What are the possible causes of loss of coolant?

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Thread: What are the possible causes of loss of coolant?

  1. #1
    in dire need of an organic chemistry lesson
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    What are the possible causes of loss of coolant?

    Since a few days I noticed coolant loss in front of the car (passenger side). Could this leak possibly be from the o-ring of the temp sensor in the lower radiator hose (per AndreasPassat)? If so, where/how exactly should I look for it?

    Or could it also be from the turbo coolant lines (per John-E)? Where are those lines?

    The Car: 2002 1.8T AWM

    Thanks



    P.S. Man I'm really getting sick and tired of this car. How much time and money should I spend on it to keep it running. Really frustrating. Especially when I don't have access to my own home garage to work on it.

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    Quote Originally Posted by Emry View Post
    Since a few days I noticed coolant loss in front of the car (passenger side). Could this leak possibly be from the o-ring of the temp sensor in the lower radiator hose (per AndreasPassat)? If so, where/how exactly should I look for it?
    Lay on the ground in front of the car, locate the lower radiator hose, the CTS is in the hard molded part of the snap on connector end that attaches to the radiator. If it's leaking coolant it should be pretty obvious. Coolant residue will be more than likely present.
    I didn't realize your were an AWM, but it still is relatively the same as a v6.

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    I was going to post a picture, but Imgur is not complying with me at the moment.

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  6. #4
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    What about water pump? I know it is more centered in front but liquids have a mysterious way of traveling! The only reason i say that is because i had a coolant leak as well that was towards the passenger side and center while the car was on the same spot for a while and after looking around found dry and wet coolant around the water pump housing. Just a thought.

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    The main places for coolant loss on the 1.8T, in general:
    1. coolant flange
    2. thermostat housing
    3. water pump seal
    4. cracked tank or faulty seal on cap
    5. oil cooler (internal)


    Coolant flange can be from leaking valve cover/CCT which compromises the rubber o-ring and causes it to swell, or just warpage from heat over time.
    Thermostat housing, the same as above.
    Water pump seal, no rhyme or reason it seems. I've had it leak at 20k miles and 80k miles.

    Check the coolant temp SWITCH in the lower rad hose and also the drain petcock. Also look around any hose connections. If you had to loosen anything or muscle around any coolant related items in your recent repairs, I'd check them first.
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    Glutton for Punishment: 16 A4 S-line Sport pkg Prem+, 04 Passat 1.8T GLS Variant Manual swapped, 2017 Q5 Prem+

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    #6. Crack in heater core inlet pipe.
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    #7 turbo coolant line... above A/C compressor , it uses two crush washers on each of it's banjo fitting ends, really gets "punky" with all the oil,heat . you do not have to remove turbonto replace ,just drop compressor
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  10. #8
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    Quote Originally Posted by Hirnbeiss View Post
    #6. Crack in heater core inlet pipe.
    There is no coolant spots in that area.

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    Quote Originally Posted by VAGguy View Post
    The main places for coolant loss on the 1.8T, in general:
    1. coolant flange
    2. thermostat housing
    3. water pump seal
    4. cracked tank or faulty seal on cap
    5. oil cooler (internal)


    Coolant flange can be from leaking valve cover/CCT which compromises the rubber o-ring and causes it to swell, or just warpage from heat over time.
    Thermostat housing, the same as above.
    Water pump seal, no rhyme or reason it seems. I've had it leak at 20k miles and 80k miles.

    Check the coolant temp SWITCH in the lower rad hose and also the drain petcock. Also look around any hose connections. If you had to loosen anything or muscle around any coolant related items in your recent repairs, I'd check them first.
    Checked all those. No coolant on those areas although I do not exclude the WP seal leak yet.

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    A friend brought his 99’ BMW 528i the other day because he lost coolant and the car OVERHEATED.
    I spotted the leak at one of the coolant hoses because it came loose off the radiator and rubbed against the AC compressor clutch.
    I fixed the hose. The moment I Poured coolant in the tank it literally gushed out from the bell housing.
    Did compression test. Cyl 6 is 0!
    I learned that blown head gasket or warped head can cause coolant leak


    Sent from my iPhone using Tapatalk

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    Quote Originally Posted by cchief22 View Post
    #7 turbo coolant line... above A/C compressor , it uses two crush washers on each of it's banjo fitting ends, really gets "punky" with all the oil,heat . you do not have to remove turbonto replace ,just drop compressor
    Chief, as of now I lean toward this turbo coolant lines because the leak (or at least the coolant drops) come from the top of the A/C compressor.
    Now, the question is what to to take to remove the compressor? Should the A/C belt come off? Should all the coolant be drained first? Should the freon be loaded again? How hard is to reach the turbo lines?

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    Tie some paper towel “diapers” around suspect joints. This helps to identify leaks that occur under hot pressure.

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    On my son's 2002 AMB 1.8T (Audi A4), we have replaced both turbo coolant lines (to and from), the water pump, and the coolant temperature flange.

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    correct me guys if I am off base, I believe A/C compressor can be unbolted from engine block (3 bolts ? ) and will drop down ,hoses to condenser can be left attached, just detach electrical and loosen belt and remove???? been awhile

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    Reminds me of the lines going to turbo. On my 01 1.8t a4 awm the lines could be removed without touching any other components. It only leaked after getting hot and then cold again and finally catastrophically failed on a short drive and luckily didn’t do any damage. Replace that pair of lines anyways as a preventative. Happened around 190k
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    thanks for helping on hose removal, I had mine in service position when I did mine so a little foggy.....O.K. a lot foggy

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    My rear coolant flange was leaking so I replaced it. That letter G between my old and new coolant flanges is my old O-ring. Also if you see any kind of rust on your transmission it's probably the same thing
    Attached Images Attached Images

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    Quote Originally Posted by hodgson316 View Post
    My rear coolant flange was leaking so I replaced it. That letter G between my old and new coolant flanges is my old O-ring. Also if you see any kind of rust on your transmission it's probably the same thing
    Very common. This flange failed on my son's B6 A4 AMB long before the two turbo coolant hoses did.
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  21. #19
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    Quote Originally Posted by matttastic View Post
    Reminds me of the lines going to turbo. On my 01 1.8t a4 awm the lines could be removed without touching any other components. It only leaked after getting hot and then cold again and finally catastrophically failed on a short drive and luckily didn’t do any damage. Replace that pair of lines anyways as a preventative. Happened around 190k
    This looks like the symptom I am dealing with. Where are the turbo lines located?

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    was unable to upload to PM but turbo coolant in pic is u-shaped oriented level to right of turbo .


    IMG_20180723_193826.jpg

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    you can see banjo fitting going into block just to the right of turbo diaphram boost actuator

  24. #22
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    Quote Originally Posted by cchief22 View Post
    you can see banjo fitting going into block just to the right of turbo diaphram boost actuator
    Did you mean this fitting?

    IMG_20180723_193826.jpg

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    yep thats where it returns to engine block, will take picture of mine tonight (extra one) and post tomw. a.m.

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    Mine was leaky water pump, did not leak much.

  27. #25
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    Quote Originally Posted by Btitans View Post
    Mine was leaky water pump, did not leak much.
    I don't exclude that possibility. The WP was last changed like 10 years ago. So may be it's at its end of life time and leaking is a warning sign.

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    smaller than I remember but here is pic and banjo fittings shown at ends, there is a 6mm bolt that bolts thru turbo to "stabilize" the assemblyIMG_20190604_075050.jpg

  29. #27
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    Quote Originally Posted by cchief22 View Post
    smaller than I remember but here is pic and banjo fittings shown at ends, there is a 6mm bolt that bolts thru turbo to "stabilize" the assembly
    Great. OK how do I access this to see if the leak from it? I could not tell from your previous picture where this fitting is actually located. Should I look under the car more toward the A/C compressor?
    If I somehow could see that the leak is from this, I would buy it from you.

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    your arrow (previous posting)points to where it attachs to block and then loops to turbo,you should be able to wriggle your hand down in there , obviously when it is cool! and feel for coolant if indeed that is where it is leaking from.

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    OK here are more pictures from the under the car. I don't think WP is leaking. I still was not able to locate the turbo lines.

    DSC_0032.jpgDSC_0033.jpgDSC_0034.jpgDSC_0036.jpg

    I didn't see leaked coolant but may be it's because the car is not driven.

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    What are the possible causes of loss of coolant?

    Are you sure the car hasn’t overheated?
    The bmw I was talking about earlier that overheated was leaking from the same spot.

    Or it maybe the coolant flange behind the engine/cct.

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