Water probs

[Milex]

Hi guys , I’ve got a wee problem with the water system on my 04 rx300 .

the car runs smooth temp gauge never goes above half way , just recently the top hose has started to suck it’s self in when car cools down , I’ve checked for leaks and smoke but there isn’t any , but I have to keep topping up the system, I have replaced the radiator cap and was wondering if it could be the thermostat causing it , as the top hose is boiling hot and the bottom one is near enough stone cold, hope one of guys can help 

[The-Acre]

44 minutes ago, Milex said:

Hi guys , I’ve got a wee problem with the water system on my 04 rx300 .

the car runs smooth temp gauge never goes above half way , just recently the top hose has started to suck it’s self in when car cools down , I’ve checked for leaks and smoke but there isn’t any , but I have to keep topping up the system, I have replaced the radiator cap and was wondering if it could be the thermostat causing it , as the top hose is boiling hot and the bottom one is near enough stone cold, hope one of guys can help 

I would certainly say the thermostat is suspect.  the bottom hose will stay cold until the coolant is hot enough to open the thermostat, then the bottom hose should get almost as hot as the top one.  If it's easy to get to it take it out and test it in boiling water.

[Milex]

Ok thanks I had idea thermostat maybe part of problem, I have just been out and taken off the small hose between radiator and overflow tank , the bend below the tank was solid with a sort of coppery coloured goo so I’ve cleaned it out and flushed tank , I’ll see how that goes and if no good I’ll change out thermostat 

[Texas]

' Coppery coloured Goo' sounds like it might be Rust from not having the correct concentration of coolant! ( and not water alone)  This rust will kill thermostats and block the smaller pathways in the radiator, sounds like it needs a good flushing ( and reverse flush), inspection of thermostat and filling/bleeding with correct coolant.

Is cabin heater working ok ( nice and hot) cause if that gets blocked up it will be a nightmare to replace.

Also need to get to bottom of why it needs topping up all the time ( this topping up should be done with neat coolant as if you are just using water then you are constantly diluting the coolant that is in there!)

paul m.