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Hi. I'm new here and new to KIA. Helping my ex-spouse diagnose and repair (if not too difficult of a problem) her 2016 3.3L Sorento, 88,000 miles. She's had it for a year. It just started having these problems.

The SUV engine is running fine. It starts fast, idles smooth, has good pick-up, and doesn't have any codes or warning lights.

When started and idled it doesn't seem to overheat with just idling. I've timed it for 35 minutes with some revving to 4,000 RPM for short periods during the test.

However, when it's then driven (after the idle test) at 45mph or faster for 20+ minutes it will begin to overheat and will not cool down unless turned off and rested. Then it quickly heats up again after resting for 20 minutes.

This is what I've observed and/or done:

1. No coolant in oil (oil filler cap or dipstick).
2. No oil in coolant (anywhere).
3. Removed thermostat (I thought it might be stuck...did not open much in boiling water).
4. Verified both hoses are good and not collapsing when hot.
5. Replaced radiator cap (old one looked fine).
6. Bubbles are being pushed into the overflow bottle when it gets really hot.
7. When I turn the heat on high it will blow hot and cold, on and off. I assume that has to do with the coolant being low in the system.
8. The bubbles being forced into the bottle seems to keep it from pulling coolant from the bottle when the radiator is low and needs the overflow coolant.
9. I noticed just under the front-most head on the driver's side I see coolant percolating around one of the little inset round indentions when the temperature gauge is showing 3/4 to hot or more.
10. The radiator/coolant system holds pressure at 17psi for 15 minutes.
11. I used a combustion test kit and no gases seems to be infiltrating the radiator.
12. It loses about 2-3 quarts as it's operated for the rest drive time (30-45 minutes).

## Questions:
1. Are there freeze plugs on the driver side of the front-most head? I'm curious if a freeze plug in the head could be leaking causing this.

2. Why aren't any codes being thrown or dash lights coming on?

3. If the head gasket is leaking could it do so only to the external part of the engine, thus causing only a coolant loss and shortage, resulting in the overheating and bubbling into the overflow bottle?

4. Do you agree the heater will blow on and off hot air because it's not getting water flow as the coolant gets low? Or possibly an air pocket trapped?

5. Where are the temperature sensors on the coolant or engine? Would they be reading correctly regardless of coolant level? I'm wondering if when the coolant is 2-3 qts low if it's causing faulty / eradic temperature gauge readings.

6. What is the process to clear air pockets and bleed this SUV?

Thank you so much! Any help you can suggest I'll consider.
 

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1. Are there freeze plugs on the driver side of the front-most head? I'm curious if a freeze plug in the head could be leaking causing this.
Very likely to be located there, yes. I'd have to take a look to be 100%. It's a normal location for them. As a general statement, if you've got a potential fluid leak that can't be readily identified, a bit of UV fluorescent dye ($21.99 at Auto Zone) added to the mix (in this case, the coolant) and a UV flashlight (see Harbor Freight #63931, $8.99) can be very helpful.

2. Why aren't any codes being thrown or dash lights coming on?
Because you haven't had an event that would throw one. The temperature indicator itself is the warning. The five potential codes (e.g., P0116) are all to detect anomalies in the sensor itself, not to flag an overtemp condition.

3. If the head gasket is leaking could it do so only to the external part of the engine, thus causing only a coolant loss and shortage, resulting in the overheating and bubbling into the overflow bottle?
Yes, it is always possible for a gap to occur such that the cooling system and cylinders are 'connected'. Checking for exhaust gas products in the coolant is a typical way of determining if that might be the case. You'd need a combustion leak test kit to perform that test. The bubbling back into your overflow tank IS a definite indication for potential head gasket issues. I'd focus on this first due to that specific symptom. Test kits aren't expensive. Here's an example of one that would get this done for less than $40 >> https://www.amazon.com/Block-Tester-BT-500-Combustion-Leak/dp/B06VVBSFTF/ref=sr_1_1_sspa

4. Do you agree the heater will blow on and off hot air because it's not getting water flow as the coolant gets low? Or possibly an air pocket trapped?
Once you cease to have coolant circulation through the core due to level, you'll have this issue. We'll get to 'burping' the thing later.

5. Where are the temperature sensors on the coolant or engine? Would they be reading correctly regardless of coolant level? I'm wondering if when the coolant is 2-3 qts low if it's causing faulty / eradic temperature gauge readings.
I doubt any of your issues are related to the sensor, but I'm attaching a couple of photos to help. Look for C311.

112832


112833



6. What is the process to clear air pockets and bleed this SUV?
Burping the baby:
A. Fill the radiator with coolant through the radiator cap and tighten the cap.

B. Push the upper/lower hoses of the radiator so as to bleed air easily.
C. Start the engine and allow coolant to come to normal operating temperature.
D. Wait for the cooling fans to turn on several times. Accelerate the engine to help purge trapped air. Shut engine off and wait until the engine is cool.
E. Refill coolant through the radiator cap.
F. Repeat A-E until the cooling fans cycle 3 to 5 times and bleed air sufficiently out of the cooling system.
G. Install the radiator cap and fill the reservoir tank to the "MAX (or F)" line with coolant.
H. Run the vehicle under idle until the cooling fan operates 2 to 3 times.
I. Stop the engine and wait untill coolant cools down.

J. Check coolant level and add coolant as needed.
 

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Discussion Starter #3
Thanks much! Mine is a 2016 Sorento LX AWD 3.3L.

I did a coolant system pressure check and it was good, as well as a combustion gas test and none was present. There is no contaminated oil or coolant and no steam/white smoke from muffler. It's as if all the coolant is being expelled externally, getting air in the system, and causing the overheat problem.

So I think my leak which was originally suspect of head gasket loss is actually a leak from a freeze plug in the front-most, driver-side end of the head, OR, the connection that is between the plastic thermostat housing and the engine. The coolant loss and hot bubbles into the overflow bottle only happen if driven at higher speeds under load (45mph). It can idle and be revved 3-4 times to 3000 RPM for an hour and not overheat...but then when driven for 10+ minutes at 45mph or faster it begins to overheat.

Can anyone confirm for me if there is a freeze plug(s) on the front-most head on driver's side end (short side...side facing driver side tire), and also how the thermostat housing area connects to the top part of the engine?

I can't see either area well and haven't had a chance to remove stuff to see more accurately. I think one of these may be leaking under certain conditions as described and I don't have a head leak. That would be awesome! I've tried two different block sealing products that have worked for me and others in the past and neither did anything at all for this Sorento. Please help! I really don't want to loan my ex one or my cars...she has a bad way with cars lol

Thanks much!
 

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Discussion Starter #4
Ok I found a picture the left hand head on eBay. That circle does look like a freeze plug AND immediately under it are the coolant passages. I have coolant bubbling from this spot so I bet it's a bad freeze plug, bad plastic coolant Y pipe connection, or bad gasket between Y pipe and head.

If this is the case, would it explain the coolant loss (1-2 quarts per day) AND the bubbles in the coolant overflow bottle? The bubbles are from steaming hot air which I suppose is doing this due to lack of pressure and low coolant allowing air to be sucked into coolant jacket???
Screenshot_20191019-003103.png
???
 

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Discussion Starter #5
That's weird. I had posted new information on the forum to help figure out my problem and the two posts were removed. Who did that?

My coolant system pressurized to 18psi and it did not have combustion gases in the coolant system either.

I believe a defective thermostat housing or its gasket is causing the problems, or the freeze plug that is near it. It holds the pressure for a good while but then seems to fail.

Has anyone else had this issue?
 

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Discussion Starter #6
Has anyone had this issue occur?

I've got an overheat and coolant loss problem that occurs only after the car is driven. I can let it idle for an hour and no problem, but when I go to drive it, after about 10-15 minutes at 45mph or faster of driving, it begins to overheat and blow hot bubbles/steam into the overflow bottle.

It's running good, ignition/timing wise...no issue at all. I've changed the radiator cap and removed the thermostat. My coolant system checks good on static cold pressure test to 18 PSI and I don't have combustion gases in it either, so I don't believe it's a cylinder head gasket failure. No oil or coolant contamination either.

I believe the gasket between the thermostat housing or the housing itself is getting hot, expanding or otherwise opening up, and allowing air in the system and some leakage. The air in the system causes air pockets and blocks flow so it begins over pressurizing and blowing the pressure into the overflow bottle.

There is a freeze plug near this area also so it could be that as well.

Has anyone else experienced this?
 

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Discussion Starter #7
Anyone have these sections they could email me or post online or that are free online? I'm helping a friend repair this and really don't foresee needing to have it on hand. Thanks!
 

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99 Kia Elan, 17 Ford Edge Sport, 15 Mustang, 08 Harley Nightrain
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Anyone have these sections they could email me or post online or that are free online? I'm helping a friend repair this and really don't foresee needing to have it on hand. Thanks!
What engine in your friends car?

Was it related to your other thread?

 

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Just curious - where are you (generally) in Colorado?

Have you actually identified the thermostat housing area as a leak situation for coolant? If you're still sorting out the actual leak location, recall this from the above post:

As a general statement, if you've got a potential fluid leak that can't be readily identified, a bit of UV fluorescent dye ($21.99 at Auto Zone) added to the mix (in this case, the coolant) and a UV flashlight (see Harbor Freight #63931, $8.99) can be very helpful.
 

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Discussion Starter #14
Outside Glenwood Springs.

I have some dye but it wouldn't do much good...when the leak springs it sprays coolant everywhere from the coolant overflow bottle fill cap . Plus I can see where leak is coming from (at least one...could be more I suppose). The leak is coming from the front head area very near or on where the t-stat housing connects to head. Or the freeze plug. I saw it percolating upward from that spot and can hear it also. Today I'm gonna investigate and remove things to see.
 

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3. Removed thermostat (I thought it might be stuck...did not open much in boiling water).
Have you done anything about that?
 

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... The leak is coming from the front head area very near or on where the t-stat housing connects to head. Or the freeze plug.....
My first suspect would be that the gasket isn't making a good seal, rather than a freeze plug leak. If you have a torque wrench, try torquing the bolts to see if any of them are not at the spec torque. But if there was damage done (gouging, ...) to the gasket or either of the 2 mating surfaces, then it's going to take more than just tightening the bolts to stop the leak.
 

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Discussion Starter #18 (Edited)
Ok will do. Does anyone know the torque spec for the bolts that hold the t-stat housing to the heads? I don't have a manual. I'd assume around 13-14 ft lbs at most...

I have all the stuff removed that's in the way to remove the housing. Gonna check the bolts tomorrow and if they seem tight I'm gonna remove the housing and inspect it and gaskets.

Thanks!
 

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Ok will do. Does anyone know the torque spec for the bolts that hold the t-stat housing to the heads? I don't have a manual. I'd assume around 13-14 ft lbs at most...
I only have it for my 2.4L, which is 9 ft-lbs. Perhaps someone else here who has access to one of the online subscription services can look it up. Or you could probably just judge fairly well how tight they are by how much force it takes to remove them (and if they're roughly the same).
 

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Ok thank you. I reckon it's the same since they're probably both plastic. Makes sense it's only 9 ft lbs being it's plastic. I cannot say I'm happy about so many plastic pieces on these vehicles. Seems like weak, cheap failure points. I wish there was an aftermarket aluminum one but I can't find one anywhere. I only find KIA ($175+gaskets $15) and Dorman ($105 with gaskets) brands plastic housings.

If there's a benefit other than padding plastics industries pockets and KIA cutting costs I don't know what sense using plastic motor accessories makes. If someone knows a valid reason please educate me! Lol
 
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