Heater core

Maintenance/Repairs
1

I replaced the heater core in my 96 s10

2.2l @ 158k miles. Well 4 weeks later the new heater core ruptures. Is this sign of bigger problem? If so, what?

2

In this case, you could have just installed a bad heater core. If you do a web search you will find lots of information about electrolysis. It is a common problem. If you have bad grounds, you can eat away at the metal. The electrochemistry is sort of like charging a battery. The usual places for problems to occur first are the heater core and rad. Go ahead and search for some specific information, but the test procedure usually calls for taking off the rad cap and warming up the engine. Then poke the battery neg terminal with one lead of a voltmeter and stick the other end into the coolant. Any more than 0.4V, IIRC is a sign of trouble. Do this with all of the accessories on too. Make sure that you do it when the main fan is ON. If you have high voltage, you need to start checking your grounds.

Any time I have a heater core go in the future, I will be checking right after installing the new one, if not before.

3

Try to lubricate the hoses before you jam them onto the new heater core. It’s easy to use too much force.

4

Excessive pressure in the cooling system caused by a faulty thermostat or a leaking head gasket is a possibility.

A cooling system pressure tester could verify if excessive pressure is the problem.
A back yard method (sort of) is to loosen the radiator cap after the vehicle has been sitting all night and release any pressure.
Tighten the cap, start the engine up and let it run for about 45 seconds or so.
Shut it off and quickly loosen the radiator cap. If you hear a pressure release hiss after that short a time then it’s possible you could have a head gasket going out.

Further diagnosis will be needed to verify a head gasket fault; hydrocarbon test, vacuum gauge, compression test, etc.

5

The radiator cap will release any excessive cooling system pressure. They are pretty much fail-safe and limit pressure to 14-15 psi. Sounds to me like you purchased a defective core…Remove it and examine it to determine the cause of the failure…