Hey scotty big fan of your videos they are a life saver for back yard mechanics like me ive got one for you that has everyone stumped.
I just did a coolant flush on my 09 hyundai sonata 2.4 ive had it for 3 or 4 years and its been an amazing daily driver neverhad any problems till now. Its a manual with about 210k miles on it. After I refilled it and burped it it gets to normal temperature while idling but when I drive it drops it drops to dead cold. my first thought was the thermostat so I got a new one and replaced it and re burped it. Its still over cooling. I burped it exactly how the owners manual says and its the zerex 50/50 pre-diluted.
Thanks for any help and suggestions
You might want to replace your temp sending unit that activates the temp gauge. A lot of crud and corrosion can build up on these and give a false reading because of higher than specified resistance. That's what happened with mine, it read really low and when I changed it out, it read normal again.
Are you talking about the coolant temperature sensor? If so I dont believe that's it but I was thinking about going ahead and changing it but when my car gets up to temp while its idling the radiator hoses are almost too hot to touch but once I drive it for about 10 miles and feel them again you can tell they are way colder
The temperature sending unit is different from the temperature sensor unit. The temperature SENDING unit looks like a brass plug screwed into a water jacket and operates your temperature gauge. The temperature SENSOR send signals to the ECU to control fuels mixture.
@doc not always true. My truck only has one sensor for everything.
Thanks, Joe, I appreciate it.
When you touch the heater inlet and outlet hoses, are they hot?
Yes once its ran enough the top hose gets warm then once it gets to operation temperature and the fan kicks on the bottom hose starts to warm up too
check the connector on your coolant temp sensor
I checked the connection it all seems to be solid nothing lose and no play with it
Check for corrosion too
you might still have some air in the system. Run it, keep the cap off and see if it improves. Since the heater inlet and outlet are warm, I don’t think a back flush of the heater core is necessary. How old is the water pump?
Ive had the car for 4 years ive not changed the water pump since ive had it. I burped it for about 2 hours last night with the front jacked up to help the air bubbles move forward and with a no spill funnel that has the radiator cap adapter with it
Does the heater blow hot at idle? Does the heater start blowing cold air when you notice the temp gauge drop? If so I would change the thermostat to the OEM is possible that is stuck open.
Yes thats exactly what its doing after I did the flush I put the original one back in and it wouldn't even stay a little warm so I got a new one and replaced it and re burped it and it does a little better now but once I hit 50+mph it starts to drop fast especially if I have the heater on
I would replace it with the OEM. It is not uncommon for parts to be defective straight from the manufacturer. When you burp it turn the heater on high and the fan speed on low. Make sure the fans cycle on and off and you have even temp on both hoses.
Ok ill find one and do it this weekend. On Sunday when it was about 72°f it did go up about a quarter on the heat gauge and stayed there most of the time I was driving do you think it would still be the thermostat?
Obviously not looking at the car myself and going based and what you’ve said. Yes it can be the thermostat. Also, make sure you install it correctly with the jiggle valve in the right orientation.
I Finally found a oem thermostat and got it delivered and put in but its still staying cold. This is the 3rd thermostat I've put in it (the one that was in it before the flush a replacement and now the oem) so it can't be the thermostat. Do you have anymore ideas?
I had a similar problem with my '03 Ram 1500. I burped it for hours and the heat would only half heat up and the gauge never got to operating temperature. The problem ended up being the water pump. Somehow the impeller came disconnected from the shaft so it didn't spin fast enough to circulate through the heater core and caused the gauge to read wrong. I would try replacing the water pump and seeing if that helps.
Mine will get to normal operation temperature while idling but once I start driving the heat gauge starts to drop especially if I have the heat on but once I get back home and let it run for a few minutes its back to operation temperature its almost as if once the thermostat opens it just loses all heat
Can ya check it with an infared thermometer right after you stop off say a highway. Hit up the radiator, hose, tstat housing for temperatures. If normal like 170-190f then it sounds like your temp sender unit.
I put a oem thermostat in and even got a vacuum air bleeder for the coolant line but still having the same issue
Update:
I took it to a hyundai dealership and they said that it needs a special vacuum tool that connects directly to the radiator because the heater core hose sits so high its impossible to burp like a normal car so I paid 130$ to get them to do it and when I got it back not only did it still have the same problem but they also somehow cracked my thermostat housing too and refused to take it back and fix either