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Overheating Car

Hello, my car has been recently overheating, despite putting water in and the overfill tank and directly into the radiator itself. The car has also been pressure tested and there has been a coolant flush done to the car. Despite all of this the car continues to overheat and when it does overheat the car spits steam, water and coolant from it when it does. The car does cool done when idling and when the heat is on but when it is driven on the road it overheats. When the car is shut down to prevent any further overheating the car will not turn on again and/or has trouble turning on. I was told by an amatuer expert that it is an aluminum cap that is under the car is becoming to hot and will need to be replaced. Unfortunatly I am ignorant when it comes to cars and am not sure who to listen too. Please help me

Where is it spitting the steam from when it overheats? That’s the part that needs to be replaced.

Amatuer [sic] expert? Aluminum cap under the car?

There are a number of possible causes of chronic overheating including
a stuck thermostat
a radiator coated and/or clogged inside
a defective radiator cap
a collapsed hose inner liner
a worn water pump (eroded impellars)
a failed cooling fan (or temp sensor or fan relay)
a headgasket leak.

The T-stat can be tested, but they’re so cheap I’d just replace it.
Clogged and inefficient radiator areas can be tested for with a pyrometer, a heat-sensing device that will show clogs.
Radiator caps are dirt-cheap to replace.
Hoses are inexpensive to replace.
The water pump’s output can be measured.
The cooling fan is easy to check.
Headgasket leaks are easy to verify (or rule out) by a number of methods.

Someone needs to look at this and diagnose it.

It spits steam from the overflow tank and the atual coolant tank

where exactly on the “coolant tank?” (I assume you mean the part on top of the radiator?) Is it where the cap is, or is it somewhere else?

It sounds very much like a leaking head/head gasket.

it is from the actual cap i believe

It sounds very much like a leaking head/head gasket.

High potential for this.

We need to hear the OP say that the fans are engaged when the overheat occurs. This would eliminate that issue. Though it would be unlikely that the fans would be needed above a certain speed.

I’d change out the rad cap/thermostat. The thermostat should have already been done if a professional has heard this complaint. If it’s the amateur-expert, and has not been done, it’s the first on the list of usual suspects along with the rad cap.

one more, this one I picked up from you a while back TSM, air bubble in the top radiator hose can also cause overheating, and is fixed by letting that air escape when the engine is running, by sticking a screw driver under the hose at the fitting until coolant comes out. but maybe not in this particular case?

I’m humbled by the credit given me, but it would be dishoest of me to accept it. Otheres here have emphasized the entrapped air possibility and the screwdriver burp. In this case, where so much had already been done, I didn;t even think of it.

But you raise an interesting way of identifying a headgasket leak. If bubbles are coming up the radiator fill hole while the engine is running, that’ll be the combustion gasses blowing through the breech and migrating up to the highest oint in the system, the fill hole.

First and foremost, you never, ever add plain water to your cooling system. Like everyone knows, water boils. that is why you only add coolant to your system. Did you add water before or after the flush was done?

Sometimes the radiator gets clogged externally with dead bugs and other debris. If you take a garden hose with a nozzle and squirt water through the fins of the radiator from the engine side out through the grille, you can clean out the air passages. Compressed air will also work. It won’t cost a thing to try this and if this isn’t the problem, you aren’t out anything.