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300tdi slight overheating problems

Discussion in 'Defender 90 / 110 / 130' started by Arierep, Feb 27, 2014.

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  1. Arierep

    Arierep Active Member

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    Hello,

    The temp gauge on my 300tdi used to run just an air under the middle, everytime, any time.
    2 weeks ago the water pump died on the run. It was quite fast, was driving at 60km/h when the auxiliary belt jumped off and I lost the alternator, PS and the pump. There was no time for the engine to overheat, as far as I know.

    The pump was replaced ASAP, and everything seemed to be normal. Then, on a 15km spirited run, the temp gauge when a little over the middle, and stayed there. The interior of the car seemed to be a little hotter, but it could be my imagination. I stopped, as I was just arriving my destination. Next morning everything went like normal.

    I did a few test runs, with no abnormal, over the middle temp gauge situations, and then some 200km, mixed city, B roads and motorway, also with no problems.


    Today I was going on the motorway at 100/110km/h, when about the 17/20min mark the temp gauge jumped again past the middle, just a little, something like 3/5, and stayed there. I then proceded into some slow traffic and urban driving, and the gauge stayed there.

    Is there any explanation for this? Is my engine overheating?
    Thermostat problem?

    Thanks
     
  2. Landyfox

    Landyfox Well-Known Member

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    May just be the gauge that's faulty - mine has done this from day one, yet recording the temp with an infrared temperature probe its spot on. :)
     
  3. THEengineer

    THEengineer whatever

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    have you bled it properly? and what condition is your radiator in? there are 2 bleed points on the 300 the rad and stat housing
     
  4. Landyfox

    Landyfox Well-Known Member

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    If I'm honest I've only ever bled the water system by removing the cap of the expansion tank and allowing it to circulate a wee bit!!!!
     
  5. Arierep

    Arierep Active Member

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    It was not me who changed the water pump and refilled the cooling fluid, so I can't be 100% sure it was bleed properly.

    It is supposed to be:
    - all caps opened
    - fill radiator
    - fill thermostat
    - fill expansion tank

    Right?
     
  6. tottot

    tottot Well-Known Member

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    Yep,sounds like air in the system you nearly all ways need to bleed again to get rid of all of it.
     
  7. Arierep

    Arierep Active Member

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    Why would air in the system only cause the temperature to raise in prolonged motorway use, and not so much in slow city traffic?

    I'll try to bleed it tomorow, as well as stick a new OEM thermostat
     
  8. THEengineer

    THEengineer whatever

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    ideally should be filled via the bottle,rad and stat housing if the plastic caps are shot get some 1/2 air vents from a plumbers merchants,they fit and easy to vent ,dont think the 300 is prone to airlocks but this is the way i filled mine everytime i done work on the cooling system
     
  9. cowasaki

    cowasaki Well-Known Member

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    There was a top tip a few days ago which I haven't tried yet but basically...

    Remove rad bung
    Remove expansion bottle cap
    Place rag around filler cap top and blow into bottle hard till rad bung overflows.
    Replace rad bung
    Remove filler bung
    Place rag around filler cap top and blow into bottle hard till rad bung overflows.
    Replace filler bung
    Replace expansion bottle cap
     
  10. Arierep

    Arierep Active Member

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    This issue is really messign with me.

    Last Saturday I replaced the thermostat and bleed the circuit.
    Whent for a motorway test and the car overheated to the last 1/4 before red.

    I disassembled the thermostat and found that the new one took a lot longer to open, and was not opening as wide as the old one.

    Slaped the old one back in place. So, old thermostat and bleed circuit.
    When for a test and the temp gauge stayed right in the middle.

    Yesterday I took the risk and when for a 150km trip, mixed motorway and mountain roads, some of them steep. The temp was in the middle the whole time.

    Came back today, another 150km, steep mountain roads and motorway. first 50km the temp was right in the middle. Then I took a 5min stop for a coffee. Back to the car, I started it and noticed that the temp gauge was a little before the middle, something like 1/5. It stayed there for the last 100km, not moving an inch.

    At the end I stoped the car, rested for 30min and went for a 10km short trip. The gauge stayed there, about 1/5 before the middle.

    What is going on? First it overheats and now it is running too cool?
     
  11. warrior

    warrior Well-Known Member

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    Sounds like you had some air in it,
     
  12. Arierep

    Arierep Active Member

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    Can my gauge/send be shot?
     
  13. warrior

    warrior Well-Known Member

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    Possibly, check it has a good ground 1st
     
  14. Arierep

    Arierep Active Member

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    Any instructions on how to do that?
    Thanks
     
  15. warrior

    warrior Well-Known Member

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    Follow the ground to where it goes and check its a good clean connection
     
  16. Arierep

    Arierep Active Member

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    So I ended up replacing the viscous unit.
    It seemed to be alright after that. I took a few high speed motorway tests, at over 120km/h, with no overheating, as well as repeated slow traffic.

    But yesterday, on a motorway with long climbs, it started to overheat again. I stoped imidiatly, cooled it down, and returned home by a B road at around 70/80km/h, without any further issues.

    So, what to check now? Hoses? Radiator?
    What would be the symptoms of a busted head gasket?

    Thanks
     
  17. warrior

    warrior Well-Known Member

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    Mines got hot last week, turned out my new thermostat was faulty
     
  18. Arierep

    Arierep Active Member

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    My thermostat was checked and rechecked, so I got that covered
     
  19. SteNova

    SteNova Well-Known Member

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    viscous failing to lock?
     
  20. Arierep

    Arierep Active Member

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    The viscous coupling is brand new

    Any ways to check for a head gasket failure?
     
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