Blown head gasket or something else?

[Don-T]

Hi everyone, I hope its ok to revive an old thread. I have a little more time to look at this M1009 now. I pulled the thermostat housing and thermostat. I also pulled all the belts off the accessory drive. I then filled the crossover up to the top of the thermostat housing with antifreeze. I started the engine and watched. Nothing at first but after about 30 seconds bubbles started to come from the driver side head. None from the passenger side. That gives me a starting point.

Now to start some research. Someplace I read a procedure for pulling heads without needlessly removing parts. I don't remember if it was on this site or another one.

 

[cucvmule]

Welcome Back!

After sitting did the engine labor to get stated, having any fluid in the cylinders can hydrolock the cylinder as fluid will not compress and some of the time can crack the piston lands between rings trying to relieve pressure to get piston cycling.

Having air bubbles in the system after sitting is normal, and adding fluids may have had trapped air in the system. I would put the water pump belt on and throttle up a few times to try and purge the system of any trapped air. But getting all the air out from just idling will be hard to do.

 

[Don-T]

Thanks for the input. After sitting for anywhere from a day to a month it starts as though there is nothing wrong. I don't think any liquid is getting into a cylinder. I have been trying to get air out of it by driving it off and on for about 8 mouths now, hoping there was air stuck in there somewhere. I no longer think that is possible.

I am beginning to think this is a cracked head. The reason being the bubbles show up about 30 seconds after the engine starts, compression pressure pushes past a crack and into a cooling passage and starts to build pressure. I think it takes that 30 seconds to get to the thermostat housing and a bit longer to show up in the radiator and then past the cap and into the overflow. As pressure builds it pushes coolant into the overflow tank. Once pressure is built up and the engine is shut off compression pressure in the cylinder is gone and the pressure in the cooling system is not enough to push back through the crack into the cylinder. The cooling system stays pressurized at whatever the cap can hold it to until I vent it. I think if it were a head gasket it would be more likely to not keep the cooling system pressurized the way it does. I may be way off but maybe it will give someone a clue as to what is really going on.

Here are some symptoms.

Steady stream of small bubbles when the engine is running. Doesn't matter if it is cold or hot. Thermostat or not. I just removed the thermostat and belts as described above and the bubbles are coming only from the driver side head.

When the engine is running with everything hooked up ut pushed coolant into the overflow bottle to the point the overflow bottle overflows and low coolant lights comes on. I won't let it run past that as I don't want it to overheat. I has not done that to my knowledge.

The coolant temperature fluctuates quite a bit once it warms up.

It starts as it should cold or hot.

Sorry for being so long winded on this.

it runs as it should cold or hot.

It does not smoke at all cold or hot.

With the radiator cap on the system builds pressure and holds it for weeks at a time.

There is no oil in the coolant.

There is no coolant in the oil.

I am almost sure I have either a blown head gasket or cracked head.

 

[dougco1]

My money says cracked head or heads and not the gaskets; oh wait, it will be your money.

You need to pull the heads and by default you will be installing new gaskets anyways.

Drop the heads off at a reputable shop and have them checked.