heating problems

[MelB]

I have a 98 ranger 3.0 4x4 and it is giving me fits... I have changed the waterpump, thermostat, radiator, and the vacuum bypass valve located by the heater core.. I have also flushed the entire system multiple times and the heater core seperately..While idling it will burn you out, but upon driving it blows cold after a few miles. Upon inspection, the coolant is going into the reservoir, therefore the cool air from the heater.. What could be causing it to do this.. A friend told me it is possibly a blown head gasket or possible cracked head... Please Help!!!!!!!

 

[RonD]

Yes, higher than normal coolant level in the overflow tank usually means head crack or head gasket issue.
And if overflow continues to bubble with engine idling then it is almost a sure sign
As coolant is pushed out to the overflow the heater hoses(high spot) are where some of the "air/exhaust" gets trapped so coolant flow to core is reduced or stopped altogether.

This is usually accompanied by white exhaust "smoke" at start up and if bad enough the oil on the dip stick will show whitish color like a milkshake, because coolant is getting into the oil.

A cooling system has no internal pressure when cold, the pressure in this system comes from coolant getting hot and then expanding, the water pump just circulates coolant it adds no pressure.

A simple test you can do when engine is cold.
Engine off
Remove rad cap and overflow hose
Start engine
If rad starts to overflow you have a problem, something is pushing the coolant out, and the only pressure source is in the cylinders, which shouldn't be "connected" to the cooling system.
A blown head gasket or cracked head allows a "connection"

Next test is to use a latex glove or plastic baggie
With engine still running place glove or baggie over rad cap opening, pinch it tight and put finger over overflow opening, system is now sealed.
If glove starts to inflate then you have pressure entering the system, only source is the cylinders........so blown head gasket or cracked head.


You can also do a "block test" this is a chemical test that tests for exhaust hydrocarbons in the coolant.
google: head gasket block test video
Test kit runs $40-$60