Materials to Maintain Your ZHP IIIII Hand Protection IIIII Tools to Maintain Your ZHP
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  1. #1
    Join Date
    Aug 2011
    Location
    Richmond, VA
    Posts
    63

    Coolant Leak From Temp Sensor on Lower Radiator Hose

    I have just complete an overhaul of the cooling system and while driving around, I found I was leaking a substantial amount of fluid from the temp sensor.

    I know there is a gasket on the sensor, that was reused, but I guess could go bad? I am able to turn the sensor in the housing slighly back and forth as well as wiggle it up and down slightly. Is there supposed to be any play in the sensor at all? Certainly doesn't seem water tight especially if the car is being driven.

    Any thoughts?

  2. #2
    Join Date
    Jan 1970
    Location
    Ocean County, NJ
    Posts
    7,273
    Definitely sounds like a bad o-ring. I believe DW knows where to pick up the proper size o-ring.
    -Be yourself; everyone else is already taken.
    ZHP Pre-Ride Briefing

    2005 ZHP, Alcantara, Silver Cube, Nav, Sharked, BMW Perf Intake, BMW Perf CF Strut Brace, CF Valve/Fuel Rail Covers,
    Shadowline Grills, CF Splitters, Fog Light Inserts, Euro-mirrors, CDV Delete, Beisan vanos, GAS DISA, BP Coded

  3. #3
    Join Date
    Aug 2011
    Location
    Richmond, VA
    Posts
    63
    Keith,

    Thanks for the reply. In messing around with the system, and just walking inside, I would assume a considerable amount of air would now have gotten into the system? I was trying to see if the system would bleed properly and all I got was a really odd surging of water/coolant mix that would come out of the expansion tank. I had not seen something like that before, but it could just be large pockets of air escaping out of the system?

    I also noticed that the upper radiator hose was very hot to the touch, which leads me to think the thermostat, which is also new, is working properly, but the lower hose was outside temperature and did not seem to heat up at all.

    Could all of these be related to a leak in the system and lots of air in the system as well?

  4. #4
    Join Date
    Apr 2011
    Location
    Dallas
    Posts
    822
    I am about to do the cooling rehab on a friend's 325i and am on the verge of ordering the parts.

    Did the new temp sensor/fan switch not come with a new o-ring?

  5. #5
    Join Date
    Aug 2011
    Location
    Richmond, VA
    Posts
    63
    I did not get a new sensor with the kit. I am picking one up today and hoping it has a new gasket.

  6. #6
    Join Date
    Jan 1970
    Location
    Ocean County, NJ
    Posts
    7,273
    Air pockets can definitely wreak all kinds of havoc with the cooling system.

    I'm thinking a new sensor, o-ring, and good bleeding will have you good to go.
    -Be yourself; everyone else is already taken.
    ZHP Pre-Ride Briefing

    2005 ZHP, Alcantara, Silver Cube, Nav, Sharked, BMW Perf Intake, BMW Perf CF Strut Brace, CF Valve/Fuel Rail Covers,
    Shadowline Grills, CF Splitters, Fog Light Inserts, Euro-mirrors, CDV Delete, Beisan vanos, GAS DISA, BP Coded

  7. #7
    Join Date
    Aug 2011
    Location
    Richmond, VA
    Posts
    63
    I put the new sensor and O-Ring in and it seems to be functioning just fine so far. I bled the system for some time and drove it around the neighborhood. Everything is dry in the compartment and I was getting some very hot heat. I'm going to drive it some more tonight for more than 5 minutes and see how it goes and refill as necessary.

    Thanks for the help!

  8. #8
    Join Date
    Oct 2011
    Location
    Silicon Valley
    Posts
    1,630
    From my experience with an aftermarket thermostat sticking shut, one of the hoses does not heat up until the thermostat opens, which is somewhere between 90C to 97C as measured by the main coolant temp sensor in the head (not the one in the radiator hose). I think the lower hose stays cold until then because it leads to the radiator.
    Quote Originally Posted by VaTechZHP View Post
    I also noticed that the upper radiator hose was very hot to the touch, which leads me to think the thermostat, which is also new, is working properly, but the lower hose was outside temperature and did not seem to heat up at all.

  9. #9
    Join Date
    Jan 1970
    Location
    Liberty Township, OH
    Posts
    37,935
    Great job VaTechnoStud.
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  10. #10
    Join Date
    Jan 1970
    Location
    Ocean County, NJ
    Posts
    7,273
    Quote Originally Posted by VaTechZHP View Post
    I put the new sensor and O-Ring in and it seems to be functioning just fine so far. I bled the system for some time and drove it around the neighborhood. Everything is dry in the compartment and I was getting some very hot heat. I'm going to drive it some more tonight for more than 5 minutes and see how it goes and refill as necessary.

    Thanks for the help!
    Nice work. Sounds like you're good to go.
    -Be yourself; everyone else is already taken.
    ZHP Pre-Ride Briefing

    2005 ZHP, Alcantara, Silver Cube, Nav, Sharked, BMW Perf Intake, BMW Perf CF Strut Brace, CF Valve/Fuel Rail Covers,
    Shadowline Grills, CF Splitters, Fog Light Inserts, Euro-mirrors, CDV Delete, Beisan vanos, GAS DISA, BP Coded

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