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Thread: Coolant leak from under exhaust manifold?

  1. #1
    Join Date
    Nov 2014
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    1995 BMW M3 Coupe

    Coolant leak from under exhaust manifold?

    Hello everyone. My newly acquired 1995 M3 has a couple of problems, one of them being it leaks coolant. I looked under the car it looks like its from under the exhaust manifold. It only leaks after being driven and in small amounts. The car drives great, doesn't overheat, there is no smoke coming out of the exhaust, and the engine revs smoothly although the CEL does come on once in a while with a code of 1266 for vanos. I don't think it has anything to do with the coolant leak though. What could be the cause of this leak?





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  2. #2
    Join Date
    Jul 2003
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    '90 Ford Tempo
    It may be leaking from the flange located on the firewall side of the cylinder head.
    Heater hoses are also in that area.

    m

  3. #3
    Join Date
    Aug 2013
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    1999 BMW M3 Coupe
    Check the coolant drain plug for the engine block. It's on the right side sort of under the headers, at least on my 1999 it is. You might have to unplug an O2 sensor to get at it.
    1999 M3/2/5 - Titanium Silver
    Ground Control Street/Track Suspension 440#/550# --- 3.46 3 clutch LSD --- Apex ARC-8 17x9 wheels --- Borla Exhaust --- PFC V3 Floating Rotors --- AFE Intake --- Shark/Conforti Software --- MM Underpanel --- TMS Pulleys

  4. #4
    Join Date
    Sep 2006
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    98 M3 sedan
    unless it is leaking from the coolant port on the driver side rear of the head then you're head gasket has an external leak at cyl 6. mine had the cyl 6 gasket leak issue so I replaced the head gasket and sure enough it was degraded at that corner and coolant was running down the block, but not leaking internally. it's pretty common for it to leak externally at the cyl 6 when you get over 150k. miles on it.
    98 M3 sedan

  5. #5
    Join Date
    Feb 2006
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    1997 E36 M3, 2008 E90 M3
    head gasket!

  6. #6
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    98 M3/4/5
    why u no use BMW blue coo-went?

    to echo what "mmark" said,
    theres a flange with a hose attached to the head. 2, 10mm bolts external housing on the driver side head at the back, with a hose attached to the heater diverter valve. this can be removed and is prone to leaking. i would check that area and see if its leaking from that and wondering over to the passenger side... take a paper towel and just wipe the back of it... these engine sit at an angle so its possible to leak over to that side..
    98 Estoril ///M3 4/5
    $$$ S54 build in progress $$$

  7. #7
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    1998 M3 Vert, 1992 318i
    Quote Originally Posted by ben4bama View Post
    unless it is leaking from the coolant port on the driver side rear of the head then you're head gasket has an external leak at cyl 6. mine had the cyl 6 gasket leak issue so I replaced the head gasket and sure enough it was degraded at that corner and coolant was running down the block, but not leaking internally. it's pretty common for it to leak externally at the cyl 6 when you get over 150k. miles on it.
    This was my issue also
    Caprica Junkie

  8. #8
    Join Date
    Nov 2014
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    1995 BMW M3 Coupe
    Thanks for the replies so far. Just noticed that if I turn on the heater white smoke comes out the exhaust and some drips of water. This happens even when the car is warmed up. Does this have anything to do with the coolant leak?

  9. #9
    Join Date
    Sep 2006
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    98 M3 sedan
    If exhaust smells sweet like coolant then yes, HG is compromised
    98 M3 sedan

  10. #10
    Join Date
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    1997 E36 M3, 2008 E90 M3
    white smoke = coolant
    blue smoke = oil
    black smoke = running rich

  11. #11
    Join Date
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    1995 BMW M3 Coupe
    I got close up to the smoke and tried to smell if it was coolant but there was no smell. If it was a head gasket shouldn't it smoke always and not just when the heater is on? Could it be the coolant leaks into the exhaust and gets burnt out through the tailpipe making smoke. When the coolant usually leaks from underneath the manifold it always falls onto the exhaust, I could see coolant on the exhaust after driving it. Maybe the heater causes it to leak more and it seeps into the exhaust causing the smoke? That's probobly a stretch though. What do you guys think?

  12. #12
    Join Date
    Feb 2006
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    1997 E36 M3, 2008 E90 M3
    Sometimes a HG will only smoke when the engine is first started, as coolant will pool in the chambers overnight. Then when you start, it gets burned off and smoke out tailpipe. During continuous driving it may be such a slow leak not to notice. Also, condensation from the tailpipe is normal and can appear white. Make sure it is truly coolant smoke!

    The exterior HG leak will more than likely burn when it drops on the exhaust. But it shouldn't have anything to do with your heater nor tailpipe smoke.

    HG's can fail multiple ways. Keep an eye on your coolant temps and oil condition

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