Single mom on disability needs help diagnosing

Anyone out there that could lead me to the problem with my 93 Cadillac Deville. It boils water in the radiator when the weather turns warm. I have not used the AC, have replaced thermostat and cap and in fact the radiator itself twice. Runs fine in cold weather. What do I look at next. I really need my car!

Could be a head gasket. Have you taken it to a mechanic?

Does this model have an electric fan? Is the fan running while the fluid boils?

How many miles on your car? Does it overheat while you’re driving, or while you’re sitting still and/or stuck in traffic?

You need to determine whether or not the cooling fan(s) are working.

Start the engine and let it idle. Open the hood and watch the fan(s). DO NOT put your hands anywhere near the fans. They could start at any time. Just wait and watch.

As the engine warms to normal operating temperature the fans should cycle on and off to maintain the proper temperature in the radiator. This may take 10 minutes or more. Be patient. If the radiator starts to boil before the fans come on the fans are not working as they should.

Try that and see what happens. Report back with the results.

This could actually be very simple.

If you really do have water in the radiator, rather than the correct 50-50 mix of antifreeze and water, that will inevitably lead to boiling simply because modern cars develop so much heat in the cooling system that they need the higher boiling point provided by the correct antifreeze/water mixture.

Additionally, severe rust and corrosion will take place if “straight” water is used in the radiator.

So–do you use just water in the cooling system, or do you in fact use the proper antifreeze/water mixture?

Thank you everyone…first, yes I use the 50/50 mixture (I have actually read the owners manual-LOL) I think I have the problem resolved. The fan does come on but not until it’s to late…so, I found on another site a guy with the exact same problem and it turns out to be an inexpensive part called the cooling fan relay…Thank you to all of you. Nice when people do random acts of kindness!

If the fan works the relay is probably OK. I’d suggest testing the coolant temperature sender mounted in the radiator. This is what tells the fans it’s time to come on, and if it’s bad it may be waiting too long.

mcparadise is correct…If the fan is turning on then the replay is probably NOT the problem. It’s probably the temp sending unit.

The TSU determines when it’s getting too hot and sends a signal to the relay to turn the fan on. Sounds like the TSU isn’t sending the signal on time.

Thank you. Yes I mispoke when I said it was the relay. I went back to the original site I found it o n and got the right name for the part-they called it a coolant temperature sensor. Now I just have to find someone to put it on for me! Thank you again!