Hyundai Forums banner
1 - 20 of 43 Posts

·
Registered
Joined
·
425 Posts
Discussion Starter · #1 ·
Last week I noticed an erratic temperature gauge while I was in stop-and-go traffic. It would go from just below halfway to nearly the red in about 7 seconds, bob around, go down a bit, then up, back down to halfway and sit for a while, etc. etc. etc. I stopped, added a little water to the reservoir and car was fine for about 20 minutes but then it started up again.

Went I got home I checked oil and it was low. I added a quart. After this the car has been fine.

Until today. It did go into the red a couple of times and sat there for a few seconds. I was surprised there were no lights or warnings of overheating! I opened the hood when I got home and didn't get the impression that the engine was particularly hot (though the upper radiator hose was hot).

I read this might be caused by air pockets in the cooling system and I need to "burp" it by taking off the radiator cap, starting the car, running the heater, and then topping up the radiator when I see the coolant level go down.

I was going to burp it but I wanted to check people's opinions as to why there was no warning of overheating. Perhaps this is a sign of another problem?

Thanks in advance!
 

·
Registered
Joined
·
425 Posts
Discussion Starter · #2 ·
I performed the burp. After the engine heated up I did see bubbles coming up occasionally for about 5 minutes. At one point the coolant level went down a little bit (just down the neck of the part the radiator cap screws into, maybe 1/2"). I did not witness anymore bubbles after this and the coolant level didn't change so after a few minutes I turned off the car and put the radiator cap back on. I'm not sure I did it right but hopefully :)

I'll report back if I still have issues, but if anyone has any other thoughts I'd appreciate it.
 

·
Registered
Joined
·
17,552 Posts
Elantra is horrible for coolant concerns..

Upper radiator hose to engine joint leaks, look at elbow hose below for signs of coolant or crusty debris on hose.

Upper radiator tank crack and leak opposite the upper hose fitting.. thermostat is about a maintanance item anymore.

Over heat an Elantra good enough to twist head, it over with, into replacement engine
 

·
Registered
Joined
·
425 Posts
Discussion Starter · #5 · (Edited)
Thanks for the replies!

Any chance a failing thermostat could cause these problems in response to colder outside air? If the thermostat is causing the problem I assume I should replace it asap? (It hasn't happened since I did the burp, but it's also been warmer this week.)

I'll take a look at the hoses, though I'm fairly certain the radiator hoses were replaced (the place I bought it from did a bunch of work under a 30-day warranty), and I haven't seen any leaking coolant. I'll also look for cracks on the tank.
 

·
Registered
Joined
·
3,151 Posts
Any chance a failing thermostat could cause these problems in response to colder outside air?
no. it's a closed system.

If the thermostat is causing the problem I assume I should replace it asap?
if it's the problem, yes. a failed thermostat can overheat and engine. i don't think you're there yet though.


(It hasn't happened since I did the burp, but it's also been warmer this week.)
then stop worrying about it. the air in the system can easily cause the problem you had.

I'll take a look at the hoses, though I'm fairly certain the radiator hoses were replaced (the place I bought it from did a bunch of work under a 30-day warranty), and I haven't seen any leaking coolant. I'll also look for cracks on the tank.
a good to do check. there's an easier one: keep an eye on the reservoir tank every now and then. if you have a leak, it'll drop. it goes up and down with engine temperature, but if its consistently dropping you have a problem.
 

·
Registered
Joined
·
425 Posts
Discussion Starter · #7 ·
Today the temperature gauge started going up and down again. If this matters, it first started happening during stop-and-go traffic.

I can't say with certainty that I got all of the air out of the system since I've never "burped" the system before and didn't really know what to expect. Is it worth trying again?

Assuming it's burped properly and the coolant level is ok, is the next step replacing the thermostat?
 

·
Registered
Joined
·
1,806 Posts
Either the fan the thermostat or the pump. have a pro check it out unless you are the handy one! You are risking overheating and potential catastrophic failure if you continue to watch it go crazy.
 

·
Registered
Joined
·
425 Posts
Discussion Starter · #10 · (Edited)
I don't notice the fans coming on when the temp gauge goes up quickly.

A few minutes ago I replaced the radiator cap with a new Stant. I don't know how old the existing Hyundai cap was, but the new cap has a much greater sense of creating a seal. The old one twists on very easily. I'm going to burp the system again tomorrow morning.

When I was looking for coolant leaks on the ground (there were none) I noticed some slightly moist black stuff (see photos). I'm not sure what that part is but I know it's near the water pump. I touched it with my fingers and didn't notice any coolant smell, but I thought it was worth bringing up in case it's significant. I don't think the coolant level in the reservoir is going down and I haven't noticeable any coolant smell in general.
 

Attachments

·
Registered
Joined
·
89 Posts
Sounds like one of the following:
1. If the thermostat is faulty it will not allow coolant to circulate in the proper manner. This will result in overheating and possible loss of coolant, if the system has a pressure release valve.
2. If the water pump is faulty, ditto. Blades can corrode inside the pump while the pump still looks fine outside. Usually this happens if the coolant has not been maintained to prevent corrosion.
3. If the fan is faulty, overheating will occur. Except, driving will force air through the radiator and the temperature will drop while you are on the move, then rise when you come to a stop.
4. Hopefully not a cracked head or leaking head gasket, which would pressurize the cooling system and result in loss of coolant each time the engine runs due to compression gases being forced into the cooling system.

A quick test of the fan is to start the car and let it sit idling for a while. Keep your eye on the temperature and check the fan operation.
 

·
Registered
Joined
·
1,806 Posts
You realize that if it does overheat and you do not catch it quick enough to shut it down you are risking engine demise, my advice, stop playing with it and get it to a pro for diagnosis and repair!
 

·
Registered
2008 Accent 3 dr 5 sp manual; 2010 Genesis Coupe 2LT track 6 sp manual
Joined
·
8,805 Posts
After the engine has thoroughly cooled down say overnight, take the radiator cap off. The radiator should be all the way filled to the neck. If not you have air in the system and a leak somewhere.

The leak may not be big enough for coolant but small enough it will suck in air when it is cooling down. When it does this you will not suck the coolant back into the radiator from the overflow tank.
 

·
Registered
Joined
·
425 Posts
Discussion Starter · #14 ·
Thank you armtdm for encouraging me to take this seriously. If it needs to go to a "pro" then I will take it. However, if this is a repair I am able to do I should pursue it. Any help anyone can give diagnosing is greatly appreciated.

Here's more info:

- The fans appear to be working fine. Additionally, how quickly the temperature gauge drops back down when this problem occurs would indicate it is not fan related (i.e. gauge going from over 3/4 to less than 1/2 in 4 seconds).

- When the gauge does go up, being on the move does not seem to have a significant effect nor does idling. However, prolonged driving without stopping, or stopping and turning off the car for a time, seems to make the problem go away.

- I just tried to burp the car this morning and there were no bubbles. However, I squeezed the upper radiator hose (which was a little hot) and bubbles came up. So I continued to squeeze it, 10 to 20 times until bubbles stopped coming up. Is that normal?

Thanks!

(Red Raspberry, when I opened the cap this morning the radiator was full.)
 

·
Registered
2008 Accent 3 dr 5 sp manual; 2010 Genesis Coupe 2LT track 6 sp manual
Joined
·
8,805 Posts
There should be absolutely no air in the system. If there is there is a leak somewhere when it cools down.
 

·
Registered
2008 Accent 3 dr 5 sp manual; 2010 Genesis Coupe 2LT track 6 sp manual
Joined
·
8,805 Posts
Yes. And is more than likely the culprit if you see no leaks or smell no coolant.

Keep an eye on your overflow tank when it is hottest after you shut it off and when it is coldest after it sits overnight. There should be a slight level difference.
 

·
Registered
Joined
·
425 Posts
Discussion Starter · #18 ·
Thanks Raspberry.

One thing I was unsure about is the tube going to the overflow tank. When I pulled it out last night to check the coolant level (it's hard to see otherwise) the coolant in the tube drained into the tank as I pulled it out, which makes the tube full of air. This happened before as well. I wondered if the system might pull in this air? And I wondered if a properly working radiator cap would prevent the coolant from draining from the tube into the overflow tank? I didn't want to test that this morning just in case I brought in more air :)
 

·
Registered
2008 Accent 3 dr 5 sp manual; 2010 Genesis Coupe 2LT track 6 sp manual
Joined
·
8,805 Posts
I have the problem with the overflow tube being full of air on my Genesis Coupe when I take off the cap. It takes at least a month to purge it of air normally and is impractical if you are troubleshooting an air leak.

What I did is replace the rubber hose with a clear vinyl one. Then find the top vent tube on the overflow, pinch it closed, and some how blow slight pressure into the top of the overflow to push coolant into the tube from the tank into the radiator. I used a rag and my lungs. :)

 

·
Registered
Joined
·
425 Posts
Discussion Starter · #20 ·
Thanks for the clever tip! Though my overflow tank is a bit different from yours. Imagine yours about 12 inches lower, where the tube comes from the radiator into the top of the overflow tank cap and down to the bottom of the tank. Also, because the neck of the overflow tank is barely wider than the tube, it'd be difficult to try and put coolant in there without taking out the tube.

I bet your Genesis is a lot of fun to drive!
 
1 - 20 of 43 Posts
Top