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Overheating (AGAIN!!!) Legacy 2.0 GT
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Thread: Overheating (AGAIN!!!) Legacy 2.0 GT

  1. #1
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    Default Overheating (AGAIN!!!) Legacy 2.0 GT

    My old 1990 Subaru (190 000km) starts overheating after 15 min of driving

    The engine was rebuilt about 4 weeks ago. We replaced head gaskets, timing belt incl. the tensioner, water pump, thermostat and radiator. In the beginning the car ran greatly, no overheating even under severe driving conditions. No leakage of coolant could be observed. But a couple of days ago the engine overheated quickly just during normal driving. In the beginning I assumed the overheating was because of the air pockets, I bled the cooling system a couple of times but the overheating problem was still there. The pressure in the cooling system seemed to be very high as I noticed yesterday that the upper radiator hose was leaking. I tightened the clamp today an that leakage stopped, but the car was still overheating.
    I live on the hill, so I needed to get back home. The engine overheating gauge was showing 90% as arrived. I checked the engine after arrival. No vapor was coming out, and there was coolant coming out of the overflow system (the radiator cap is alright). But I also found there was something else leaking, it was in the area of water pump. That area was not leaking yesterday. I don't think that was the cause of the problem, as it was not leaking as the overheating started a couple of days ago and I assume that this leakage occurred due to the very high pressure in the cooling system.
    The interesting thing is I can't here the water flow through the system inside when I turn on the engine (I used to hear that sound before). The heater in the cabin is working, however it only starts to heat after about 5 min of driving.

    I have no clue what it could be. Can anybody help me with this? I'm desperate. It took us huge effort to replace the head gaskets etc, and now a similar problem arises.


  2. #2
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    When theres a leak and coolant comes out, air is coming in. Another air pocket could have formed. Also, you could have gotten a bad T stat, that happens a lot. When some go bad they stay closed. But most should be fail safe so when it does fail it stays open when it goes. Retrace your steps. Tighten down bolts to make sure they are at their correct specs. Check the t stat and or replace it. Wash down the motor and then tak it to a dry spot and look for leaks.
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    Quote Originally Posted by Reason View Post
    When theres a leak and coolant comes out, air is coming in. Another air pocket could have formed. Also, you could have gotten a bad T stat, that happens a lot. When some go bad they stay closed. But most should be fail safe so when it does fail it stays open when it goes. Retrace your steps. Tighten down bolts to make sure they are at their correct specs. Check the t stat and or replace it. Wash down the motor and then tak it to a dry spot and look for leaks.
    Thanks for the valuable comment. In fact I bought my thermostat (installed about 4 weeks ago) from an engine guy. He said that one would the work. On the other hand our subaru people said to throw it way as this one is shorter that the original one. Let's see what happens when I take it out and check ...

    But what are typical thermostat related overheating symptoms in older Legacies? For example, it was kind of funny with the engine temp. gauge today: I drove up the hill and it went slowly up and down - from 50 to 70 %, and then back to 50 and up to 90%. It never happened when I had my head gaskets blown.

  4. #4
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    Also try to run the system with the t stat out before you buy another one.
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    Quote Originally Posted by Reason View Post
    Also try to run the system with the t stat out before you buy another one.
    I'M GOING MAD!

    Here's what I've done today:
    1) tightened the hose that was leaking
    2) proved the water pump was definitely not leaking
    3) took out the thermostat and tested it using an old but functioning one as a reference (hot water test in a pan)
    3) checked there was no external leakage of coolant out of the system
    4) bled the system to get rid of the air
    5) drove the car for about 5 min - she overheated

    6) had a rest and a beer ...

    7) took out the thermostat
    8) bled the system
    9) she overheated again!

    My observations:
    - the coolant level was constant (by the way it was not the case as I had my head gaskets blown)
    - the heater was not working well (I clearly noticed that as I was cooling down the engine on my way back home: the heater didn't blow warm air despite the engine was on)
    - the engine temp. gauge didn't tend to fall down when I stopped to cool down the engine (the engine was on)
    - and the most interesting thing: I couldn't hear that sound of flowing coolant each time I turned the engine on (but I used to hear that sound before)

    So the question is:why cannot this sound of flowing coolant while turning on the engine be heard anymore?
    Does this overheating problem have anything to do with the absence of coolant circulation or is it somehow related to the heating system?

    I'm even starting to think that the water pump isn't working at all. Or there is s a physical obstacle somewhere in the cooling system causing therefore absence of circulation.

    DO YOU GUYS HAVE ANY IDEA ???

    I really want to keep this car! I actually quite love it.

  6. #6
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    Here's my update:

    1) I removed the heat core from the system by simple short cutting (I just connected those two pipes coming from the main system using a short hose)
    2) I tried to bleed the system, but there was only a little air coming out.
    3) I went for a ride assuming there's no much air left but
    she overheated again!

    My observations:

    - while bleeding the system the both upper and lower radiator hoses seemed to be pretty cool or just warm (the radiator fans were not on!): it looked to me there was no circulation through the radiator
    - also the water level in the reservoir was almost constant even if I turned off and on the engine - the water was not sucked in as it should be!
    - while revolving motor at higher rpms (over 3000) there were no bubbles coming out of the cooling system so I assume the head gaskets are ok

    It's unbelievable: the only thing that I can consider as a problem for overheating is a water pump. But it was brand new as I installed it!

    I know it's not easy to check whether the water pump is working properly. But are there any typical symptoms that would indicate a faulty water pump?
    Last edited by New Subaru Fan; 12-28-2009 at 10:36 AM.

  7. #7
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    FINALLY SUCCESS!!!

    After 4 days of struggle I figured it out. There was just a tough air pocket.
    Apparently those older Legacies are meant to be bled under vacuum, because there's no air outlet valve on the radiator. My friend has a 1999 Legacy and the bleeding was not an issue at all because the air trapped in the cooling system was coming out freely as we were adding more coolant.

    In my case I just lifted the right side of the car as much as I could, disconnected the upper radiator hose and turned it upwards. Then I turned on the engine and was slowly adding coolant until it appeared in the hose. Shortly after that the coolant started to come out of the radiator. Then I quickly connected the hose to the radiator. Although pretty pessimistic I decided to give her another go. She didn't overheat this time!!!!

    And now my car is back and I can happily celebrate the New Year's Eve!

    You have a good one too! Cheers

    PS: By the way I'm driving without a thermostat now. Do you guys think it would be a good idea to keep it like that? This turbo engine tends to warm up very quickly even without a t-stat.
    What are the pros and contras of not a having it?

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