Overheating - Cooling fan didn't come on

[austspider]

I started to car (74 Spider) today and let it idle for a while. Fan usually comes on when gauge is just past halfway. Today the fan didn't come on and the coolant started spilling out of the overflow bottle. I then shut it down immediatly. I know the fan works but as this has not happened before I am not sure where to start. Also both top & bottom hose were hot.
Your help would be appreciated.

[TulsaSpider]

There are numerous posts on this. First make sure your fan is working properly by grounding the neg wire. It should come on.

[perthling]

Could be a blocked radiator, blocked thermostat... also check your oil cap to make sure there's no 'chocolate milkshake' under the cap. That would indicate a blown head gasket.

[divace73]

I bet is the air pocket in the head????

When the fan didn't come on you need to feel the bottom of the radiator compared to the top. If the bottom is cooler, it wont come on.
The reason for it being cooler is that the thermostat hasn't open and this could be due to a number of reasons but most commonly is that the head hasn't been filled from the highest point, bled and burped properly. You could have a coolant leak somewhere where the level has dropped in the head.

Would lie to find out what is was.

[azruss]

first things first. check your fuse

[austspider]

Thanks guys. The fuse is ok. The fan works as I connected it directly to a 12v battery.
The radiator was recored less than 12 months ago. The top and bottom hoses were hot but I think the bottom one was slightly cooler. Alot of pressure built up in the system as it filled the overflow tank and came out of the top.
I will remove the thermostat on the weekend and see if it is OK.

[austspider]

Guys,

I tried to replace the thermostat but could remove the old one (located in the head), so I will get a pro to do it. Tried to burp the system but I don't think it worked as the fan still didn't come on and when I turned the engine off, a heap of fluid came out of the radiator as I did not put the cap on. Also, the engine now sounds rough so I not sure what is going on. Hopefully the engine is not damaged. I checked the oil and there doesn't have any water in it and also checked inside the cam box and again no water in there. There engine was perfect only a couple of weeks ago.
Any suggestions?

[So Cal Mark]

hard to do any prolonged diagnosis if it's overheating, but I'd pull the plug wires off one at a time with the engine idling. If one or more cylinders are weak that will isolate which cyl is the problem

[austspider]

Mark,
I tried that and each one made the engine run worse. I think the noise is exhaust related as I found a leak at the front of the small muffler. The compression is good. Once I get the cooling issue fixed, I will be able to get the exhaust system checked. Not sure what else to do.

[So Cal Mark]

does it just sound rough but run smoothly?

[austspider]

Mark.
I think that is a good description. Idles ok but sounds rough on acceleration.