Cooling system Service on 1996 Geo Prizm with 112k miles

Hey guys…

Today or tomorrow I will be changing the radiator for this 1996 Geo Prizm LSI (1.8L, automatic transm.) with 112k miles on it. The radiator has developed a tiny fissure in the upper plastic reservoir, just below the filler neck. This crack lets some of the coolant escape until the whole system heats up and the crack closes due to thermal expansion. I am also going to change the upper and lower radiator hoses.

The questions are:

1) Since I am pretty much tearing this cooling system apart, should I change anything else besides what’s mentioned ? The owner claims the water pump was changed in Dec.2004 at 65k miles when the timing belt service was done.

2) Should I look for any issues with the engine/transmission/etc, etc, since apparently this car has been driven with this condition for the past 12-18 months (approx 12-15k miles). The owner kept filling the coolant tank and radiator about once every 2 months or so, whenever he remembered to check. However, I suspect that most likely the coolant was expelled through that fissure in the next 2-3 driving cycles, immediately after he was refilling, so that most of the time the car had been driven without enough coolant. When I checked the car, the expansion bottle was bone dry and the coolant level in the radiator was low to about a quarter of an inch above where the aluminum part begins. In other words the upper plastic reservoir of the radiator was only capable of holding only about 1/4 to 3/8 of an inch of coolant, up to where the fissure began. Despite this condition, apparently the car never overheated, or given any signs of distress; the engine runs very smooth from what I could tell.

3) Should I do a chemical flush of the system, since the last time the coolant was changed was also in Dec.2004 when the timing belt service was done. Apparently Prestone 150k miles/5 years coolant was used at that time.

Thank you for your help.

Forget the chemical coolant flush. Fix the parts you mention like radiator, thermostat, cap, hoses, and new coolant.

This car is 14 years old and going too far is not worth it.

I would flush the system with water, install a new radiator, thermostat, radiator cap, hoses, and refill with the correct anti-freeze mixture.

That’s all you need to do.

When you’re finished make sure you bleed all the air out of the cooling system. No air pockets allowed.

Thank you guys…I had completely forgotten about the thermostat.

I would do the heater hoses too while you are at it and also check the condition of the serpentine belt.