Car Won't Start - Head Gasket?

[ChrisChattaway]

I have an 08 hatchback that I am having a problem with right now.

At the moment the car won't start and I am not sure why. I think (actually I am sure) it has a leaking head gasket, yet I am not sure why it won't start. In my experience with failing head gaskets, they have always started and either overheated, blown white smoke, or both, but they would always start. Is there any reason why this one would not start?

Evidence for failing head gasket:
1. Compression: 155 - 185 - 190 - 165
2. On a cold engine with no pressure in the cooling system, if I crank the engine and then remove the pressure cap a hiss of pressure relief is heard. This can be repeated. relive the pressure, crank the engine, pressure hiss on cap removal.

Recent history.
- We have not owned the car for long. Maybe 4 weeks.
- There is a slight smell of coolant when in the car. Very mild.
- Previous owner had replaced some of the coolant hoses on the car recently. Two are brand new (top rad hose and one of the heater core hoses).
- My daughter was recently driving the car and had the lower rad hose fail very near the clamp. Was leaking for about 1/2 a block before she stopped. Once stopped the car dropped most of its coolant. I was able to make a temporary repair by cutting the bad end off and re-clamping it. This sealed it up and allowed the cooling system to pressurize again. One note, this hose looks slightly bulged too, especially near the end. The hose failure was Wednesday night. The car got driven Thursday and Friday, it would no longer start Saturday morning.
- I can see that the heater core hose that was not changed looks bulged. I am now assuming that this is due to the extra stress it is getting from compression leaking into the cooling jacket. This would also be the reason the other hoses were changed.

Does anyone understand why the car would not (will not) start????

[avguy]

Did you check for spark, and try spraying in some starter fluid?

[ChrisChattaway]

Yes. I have actually done quite a bit of troubleshooting so far.

1. Checked for spark - it is there on all four plugs.
2. Checked for fuel - I didn't do a fuel pressure check but there is fuel pressure in the rail and if I drain it the pump restores the pressure the next time it runs.
3. Checked the mechanical timing of the engine - just wanted to make sure the belt didn't skip a tooth.
4. Checked the throttle body. It seems to be working OK and the sensors are feeding back to the ECM OK. Butterfly moves to what I assume is start position when key is turned to the on position. Although the butterfly doesn't move when the throttle pedal is pressed, but I assume it wouldn't react to the pedal until the engine started anyway. I even when so far as to hold the butterfly further open to confirm it was getting enough air.
5. Sprayed some started fluid into the intake, still doesn't start.
6. Confirmed the exhaust isn't blocked by removing the O2 sensor.

The only thing I can find wrong is that the head gasket is leaking pressure back into the cooling jacket. I think it should start even if it didn't run well with 2 compromised holes. At least that is what my experience tells me should happen.

Why won't it at least start??

Does anyone have experience with a failing head gasket causing a crank but no start condition?

[avguy]

You said it doesn't start, but is there also not even just a bit of sputtering? Were the 2 plugs from the lower compression cylinders wet when you removed them? Is there any sign of coolant in the oil? Have you tried starting it with the gas pedal to the floor? (clear flood mode)

[ChrisChattaway]

There is a bit of sputtering.

Yes, the plugs are wet, but you would expect that from a blown head gasket. I can see some water in all the cylinders.

I don't see coolant in the oil, nor do I see oil in the coolant. That said the car may not have run enough to get them thoroughly mixed so then would show, or it is simply a coolant jacket to cylinder breach.

"Clear Flood Mode" - I did try this but I don't see the butterfly in the throttle body move beyond the start position. How long should this take? Is there a sequence to be followed? I assume the butterfly should move to full open-> this was how clearing a flood on a carbureted engine works.

[avguy]

... "Clear Flood Mode" - I did try this but I don't see the butterfly in the throttle body move beyond the start position. .....

I've never watched the throttle plate on my Aveo like you did, so I can't say how far open it actually goes. However, pushing the pedal all the way down should always cause it to be as far open as it goes. If you have a realtime OBD scanner it should show close to 100% with the pedal all the way down. In any case, it appears it won't help get your vehicle started.

Based on what you wrote, I think its very likely that 2 cylinders are not firing at all. So it would appear that even though the 2 good cylinders are doing their best (sputtering), these small engines just can't get running on half power. Hope the HG repair goes well for you.

[ChrisChattaway]

Just to round out this thread. It was the head gasket that was preventing starting. I pulled the head. Had it pressure checked and skimmed. After reassembly the car started right up.