Overheating & turbocharger issues with my 2010 Hyundai Sonata: What now

When the temperature started rising, I checked the engine bay and saw that the AC fan was running and the coolant tank was full to the brim.

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I own a 2010 Hyundai Sonata Transform, it has done approx 1.85 Lakh Kms, timing belt and bearings changed. I had dyno'd the car at RD Bangalore in 2014 at about 80K Kms and installed a Dual Channel Dieseltronic and it has been running amazingly all these years with no issue.

Fast Forward to the past 3 months, I started having temp rise issues and then went ahead and did a temperature sensor, radiator cap, and thermostat replacement. Heating problem still persists.

Next, I flush the radiator & have it chemical washed too, looks brand new, and although the lower fins have gotten worn out here and there, the heating problem still persists.

Next, I went to the heavy step and had the water pump checked and the water pump gasket replaced, but the heating problem still persisted.

Though it is to be noted, that whenever the heating problem shows up, the car has to be driven for almost 2 hours and only then does it show up, when the temperature starts rising, I check the engine compartment to see the A/C fan running and the coolant tank full to the brim and overflow pipe is tossing coolant out, a few times I even noticed bubbling (like its boiling) in the coolant tank and a few times, as well as bubbling froth coming out when the radiator cap was removed and the car was idling. There was no oil content or anything else present in the froth from the radiator itself.

From the start of this heating issue, I have removed the DieselTronic Box and kept the vehicle Stock.

Also, all through these issues it was scanned at the dealership and the were no errors except for a neutral switch error which it had shown even earlier but never showed any problem and the vehicle drove fine. So, after taking a lot of advice from a lot of people we went one by one as written above to sort this issue out, I even went the extra mile to have the fan control module replaced in case it was that issue but still heating issue crops up.

This along with advice from various people led me to finally rule out taking the car in to replace the head gasket at a recommended engine workshop in town that specializes in pure engine work. After the head gasket was replaced, I drove it for above 1200 Kms and I see the temperature rising again, it was certainly saddening to see this again.

This time it rose above the half mark, it would have barely driven about 20 Kms without the AC being on, and about 2 mins above the half mark she went to a dead stop, I tried cranking it a few times, but even though the crank was there, it refused to start.

Long story short, I have it towed on a flatbed to the showroom, and the showroom guys suspect its engine failure and whatnot, and they say we would have to open it up completely, I even ask for a compression test but they don't seem to have it, I decide to take the car home and ask the engine workshop technicians to come and take a look at it as they have given me warranty on the engine work, they show up after two days and upon investigating the problem, find the turbo core has been damaged and hence blocked the exhaust and that is the reason it won't start, they inform me that it has to be changed. The Sonata Transform runs a Garrett Turbo and they have stopped manufacturing this model.

I proceeded to have the Turbo + Manifold + EGR removed at home, they disassembled the turbo and it seems the turbo shaft had broken and that is what caused the turbo to fail, the car was kept at home for about a month until I found a guy who has been in the turbo repairs business for a long time, he advises to acquire a J-Rone Turbo Core against a TLC Brazil. Anyway, I send it to him for repairs and when I go to collect it, I take along with the EGR, Catalytic Converter & Rear Mufflers, the turbo core work is done and he completes the cleaning in two hours and returns the turbo with a 1-year warranty clause.

The turbo intercooler and its hoses are chemically washed and cleaned as it had a lot of oil kickback into it due to the turbo failure, and then everything is assembled back.

After my guys fit this back on, the new problem is that the turbo boost does not kick in around 1.5-2 RPM, which it used to, and there seems to be no turbo whistle as it's not functioning the way it should. The turbo kicks in randomly and sometimes while I gear down and accelerate the car revs into 2k and 3k rpm but the speed is just around 40-60. Now when this happens at times if I press the clutch and accelerate or shift to neutral and floor the accelerator I hear the default blow-off valve kick in and after that the turbo works, but otherwise the turbo is just not kicking in the way it should.

I then proceed to take the car to the turbo repair guy and he adjusts the wastegate actuator anti-clockwise, basically the lesser the thread on the top of the wastegate nut the more the boost, and if the opposite side the lesser the boost.

He adjusts it about three times, upon adjusting it first, when started and in neutral, upon acceleration, the RPM only comes to about 3K and not more, then he adjusts it again and now we are seeing it pass 4.5 and come to just near 5K RPM. Mind you the RPM meter for the Sonata Transform is 6000 RPM but it never goes full 6000RPM, while he does these adjustments, there is no black smoke from the exhaust as well. Now that he's done the adjustment the 3rd time, it's at 5K RPM on full acceleration while on neutral, he proceeds to say let's drive it and see. Upon driving it, I see the car boost now kicking in, we drive it up and down a stretch of 12 kms about two to three times, and he says it's fine and that this is all that can be done on the turbo and nothing else can be adjusted. I decided it could be fine and bring it back home.

The next day, we are back at the turbo not kicking in when it should, and also when I accelerate I can hear the sound of water sloshing in the dash, could this be the coolant? I decided to call my engine mechanic and he recommended I take it back to the turbo guy until it was repaired perfectly. He asked if it had overheated and I said it went above the half mark just once when the turbo failed first, but ever since it has been fit back and driven 1200Kms it has not overheated. During the 1200Kms of driving I checked multiple times to see if the coolant expansion tank topped out or boiled but no such thing after the head gasket work, there were times when I check the next morning and the suction/expansion of the coolant reservoir has happened how it should happen.

Now the only thing I think of is showing it back to the dealership. So I go ahead with that and they scan the car, It shows the neutral switch error and an under boost error, they drive it and first-hand witness the issue I am having. The showroom head is in charge of the car and they even experience an overheat on one test drive, but they are hesitant to touch the turbo and say they will adjust it only in my presence as they have not done the work, luckily there is another Sonata in the showroom so they adjust the nut/length of the wastegate actuator to the setting of that car.

They put everything back together and then we drive the car, the car seems to be accelerating upward to about 80-90 in the RPM range of 2500-3000 K RPM but with no turbo whistle/turbo support and luckily the car is not getting stuck in the 20-40-50 KM speed area while the RPM drives upward, but there is still no turbo kick-in. We drive a 6KM stretch one way and on the way back, when I start accelerating the turbo kicks in this time, at the end of the stretch when I downshift, and accelerate no turbo function and just a slow dull gradual climb into 60-70.

So now, I am just not sure what to do next, I am asking the engine guys to have a look at this in the coming days and am even thinking of having the turbo taken off and sent to re-calibrate/check if it was done properly at first etc. I hear that it can be calibrated and tested on a machine, is this info correct? Is there anyone who specializes in turbo work/calibration in the south?

I am open to options in Kerala, Bangalore and Chennai. Someone, please advise on what could be causing this issue. I do not know what to do now!

Also, please see the relevant pics attached of the damaged turbo, new turbo core and current nut adjustment of wastegate taken two days ago.

Attached thumbnails

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