Mysterious coolant leak

[fzslg]

Hi everyone,
My car has been losing coolant slowly for months without visible leak anywhere, overheating, oil in coolant, milky oil, sweet smell and bubble in recovery tank. The coolant level in tank droped about 1cm every 40-50km driving in average. There is minor condensation on top of oil fill cap, it reappears few days after I wipe it, but oil from dipstick is clear and clean. After cold start, some damp white smoke and a few drips from tailpipe lasted about 15 minutes and didn't reappear after engine completely warmed up. Every time when I loose the recovery tank cap with engine completely cold, I can hear a popping sound that seems like air in coolant system escaping out. The coolant system can hold 18 psi pressure for 5 hours with cold engine. When kept connecting pressure tester and started engine without pumping pressure, the pressure on gauge didn't increase quickly, stayed at 5 psi after engine warmed up, then I pumped it to 15 psi, it slowly went up to 19 at most after 1 hour, and finally when engine got cold I saw coolant level was 0.5cm lower than it was before this test. But I still did not see any leak. Moreover, the recovery tank cap has been changed, the dealer also checked transmission pan and spark plug, and did TK test, they couldn't find the leak too. I'm at a loss. Is it likely a small head gasket leak or head crack?

 

[Ian Bungart]

hey OP, I would suggest a head gasket leak, not so much a cracked head.

 

[peterk9]

Hi everyone,
My car has been losing coolant slowly for months without visible leak anywhere, overheating, oil in coolant, milky oil, sweet smell and bubble in recovery tank. The coolant level in tank droped about 1cm every 40-50km driving in average. There is minor condensation on top of oil fill cap, it reappears few days after I wipe it, but oil from dipstick is clear and clean. After cold start, some damp white smoke and a few drips from tailpipe lasted about 15 minutes and didn't reappear after engine completely warmed up. Every time when I loose the recovery tank cap with engine completely cold, I can hear a popping sound that seems like air in coolant system escaping out. The coolant system can hold 18 psi pressure for 5 hours with cold engine. When kept connecting pressure tester and started engine without pumping pressure, the pressure on gauge didn't increase quickly, stayed at 5 psi after engine warmed up, then I pumped it to 15 psi, it slowly went up to 19 at most after 1 hour, and finally when engine got cold I saw coolant level was 0.5cm lower than it was before this test. But I still did not see any leak. Moreover, the recovery tank cap has been changed, the dealer also checked transmission pan and spark plug, and did TK test, they couldn't find the leak too. I'm at a loss. Is it likely a small head gasket leak or head crack?

Welcome to the Forum.
What kind of a 2011 Ford do you have? This is the 2011 - 2019 Explorer Forum.

Peter

 

[blwnsmoke]

Welcome to the Forum.
What kind of a 2011 Ford do you have? This is the 2011 - 2019 Explorer Forum.

Peter

2011 Ford Terri.

 

[KayGee]

probably 2011 ford Territory (Oz and China)- probably couldn't fit it all with the hard character limit.

 

[Turdle]

OP is down under, so I googled ford territory

Ford Territory (Australia) - Wikipedia

 

[Turdle]

Moved again to ford lincoln mercury sub forum

 

[fzslg]

hey OP, I would suggest a head gasket leak, not so much a cracked head.

But no typical symptom of blown head gasket such as overheating, milky oil and bubble in overflow tank. Could be an early stage minor head gasket leak?

 

[fzslg]

OP is down under, so I googled ford territory

Ford Territory (Australia) - Wikipedia

Yes, Australia version, same engine to explorer.

 

[fzslg]

Welcome to the Forum.
What kind of a 2011 Ford do you have? This is the 2011 - 2019 Explorer Forum.

Peter

2011 territory, Australia version, same engine to explorer.

 

[Ian Bungart]

from my experience this is the first signs of a small head gasket leak

But no typical symptom of blown head gasket such as overheating, milky oil and bubble in overflow tank. Could be an early stage minor head gasket leak?

now the funny part is the leak may stay this way for the life of the car if it does not over heat or the engine decides it is fine with it. but it could also spread without warning too, I guess if no issues with drivability or cooling of the engine I would suggest driving it and then if it does spread and you realize it DO NOT let the car over heat. or you can get it fixed now and not run the risk of the car leaving you stranded somewhere, 4.0 engine is a fantastic engine if it never overheats and with this temperamental engine its really important to change the oil every 3,000 miles with oil filter, and plugs every year, (NOT PROMOTING FORD) but I use all motorcraft oil, parts, ETC.. and at 188,000 miles of course it has had issues but she still runs like the day I bought her with 75,000 miles. hope this helps

 

[fzslg]

from my experience this is the first signs of a small head gasket leak

now the funny part is the leak may stay this way for the life of the car if it does not over heat or the engine decides it is fine with it. but it could also spread without warning too, I guess if no issues with drivability or cooling of the engine I would suggest driving it and then if it does spread and you realize it DO NOT let the car over heat. or you can get it fixed now and not run the risk of the car leaving you stranded somewhere, 4.0 engine is a fantastic engine if it never overheats and with this temperamental engine its really important to change the oil every 3,000 miles with oil filter, and plugs every year, (NOT PROMOTING FORD) but I use all motorcraft oil, parts, ETC.. and at 188,000 miles of course it has had issues but she still runs like the day I bought her with 75,000 miles. hope this helps

Thank you. So far so good with this car except I have to top up coolant every week and sometimes engine slightly shake when idling.
Today I checked another same model car of my friend, and found there are many things different between his car and my car.
Firstly, his car has much less and thinner damp smoke than mine after cold start, and there is completely no condensation on the underside of oil cap.
Moreover, I felt his engine is running more smoothly when I put my hand on the car.
Besides, a much higher pressure can be built up in his coolant system, the pressure meter on his car showed 8.5 psi after engine was completely hot (thermostat opened). For my car, the pressure just stayed at 4.5 psi after engine was hot and thermostat opened, and then it needed to take 30-40 more minutes to slowly get to 8 psi with engine idling. So I think the low pressure may be caused by a coolant leak during engine warming up.
Now these are all the symptoms which seem still not obvious enough for a blown head gasket or engine crack. And I have put uv dye into coolant but still found no external leak.
So confused, maybe have to remove the head. I prefer to fix it because the internal leak may damage the engine slowly.

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[Ian Bungart]

If it is a head gasket leak more than likely it is dumping into a cylinder, check the bottom of the oil cap for the dye and even the tail pipe, it’s a long shot but it would definitely point O a head gasket leak

 

[fzslg]

If it is a head gasket leak more than likely it is dumping into a cylinder, check the bottom of the oil cap for the dye and even the tail pipe, it’s a long shot but it would definitely point O a head gasket leak

I put uv dye into coolant and after engine cold start I found the water drips at tailpipe is slightly fluorescent, but then I found 2 other cars also have slightly fluorescent water drips at tailpipe after cold start. So that can't be an evidence. And the engine oil came with a factory UV sensitive unfortunately. So still couldn't find visible leak by uv dye.

 

[BrooklynBay]

Connect a cooling system pressure tester like this one:

 

[fzslg]

Connect a cooling system pressure tester like this one:

View attachment 162780

Thanks. I have a very similar one.

 

[fzslg]

Yesterday I started engine and left immediately for a 10 miles nonstop driving, after engine cold I saw the coolant level didn't drop any!

Last week I started engine and just left it idling for half hours, then after engine cold I saw coolant level dropped 0.5cm.

So it seems that the car is losing coolant only when engine is idling or running at very low rpm, especially in the first half hours after engine starting. What could it be?

 

[BrooklynBay]

It probably only happens when the engine reaches a certain temperature. Metal, gaskets, and other parts expand when it gets hot, and contract when it cools down. The pressure in the system is at a certain psi at the time of the leaking condition.

 

[fzslg]

It probably only happens when the engine reaches a certain temperature. Metal, gaskets, and other parts expand when it gets hot, and contract when it cools down. The pressure in the system is at a certain psi at the time of the leaking condition.

If contract when it cools down, I just wonder why the cooling system can pass pressure test when engine is cold? I am confused.

 

[BrooklynBay]

There might be seepage during the contracting & expanding process. Did you check the head gasket & bolts?