Isuzu KB 250 diesel- coolant light keeps coming on - will come on for a week the whole time then go away for a week (have replaced radiator cap) the vehicle is loosing water but see no water dripping.

Question edited for clarity and add maker.
Question moved to maker category.

So the pump wasn't new? Perhaps it was broken?

Air locks in the system?

Help in the link

https://www.google.com/search?q=Isuzu+kb+250+4ja1+stalls+while+idling

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cam timing
injector timing?
what country.
we dont have KB here in USA< zero and we are a USA forum.
so not stating country , makes for wrong aswers as engines vary by country as does fuel systems (laws gov, smog,etc)

You could have a pin hole in your hose or in your radiator.

replace thermostat.then bleed coolant system, this is how you do it.fill the cooling coolant system with 50 / 50 dexcool and water to raise boiling point,straight water will evaporate boil away cause engine to overheat catch fire thats why you need 50 / 50 mixture antifreeze and water.to bleed coolant system first fill coolant system until coolant stay at the full cold mark on the the coolant overflow jug,then you start engine allow it to idle,place the heater and ac control in any ac setting except max and the temperature control to the highest setting,run engine until lower hose to water pump is hot. with the engine hot run the engine speed up to 3000 rpm and allow it return to idle, repeat this 5 times. slowly open the bleed valve on the thermostat housing or look for bleed valve at the water pump heater hose.open bleed valve for 15 seconds to expel any trapped air.then top off the coolant as necessary,and when top radiator hose hot thermostat open up.keep adding cooling to overflow until coolant level stop at full cold mark dont over fill coolant.if engine seem like overheating while looking at cooling gauge turn off engine wait a while until cool off add more coolant until coolant level stay stable and dont drop any.when open radiator overflow cap use large rag over the radiator cap to keep from getting scald open radiator cap a little at a time but dont open radiator cap until engine cool down first.replace the radiator overflow cap, thermostat,and engine coolant temperature sensor and check the cooling fans fuses and relays see what happens.

you need to replace thermostat and radiator cap.look under hood around engine compartment.look for a radiator cap near radiator,add 50/50 antifreeze and water to coolant system to bring up boiling point.pure water will cause engine run hotter because water evaporate away,remove radiator pour coolant in the radiator until coolant stop dropping in the radiator now some vechicle pour coolant in the coolant overflow jug,pour coolant until coolant level stop dropping and the coolant level stay at cold full mark.start engie let idle few minutes, watch coolant level in radiator if coolant start dropping add more coolant, when coolant level stop dropping put radiator cap back on let engine idle until both top radaitor hose and bottom coolant hose get warm turn off engine wait until it get cool then take a large rag slightly open radiator just a litle at a time to keep from getting scaled.once radiator remove add more coolant if low,put radiator cap back on start the engine let it idle watch the temp gauge if temperature gauge going hot zone stop engine wait until cool then add more coolant,keep doing this until engine stop overheating going into hot zone and coolant level stop dropping,make the coolant overflow jug coolant level stay at full cold mark, dont let jug run empty if so air will get in the coolant system causing engine to overheat.

There should be a radiator cap as it controls what goes into the overfill tank. You might consider replacing it. If there are no leaks in the radiator or hoses, there are only 3 places the coolant can go (water pump leak, blown gasket, or out throught the radiator cap). Hope its the cap because that's the cheapest. Good luck!

i'm getting "internal control module keep alive memory?" for fault p0603. which i think has nothing to do with using coolant. i assume you're finding no leaks, so it's leaking somewhere you can't see. does it smell of antifreeze in the interior? is the carpet wet? the heater core might be leaking into the interior. there could be a slow leak on the top of the engine and it's boiling away before it has a chance to pool. fill your reservoir fully. let the engine get hot. inspect for steam in the engine compartment.

make sure ur fan clutch is puling some air and replace rad cap with new onr u may have to replace radiator long trips not getting enough water cooled

possibly check radiator no leaks first then check coolant bottle reservoir if not full fill up with 50/50 water /coolant then tajke the cap off the radiator/ turn the car on and fill the radiator it will burp until its full then putr cap on and the coolant reservoir cap on then check to see if the light is on/ Please rate my response thank you very much

NEVER open the radiator when the car (or any other engine) is running!! The radiator is part of the pressurized cooling system (under that cap is coolant at 15psi)

Correct way to check the coolant in the radiator, is wait until the engine is COLD, then remove the radiator cap and re-fill.