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Discussion Starter #1 (Edited)
For a 2010 jetta 2.5 MKV 109,000 miles

Coolant disappearing (no visible leaks anywhere). Had mechanic look at it and he suggested testing the oil cooler. He also stated he tested to see if it was the head gasket. Assuming he did the necessary tests for that. I did ask, but didn't state which specific tests. Anyway, replaced the oil cooler (per his recommendation...known issue with these cars), the thermostat (cuz dammit that's a hard part to get to) and the oil filter housing. Did this all this with help from mechanic friend. My friend noted the gasket on the oil filter housing did seem a bit damaged on upper left hand corner and there even was some flaky white substance on the engine where that gasket would be flush on oil filter housing. To make this short (I'm trying folks)--it took a couple days for the coolant level to remain steady (went down a day or two after driving) then after two days of level staying put, it dropped again just below the MIN level. AND there is still milky crud on top of dipstick and under oil cap. Engine is running well. And no other known performance issues (i.e., no overheating or firm coolant hoses). Any suggestions on how to diagnose problem further. Thank you for reading and your response.
 

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Follow up question to the milky substance. Do you drive a lot of short trips?


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Discussion Starter #3
Follow up question to the milky substance. Do you drive a lot of short trips?


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Thank you for responding. I have taken the freeway (reside in LA) on a few occasions since replacing the oil cooler (almost a week ago) and it was the next day (after a freeway trip of approx 60 mi roundtrip the night before) that I noticed the coolant had dipped again from the Max level to below the Min level by about a centimeter. It was cool that night, so I suppose it's possible it's condensation, but something tells me it may be more than that. Overall I'd say I drive short trips, but car does get to operating temperature every time since I've started keeping an eye on this. Even though I did flush the coolant AND change the oil after installing the new oil cooler, is it possible there is still coolant mixed with the oil and this is just the residual mixture from before? But disappearing coolant is the other mystery.
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Aah. The long struggle to acknowledge its really the headgasket.

The sludge is either from short travel, so driving with an engine and oil that never gets the time to heat up.
Or a sign of a headgasket failure.
If you did a few longer highway trips. It should become less. Till it goes away.

My ajm, 1.9 85kw tdi in an audi b5.5, Had the same.
No overheating, no hard hoses. In the beginning ;)
So i just drove on. Filling it up regularly.
Changing the thermostat. Changing this, that.

But then after some months, when driving up hill, pushing it a bit, it would heat up shortly. And then return to normal.
Heatercore would stop getting warm.
And then the coolant pressure made the fuel heatervalve leak. Then a coolanthose burst.

And then i finally admitted it. Got it tested properly. And got a new headgasket ;)

Just get it pressure tested properly. It will probably leak.
 

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For a 2010 jetta 2.5 MKV 109,000 miles

Coolant disappearing (no visible leaks anywhere). Had mechanic look at it and he suggested testing the oil cooler. He also stated he tested to see if it was the head gasket. Assuming he did the necessary tests for that. I did ask, but didn't state which specific tests. Anyway, replaced the oil cooler (per his recommendation...known issue with these cars), the thermostat (cuz dammit that's a hard part to get to) and the oil filter housing. Did this all this with help from mechanic friend. My friend noted the gasket on the oil filter housing did seem a bit damaged on upper left hand corner and there even was some flaky white substance on the engine where that gasket would be flush on oil filter housing. To make this short (I'm trying folks)--it took a couple days for the coolant level to remain steady (went down a day or two after driving) then after two days of level staying put, it dropped again just below the MIN level. AND there is still milky crud on top of dipstick and under oil cap. Engine is running well. And no other known performance issues (i.e., no overheating or firm coolant hoses). Any suggestions on how to diagnose problem further. Thank you for reading and your response.
So you are the second 2010 2.5 this week to post with unexplained coolant loss. You may want to find a coolant pressure tester and test the coolant system, apply a max pressure of 1.0bar or 14.5psi to the system and see if you can find any external leaks. Keep in mind that the rate of pressure loss will correspond to the size of the leak. If you do not find and external leaks then its internal. You can use a block tester to check for combustion gasses in coolant, these are about $30 for the kit and some of the big box auto store do have them for rent. You could also try a leak down tester and compression gauge to try an isolate its location to a cylinder/s.
 

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Discussion Starter #6
Aah. The long struggle to acknowledge its really the headgasket.

The sludge is either from short travel, so driving with an engine and oil that never gets the time to heat up.
Or a sign of a headgasket failure.
If you did a few longer highway trips. It should become less. Till it goes away.

My ajm, 1.9 85kw tdi in an audi b5.5, Had the same.
No overheating, no hard hoses. In the beginning ;)
So i just drove on. Filling it up regularly.
Changing the thermostat. Changing this, that.

But then after some months, when driving up hill, pushing it a bit, it would heat up shortly. And then return to normal.
Heatercore would stop getting warm.
And then the coolant pressure made the fuel heatervalve leak. Then a coolanthose burst.

And then i finally admitted it. Got it tested properly. And got a new headgasket ;)

Just get it pressure tested properly. It will probably leak.
Thanks for your response. Definitely going to do so more testing.
 

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Discussion Starter #7
So you are the second 2010 2.5 this week to post with unexplained coolant loss. You may want to find a coolant pressure tester and test the coolant system, apply a max pressure of 1.0bar or 14.5psi to the system and see if you can find any external leaks. Keep in mind that the rate of pressure loss will correspond to the size of the leak. If you do not find and external leaks then its internal. You can use a block tester to check for combustion gasses in coolant, these are about $30 for the kit and some of the big box auto store do have them for rent. You could also try a leak down tester and compression gauge to try an isolate its location to a cylinder/s.
Thanks for your response. Will be doing more testing to figure this out. I'll post again when I get it all sorted.
 

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Discussion Starter #8 (Edited)
UPDATE: So, I did a coolant pressure test and best I can tell if anything (and this is based also on the milky oil, too) there is an extremely slow leak. After about six minutes (and I did this test 3x's), the reading only went down about 1psi..and after about 20 min, down about 2psi or maybe even 3psi at most. I also did the coolant combustion check as recommended and coolant did not change color (see pic). HOWEVER, coolant is still disappearing and now...drum roll, please...the red oil pressure warning light went on the other day AND oil dipstick is showing more milky oil (see pic)...AND...the engine is making a strange whining (if that's the best description) sound. Have a mechanic friend on his way over to check it out, but feel I'm just gonna have to get over to a VW dealership for a more extensive diagnosis.

***
Mechanic friend stopped by...
So engine whining noise comes on after car has warmed up a bit. Did also notice some oil/water moisture along with vacuum delete hose. Hadn't noticed that before. And oil pressure warning light will come on after a min of driving car. This may be because the viscosity has changed due to the coolant and oil mixing. After short drive, whining noise will be more prevalent with stepping on the gas pedal a bit. So not exactly sure what that is all about. Next stop, VW dealership.

Will keep updating.
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