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Cooling system issue

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Nov 8, 2016, 11:53 PM

Post #1 of 7 (834 views)
Cooling system issue Sign In

 Hi Everybody.  I just bought a 02 Hyundai elantra with 85k. I wanted a winter beater and it was only $1000 so I don't expect much.  Runs  great but I'm having a cooling system issue. I'm getting the no heat at idle problem which is usually the heater core. It did this from the start.  Here are the things I have done: flush and fill whole system including heater core ,  replaced thermostat,  replaced  radiator cap twice, bled  /burped system.  When bleeding system,squeezing hoses,  topping off fluid, I can get it to blow hot  air, but then it goes back to cool air at idle the next day.  All hoses get warm including the heater core hoses. Lower radiator hose  is cooler of course.  I have been adding a couple ounces of coolant here and there  so I thought I had a leak but nothing is on the ground.  No major white smoke ,  over heating ,  or milky oil so I don't think it's a head gasket. Oil looks like new.  I was going to further test for this though.   Temp gauge is normal and car heats up like it should and I have good heat  when driving. Another thing to mention is the caps that I have tried (6 pound caps) all keep turning and don't stop. It's like the radiator neck is worn and they are not tightening.  Is this normal or is the radiator bad? I'm wondering if coolant is escaping cause of the caps. But,  I don't see any major signs.   Not sure where to go with this. I can't find any leaks and hope it's  something as simple as replacing the radiator.  Any help/suggestions/comments are greatly appreciated .  Thanks a million!

Tom Greenleaf
Ultimate Carjunky / Moderator
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Nov 9, 2016, 2:58 AM

Post #2 of 7 (828 views)
Re: Cooling system issue Sign In

OK - first you need the radiator neck the holds the cap to be good for all reasons and bet not so costly to toss whole radiator. Required for proper fill, testing, purge of air out of system and arguably low to zero pressure will effect heater output so that's first.

Squeezing hose to purge air is one small trick but need to really be sure system is full and holds pressure up to a normal 15 (most about that) pressure and should tolerate that for a pressure cap suggested for this not a lower pressure - imperative as boiling points even Winter Beater will warm up plenty at stops and require fan for radiator also.

Water pump may not be able to pump enough at low RPM with these symptoms. Arggg - really best test is going to be replace it as you really can see the impellers then when that close who leave the old one?

You may need more work. I can't see how to pressure test for other issues without the neck for cap working which would be how you could pressure test and check for assorted leaks and really help to rule out head gasket which is still at large till you can test every which way.

Good luck. Wish I could find any decent Winter Beater but they all seem the later - already beaten beyond any hope :-(


Hammer Time
Ultimate Carjunky / Moderator
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Nov 9, 2016, 4:35 AM

Post #3 of 7 (822 views)
Re: Cooling system issue Sign In

6lb cap? Nothing uses a 6lb cap.

The spec on this car is 12 - 16 PSI


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.


Nov 9, 2016, 7:42 PM

Post #4 of 7 (809 views)
Re: Cooling system issue Sign In

sorry, i ddint see the 1 in front of the 6. Its a 16 psi cap which is what it should be. Went to a dealer today and they told me that the cap should definitely not turn. So....Im thinking the neck which is plastic is worn and i need a new radiator since i tried 3 different caps. Also, stopped and talked to a mechanic and he came out and looked at the cap. He said I was turning it too much and the two "things" that stick out on the side of the cap should be facing to the side. Im assuming that the system is allowing air in it since the cap is not sealing well and air=my problem of no heat at idle although it sems to be better after he showed me where to keep the cap. Who would have known a cap could be so complicated. I really hate cars! Thanks

Tom Greenleaf
Ultimate Carjunky / Moderator
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Nov 10, 2016, 2:47 AM

Post #5 of 7 (800 views)
Re: Cooling system issue Sign In

Any liquid cooled vehicle you have to know how the pressure cap operates as it's critical to boiling point of coolant. Know each vehicle and how they do it and which is a pressure cap or isn't. Some will use a plug cap on radiators and the pressure cap on a remote tank and should be marked with a pressure and or arrows to line up.

Totally of importance if are the owner of the car as said. Many don't use a cap at all on radiators and may put a cap on a replacement or rather access hole - I can't know all those variables.

Any violation of ability to hold proper pressure will cause a problem. Leaks coolant out or can suck air back in - neither right or good for the car/vehicle.

A first thing noticed is commonly heater isn't working properly can be long before serious engine damage that really can occur. You have to know that much or really shouldn't be working on that car till understood.

Hey - duly noted you hate this stuff. No problem with that whatsoever. Not all things are for all folks and never was.

Quite seriously, owner's manuals are a must to have for each vehicle and about always written such that the most entry level novice can understand. Boring read but the list service intervals, what fluids to use and how often to change plus how things are operated.

I swear 99% of people will never even glance at one and used aren't even sure the vehicle has one or not! Can get them used or print out from on line,



Nov 17, 2016, 1:43 PM

Post #6 of 7 (771 views)
Re: Cooling system issue Sign In

Head gasket is common for poor heat on this car. Combustion bubbles find
their way to the heater core and stop the flow.

Perform chemical block test.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 17, 2016, 2:04 PM

Post #7 of 7 (770 views)
Re: Cooling system issue Sign In

Include that check but find it almost uselessly unreliable, T

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