Coolant System Problem Options

[80gumdrops]

Howdy. Got a UK '96 ST202 3S-GE.

Firstly, when I start the engine I can hear air bubbles circulating around the cooling system (happens about 3 seconds from ignition).

I've checked that the coolant is fully topped up.

On two occasions I haven't heard any bubbles.. when that happens, no hot air comes in and the engine temp rises above normal. When this has happened I've felt the pipes and found that the top pipe and top of the radiator is hot and the bottom pipe and bottom of radiator is cold.

First time it happened I decided to get the thermostat replaced.

Second time, I added coolant and gave the pipes a squeeze, which must've dislodged some air, because it started working again.

Last night, I heard a few bubbles as usual and had heat as usual, but about 5 mins into the journey I gave it some welly up a hill, lost hot air and the engine started to overheat again.

After a 5 min rest, I started the engine and heard LOADS of air bubbles circulate.

Any ideas folks?

Cheers.

[80gumdrops]

When I fire up the engine I've noticed that it over-revs until I can hear the bubbles move through.

Could that be a pump issue?

Also I've noticed that if I drive with the heat all the way up, it will be cold for the first 4 mins of the journey and then suddenly (like in 3 seconds) start coming through hot.

[xrav22]

When I fire up the engine I've noticed that it over-revs until I can hear the bubbles move through.

Could that be a pump issue?

Also I've noticed that if I drive with the heat all the way up, it will be cold for the first 4 mins of the journey and then suddenly (like in 3 seconds) start coming through hot.

I think you have to change the water pump for starters. If you don't know the last time it was done no way to tell how old it is..
look inside the radiator and make sure it is not corroded. that could stop the coolant from flowing properly.
sqeeze the top radiator hose it it is vey solid after warming up then the pump may be good still.