Have I burst my head gasket?

[JohnL]

On a Toyota MR2 mk1 with almost-to-the-moon mileage. Symptoms:

Overheating
Using lots of coolant
Coolant squirting out of the open filler cap when the engine is started
Dirty coolant (recently replaced)

Assuming the answer is yes -

Is there any way of telling if I've completely f**ked the engine, or will I have to take the head off to find out anyway? How likely is it that the engine is damaged?

[kevinday]

Probably, but check out the water pump, it may not be turning properly causing massive overheating and airlocks/blowbacks.

[deltaf]

Hi John L. If its throwing coolant outa the rad cap or expansion tank when cold, it means a buggered gasket.
Engine may still be ok tho if thats fixed.
If ya get the head off it, check it to see if its warped with a straight edge, if its not then youre prob ok.
Dont forget to change the oil and filter afterwards as some of the coolant will be in there as well as all the crap from the gasket.

[JohnL]

deltaf said: Hi John L. If its throwing coolant outa the rad cap or expansion tank when cold, it means a buggered gasket.

Haven't checked it cold, definitely does it when hot.

[JohnL]

kevinday said: Probably, but check out the water pump, it may not be turning properly causing massive overheating and airlocks/blowbacks.

I'll definitely check this out, a lot less work than a heda gasket!

[grahambell]

Any sign of moisture or 'mayonnaise' on the oil filler cap or dipstick indicating that the coolant is mixing with the oil? Often the case with a blown head gasket.

[incorrigible]

The gasket could blow as GB suggests, can also blow combustion to waterway (causing the pressure you describe) * If you get the head off, check that the block is straight too (usually the head that goes though as someone said) the longer you drive it lick that the more damage will be done though combustions gasses moving at estreme heat through your engine, like water across an ice cube

* Before you take the head off, do a compression test as a blow in the gasket will show up as either

1 leaking from the cylinders (into either oil or water, shown up by compression test (syptom either overly presurised water or oil system))
2 Leaking between oil and water (mayonaise in the oil filler cap)