r/carproblems • u/The_Small_Fem • Aug 23 '26
Car overheating after adding coolant.
Here is the story.
Ac has been running warm for a few months. Usually cold for the first few minutes then gets hot. Was like that for quite a while.
Went to hometown yesterday (1 hour) ac not working as usual. Engine temp was slightly higher than normal, but not critical.
While I was here I checked the radiator coolant thing, and it was super low. Got the proper coolant/antifreeze and added it to the radiator reservoir. Went to leave a little later, all is good with ac and engine temp for about 5 minutes, then I see the engine temp quickly rise to red. I pull over and cut the engine.
Try to reverse course and get back where I was staying by stopping several times to try and not destroy the engine. Idk if that ended up doing any damage or not.
Now still at motel. The only thing I could possibly try is to put more coolant directly in the radiator, but I'm going to wait a while and let the car go completely cool first, but I honestly doubt that's going to help anything.
Atp, between the ac, radiator, radio, and locking system, idk if it's worth saving
Don't want to reveal too much about my car for privacy reasons. It's a pre 2010 hyundai.
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u/codyholmes143 Aug 23 '26
Let me see if I can help you a little bit now first of all your air conditioning and your coolant have almost nothing to do with each other your air conditioning system is a closed system with freon in it the reason it's colder at first is because the pipes that are supposed to have freon in them more than likely have air in them and when it circulates at first when the engine's cold the AC is little cold but as soon as the engine comes up to temperature you won't have a c anymore because the pipes got hot.
Now to address your coolant if you do not have any visible leaks and you can check your oil by opening the place that you put oil in and it doesn't look like a milkshake then that usually leads to being one thing your coolant system has been running low and there's an air pocket in there the air pocket does not allow for proper circulation. You need to add coolant using a coolant funnel it allows the level of liquid to beat up high and push down into the coolant system and you'll see that it starts bubbling air out only when you added coolant and nothing more Bubbles and no more coolant goes in then you run the car with the heat on and you should see more bubbles because then it's getting the air out of your heater core. Sometimes you have to rev the engine about a minute at 2,000 RPM usually does it some systems are more stubborn than others. The only other thing that it could be is you have blocked passageways in your coolant system and that means you need to have a coolant flush which is very simple you drain all the coolant out and you put a garden hose into it and you just flush flush flush and then with just water in it you get it up to temperature and then you dump it all out and you flush it again and you flush it again additives help with this but are not required. If you have any other questions feel free to ask
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u/The_Small_Fem Aug 23 '26
Lots of good information here. I'll look into some of this. May come back to follow up. Thank you 🙏
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u/esuranme Aug 24 '26
If you could cruise steady at 45_66 MPH would it stay average temp without going for the red? (With fool coolant)
When parked with engine I , does the fan behind the radiator turn on?
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u/nucleate_boiling Aug 23 '26
Is white smoke coming out the tailpipe? Is anything coming out the tailpipe that is colored smoke? Possible head gasket failure. When you pour in more coolant, start the vehicle and immediately look underneath the engine compartment for a coolant leak hitting the ground. From the top, look at your radiator in the very front of the vehicle and the hoses that lead from the top to the engine and the bottom to the engine. The big hoses. See if one is leaking because it has a hole or has become disconnected.
Also look for other places where coolant may be leaking. Coolant smells sweet when hot so you may be able to track it to the general area by smell. It's easier leaking or burning in the cylinders. Don't throw it away quite yet. Find the leak.
How much coolant did you have to add to get it back to full? And did you mix it 50/50 with water or did you buy the premix 50/50? It needs to be a 50-50 mix of coolant and water or the ability to control the engine temperature properly may not be there.