Page 1 of 2 12 LastLast
Results 1 to 10 of 16

Thread: Coolant leak--can't track it down

  1. #1

    Coolant leak--can't track it down

    I know this has been asked about a thousand times--I have a coolant leak, and I can't figure out where it's coming from. I'm trying to figure out if there's a place that poses a higher failure rate than others. I'm not sure I can afford a complete cooling system overhaul at the moment, though I probably need one. Car has 144k miles.

    Anyways, here's what happens--Coolant will leak out over the course of about 2 days of driving, but it will only fall to a certain level. At this level, the car runs fine and the temp needle remains centered. The only indication I get is the low coolant light cycles on and off. It'll be on for about 5 mins, then off for 30. Something like that. If I take the cap off the expansion tank, it's dry. I fill to the proper level, bleed the system, and it's good for 2 more days.

    I cannot for the life of me find where the leak is coming from. Under the car looking up, and looking under the hood, I can see nothing.

    The car has a new OEM lower radiator hose, and a slightly dubious used radiator from a Ci. (rolls eyes) I've replaced the expansion tank like 3 times over the 3 years I've had it.

    My question is, after the expansion tank, is there another likely failure spot that I could start with replacing?

  2. #2
    Join Date
    Jun 2012
    Location
    Socal
    Posts
    1,241
    Pretty much everything along the cooling system is suspect lol Usually it's the tank, upper/lower hoses, water pump, and radiator. I guess you could start with the hoses since those are the cheapest.

  3. #3
    Quote Originally Posted by sillieidiot View Post
    Pretty much everything along the cooling system is suspect lol Usually it's the tank, upper/lower hoses, water pump, and radiator. I guess you could start with the hoses since those are the cheapest.
    Rats. Is there some sort of safe dye I could put in the coolant to try and make the leak more apparent? Gently pump air in and listen for hissing?

    The water pump has never been replaced. I replaced the radiator about 10k back with a beautiful new one, and my then-mechanic broke the fan shrowd and destroyed the radiator, so he replaced it with a used one. So it could be the radiator. RIP car

  4. #4
    Join Date
    Nov 2012
    Location
    22841
    Posts
    9,537
    The o-ring on the temp sensor that sits in the lower radiator hose is prone to leaking. Also the water pump can leak but you won't be able to see it unless you remove it.


    Sent from my Pixel 2 XL using Tapatalk

    His - 2004 Imola Red / Alcantara 330i | 6MT | ZHP |

    Her's - 2005 Black Sapphire Metallic / Black Leather 330i | 6MT | ZHP |

  5. #5
    Join Date
    Jun 2012
    Location
    Socal
    Posts
    1,241
    Quote Originally Posted by usinjin View Post
    Rats. Is there some sort of safe dye I could put in the coolant to try and make the leak more apparent? Gently pump air in and listen for hissing?

    The water pump has never been replaced. I replaced the radiator about 10k back with a beautiful new one, and my then-mechanic broke the fan shrowd and destroyed the radiator, so he replaced it with a used one. So it could be the radiator. RIP car
    The coolant itself is already colored. Probably best that you try to really clean all the areas down then look to see if you can find the leak. You'll see either the coolant or if dry, it'll be white flakes. I would definitely replace the water pump if it's never been replaced. This things don't last long at all.

    I think you'll have to look for dry residue of the coolant. It sounds like the coolant is evaporating somewhere.

  6. #6
    Sounds like the pump is a good place to start. The coolant sensor and o ring is actually also fairly new forgot to mention.

  7. #7
    Join Date
    Feb 2011
    Location
    Lexington, KY
    Posts
    4,291
    Are there not coolant lines that go under the intake to feed into the interior radiator (for cabin heating)? Could those be leaking as well?

    I think you could see if there was a leak at the water pump.
    325i, 2005, 5MT, Silvergrey, leatherette, Sport package; CDV delete, KONI STR-T & KYB Excel-G, Weisslichts, Stewart H2O pump

    328i, 2010, 6MT, Spacegrey, dakota leather, M-sport packages; all stock
    http://s900.photobucket.com/user/othibau/media/Junesig.jpg.html][IMG]http://i900.photobucket.com/albums/ac208/othibau/Junesig.jpg

  8. #8
    Join Date
    Oct 2016
    Location
    Franklin, TN
    Posts
    200
    I have to top mine off every month or 2. Everything looks clean and dry... very frustrating. Cooling system was changed 40k ago.

  9. #9
    Join Date
    Jan 1970
    Location
    Huntsville, AL
    Posts
    4,085

    Coolant leak--can't track it down

    Pull your belt and pulley to check your water pump weep hole. You may want to rent or borrow a pressure tester while doing the inspection

    https://youtu.be/9476cw9ByRk

    Sent from my iPhone Xs using Tapatalk

    Dinan; Hign Flow Intake System, & Strut Tower Brace
    Turner Motorsports; Underdrive Power Pulleys
    Koni Sport, Bridgestone; Potenza RE-11, Coby Wheel
    Stewart High Performance Water Pump
    Hawk High Performance Street 5.0 Brake Pads
    Brembo Rotor

    The purposeful face of a formidable athlete:

    The spine-tingling 330i Performance Package.

    Purchased CPO on 12/23/2006 with 28,090 miles

  10. #10
    Spray the entire engine with water; let it dry, then drive it like you stole it. Look inside the engine after and find out where the blue cruddy shit is.

Page 1 of 2 12 LastLast

Similar Threads

  1. COOLANT LEAK BUT WHERE?
    By Smilez in forum Mechanical | Troubleshooting
    Replies: 3
    Last Post: 10-12-2016, 01:23 PM
  2. Weird coolant leak...
    By ecrabb in forum Mechanical | Troubleshooting
    Replies: 16
    Last Post: 06-25-2016, 11:02 PM
  3. Coolant Leak
    By san in forum Mechanical | Troubleshooting
    Replies: 42
    Last Post: 11-24-2014, 06:46 PM
  4. Coolant leak
    By Dave1027 in forum Mechanical | Troubleshooting
    Replies: 37
    Last Post: 04-27-2013, 11:24 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •