Mysteriously dissappearing rad fluid

[TheOtherLeft]

Hiya fellas,

I'm having another problem but this time with the radiator. During the spate of hot weather (30+ degree days) and long driving the fluid in my overflow bottle seems to be dissappearing. There are no other signs of anything wrong:
- Temp gauge normal
- With rad cap off, engin running and warm there are no air bubbles in the rad.
- No brown residue in the rad fluid - it's still fluro green
- No milky residue in the oil cap
- No sweet smell from the exhaust.
- No sign of overflowing from the overflow bottle - no white residue near the outlet tube coming from the overflow bottle or anywhere for that matter

Does anyone know what this could be from?

[RAY185]

Small leak somewhere. Have it pressure tested.

[mkpatrol]

What sort of car?

Pressure test it with the plugs/injectors out, you can still have a blown head gasket without all those symptoms.

Also check the heater core, depending on the car they can leak onto the carpet or out the AC drain.

[351ciofgrunt]

Check for signs of leaking around the waterpump gasket and also check all your welch plugs

[gingerbreadman]

maybe a leak in overflow bottle. hot engine compartment may not show that leak easily.

[chunks]

Start by getting the system pressure tested and go from there.

[TheOtherLeft]

Appears there is a small leak from the radiator, where the core (aluminium) meets the top part (plastic). Is it necessary to install a new radiator or will that radiator stop leak stuff work? I've heard the stop leak stuff tends to block up other things as well. Is this correct? Which is the better brand?

[simkell]

Why not take it in and just get it fixed. If you remove the radiator it will keep the cost down.

[TheOtherLeft]

Why not take it in and just get it fixed. If you remove the radiator it will keep the cost down.

Mechanic said repairing the hole is only a temporary fix - average 6 months and then leaks again. It's an aluminium/plastic tank.

[chunks]

If its leaking from the actual core, get a whole new radiator. If its leaking from the tank get a new tank and seal put on. Also thoroughly flush your cooling system and heater core before fitting the new one.