My guess is blown head gasket and/or warped head. I suggest a leak down test. Also possible stuck rings.

 

I replaced the head gasket. Would a warped head be a sudden event? I would think that it would be gradual. I do recall that the engine temperature was not high as I was pulling over.

I updated 1st post to include my version of the leak down test.

 

A proper leak down test with compressed air is the next logical step.

 

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.

 

Variable valve timing failure on front bank so they don't open?????? Not sure of exactly what such controls are on your engine.

 

Most people would have brought the head to a machine shop in your situation. You do not know for sure if your head was warped, not up to spec, cracked, etc.. You are literally rebuilding your whole engine so why skipped out the most important step.

Check out the "head replacement" by T_duck. He is still troubleshooting his misfire, but at least, he doesn't have to worry about the head.

 

Generally it is considered a good idea to get the heads machined when they are removed.

 

I am not going for perfection. The question is, could a head suddenly warp, with the engine temperature not over heating, and cause all 3 cylinders to have nearly the same low compression ~50 psi?

 

Brother... SLOW DOWN!!!!
What was the Check Engine Light DTC?

 

There was no code after the incident, I don't think the vehicle was on longer enough to stay. I tried it now, with the engine taken apart and there are 9 DTCs; I don't trust any of them at this point.

 

There would have to be a pending DTC, unless it was cleared out... I have a tough time believing that Cylinder 4, 5, & 6 lost compression at the same time, unless the cam for that bank jumped time...

 

When I looked at the timing belt, both the rear and front pulley's were perfectly aligned.

 

Worn valves or valve seats? Carbon fouling the valves?

 

There may be. But there is no way that is the root cause, since the issue was sudden and across the 3 cylinders.

 

Worn cylinders due to low oil level caused by oil burning from VCM.

 

I just measured the oil and it is not low.

 

We are talking about the front (near the radiator) when you say 4,5,6?

 

Think about what's common= cyl 5. What could go wrong with cyl 5 to cause 4 & 6 to be affected?

 

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.

 

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

 

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.

 

WHat are the 9 DTC's?

 

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.

 

Air is pushing past the rings.

 

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.

 

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.

 

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!

 

Bluecivic107 summed it up quite well here.

I am just sitting back and enjoy the show--it's quite entertaining.

 

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?

 

Coolant levels were normal. Leakdown air pressure was 50psi.

 

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.

 

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.

 

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.

 

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.