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Thread: Random Overheating

  1. #1
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    Random Overheating

    Dear 4BD1,
    Why have you decided to start overheating (even with a/c off!) since performing a full wash down of the engine/ bay??? You never overheat!!!

    I've recently replaced your thermostat with an OEM one and flushed your cooling system, including removal of radiator hoses and thermostat housing as required, before refilling with suitable coolant. An external inspection of your cooling system hasn't indicated any leaks and your coolant is bright green! There is no mixing of water/ oil.

    The 'fuel screw' hasn't been adjusted in recent times (other than about 12 months ago) and no significant heating has been observed...Until now.

    I have recently started using a fuel additive, namely "Diesel Power" which claims to clean fuel system, including injectors, minimise engine 'wear and tear' and aid engine performance.

    Would like to know how I can fix you...

    Cheers Joe

  2. #2
    Bearman's Avatar
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    G'day Joe, 4BD1's just don't overheat (normally). Did it coincide with the thermostat replacement. If so maybe a dud one, pull it out and put in a saucepan and bring to the boil and see if it opens fully (should be at 82C). Otherwise I'd be looking at the water pump.
    Cheers......Brian
    1985 110 V8 County
    1998 110 Perentie GS Cargo 6X6 ARN 202516 (Brutus)

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    Hey Brian, cheers for the quick turn around! Unfortunately the overheating did not coincide with the change out of the thermo. I changed the thermo some two months ago. I too am starting to suspect the water pump might be shot however my experience with water pump failures suggests that they start to weep through the bearing immediately prior to failure. Are water pumps in these engines susceptible to failure???

    Thanks

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    Dicky temp sensor from water ingress making it show higher temp through more resistance would be my first thought

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    Quote Originally Posted by 110Landy86 View Post
    Hey Brian, cheers for the quick turn around! Unfortunately the overheating did not coincide with the change out of the thermo. I changed the thermo some two months ago. I too am starting to suspect the water pump might be shot however my experience with water pump failures suggests that they start to weep through the bearing immediately prior to failure. Are water pumps in these engines susceptible to failure???

    Thanks
    They don't normally give any problem but there is always the exception. Did you change the thermostat before or after the overheating problem? As Lokka said might be worth checking the water temp sender, it may have got water into the electrical side of things when you washed the engine. Is it actually getting hot or are you relying on the temp gauge?
    Cheers......Brian
    1985 110 V8 County
    1998 110 Perentie GS Cargo 6X6 ARN 202516 (Brutus)

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    Quote Originally Posted by lokka View Post
    Dicky temp sensor from water ingress making it show higher temp through more resistance would be my first thought
    This would be my first stop too. I was convinced for a long time I had a heating problem, I had to drive really slowly to keep the needle down. The sender was lying to me.

    Stick another temp probe on the thermostat housing and go for a drive.

    If it's boiling on the other hand, you must be doing something awful. I've had mine blowing steam twice, both times on the same ski-field road (climb to 2000m in 3rd-4th gear.

    http://users.actrix.co.nz/dougal.ell...20steam%20.avi
    That's not me laughing.

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    The temperature of my 4BD1T used to randomly spike up to 100* now and then. It would only stay there for usually less than a minute then creep back to normal. I know the engine (at least the water) was actually getting hot as the 'Watchdog' temperature monitor confirmed it, both temp gauges were in sinc.
    I tried 3 different thermos including a brand new genuine Isuzu and everything else appeared ok.
    The only thing that actually made a difference was running the pressure cap on the header tank at the first 'click' undone. It's not loose, just undone a bit.
    It leaks a little coolant past the cap if it's topped up, but obviously it's not as tight as done up completely.
    If I run with the cap like this the engine temp is always normal and stable.
    One day I'll see if I can get a new cap with a lower pressure rating and try that.

    Cheers, Murray
    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


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    Thanks guys, I will explore these suggestions. Didn't think about the dicky temp sender!!! Could be a simple fix after all. Fingers crossed

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    Engine temp

    Quote Originally Posted by rijidij View Post
    The temperature of my 4BD1T used to randomly spike up to 100* now and then. It would only stay there for usually less than a minute then creep back to normal. I know the engine (at least the water) was actually getting hot as the 'Watchdog' temperature monitor confirmed it, both temp gauges were in sinc.
    I tried 3 different thermos including a brand new genuine Isuzu and everything else appeared ok.
    The only thing that actually made a difference was running the pressure cap on the header tank at the first 'click' undone. It's not loose, just undone a bit.
    It leaks a little coolant past the cap if it's topped up, but obviously it's not as tight as done up completely.
    If I run with the cap like this the engine temp is always normal and stable.
    One day I'll see if I can get a new cap with a lower pressure rating and try that.

    Cheers, Murray
    Hi Murray hows that 2A swb going?
    I'm using the truck motor with the larger thermostat, which I changed to a 77C instead of the 82C factory fit. Engine temp is approx 77-80C on a cooler day with up to around 82-85 on the hotter (35C+) days.
    I have Ford EF-EL thermos and a thermal switch in the thermostat housing that switches the fans on at 85C and off at 80C.
    The fans have not cut in for about 3 weeks, unless I manually switch them on!
    I'm using the first notch on the expansion tank cap, mainly due to a small weep out of the top hose, and I have never had an overheating problem.

  10. #10
    rijidij's Avatar
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    Quote Originally Posted by landrover dave View Post
    Hi Murray hows that 2A swb going?
    I'm using the truck motor with the larger thermostat, which I changed to a 77C instead of the 82C factory fit. Engine temp is approx 77-80C on a cooler day with up to around 82-85 on the hotter (35C+) days.
    I have Ford EF-EL thermos and a thermal switch in the thermostat housing that switches the fans on at 85C and off at 80C.
    The fans have not cut in for about 3 weeks, unless I manually switch them on!
    I'm using the first notch on the expansion tank cap, mainly due to a small weep out of the top hose, and I have never had an overheating problem.
    The 2A Shorty should be on the road within a few weeks at last.

    My issues with the Isuzu overheating were just temporary spikes in temperature. I always suspected something like an air lock in the system. Once I loosened the cap and it seemed to solve the problem, I didn't bother investigating further.

    Murray
    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


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