fzslg

Need suggestion for a mysterious coolant leak

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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 30-40 miles driving in average. Coolant level kept lowering even after it was below MIN marking.

There is minor condensation on under-side of oil fill cap, it always reappears few days after I clean it, does this show a very minor water or coolant keeps going into oil? But oil from dipstick looks clear and clean.

3 minutes after cold start, much damp white smoke and a few drips keep coming out from tailpipe for about 15 minutes then completely disappear after engine completely warms up.

Every time when I remove the overflow tank cap with completely cold engine, I can hear a popping sound that seems like some air in coolant system escaping out. Does this show a small pressure from engine is leaking to coolant system?

For pressure test, the coolant system can hold 18 psi pressure very well for more than 5 hours with cold engine. When I kept connecting pressure tester to overflow tank 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 idling, and finally when engine got cold I saw coolant level was 0.5cm lower (or about 5oz less) than it was before this test. But I still did not see any external leak.

Moreover, the recovery tank cap has been changed, the dealer also checked transmission pan and spark plug, and did TK test (combustion gas detection) , they couldn't find the leak too.

I'm at a loss. Any suggestion? Could it be a very small and early stage blown head gasket or head crack without obvious symptoms?

 

There comes a new clue. As I mentioned, after 1 hour high pressure test with engine idling yesterday, coolant level droped 0.5cm. Today I started my car and just leave it idling for half hours without pumping additional pressure, after engine was cold, I saw the coolant level still droped about 0.5cm. So no matter the engine was running for 1 hour or half hours, and no matter there was high pressure or normal pressure in coolant system, my car lost the same amount of coolant. It seems the car loses coolant only in the first half hour after engine cold start. What can be the cause?

 

Edited by fzslg (see edit history)

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Just now, Ben Bruce aka First Born said:

No disrespect meant, but with a car that new, I believe the dealer would know best.  

 

  Ben

 

They diagnosed for 1 hour, then just said they couldn't find any leak with this car.

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1 minute ago, Ben Bruce aka First Born said:

Sometimes one has to live with a problem until it grows to a size that can be found.

 

  Good luck.

 

  Ben

Thanks, but if it is a internal leak, could it slowly damage the engine?

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If it is a small head gasket leak it could be burning off with no visible sign. But, the coolant will clean the combustion chamber. If you take out the spark plugs and one is perfectly clean, that is the cylinder with the leak. If 2 adjacent cylinders, the gasket is blown between them. Such leaks can persist for a long time with no apparent damage but, it looks like it's time to shop for a newer car.

 

There are stop leak preparations that can cure leaks. Sometimes they work.

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I had issues with our 2013 Dodge van that the dealer could not locate.  Took it to a good independent repair shop who took the time to examine all symptoms of the problem and repair it.  It took three visits as the problem would only manifest itself under specific operating and ambient temp conditions.  Never overlook the independent guys.

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2 hours ago, Rusty_OToole said:

If it is a small head gasket leak it could be burning off with no visible sign. But, the coolant will clean the combustion chamber. If you take out the spark plugs and one is perfectly clean, that is the cylinder with the leak. If 2 adjacent cylinders, the gasket is blown between them. Such leaks can persist for a long time with no apparent damage but, it looks like it's time to shop for a newer car.

 

There are stop leak preparations that can cure leaks. Sometimes they work.

 The dealer guy said they removed the spark plugs and found no evidence of leak, but maybe they didn't look down the plug hole to check cylinder chambers. Is it possible a small leak would not present at spark plugs?

I bought this car just half years ago, it still looks new and has done only 100,000km. So I prefer to fix it.

Can these stop leak products even cause a worse problem such as clogging coolant system?

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1 hour ago, joe_padavano said:

A leakdown tester should allow you to find a leaking head gasket.

Yes, I think that is the next test I have to do.

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1 hour ago, TerryB said:

I had issues with our 2013 Dodge van that the dealer could not locate.  Took it to a good independent repair shop who took the time to examine all symptoms of the problem and repair it.  It took three visits as the problem would only manifest itself under specific operating and ambient temp conditions.  Never overlook the independent guys.

Maybe the dealers won't  spend a lot of time trying to solve issues that are unusual or not quickly solved.

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12 minutes ago, fzslg said:

Maybe the dealers won't  spend a lot of time trying to solve issues that are unusual or not quickly solved.

 

Most dealership "mechanics" are only parts-changers. They plug in to the diagnostic connector, they read the codes, and they replace the parts that the computer tells them to replace. They have little or no diagnostic skills and thus a problem like this that doesn't set a code will be a complete mystery to them. Sadly, this is the state of auto repair today.  The suggestion not to overlook the independents is a good one in that independent repair shops (especially older, well established ones) will have much more experience with actual diagnosis.

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If coolant is getting into the combustion chamber the spark plug would be clean.

 

This kind of thing can be very hard to find. I had a coolant loss on a Dodge Caravan, it would lose a liter of coolant in 50 miles. I couldn't find where it was going. One day I parked it on 4 inches of fresh snow and let it run for half an hour, nothing dripped on the ground. Spark plugs were normal. I never did figure out where the coolant was going, I bought another car, tore the engine down thinking it might be the water pump, which is buried in the guts of the engine on those models, but the water pump and hoses were fine. I'm still puzzled.

 

On another car there was a leak in the rad hose where rubbing against a bracket cut into it. Nothing showed and it did not leak when the engine was stopped, only when it was running and under pressure. One day I happened to look under the hood with the engine running, moved the hose and saw a few drips. I had previously inspected everything under there, with the engine off, and found nothing.

 

In a third case, a Lincoln Town Car, the culprit was a cracked intake manifold. Some of them had a plastic intake that also included a water passage and they could deteriorate and crack when they got old. The leak dripped on the coil and shorted it out. I replaced 3 coils before figuring it out, that one I tried to fix with JB Weld but it only cracked someplace else. So I scrapped the car. It had over 300,000 miles on it.

Edited by Rusty_OToole (see edit history)

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I'm inclined to a head gasket leak, unless this has some modern/exotic plumbing I'm not familiar with where coolants getting in...

On the stop leak, in my jalopy days we lived on stop leak and block seal, and while I remember people saying it'd stop up the radiator instead of  the leak, can't recall ever having such problems---that being said, radiators, main and/or heater, may be quite different designs now...

Edited by Bud Tierney
addition (see edit history)

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21 hours ago, joe_padavano said:

 

Most dealership "mechanics" are only parts-changers. They plug in to the diagnostic connector, they read the codes, and they replace the parts that the computer tells them to replace. They have little or no diagnostic skills and thus a problem like this that doesn't set a code will be a complete mystery to them. Sadly, this is the state of auto repair today.  The suggestion not to overlook the independents is a good one in that independent repair shops (especially older, well established ones) will have much more experience with actual diagnosis.

Yes, I saw the dealer shop is full of young boys. I will look for an independent repair shop. Thank you for your suggestion.

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21 hours ago, Rusty_OToole said:

If coolant is getting into the combustion chamber the spark plug would be clean.

 

This kind of thing can be very hard to find. I had a coolant loss on a Dodge Caravan, it would lose a liter of coolant in 50 miles. I couldn't find where it was going. One day I parked it on 4 inches of fresh snow and let it run for half an hour, nothing dripped on the ground. Spark plugs were normal. I never did figure out where the coolant was going, I bought another car, tore the engine down thinking it might be the water pump, which is buried in the guts of the engine on those models, but the water pump and hoses were fine. I'm still puzzled.

 

On another car there was a leak in the rad hose where rubbing against a bracket cut into it. Nothing showed and it did not leak when the engine was stopped, only when it was running and under pressure. One day I happened to look under the hood with the engine running, moved the hose and saw a few drips. I had previously inspected everything under there, with the engine off, and found nothing.

 

In a third case, a Lincoln Town Car, the culprit was a cracked intake manifold. Some of them had a plastic intake that also included a water passage and they could deteriorate and crack when they got old. The leak dripped on the coil and shorted it out. I replaced 3 coils before figuring it out, that one I tried to fix with JB Weld but it only cracked someplace else. So I scrapped the car. It had over 300,000 miles on it.

I have put the uv dye in coolant, but still couldn't find any external leak by using uv torch.

If the leak into combustion chamber is small enough, can the coolant only clean the chamber but not the spark plug?

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19 hours ago, Bud Tierney said:

I'm inclined to a head gasket leak, unless this has some modern/exotic plumbing I'm not familiar with where coolants getting in...

On the stop leak, in my jalopy days we lived on stop leak and block seal, and while I remember people saying it'd stop up the radiator instead of  the leak, can't recall ever having such problems---that being said, radiators, main and/or heater, may be quite different designs now...

Today I noticed that no matter cold start or hot start, no matter start in the early morning or sunny afternoon, much damp white smoke and few drips always appear at the tailpipe after engine start and till engine completely warms up.

The debate about stop leak products is always there, I would try if my car is very old, but it has done just 100,000km.

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25 minutes ago, fzslg said:

Today I noticed that no matter cold start or hot start, no matter start in the early morning or sunny afternoon, much damp white smoke and few drips always appear at the tailpipe after engine start and till engine completely warms up.

The debate about stop leak products is always there, I would try if my car is very old, but it has done just 100,000km.

 

Don't confuse humidity in the air with a real internal engine leak.  The air sucked into the engine always has some humidity in it, and water vapor is a byproduct of combustion. There will always be some water vapor (and often liquid) at the tailpipe when you start the engine until it warms up.  That doesn't mean that there ISN'T a head gasket leak (which may or may not be sealing itself as the engine comes up to temperature and parts expand), but some water is normal.

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49 minutes ago, joe_padavano said:

 

Don't confuse humidity in the air with a real internal engine leak.  The air sucked into the engine always has some humidity in it, and water vapor is a byproduct of combustion. There will always be some water vapor (and often liquid) at the tailpipe when you start the engine until it warms up.  That doesn't mean that there ISN'T a head gasket leak (which may or may not be sealing itself as the engine comes up to temperature and parts expand), but some water is normal.

I put the uv dye in and still couldn't find any leak by using uv torch. But during the engine was warming up, I found the water drips at the tailpipe are with slight UV sensitive. The water looks like just normal clear water without any color, but looks slightly fluorescent under the uv light, but it is not as green and bright as the fresh coolant under uv light. And this disappeared after smoke and drips stoped coming out and tailpipe became dry. If there should be nothing else with UV sensitive in the car, I think it must be coolant which was burned to vapor and lost its color first but still coming out with a very slight UV sensitive. What do you think?

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1 hour ago, fzslg said:

What do you think?

 

I think that is a reasonable conclusion.  I'd suggest that your problem is either a head gasket or a crack that is closing up as the engine heats up.

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If there is coolant or water getting into the combustion chamber the spark plug will be clean. It isn't possible to clean the combustion chamber and not clean the spark plug .

 

When you burn gas each gallon produces 1.07 gallons of water.

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