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Generation 2 Pajero NH - NL Models 1991 - 2000

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  #11  
Old 1 Week Ago
pharb pharb is offline
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Have twice had the water pump mounting O ring leak when at operating temperature, but not when cold.

Both times took quite some time to find as the coolant would also evaporate as soon as it leaked out when at operating temp.

However this is unrelated to pressurising or overheating.
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  #12  
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Quote:
Originally Posted by nj swb View Post
Reasonable assumption, but I've heard stories that sometimes the leak (e.g. a crack) only opens at higher temperatures, and will close again as the engine cools. Real or myth I don't know.



But this is a good question. On releasing the radiator cap, if escaping air is heard, is it over-pressure venting out, or vacuum sucking in? Is the radiator cap somehow not letting the overflow return?



Are the radiator hoses tight when its cold (before releasing the cap) or soft / spongy?
The hoses are tight when cold spits a little coolant out when cap is opened.. Am going to pull the motor and auto trans to convert to manual soon so I will rip the head off and have a look while engine is out.. I have a spare head on my other motor so I might just swap it over and send mine off for crack testing, although I am not hopeful of a good outcome

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  #13  
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disco stu disco stu is offline
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Can you pressure test cooling system while it's hot to check it's leaking pressure before going ahead and ripping the head off? Just thinking of some way for you to check if it's needed before committing to the work/expense you are intending

Combined with the test erad mentioned for exhaust gases in cooling system water, might save you some time and money
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  #14  
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erad erad is offline
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I once had a Range Rover which used to leak a had gasket only when hot. On a long uphill section, I could feel the power drop when the temperature gauge reached a certain point. I had to guess which head was blown, so I opted for the one which was hardest to remove. Once it was off, I could a trace where the casket had (hopefully) blown. I had the head shaved slightly and put a new gasket on. No more overheating problems after that. All cylinder compression testing showed no leaks because by the time the spark plugs were removes, it had cooled down sufficiently for the gasket to seal again.

Aluminium heads on cast iron blocks are a potential source of problems, although in this case the Rangie had an aluminium block (with cast iron liners pressed into place).. Even so, this would have caused the problem because Aluminium expands at a faster rate than Cast Iron.
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  #15  
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Quote:
Originally Posted by disco stu View Post
Can you pressure test cooling system while it's hot to check it's leaking pressure before going ahead and ripping the head off? Just thinking of some way for you to check if it's needed before committing to the work/expense you are intending

Combined with the test erad mentioned for exhaust gases in cooling system water, might save you some time and money
Yeah stu.... It holds pressure when cold and builds pressure when hot.. Went and picked up a mates caravan today and it hated it... 120 c most of the way home... Just trying to show its weakness and where the weakness is..
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