David from Engine Saver Low Water Alarms replied:

Try a new radiator cap and make sure the overflow hose has no leak between the radiator and the overflow tank.

If the system has been pressure tested ok it sounds as though the expansion recovery system is not working.

Hope this is helpfull

David from Engine Saver Low Water Alarms replied:

The majority of radiator caps have 2 seals, the main top seal & a small one way seal in the base, to allow recovery from the overflow tank.

Remove the radiator cap, immerse it in a bucket of water & run your finger under to bottom seal to remove any foreign matter which may prevent a complete seal.

Test the overflow hose by applying simple mouth vacuum to it.
Block with the tongue to seal and see if it holds vacuum

(Of course do this with full regard to wh&s procedures after consultation the appropriate materials date sheets for the type of coolant involved)

If you don't have a recovery problem, the system should be retested for small leaks.
They can be notoriously hard to find with a normal pressure test.

Stephen M (NSW) replied:

Also check to make sure the long tube in the recovery bottle hasnt come off. This will cause the water to be pushed into overflow bottle when needed but wont allow it be sucked back in again. Also found on my wifes pulsar a few years ago when she owned it after having a service/flush etc they connected the hose on top of the overflow bottle to the wrong tube which was allowing the water to be pushed into the bottle but couldnt be sucked back into radiator. Took me a few hours to work out what the hell was going on. Empty radiator but overflow bottle was overflowing all the time needless to say I no longer use his services. Also make sure the little rubber tubing running from the radiator to the overflow bottle is not sucking itself together when trying to suck coolant back into the radiator.Just another thing that could possibly be causing you the trouble. Regards Steve M

Neil & Pauline replied:

A simple frustration option is that there is something in the recovery bottle that blocks the return of fluid. Acts like a valve. I had a small piece of plastic in mine. Best non return valve you could get!
May well be the wrong radiator cap. There are very subtle differences.

Neil

Member - Davoe (Yalgoo) replied:

pressure tests are a complete waste of time ond will only find a fault with a 2 inch hole in your radiator.

Have you checked for bubbles in radiator? hopefully only a rad cap but that is rarely the case

Member - Phil B (WA) replied:

Had a similar problem in my 80 series - losing water but nothing showing on pressure test. Eventually found a crack in bottom tank that only leaked when the radiator shop put extra pressure into the system.
The crack wasn't opening on the normal pressure test pressure.
Sorry but I cant remember what pressure they eventually used.
I hope this helps

Phil

donks1 replied:

hi there

there was a recal on these radiators for the nm pajeros

some just had new coolant but others had the radiator replaced

if you give me the vin no. i can check it for you now

might save you some time and cash

donks

Member - Matt (Perth-WA) replied:

Mike you didnt say if it is petrol or diesel...if petrol I would suggest getting it to a mechanic to do a HC test on the coolant. This will test for the presence of combustion bypass in the coolant from a blown head gasket or cracket head/block.

Have you looked for bubbles in the coolant as others have suggested...this a crude check to see if your pressurisation problems are due to gasket/cracks. The combustion pressure gets into the coolant and overpressurises and fills the overflow tank.

If you have replaced the radiator cap, checked the recovery hoses and there is an air-gap in the tank I would suggest there isnt anything wrong with the recovery system. The recovery tank is ost likely filling due to the combustion pressures.

The HC test takes five minutes and is very conclusive if you do suspect the gasket etc but if its diesel there will be no HC but there may be bubbles visible when running with the radiator cap off.

All the best

Matt.

nowimnumberone replied:

another place to look might be the water pump on the way out
they wont leak all the time.
on the v6 there behind the timing belt covers in the middle of the motor and it has to travel a fair way before it comes out where you can actually see water leaking so tyhe problem is if its only a slight leak at the moment you might not see it yet.