Catastrophic 16v failures solved
 

I had posted earlier about a catastrophic failure that occured to a 4.7L motor I had installed in my track car. It had a loud ticking sound, which I attempted to diagnose without doing any dismantling of the motor. On a test drive, the engine suffered a catastrophic failure blowing out a cylinder. When I did the post-mortem, it was apparent that something had gotten into the cylinder by the hammer marks on the piston crown and in the combustion chamber, causing the cylinder the burst.

I was really disappointed by this failure. I like to believe that I'm careful when working on my stuff, and the reality that I had allowed something to get into the cylinder on assembly was very disheartening.

The 4.7L was installed to replace the original 4.5L which had locked up while idling in the shop. It started making a ticking sound that got louder and louder. I was doing something at the workbench when this occured, and by the time I got to the car to shut it down it had stopped on its own. When I went to turn the crank, it was seized.

Here's a pic of the damage to the 4.7L.

http://i710.photobucket.com/albums/w...47cylbreak.jpg


After pulling the head off the 4.7L and seeing the damage, since I had all the tools out, I pulled the head off of the locked up 4.5L, and this is what I found.


http://i710.photobucket.com/albums/w...45cylbreak.jpg


This completely blew me away, as this motor was the stock engine that had come in the car and had never been opened up. It ran two successful track days, with a 5 hour road trip to and from both time. When I saw that this had the same failure as the 4.7L, it was puzzling to say the least.

So today, Tom Middleton and I were cleaning up the shop, and decided to complete the dismantling of these two motors so we could scrap them. We pulled the other head off the 4.5L, and this is was we found:


http://i710.photobucket.com/albums/w...ps76a4f312.jpg

And this is what the piston crown looked like:

http://i710.photobucket.com/albums/w...ps0ffc1d7e.jpg


Very interesting!

Just confirm the failure mode, we took a closer look at the 4.7L combustion chamber that had the failed cylinder.

http://i710.photobucket.com/albums/w...ps7fd297a0.jpg

Confirmed! So, the moral of the story. Watch your valve seats. Both motors had a long history of not being run. I was told my track car sat in a ditch for five years before I acquired it. The 4.7L likewise had sat around for probably close to five years before I installed it and ran it.

Any ideas on what could have caused this failure in both motors? Any preventive ideas to keep it from happening?

Seats falling out of these heads is very rare.

Seeing that both engines failed in the same vehicle, you would almost have to think that there might be something in common.....or you are one of the unluckiest guys on earth.

Did any of the parts from the two engines get swapped between the two? Thermostat? Temperature sender? Water pump?

Heat makes valve seats fall out. I'd sure make sure that the cooling system, in the car, is working and the temperature gauge is telling the truth, before I'd stick in another engine.

Gruesome picts.

No help to offer, but those pictures did cause me physical pain...ouch.

Wwoooooowwwwwww

Wow......

Im sure Adam will chime in too.. but as far as items re-used in the swap. The intake setup was re-used and was the first thing we thought caused the problem (something inside the intake coming loose and dropping into the bore). It is also using the same radiator/fan setup..but I believe each engine had its own thermostat and waterpump.

Not sure if this is physically possible but thought maybe if the engines were sitting for a while and the valve got stuck to the seat...and then broke free after startup..possibly causing the seat to loosen up..and eventually work its way out?

Like Adam said, the first 4.5 engine ran a couple track days (including driving to Spokane and back twice...400ish miles each way)..before it just seized.

The 4.7 always made noise (search renny for the startup thread)....

Maybe Adam is the unluckiest guy around.???? If my track car engine explodes after he helps me with it.. we'll know for sure LOL...

Those are some frightful pictures! Hope you never have another one like those!

bizzare......since I have quite a bit of track time on 16V engines.....here is my .02

I think engines that sit for extended periods WITH coolant is extremely bad....it can literally corrode holes in the heads among other issues....I have seen it actually rust through main studs.....not to mention a nearly destroyed water pump impeller...

Like Doc Brown said it clearly reduces the cooling capacity of the engine....so over heating is possible.....or at least "spot" overheating due to the corroded holes in the head.....

my race car sat for only 1 year...with distilled water only.....there STILL was quite a bit of rust in the radiator-block......it took a while to flush out the radiator with a hose...

however I still think 16V engines make excellent track engines.....being non interference is HUGE....they also are much cheaper as well....and lighter....

Well if its heat that may be the problem, I'll definitely keep an eye on it.
The car is in getting a cage installed. I just wired up a set of contour fans, which will provide better cooling than the previous set up which was just the stock A/C fan. It was my intent to install some analog gauges, so I'll be able to get accurate readings.

Tom is right as far as what was swapped over. And is also correct that the 4.7L was making noise from start up.

Unlucky? I guess its all relative. "Lucky" that it didn't happen on the track at triple digit speeds one way to look at it. One failure IN the shop, the other a block from my home. That's lucky to me. It's all in the perspective I guess.

So... let's not put a damper on postings where someone shares their misfortunes or mistakes with the list. I've always done this freely where others I know choose to keep these kinds of things to themselves. I feel its more important to the list to share when these things happen rather than not have the balls to due to fear of embarrasment or being second guessed. JHMO.

Seems way too coincidental. Did you find anything in the cylinders or the pans to suggest a foreign object?

My, at present, pessimistic mind thinks sabotage.

It's kind of hard to imagine any other possibility. Two failures exactly alike? Even one engine failing this way is insane. But two?

LOL..you guys kill me... I know his shop partner is a cut throat win at all costs guy...but I know him personally and he wouldn't do that.... :D LOL...

There was no "object" in the bore or anywhere......
I think the real common bond here between these two engines is that they sat for a long long time..before being put to use.... one lasted a little while....the other not at all....

So, what can cause the bores to heat up so much that the valve seat separates from the head?...bad coolant flow? Corrosion? (will have to look at the coolant passages)?

There's no question that acidic coolant is going to turn out to be the "biggest" factor in the "future" of these vehicles. I've not taken an engine apart, in the last 6 months, that wasn't weeks or months from coolant leaking into the combustion chambers, from head gasket deterioration.

The last time I needed a good used 4.7 liter engine, I took 6 of them apart, before I found one that was even usable....the rest had both the heads and the blocks "eaten" away from old acidic coolant.

I'm saddened by the people that are buying uber low mileage vehicles, for high prices, that have been sitting, for years, with the old coolant in them. These engines are going to have much damage and cost thousands of dollars to fix....if they can be fixed, at all. Most likely, these vehicles will end up always being "low mileage" vehicles.....more by necessity than from desire.

All that being said, I've not seen any ports or valve seats that have been attacked by "internal" coolant. Coolant getting to this area would mean that the heads were literally "swiss cheese" and most likely the engine would never run, due to coolant getting into the intake system.

While it is possible that "external source" water can get into a port and errode the head, exposing the valve seat to failure, removal of the valves from these two ports shouild either confirm or deny that possibility.

It's certainly worth look at, in order to try and solve the mystery.

Another thing to look at would be the actual head gaskets. Had they deteriorated to the point where water flow through the heads would be compromised or changed? Minor, subtle, changes to water flow can and will cause "hot spots.

Remember how the water flows to cool things. The head gasket is a "wall" between the cylinders and the head. The coolant frows from the water pump, past all the cylinders, to the rear of the engine, and then returns through the cylinder heads. The coolant gets hotter and builds more pressure, as it travels. Holes in the heads gaskets (by design or from deterioration) can allow coolant to "escape" from the cylinder area and feed into the cylinder head. It doesn't take much of this, before the flow path is disturbed and coolant no longer gets to where it needs to go.

This is a very interesting failure and certainly worth the time and trouble to look carefully at.

FWIW, neat distilled water is more corrosive than distilled water with ethylene glycol mixed in.

Also, the nigh-onto-indestructible toyota 2L diesel engine has this same (well, a similar) failure mode. The precombustion chambers can crack and fall into the cylinders, resulting in that type of damage, so it isn't unheard of.