[willyfixit]

Is the cam turning? Not just the cam gear.

 

[DIY Fan]

The block hairline cracked across cylinders 4, 5, and 6. Or the front head hairline cracked.

 

[Odyssey3425]

Is the cam turning? Not just the cam gear.

Yeah, the cam turns with the pulley. I took off the inlet & exhaust rocker arms and then ran the compression test. It was ~20 psi. But I think that makes since because no new air is being introduced.

 

[OdDIY]

Are you the only person to drive the car? Is it possible that another driver got it hot? A warped head/gasket failure seems the most likely cause.

 

[Odyssey3425]

I ordered a leak down tester to get the numeric leak rate. But the fact that it retained air pressure for 20 to 30 seconds tells me that the leak rate is small. We will see though.

I am still searching for a failure mode that can explain the observations.

My rigged way of leak down test was completely flawed; the compression test hose has a 1-way valve at the spark plug hole. So that explains why it was able to retain pressure, in that, I was only measuring the hose. I shoved a wire in there to keep it open to allow the cylinder to receive compressed air. I pressurized cylinder 4 and it seemed that the majority of the sound was coming from underneath, not the valves or the cylinder head gasket. Then I pressurized cylinder 1 (good cylinder) and it sounded similar but not as loud.

 

[bluecivic107]

WHat are the 9 DTC's?

 

[Odyssey3425]

I ran a proper leak down test using 50 psi and cylinders 4, 5, & 6 were ~40 to 45%. The air was coming out of the dip stick.

Is the issue the piston rings? I don't understand why all 3 cylinders would suddenly fail at the same time. What could cause this? I want to make sure I address the root cause.

 

[DIY Fan]

Air is pushing past the rings.

 

[dvpatel]

Is it just me or is there a whole lot of speculation going on? No codes, some stuff being not answered, engine torn apart already without DTCs, initial compression tests may or may not be inaccurate? I am having trouble following this one.

 

[DIY Fan]

If I was working on a car with similar symptoms I would perform a dry compression test, then a leak down test, then a wet compression test. The tests would have narrowed down the possible causes of the low compression prior to any tear down. Just my opinion.

 

[bluecivic107]

This OP is shady as hell….can remove the head no problem, but don’t trust the 9 DTCs… Welcome to the the Wild West!

 

[maxud]

Did you clean the valves before you took picture of that head? They look awfully clean, which could mean coolant was getting into the combustion chamber.
How was coolant level before you tore it apart?
Leakdown test is a percentage of blow by, how much air pressure are you putting into the cylinder, while you get your numbers?

 

[maxud]

thinking about it more, you did the most basic test you needed to do already, compression.
IF you did the test correctly, those numbers are not enough to create proper combustion, so that leads to the question, where is it loosing compression.
Did you inspect valve seats? Cylinder bores? Anything jumped at you.
I agree that having all 3 cylinders fail at once is a bit of a stretch. I have seen burned up valves and bent valves due to timing belt breakage. You say you have none of those issues.

If I had to hypothesize, it almost sounds like your head is warped, which is how coolant may have gotten into the cylinders in the first place. Not letting machine shop
look over the head was a major mistake. They will ensure your valves are sealing and head is flat within spec.

At this point in time, see if you can hear air in the coolant passages, which is my guess where its going.

 

[Odyssey3425]

Update: I removed pistons 4, 5, & 6 and they all have their rings seized to the piston. I think this is my low compression culprit. I also discovered that my front catalytic converter's catalyst substrate is broken and missing, so basically it becomes an open tube; I don't think it is related unless the one under the vehicle was plugged from the front's debris. See images.

After researching more, I found another thread that experienced something very similar, van-shut-off-on-the-highway. In that, there was sudden low compression in cylinders 4, 5, & 6 and his front catalytic convert was plugged. My take away was that he unseized his piston rings with chemicals and limped along.

Any ideas on root cause that would cause all 3 cylinders to suddenly failed?
My hypotheses are:

1. VCM was on and was overloading the front cylinders which caused carbon deposits on the rings
2. The front catalytic converter broke and clogged the catalytic convert underneath the vehicle which caused carbon deposits on the rings, while VCM was on so it only impacted the front cylinders

I will check to see if the catalytic convert underneath is clogged.

 

[WiiMaster]

VCM at most could only overload cylinder 4. Cylinder 5 and 6 do not have VCM in any form.

 

[maxud]

Any ideas on root cause that would cause all 3 cylinders to suddenly failed?

If you are not going to reply to questions that were asked, I think you will find yourself talking to an empty room

Stuck rings are common issue with older engines. I don't think its the smoking gun here, but definitely needs to be addressed.
How are you tearing this engine apart? Is it still in the car? Is the front head off?
Debris from a catalytic converter had been known to wear out engines (hyundai), but I imagine you would have p0430 code with
your front cat looking like that.

 

[DIY Fan]

Glad you found the problem. I saw an Acura technician replace the rings on an MDX J37 in 5 hours. Amazing how quickly the pros can do it.

 

[Odyssey3425]

VCM at most could only overload cylinder 4. Cylinder 5 and 6 do not have VCM in any form.

2007 EXL is VCM1 which disables cylinders 1, 2, & 3. Therefore cylinders 4, 5, & 6 are being overloaded when VCM is on.

 

[Odyssey3425]

thinking about it more, you did the most basic test you needed to do already, compression.
IF you did the test correctly, those numbers are not enough to create proper combustion, so that leads to the question, where is it loosing compression.
Did you inspect valve seats? Cylinder bores? Anything jumped at you.
I agree that having all 3 cylinders fail at once is a bit of a stretch. I have seen burned up valves and bent valves due to timing belt breakage. You say you have none of those issues.

If I had to hypothesize, it almost sounds like your head is warped, which is how coolant may have gotten into the cylinders in the first place. Not letting machine shop
look over the head was a major mistake. They will ensure your valves are sealing and head is flat within spec.

At this point in time, see if you can hear air in the coolant passages, which is my guess where its going.

No need to check for warped head, I am only looking for primary issue, I don't need optimal performance. As I said previously, the leakdown test showed that air was coming out of the dip stick; meaning majority of the air is passing over the piston cylinders.

 

[maxud]

2007 EXL is VCM1 which disables cylinders 1, 2, & 3. Therefore cylinders 4, 5, & 6 are being overloaded when VCM is on.

You do realize that all pistons move at all times, right?
Nothing is getting overloaded in front bank, the only difference is there is always combustion in the front bank and no combustion in the rear bank when vcm is active.
So in fact its exactly the opposite, the rear bank suffers the VCM curse.
The front bank is working like the normal engine, not burning oil, nor stressing the piston rings.