HG Internal Inspection?

[Nomis]

All of the blown HG pics I've seen on this forum have had a distinct outward radiating deformation on the metal ring that runs the perimeter of the bore on the No. 6 cylinder - nothing new here as this is common knowledge on the boards.

This deformation appears to be the root cause of gasket failure. Most likely the deformation did not occur at the manufacturer and is more likely a gradual process by which the unsupported portion of the perimter is being pounded out by the combustion process over time.

Here's my question:
Is this deformation observable prior to disassembly - i.e. would it be obvious that the HG was stretching outward leaving a small section where a gap is observed between the block and head?

If one had access to a micro-camera on a flex shaft and inserted it through the plug hole at or near BDC on the No.6 cylinder - would one be able to see if the gasket was beginning to bend outward and deform? If so - one could likely presume that gasket failure is immenent.


What are your thoughts?

 

[KliersLC]

Sounds like a good plan, I'll be interested to see if this works
Good luck,
Dan

 

[cruiserdan]

If you had a bore scope or some other optical tool you may be able to spot the ring. If it overhangs the cylinder wall it should be visible with the properly expensive tool. It would certainly be nice to be able to see one comming, so to speak.

 

[Nomis]

Excellent. Now we just have to locate some chap with access to a bore scope or the like - as I currently do not possess one.

 

[Beowulf]

My urologist uses a bore scope on me every 3 months. I'll see him again in March and maybe he'll let me borrow it over a weekend.

-B-

 

[turbocruiser]

My urologist uses a bore scope on me every 3 months. I'll see him again in March and maybe he'll let me borrow it over a weekend.

-B-

So is your o-ring deformed? Do you use Toyota Red or Prestone Green? Any sludge??? Pray tell!

 

[elmariachi]

My urologist uses a bore scope on me every 3 months. I'll see him again in March and maybe he'll let me borrow it over a weekend.

-B-

I don't believe I would have told that one.

 

[IdahoDoug]

Every 3 months? You must have checked the wrong box, Beo!!

I don't think you'll be able to see the deformation of the compresson ring as the ring does not protrude into the cylinder from memory. Be advised that even if you could, the failures are not from the compression ring. The failures seem to center around the two triangular water ports on the extreme rear of the head.

Further discounting this novel approach, the failures begin away from the ring and progressively allow coolant to creep ever closer to the compression ring as the coolant separates more and more HG from the block or head until one day it gets to the cylinder. So, once you see anything visible from the cylinder end, the fox is in the henhouse.

It's the eternal connundrum of a HG failure that there is no way to confirm that one is about to fail. It's all going on in the thin gap between the head and block and the first visual evidence of it coincides with and is indeed defined as its failure.

DougM

 

[Nomis]

I don't believe I stated that the ring protrudes into the cylinder - rather the opposite - the ring is forced outward - towards the water jacket and it is this outward projection that may leave a discernable gap between the head and the block.

Doug, If you will permit me the use one of the photos you took of the failed HG.
We clearly see the ring projected outwards at the 11 O'clock position - towards the water jacket.

Picture the head gasket sandwiched horizontally between the block and the head. Now if the ring is forced outward towards the jacket and away from the cylinder bore then there should be some empty space near the edge of the cylinder bore where the ring once was occupying - but is no longer. It is this gap located between the head and block that I am referring to.

So if one were to take a peek inside and see a gap forming near the aforementioned 11 O'clock position of the cyliner bore - then bad news, failure is imminent. No gap - then you're okay, at least for the time being.

I hope that makes more sense. I also hope I didn't come across the wrong way as I did not mean to.

 

[RavenTai]

I have wondered about this, you will need either a 90 degree adapter for a rigid bore scope or a articulation bore scope. I have considered trying to borrow one during a slow day at work but there are not many of those.

another possibility, on some of the pictured failed HG's the gasket was pushed out at the back of the motor, it appears to be late in the failure process but if one were to find this flag of gasket protruding I think it would be fairly conclusive of a badly blown gasket, maybe more like a autopsy than a leading symptom though.

you can see an impression of the edge of the head in this picture

 

[IdahoDoug]

Nomis,

No worries about bringing up an interesting diagnostic technique! None - I thought it was innovative thinking. Ask me some time about my doctor buddy coming over with his pricey scope to help me figure out if something was caught in our jacuzzi tub drain. The thing got caught good down there and for awhile we were comparing the cost of the thing vs literally cutting a hole in the siding of the house to retrieve it. He still uses it for its intended purpose bearing the scars of its intrepid voyage in an unintended purpose.

Back to the cylinder ring. I guess what I'm saying is that if you look at a particular engine and you see the ring has retreated somewhat, then consider what you've learned. That the ring has retreated somewhat - that's it. You don't have a specific measurement (say - it has retreated .079mm). And you don't have several such measurements (say - of the 16 we've examined this one is mid pack, or that it's retreated 72% farther) to compare it to. And you don't have any data to correlate it with such as "head gasket failure within a month occured in 80% of the rings that retreated more than .079mm".

So I guess what I'm saying is that it would be fascinating to see this kind of imagery. At least for me - can't speak for others. But it would not provide any type of actionable data for someone to be guided as to whether they have imminent failure or this is just normal distortion.

And all of this should be again considered within the context that ring movement may not mean a thing. It may or may not be related to the failures.

Having said ALL that, I may be in possession of the only FZJ head gasket that was installed for some 500 miles and then removed and I think it also had that "no longer round, but has some corners" look to it. Which may mean that the ring distortion is entirely normal and occurs right away in a new engine and never changes. In our immediate discussion we're assuming the ring moves over time but this may not be the case at all. I'll check tomorrow on that 'cause now I'm curious too.

Even an optical device that could go look at the gasket's condition in the areas of the water gallery would not produce usable data. Hope I'm not coming across as a pessimist as it is not my nature. Looking at the water gallery, the camera would come up against the grey elongated ovals on the left side of the picture. The galleries are that big, but the eighth inch holes are all the water that's allowed through by design. That's the intake side. Now look at how swollen their counterparts are on the exhaust side (one I removed to cut up). If your camera came up against these showing clear signs of damage (likely coolant gone acidic and attacking the gasket, literally dissolving and breaking it down), we would again not be able to use it as a decision point without widespread internal views of representative engines, etc.

I'd love to check this stuff out, but I think it's important to mentally take it a step further and see if you can make a decision to replace/not replace based on it? That would after all be the only value added other than entertainment (which I applaud). I would have to say no - you could not make such a decision from a logic standpoint.

Don't let this stop you or anyone who's got an innovative imaging potential for this. Please.

DougM

 

[Nomis]

I guess what I'm saying is that if you look at a particular engine and you see the ring has retreated somewhat, then consider what you've learned. That the ring has retreated somewhat - that's it. You don't have a specific measurement (say - it has retreated .079mm). And you don't have several such measurements (say - of the 16 we've examined this one is mid pack, or that it's retreated 72% farther) to compare it to. And you don't have any data to correlate it with such as "head gasket failure within a month occured in 80% of the rings that retreated more than .079mm". DougM

Agreed, we would have to view quite a few gaskets and take notes as to which ones had the characteristic deformation and which didn't. Then wait and see which of those that exhibited the deformation blow, vs, those without the deformation that blew. This should point either to a direct correlation or no correlation at all. I'd be leaning towards the prior at this point, but I don't have any data to back that up.

Having said ALL that, I may be in possession of the only FZJ head gasket that was installed for some 500 miles and then removed and I think it also had that "no longer round, but has some corners" look to it. Which may mean that the ring distortion is entirely normal and occurs right away in a new engine and never changes. In our immediate discussion we're assuming the ring moves over time but this may not be the case at all. DougM

I would be very suprised if this is the case. I would expect that the tension that the head and block exert on the gasket would keep it firmly planted.
The ring may dent outward when two circumstances occur - the gasket material surrounding the water jacket disintigrates making an already weak section - weaker and the now relatively unsupported section of ring is pounded slightly outward with each combustion cycle. The gasket deforms to the point where it can no longer seal and failure occurs.

Let us know what you find.

 

[powderpig]

The picture that you used Nomis is showing a few spots where the compression ring has failed. The black carbon at the 1 and 5 position also show compression leakage(major), there is also a couple of small spots of carbon in a couple of spots. These are also cause of compression leaking into the coolant. So on that particular head gasket(a real nasty one at that). It was not only that rings deforming, it was also the seal was broken for what ever reason allowing compression to leak into the coolant. The fire ring is not doing it job what so ever.
I will get a head back hopefully tomorrow and will see the interface area to see if it is possiable to see this ring easly. I currently have the head off and the block exposed. This gasket on this one was actually starting to be cut by the heat in that area, with carbon track in may cylinders, thus a loss of compression in several cylinders. He reported a steady stream of bubbles even at just off idle. later robbie

 

[landtank]

With these pics and the one I had in hand, it would be easier to just examine the rear of the block/head interface on the outside. The gasket gets squished out. You can see this on the 2 examples above. A flashlight and an mirror is all you should need.

 

[cruiserdan]

My urologist uses a bore scope on me every 3 months. I'll see him again in March and maybe he'll let me borrow it over a weekend.

-B-

NO WAY would I use that scope in my engine after where it's been.....

 

[IdahoDoug]

Checked the 'slightly used gasket' - it's actually quite round, but still has a slight deformation to it. By that, it had a very slight bulge developing on several cylinders. Must be the 'set' they take for whatever reason after having several thousand pounds of clamping force on them.

DougM

 

[lacruiser]

So I got a question about these blowing head gaskets.

Are they all, or the majority of them, blowing in the rear of the head? Like number 6 cylinder?

 

[cruiserdan]

Yes. Fire ring separation in #6.

 

[RavenTai]

Just went and looked at my 80 and I do have extrudeding gasket and quite a bit of it. Distinct black with shiny spots of carbon fiber, looks very close to the picture I posted up above

this is really s***ty timing.

you can get an eye on it (with difficulty) by putting a mirror in to behind the motor from the passenger side low looking back up at the head block interface, look for where the aluminum of the head and the rust of the block meet.

 

[Rich]

Just went and looked at my 80 and I do have extrudeding gasket and quite a bit of it. Distinct black with shiny spots of carbon fiber, looks very close to the picture I posted up above ...

Are you certain the gasket is not exposed from day one of engine assembly?