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Thread: Overheated and Now...

  1. #1
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    Overheated and Now...

    Hi all, looking for some advice on what to check next.

    I lent my '01 4.6 p38 to my brother and while towing a trailer with two dirtbikes up a gravel hill on a hot day the lower coolant hose blew (from water pump to thermostat). He happened to be looking at the temp gauge when it happened so he noticed the spike in temp and shut the car off straight away. Now, the engine heats up at a normal pace but continues to steadily rise to over 108oC before I switch it off.

    Symptoms are:

    • Water is boiling in the expansion tank
    • Top radiator hose is hot and tight
    • Heater core pipes are hot
    • Heater is blowing cold (brother said he was able to feel hot air on the day but only when the radiator caps was removed, but I am unable to recreate that)
    • No hot air coming from heater
    • Bottom radiator hose warm/hot
    • Radiator warm/hot
    • Engine temp consistently climbs
    • A/C condenser fans come on
    • Viscous fan can be stopped by hand when engine is hot
    • Bubbles in the expansion tank coming from the small radiator hose that routes around the battery
    • Bubbles in the expansion tank coming from the bottom of the tank - smells suspiciously like exhaust/engine fumes


    I have done/tested the following:

    1. Removed and tested the thermostat and it opens as normal when boiling water is poured into/over it,
    2. Switched expansion tank lid with a known working one,
    3. Flushed heater core
    4. Did a dry compression test with the following results:
      1. 165-170
      2. 150-155
      3. 160-165
      4. 155-160
      5. 150-155
      6. 145-150
      7. 145-150
      8. 155

    Any ideas on what to test next?
    1995 P38 Range Rover 4.6 (Overlander) - "Bryan"
    1996 P38 Range Rover 4.6 (Overlander) - "Montgomery"

    1996 P38 Range Rover 4.6 (Road) - "Arthur"
    2001 P38 Range Rover 4.6 (Road) - "Albert"

  2. #2
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    Quote Originally Posted by bowlink View Post

    1. Removed and tested the thermostat and it opens as normal when boiling water is poured into/over it,


    Just an observation. That doesn't eliminate the thermostat. Better to put it into a pan filled with cold water, with a thermometer, and raise the temp on a stove. watch for the stat to start to open and check the temp. A lot of the symptoms you describe could be caused by the stat.

    Air lock is my next guess.

    ( Trying really hard not to mention hg )
    ​JayTee

    Nullus Anxietus

    ​Getting involved in discussions is the best way to learn.

    2000 D2 TD5 Auto: Tins
    1994 D1 300TDi Manual: Dave
    1980 SIII Petrol Tray: Doris
    OKApotamus #74
    Nanocom, D2 TD5 only.

  3. #3
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    The next step I guess would be removing the heads, hopefully not a slipped liner as well... But you can't really tell what's going on without pulling them.


    Edit:

    Sorry that's sounded a bit brusque.

    An air lock is a possibility, but that will not explain the fumes in the header tank.

    You can also buy test strips to test for Combustion gases in the coolant, if that comes back positive, see above.

  4. #4
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    Worked on it most of the day today and managed to get all the air out which made the heater blow hot, although not consistently.

    Everything was pointing towards a shut thermostat so instead of testing a potentially faulty one, I swapped it out with a known working one from my other p38. I thought this because the top of the radiator was still very hot to touch and the bottom was lukewarm when the nanocom said the engine temp was 120+oC. It didn't make a change unfortunately.
    I also tried reverse flushing the radiator thinking maybe it was blocked but it was all clean so no issue there. The expansion tank's cap wasn't letting any pressure out whatsoever so again tried swapping it with a p38 that was running fine but no change.






    I am going to get one of those sniffer tests that detect CO2 for the expansion tank. That will be a definitive answer for if there are exhaust gases in the system, so then just need to flip a coin and pick a bank to pull to bits for the head gasket
    1995 P38 Range Rover 4.6 (Overlander) - "Bryan"
    1996 P38 Range Rover 4.6 (Overlander) - "Montgomery"

    1996 P38 Range Rover 4.6 (Road) - "Arthur"
    2001 P38 Range Rover 4.6 (Road) - "Albert"

  5. #5
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    Cross pollination from another thread............... could also be that the vanes on your water pump have rusted to nothing.

    DL

  6. #6
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    Interesting fault. It would explain a seemingly lack of circulation similar to a thermostat jamming shut. The RR has done 180kms and has only had two owners prior, the second having it for 15 years and servicing it regularly. The condition of the metal coolant pipes were good as well so I don't think that would be the cause. I like your thinking though
    1995 P38 Range Rover 4.6 (Overlander) - "Bryan"
    1996 P38 Range Rover 4.6 (Overlander) - "Montgomery"

    1996 P38 Range Rover 4.6 (Road) - "Arthur"
    2001 P38 Range Rover 4.6 (Road) - "Albert"

  7. #7
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    Not hard to get to water pump. I would strip it off. Cheers

  8. #8
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    True, it’s worth checking while I wait for the CO2 sniffer to arrive. I’ve previously tried getting the fan off and it was nothing short of tight, so I’ll give it a good crack and see what I find
    1995 P38 Range Rover 4.6 (Overlander) - "Bryan"
    1996 P38 Range Rover 4.6 (Overlander) - "Montgomery"

    1996 P38 Range Rover 4.6 (Road) - "Arthur"
    2001 P38 Range Rover 4.6 (Road) - "Albert"

  9. #9
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    Did you properly bleed all the air out of the system?
    That would be my first step, sounds like air in system to me.
    Also, if you can stop the fan by hand, you need a new viscous fan hub, that could have been the cause of overheating in the first place.

  10. #10
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    With heater blowing cold and temperature rising, maybe this points to poor coolant circulation, so - air lock, corroded impellor or blocked radiator. Blocked radiator might explain the blown lower hose. You might get a view of a few channels up through the drainage bung, but at that age it is probably up for a replacement, particularly if investing in a head recon job. Just a thought.
    HTH
    Steve
    '97 HSE

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