Overheating
Results 1 to 7 of 7

This is a discussion on Overheating within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; 10 to 15 min of driving in moderate city driving conditions (revs under 4k) with outside temperature ranging from 35-55F ...

  1. #1
    Registered User WagonGuy's Avatar
    Join Date
    Sep 2005
    Location
    Chicago
    Posts
    585

    Overheating

    10 to 15 min of driving in moderate city driving conditions (revs under 4k) with outside temperature ranging from 35-55F causes the engine to overheat. The temperature gauge goes up and down in the range between normal and almost boiling (red line).

    In a previous thread I have rulled out the second fan isn't supposed to be working so it means that once a higher temp kicks in one of the fans comes on properly.

    The cooling system is filled up properly with the coolant level at 'max'.

    I notice that the temperature goes up mostly when either stopped in a traffic or moving very slowly.

    One thing to notice is that I was involved in an accident 2 months ago and the radiator had to be changed. I was assured that the shop uses only genuine and brand new subaru parts so I doubt the core is bad.

    The only thing I may question is the quality of the coolant. I know subaru requires special genuine subaru coolant since the engine is made of aluminum. And I doubt the shop went as far as using the right coolant at the exact proportions. So that's one thing I may look into.

    Other then that anyone has any other suggestions? Can the thermostat be a primary suspect?
    Blobeye Syndicate #1337
    man vs technology blog
    MvT@YouTube

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #2
    Administrator Trainrex's Avatar
    Join Date
    May 2003
    Posts
    26,591
    I Support ClubWRX
    If the fans are working, you don't have a leak, and you aren't showing signs of a bad head gasket, I would lean towards the thermostat, or the system needing a good burping.

  4. #3
    ODJ
    ODJ is offline
    Registered User ODJ's Avatar
    Join Date
    Jan 2006
    Location
    Tampa, FL
    Posts
    357
    Quote Originally Posted by Trainrex View Post
    or the system needing a good burping.
    This was my first thought. When I replaced my coolant recently, I was quite surprised how long it took to refill the system. I could only add a small amount of coolant before the upper reservoir would overflow. Then I would have to squeeze the radiator hose to release some air so I could add a little more coolant. The whole process took me a good 20 or 30 minutes.

    It's not hard to imagine that a busy mechanic's shop might not take the time to make sure there was absolutely no air left in the system.

    Of course, they also might have forgotten to run your heater on full blast for a while, then top up the coolant again.
    UNSPOILT BY PROGRESS

  5. #4
    Registered User WagonGuy's Avatar
    Join Date
    Sep 2005
    Location
    Chicago
    Posts
    585
    Thanks guys. I'm on it.

    Now that I think about it the symptoms do reflect an air bubble (area) somewhere near the temp sensor probably as the temp gauge goes up in a matter of simply seconds (2-3).

    Will keep you posted.
    Blobeye Syndicate #1337
    man vs technology blog
    MvT@YouTube

  6. #5
    He simply abides. SD_GR's Avatar
    Join Date
    Jul 2002
    Location
    CA, US
    Posts
    22,559
    I Support ClubWRX
    Turn it off, let it cool. Pull the rad cap off, top it up if needed. Turn it on, keep your face out of it in case it spews. Look and see if you have circulation. If you do, burp it. You're already half there anyway; all you have to do is squeeze the top hose and/or anything else you can get your hands on without losing a finger. Careful.
    WRX Info Links, Courtesy TheJ
    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

  7. #6
    Registered User WagonGuy's Avatar
    Join Date
    Sep 2005
    Location
    Chicago
    Posts
    585
    Thanks for all of the tips from all you pros.

    The 'burping' trick did it. What's funny though is that it was one of the first things I did once I encountered it for the first time. However here's the catch...the system must have been so full of air (full of air - lol) that one time did not matter.

    This time I did it with cold engine and then once it was warmed up. It did threw up a little but then more air came out and I did touch the tensioning wheel with one of my fingers while it was running.

    I took it out for a spin afterwards. Went WOT several times with heat on/off did several WOTs followed by complete stops to simulate exteme city driving conditions. Needless to say the needle did not pass 1/3 of the safe zone.

    One strange thing I have noticed though once I parked with the engine running was that once I gave it a little throttle (800-1100 rpms) I could hear 'bubbling' coming from behind the driver's side dashboard. I wonder if there's more air trapped in the heating core?

    My conclussion is that the sudden temperature spikes were attributed to hot air bubbles escaping the cabing heating core into the cooling shield of the engine. Once the bubble reached the temp sensor it spiked the reading hence the quick rise and fall of the gauge needle.

    Anyhow, here's my report, thanks for reading.

    WagonGuy
    Blobeye Syndicate #1337
    man vs technology blog
    MvT@YouTube

  8. #7
    Administrator Trainrex's Avatar
    Join Date
    May 2003
    Posts
    26,591
    I Support ClubWRX
    Cool

Posting Permissions

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