I have a 1996 saturn 1.9 litre. Ohc. I replased water pump and still getting very warm. I found a pin hole in the underside of the radiator cap. Its on the bottom on the part above the water hole. Could this make it get warm enough to bubble after 20mins of driving? Also i havent put anti freeze yet cause i wanted to make sure it isnt leaking, but shouldnt it run ok without anti freeze n summer heat? And should i put bars head treatment in when i put in the anti freeze?

Pressure test the radiator for leaks if it holds pressure start the engine. And check if pressure rises and keeps rising ,if it does it points to blown gasket or cracked head. A faulty thermostat can make it over heat so check it out . I would not mix the anti freeze as a lot of them don't mix well. put the anti freeze in all year as it stops corrosion of the cooling system.

Use anit-freeze anti-boil additive in the radiator at the correct percentage as it stops bubbles forming on the hot bits of the engine and allows for more efficient cooling of the block and head and stops the block freezing when the ambient temperature drops too low.. It also stops corrosion in the coolant parts. Some additives will not mix with bars or others so be careful when adding anything to the system.

Check the dipstick and underside of oil filler cap for signs of oil/coolant mixture(chocolate milk).If so, bad news, you have signs of a blown head gasket. Also make sure your radiator isn't plugged. You can check this by running your hand along the surface of the radiator when warm, with the engine off of course. You should not feel any cold spots. I'm assuming your cooling fan(s) are working.

take it to a radiator shop and have the system pressure tested
if the pressure remains static at pressure start the engine and see if the pressure drops
if it does indicates a water pump seal when running
check the drain hole under the pump housing for stains and water marks
something the garage should have done

How the radiator cap? It need to hold pressure,13 to 20 is the specification,you may want to change thermostat.The radiator is a definate

If you look on the under side of the water pump you will see a small hole. This is called a weep hole. If the seal in the water pump shaft is going out it will usually leave a trail of coolant from the hole. When you start you car in the morning the coolant is cold. As the coolant warms up the thermostat opens and releases the hotter coolant to the radiator. Start the vehicle when cold with the radiator cap removed let it warm up as normal. You can purchase a cheap automotive thermometer to place in the radiator to tell you when the coolant temp is rising. When the thermostat opens the pump will push the coolant through the radiator. You can usually actually see this if you look into the top of the radiator if you crack the throttle sharply. If your thermostat is opening and the water pump is working and you have an overheating condition I would check to see if the tubes in the radiator are restricted.

Take off your radiator cap when it is cold. Start your engine and look inside the radiator and see if the water is circulating when it gets warm. Rev the engine while watching inside the radiator hole. Be sure to be careful to not get burnt by letting it get to hot. You just want to see if the water is going around. If it is not, you could have a bad water pump.

If you plugged the original leak (which sounds like the head gasket) and then the radiator was leaking, and you are having water coming out of the exhaust, then you need to replace the head gaskets. It sounds like you had a blown head gasket from the start. Here's what to do.

1. Replace the head gaskets (will need intake manifold gasket as it need to come off for this procedure).

2. Replace thermostat, radiator cap (if radiator is still good)

3. Replace water pump; the water pump may have stopped working (mechanical), which in turn caused the pressure to build an blow the head gasket (the cause of the pump would be a bad thermostat. If the truck was overheating, then the thermostat was bad to begin with, then the pump, then the head gasket, so then the only place left for the water to go is out the exhaust.

Here is a list of replacements:

^ water pump
^ thermostat
^ head gaskets
^ valve cover gaskets
^ radiator cap (if radiator is good)
^ radiator : if leak from cap caused any damage to radiator (should still be good)

**Also check the radiator hoses to ensure they do not have any "bubbles". Hot water over time (with anti-freeze) erodes the inside of the hoses, and begins to "dig" holes and grooves in the hose, which evetually cause leaks. Consider replacing these as well for safe measure.

Please, let me know if you need further assistance.

carsandcomps,

Guru, Premium Expert @ Fixya.com

There are products out there like stop leak that MIGHT stop the radiator leak. However... the only real repair is either to have it soldered (if the end caps are not plastic) or replace the radiator all together.

Adding a product like "Stop Leak" most often starts to introduce other problems to your vehicle like a future water pump seal failure or clogs in the smaller water passages in the engine block, heads and manifolds and the thermostat heater bypass hole. Anyone that has ever done any major engine repairs will know immediately if stop leak was used in a cooling system.

The best fix is to replace the radiator.

Many radiators today can not be repaired

Stop leak is in most any auto parts store. Just be advised of what you can expect down the road.

specifically

1. warmer than usual engine operating temps
2. water pump seal failure
3. heatrer core clog (no heat)
4. passenger heat control temp valve clog (no heat)
The choice is yours. Personally I would not do the "Stop Leak" treatment attempt. Sometimes it works other times it does not.

Is it greenish yellow? Determine the location of the leak to find your problem. Could be: weep hole on the water pump, hose to and from heater core, radiator, one of two large radiator hoses, faulty radiator cap, cracked reservoir. If it's the water pump it will be near your belt(s) area on the driver's side of the motor.