Wish it was sooner, but I will def keep you all posted.

pm26 · August 30, 2011

I assume this is a 5.3 AFM engine, correct?

BTW, a pushrod engine uses pushrods and rocker arms to activate the valves, whereas no pushrods are necessary in an overhead cam engine.

cliobogger · August 30, 2011

i bet the engine (whatever part caused the issues to begin with) was a lemon from the factory. which is sad, there aren't many of them. sad you got one...

kdixer · August 30, 2011

The cam was likely damaged from the faulty lifters. The 5.3 has hydraulic roller lifters from the factory. If one or two of your lifters "broke" in a way they could not roll anymore, it most likely scored the cam lobes for that cylinder. Basically your cam is located in the center of your engine. The roller lifters move up and down with the cam lobes. Push rods rest on the lifters and extend up thru ports in the heads and rest under the end of the rocker arms. When the lifter rises, so does the pushrod and the inboard side of the rocker arm. The rocker arm pivots and the outboard end pushes down on the valves opening them. The pushrod is simply an extension since the cam is located away from the head.

It might not be an interference engine by design, but it can easily happen when things start to come apart. Some photos would be more helpfull. Typically valves don't just bend without a little help. It could even be something as freaky as a socket or bolt being left in the engine somewhere (intake port).

nickvrebel · August 30, 2011

and to answer the question more on programmers:

out of the box programmers are usually set up where you can't do anything incredibly stupid.

however, custom tuning software has no limitations.

from experience these motors an spin to 6,000 rpms on a regular basis. people on performance forums that have high rev cams spin their stock bottom ends faster but the smart ones install ARP rod bolts on the stock connecting rods to eliminate the factory weak point.

Doug_Scott · August 30, 2011

I would love to see pics of the engine. This sort of thing is what I really liked about being a mechanic. Trying to figure out what happened.

441G · August 30, 2011

too much timing from a custom tune can hurt rods

wavery · August 31, 2011

If it were me, I'd let them fix the engine. Be sure to tell them that you want all the bad parts.....I'll bet a dollar they don't charge you.... If they do, just take them to small claims court. It'll be a slam dunk. There's not a judge alive that would put up with that crap........... unless you show up in court with piercings, tattoos, gang clothing, a t-shirt that says "I hate judges", bad breath and a bad attitude.

redjewel2ss · August 31, 2011

If it were me, I'd let them fix the engine. Be sure to tell them that you want all the bad parts.....I'll bet a dollar they don't charge you.... If they do, just take them to small claims court. It'll be a slam dunk. There's not a judge alive that would put up with that crap........... unless you show up in court with piercings, tattoos, gang clothing, a t-shirt that says "I hate judges", bad breath and a bad attitude.