Engine Overheating

Asked by Jul 28, 2015 at 08:01 PM about the 2011 Hyundai Elantra GLS Sedan FWD

Question type: Maintenance & Repair

Nobody I talk to can directly answer
this question for me: Just because
me heater core has a small leak, why
would that cause my engine to
overheat randomly? Reservoir is
always full, there are no ground
leaks, and all other cooling system
components seem to be in top

16 Answers



6 people found this helpful.

Straight answer: No. A small leak in heater core will not cause overheating engine, as long as coolant is kept up. Poly-Boi is on the right track. Could be.

4 people found this helpful.

If your heater core is leaking anti freeze is not going to be on the ground but most likely on the passenger side floor and the reason its still over heating is because the cooling system can not build up pressure because of the heater core leak but I have something you can try that worked for me when I had a small leak in my heater core its called Bars Radiator and Cooling System Stop Leak just follow instructions on bottle and it should stop that leak as long as its a small leak. Now if for some reason that it does not work do not continue to add more hoping it will work that is when you may clog up the cooling system and also no promises that it is going to work but it is worth a try.

3 people found this helpful.

I thought it was the thermostat as well, but my dealer has been giving me the complete run around trying to diagnose everything. It will go for about 2 days problem free. And then other times, the engine will stay cold for an unusual amount of time, and then jump all the way up to near overheating. I've never let it get higher than 3/4 though. And then other times, the temp will stay normal, and the begin to dance around without running hot.

10 people found this helpful.

Thanks firebird338!! How much does that stuff cost?


well... the heater core has nothing to do with the over heating...but id add a little alumaseal $2.00. check fans also..you didnt say when/where you are driving...also fb brought up pressure..good point.. but it has to get hot to build pressure and your core should leak more... you did get all the air out of the system...dealer pressure tested the system ?leak get worse??


It runs about $ 5.00 to $ 10.00


I have to go against the trend here....NEVER put the stopleak crap in your cooling system, NEVER. Always fix the problem that is causing the issue.

10 people found this helpful.

Sorry Bob to late already have used it and it works and has continued to work for a year now and still no leak or clogged cooling system.


bob right..but really..my dad during ww2 in his take said they put some chicken yokes in his tank..and it got them thru.. anything in moderation is ok...no...

It always tends to run hot when it's really humid outside. I live in northern MS. It will also run hot if I try to use the air conditioner OR if my rpm's get any higher than 3K. Yes, the dealer pressure tested the system the first time I took it to them. Said it was not the heater core (Even though there was a small puddle on the driver side floor.) They told me it was my resistor on my radiator fan. Fixed it. PROBLEM WAS NOT SOLVED. Took it back to them and they said it was the heater core and they want $859 to fix it. My driver side has been so wet for the past 2 weeks that my airbag light is on. Dealer wants $100 to fix that also, even though they missed the problem to begin with. I'm in college, and take great care of my car at all times with whatever money I have. This is the very first problem my car has had and it's at 103K miles.

2 people found this helpful.

water pump

4 people found this helpful.

Have u replace thermostat yet, have u look at water pumb...

2 people found this helpful.

Keep us posted if u do change them cause I wanna know how it turns out after the run around and spending......good luck


(I just recently stumbled across this thread again) Turns the issue was a bad o-ring on the heater core outflow pipe. That explains why the puddle on my driver side floor board took weeks to finally become saturated. It also explains why the bottles of coolant that I consistently put in there seemed to go "no where." It was just steadily pooling up in my floor. Once they fixed the o-ring, I was left with the task of trying to remove coolant from every floor board space in my car. I used a Rug Doctor, and with consistency, the coolant smell and the coolant itself has finally went away after a year lol My car now has 140K miles and everything seems to be going just fine so far. Hopefully it lasts me another 2 years so I can finished paying for it haha

1 people found this helpful.

How much did the :-)ring cost you?

1 people found this helpful.

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