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Alright so a couple months back my car started overheating. Cold air out of heater when on full heat setting. I changed the thermostat and coolant. Problem fixed. A month or so later it started overheating again. I thought it was a bad thermostat so i changed it again. Problem fixed. A month or so later it did the same thing. I figured somehow maybe air was in the system so i burped the system and it fixed it. Every once in a while i have to do the same thing. So somehow air is getting in my system? Its not loosing and coolant. Not much at least. Ive checked the outside of my engine multiple times everywhere and no sign of any leaks. None. Usually it starts with the heater not working as it should (no cold air on hot setting) and then the temp fluctuates. No leaks. No smoke out of tailpipe either. No oil and coolant mix. What could be the issue? Ive talked to many car people about it and they seem baffled by it. ????
 

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You likely overheated it and the head is warped now. Most likely leaking into the cylinder. That’s why burping it temporarily works. The compression pressure is feeding into cooling system.

When low on coolant water pump has nothing to move so no heated water moving through your heater. That’s why you don’t have heat.

To fix it correctly will require a head gasket or possibly a new head or block. Temporary fix look into leak sealers. I normally avoid them but not sure of your situation

BTW an internal leak like this will show up in your oil (very bad can ruin entire engine) or being lost out the exhaust as steam. Once warmed up should not be steaming from exhaust.

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What baffles me is it didnt overheat much. I never let it get to max. Most it has been was 3/4 of the way up. I dont think it could warp the head. There is no coolant in oil or vise versa what so ever. It does steam out from exhaust but its normal. Averages 20-30 degrees where i live in winter. Exhust also does not smell like coolant at all. Ive even had another person smell the exhaust and he dont think it smells like it either. I really doubt its a head gasket or warped head. Im still baffled.
You likely overheated it and the head is warped now. Most likely leaking into the cylinder. That’s why burping it temporarily works. The compression pressure is feeding into cooling system.

When low on coolant water pump has nothing to move so no heated water moving through your heater. That’s why you don’t have heat.

To fix it correctly will require a head gasket or possibly a new head or block. Temporary fix look into leak sealers. I normally avoid them but not sure of your situation

BTW an internal leak like this will show up in your oil (very bad can ruin entire engine) or being lost out the exhaust as steam. Once warmed up should not be steaming from exhaust.

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Doesn’t take but one time. It’s leaking slowly and if you see no drips or runs likely an internal leak.

Verify you have a good radiator cap and the overflow reservoir is hooked up and not leaking. The fact you have had the heat go out several times is proof your losing fluid. The fluid that low will essentially be operating the engine with the head not properly cooled. As I said earlier some diagnostic tests may help pinpoint which cylinder is leaking. Remove the plugs and inspect. The cylinder(s) that are being steam cleaned will have clean plug(s) compared to others with a bit of ash on them.


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Discussion Starter #5
Doesn’t take but one time. It’s leaking slowly and if you see no drips or runs likely an internal leak.

Verify you have a good radiator cap and the overflow reservoir is hooked up and not leaking. The fact you have had the heat go out several times is proof your losing fluid. The fluid that low will essentially be operating the engine with the head not properly cooled. As I said earlier some diagnostic tests may help pinpoint which cylinder is leaking. Remove the plugs and inspect. The cylinder(s) that are being steam cleaned will have clean plug(s) compared to others with a bit of ash on them.


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Just wanted to update you. It overheated again today. I bled the system of air and went to orileys and got a combustion gas tester. Did the test 3 different times. All passed so no head gasket failure. Im completely stumped by this whole thing. Id honestly rather it been positive for combustion gas in the coolant so i knew what was wrong.
 

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Just wanted to update you. It overheated again today. I bled the system of air and went to orileys and got a combustion gas tester. Did the test 3 different times. All passed so no head gasket failure. Im completely stumped by this whole thing. Id honestly rather it been positive for combustion gas in the coolant so i knew what was wrong.
Have you checked the water pump for any leaks? It could be leaking and pushing air into the system. This could increase the pressure in the whole system and prevent water/coolant from circulating freely resulting in overheating.

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My '08 with about 110k miles was doing the same thing. I pressure tested and the system held steady at 15psi. I Put dye in the coolant and continued to check everything with a UV light, still nothing. This went on for a few weeks with coolant needing to be added every few days. So yesterday i check the oil and see little droplets of dye on my dipstick and I thought for sure it was a head gasket. So I pull into the garage and notice dye on the driveway. The leak ended up being from the water pump area and unfortunately looks to be a cracked block.
241970
241971
 

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Sorry for my ignorance but are the pics a K20? I know the R18 is notorious for cracks in the block.

If you have pressure in the cooling system from air I’m not aware of any other source but compression pressures. What did the plugs look like?
I guess it’s possible you have a cracked block but you should be seeing lots of fluid and drips on ground Or in the oil. A dye may be a good try.

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Discussion Starter #9
I
My '08 with about 110k miles was doing the same thing. I pressure tested and the system held steady at 15psi. I Put dye in the coolant and continued to check everything with a UV light, still nothing. This went on for a few weeks with coolant needing to be added every few days. So yesterday i check the oil and see little droplets of dye on my dipstick and I thought for sure it was a head gasket. So I pull into the garage and notice dye on the driveway. The leak ended up being from the water pump area and unfortunately looks to be a cracked block. View attachment 241970 View attachment 241971
I have no leaks. Im currently doing a head gasket at the moment. Car started blowing white smoke out the tailpipe. No sign of oil in coolant or the other way.
 

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Inspect head and block carefully for small cracks. Between valves is sometimes difficult to see.


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Sorry for my ignorance but are the pics a K20? I know the R18 is notorious for cracks in the block.

If you have pressure in the cooling system from air I’m not aware of any other source but compression pressures. What did the plugs look like?
I guess it’s possible you have a cracked block but you should be seeing lots of fluid and drips on ground Or in the oil. A dye may be a good try.

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It is a K20. I did use dye, and noticed it on my dipstick. Pulled the car into the garage to do a head gasket and saw the dye on the driveway. That’s what led me to the area behind the thermostat housing and other threads on here with the same issue.
 
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