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Discussion Starter #1
Last year our 2.2 CRDi with approx 130 000ks started overfilling the coolant overflow reservoir and not back draining on engine cool. Pressure test turned up negative. Changed radiator cap and seemed to go away but it has been stress free local driving.Recently (now around 140 000ks) after hitching up the camper and hitting the hills it started again. At no stage was overheating indicated, engine runs fine, and if i stopped approx. every 100 ks and transferred coolant back into radiator (don't you hate the taste of coolant - especially warm!) no apparent coolant loss, but of course air space inside radiator which was still under pressure when cooled.Only online thread i have found is a 2009 Hyundai Santa Fe with pretty much the same motor and symptoms before a blown head gasket was found between a couple of pots. His was repaired under warranty in 2014. Mine is booked in for further investigation but i'm bracing myself for a large bill!


I will keep you posted on how this pans out.
 

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It is possible to test the coolant for exhaust contamination. If you suspect the head gasket, then also look at the oil for water contamination.
Sooner you get it fixed the less it will cost.
 

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Discussion Starter #3
Yep. Thanks for that. Oil fine. Sniff test apparently is not always reliable. The other problem is that the coolant in the expansion tank is holding it's level now that i'm home and the vehicle is being tested.
 

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Discussion Starter #4
Checked yesterday by local Kia service centre. Passed pressure test and combustion gas test. Replaced coolant and took for an extended test run. Of course did not play up during this. Have ordered a new genuine Kia radiator cap as a 'maybe' measure.
 

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Well at least you have ruled out the expensive possibilities. Some cars vent excess pressure from the rad cap and some vent from the reservoir cap. Whichever you have there will be a small flexible pipe for the run-off. Quick test : Locate the open end of that pipe and tie a plastic bag to it so if it is venting you will see coolant in the bag. The pressure caps are cheap anyway so I would inspect them both to see if there is any sign of the seal failing or weeping.
 

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Discussion Starter #6
Yep. If only it was that easy Turnup! I am not convinced. I will wait and see if the genuine rad cap makes a difference. The current non gen cap is rated at 1.1 bar which i believe is spec; and looks in perfect condition as does the radiator opening seat.The coolant is visibly evident ( and can be smelt) exiting an overflow tube on the expansion tank if I do not transfer coolant back to the radiator once it fills.I also came across some info saying a dodgy water pump could also cause cavitation (air bubbles) in a pressurised system.
 

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So the cap on the expansion tank is the pressure relief valve too and that is the one which I would change. Cavitation in water pump sounds implausible to me and anyway cannot "make" air - cavitation is water vapour which will re-condense as soon as the (local) pressure returns to normal.
 

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Discussion Starter #8
OK. Thanks. Expansion tank is not pressurized in my Kia Turnup. Simple sealed cap. Overflow tube exits at the top of the bottle.
 

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Trying to get my head around this.
Expansion tank runs at atmospheric pressure because the overflow pipe is open.....somewhere there is a pressure relief valve which allows expansion into the tank, but the displaced water is not returning to the cooling system as the water contracts again, drawing in air from somewhere. So perhaps wherever the expansion pressure relief valve is it also should allow reverse flow during cooling (or via a separate one way valve) but (however that works)it is not functioning.
 

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Discussion Starter #11
The PRV is in the radiator cap. What I am calling the expansion tank is the plastic overflow tank.I reckon the air is being generated inside the closed cooling system pushing the coolant out. When the engine cools, the coolant doesn't get sucked back into the radiator because the air which comes to the top of the radiator tank and creates an air gap at the radiator neck possibly breaks the syphon effect. Does that make sense?
This is why I am also thinking head gasket or crack as Noublue suggests. The Kia guys are really just scratching their collective heads but I guess a new radiator cap is an easy starting point.
 

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Well there is no known process whereby air is "generated" - if has to come from somewhere.
So the rad cap releases pressure into the expansion tank which operates at atmospheric pressure. Begs the question "via what pathdoes the displaced water return to thesystem asit cools?" However that works, either it is not allowing coolant to return, or in fact it is allowing air in. My guess is that the PRV also has a return valve and the problem is somewhere there.

Cracked head - I though you had determined that there were no combustion products present in the coolant?
 

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Discussion Starter #13
Yep. The pressure and combustion gas test showed negative ..... at the time of the test. I have heard that the test is not always accurate. Our issue only seems to get serious when we load the motor such as towing our camper up hills. It appears to behave itself around home which makes it hard for the techs to diagnose.The smaller spring loaded return valve under the radiator cap allows coolant to return to the radiator as the engine cools, using the syphon principle. It can only work if it is in a continuous sealed system though. As I read it, the presence of air at the top of my radiator breaks that syphon action just as air in a syphon hose will interrupt the flow.
 

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Discussion Starter #14
Well i finally bit the bullet and pulled down the Sorento engine. It was obvious that the local Kia guys were going to milk the situation for as long as they could .... to avoid getting their hands dirty maybe!Big job for a layperson but I enjoyed the challenge .. mostly,... and learn't heaps in the process. I also got to replace the front timing cover crankshaft oil seal which had been leaking for a time, and gotthe opportunity to clean out the soot and oil residue in the intake system.No obvious gasket leak or pathway but engine re-conditioner found a low spot in the head surface adjacent to a couple of pots and removed 0.2mm (8 thou). So far I have barely done 400 ks and done a short trip with camper up some hills to load the engine. Coolant is right where it should be.
I had never pulled down a diesel before and it has been a long time since i have rebuilt any engine. I certainly have plenty of respect for diesel mechanics after this. I found it physically taxing at times and the smell of diesel tends to hang around forever!
Overall, i was impressed with the engineering of these engines, and also satisfied with the soot levels in the EGR system.
I will post my notes for anyone else who may be interested in getting their hands dirty!

uploads/19374/Cylinder_head_removal_and_head_gasket_replacement_Kia_Sorento_XM_2.pdf
 

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Discussion Starter #15
Now engine just shy of 160000ks. Engine has been fine since gasket rebuild 15 months ago and holding coolant perfectly of course. The other day the engine made loud timing chain rattle noises on start up warm. Stopped engine and immediate restart quiet. Has not missed a beat since but i suspect tensioner is on way out or a temporary oil blockage caused lack of tension on the chain. Online search tells me tensioner problems are common with the 3.5 l petrol V6 but didn't find much re the D4HB engine. Watch here for the next exciting installment!
 

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Discussion Starter #16
Ahh.! Nothing to do with timing chain...thankfully! Alternator pulley has a clutch which was on the way out... Confirmed by loading the electrical system at idle - high beam and driving lights on. Who would have thought. It is designed to free wheel to reduce load on the auxiliary belt and improve engine efficiency when suddenly decelerating. I ordered a replacement pulley with the required special hollow splined socket and replaced it myself. Worst part of the job was removing the alternator from the vehicle as it is impossible to access the pulley in situ.
I also had to cut away a small section of the thermo fan housing frame in order to get the alternator unit out. Later models with the internal power steering pump may be easier. A rattle gun was required to undo the pulley.
Scary thing is that by the time i got the part ... a couple of weeks and 150ks the rattle had gone. I bet there are a few cars driving around with seized alternator pulley clutches. If you keep throwing auxiliary belts that may be the cause.
 
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