adobian

2017 Q7. Prestige.

This car overheated at one point. My mechanic friend said there was coolant in the oil. I guess the head gasket was blown. He replaced the head gasket for me. Change oil change coolant. He's swapped out the water pump but he said the thermostat was still fine. I took it out and it drove fine. When I turn on the heater I get heat. But I never took it on the highway. Last night I decided to drive on the freeway and 1 hour into the drive after 63 mi the heat from the heater off sudden disappeared. Same symptoms like last time when it was leaking coolant.

So I glance at the temperature gauge and I noticed a shot up. I pulled over right away. Waiting for it to cool down. I slept there on the car for 5 hours. Then this morning I woke up and drove back. The temperature shot up again so I decided to take the surface road driving only 20 mph with occasional breaks in between.

I made it home in 3 hours, driving 65 miles. The radiator fan was on the whole time
Occasionally it shot up all the way so I stop immediately, I pulled over and shut off the engine. And take a break

Could this be heater core that clogged up? Or could it be the thermostat that is broken?

Before it was overheating the last time I put a lot of stop leak materials in it. But I thought my friend flushed out the old coolant. Possibly he didn't get everything out.

Is there an easy way to flush out the heater core?
Could it be that the system hasn't been bled correctly cuz I don't think my friend knew how to do it.

retom

There could several reasons for this: not correctly bled cooling system, a blockage in this system or a faulty thermostat.There are effective ways to flush the entire cooling system. A professional should be able to handle it easily and check the patency of the entire cooling system. I would also replace the thermostat because it is not complicated and expensive and may be the source of the problem. It is also worth cleaning the radiator from the outside because in the cars with higher milage it can simply be heavily soiled by dead insects and other road debris and its efficiency is limited by this.
Also check the coolant to see if there are still any traces of oil in it. Head gasket replacement is rather a complex repair and it is good to make sure that this repair was made properly.

Dtomasi

The engine is kaput. What has happened is the car overheated, blew a head gasket and either warped the head or burned a channel through a coolant passage. There is on way to fix this short of milling the head. Plus the engine has overheated multiple times which probably cause more damage to the cylinders and pistons. If you want to hang on to the car, replace the engine with a good used one. You're just throwing money away trying to fix it. Btw the reason the heat went out is because you now have exhaust gas in the coolant system from the blown gasket.

adobian

I will try flushing first.

Irontite ThoroFlush (468-9110-16) https://a.co/d/060lzhq

adobian

Sad to hear this. My last Audi ever here.

But it is not easy to find a used Q7 engine. And even harder to find ones that guarantee to work.

adobian

Engine is like $7000.

What can I do now?
Did you say something about milling?

adobian

Strange that i was able to drive 65 miles on highway with no problem. Car drove wonderfully.

adobian

So you are saying the car computer could detect the exhaust going to the coolant and automatically shut down the heat?

The car up till this moment has no engine noise, it drives fine with plenty of acceleration.

Dtomasi

Nothing wrong with Audi, any car not maintained probably with have issues. Here's a good article that you should read. Not Audi but the concept is the same. Good luck!
https://www.hansonsubaru.com/service...0and%20coolant.

richsurf

I find it hard to believe your mechanic didn’t change the thermostat which is one of the cheapest components in the system. Ask him if he did a hot water test on it. It’s basically heating water on the stove with the thermostat in it and monitoring the temp. If you have a 180degF unit it should open when the water reaches that temp. I always replace them doing a cooling system job just because it is so easy and inexpensive.
ebay has a few engines for sale but they are pricey.
maybe call Audi of America and see if they can help. My experience is they won’t. Sorry to hear about your bad situation.