My radiator overflow bottle has overflowed several times. There is staining down the sides of the bottle.

When the car was warm the other day the bottle was full almost up to the cap. When cold it sits on the "full" mark where it should.

If I run the car with the radiator cap off, the water gradually overflows out the top. After 10 mins of idling the water is steaming and fine bubbles rise up. There is no oil in the coolant that I can see, or water on the dipstick.

The car does not use any water at all. It does not run hot in traffic or on the highway on our present hot summer days. I drained and refilled the cooling system 6 months ago and have not had to add any water since.

The car does not run rough and gets excellent fuel economy for a 2.6. I've been driving 500+ ks a week and nothing's changed in the performance of the vehicle.

What do you think? Does water expand when hot? Would a cooling system filled in winter have too much water because of expansion in the summer? (doesn't seem likely) Could it be head gasket? Like i said there's no oil in the water as yet.

Try this.

Buy a new over flow botttle cap mine had holes in and wouldnt suck water back into the radiator, would fill the bottle till it overflows and not suck it back in when it warmed it up.

Might not be the problem but wouldnt hurt trying it. only costs a few bux.

Try this.

Buy a new over flow botttle cap mine had holes in and wouldnt suck water back into the radiator, would fill the bottle till it overflows and not suck it back in when it warmed it up.

Might not be the problem but wouldnt hurt trying it. only costs a few bux.

Yep i'd do that, and whack a new radiator cap on... for the sake of not having to worry in the future. See if that does the trick; otherwise everything sounds normal mate.

Thanks guys. I'll do what you suggested and keep watching it to see what happens.

Hi, from what you have described, fine bubbles in water, you have the same problem I had a few months back. blown head gasket. Did not use much water but pressurised the overflow tank without putting water in the oil. does anyone know if mitsubishi ever addressed the cracking heads, blocks and rocker covers in the 2.6 litre motors. not to mention the rear cam bearing running (melting) if you inadvertantly over tightened the rear rocker cover bolt? If they did anything other than using a different motor, which they did, what did they do?:D

by the sounds of it - the radiator / overflow is working 'properly'

reason for the overflow, is to allow for the engine to be run at different temps at different times of the year (winter / summer & cold (startup) and operating temp)

in thoery you dont need to drain coolant out of the motor in winter, as the extra that isnt needed as such - doesnt get 'sucked back into' the radiator when the motor is cooling down.

definatly put a new radiator cap on it if your concerned about it not sucking the water back from the overflow.


if you are really worried about the head gasket - pressure test the system, but be careful as it can make slow problems accelerate in severity VERY quickly.

i always thought slight / small bubbles in the rad at operating temp was normal - but it depends how much air could still be trapped in the system.

steps i would take from here:
1) new rad cap as mentioned by others
2) leave it be for a while - but check on it every couple of days
3) if still concerned, pressure test the cooling system - but be prepared for it to instantly cost money - if the gasket fully lets go, heater core pops etc from the pressure..

Run it until hot, leave it to cool and then check the level in the radiator.

If the radiator is full after cooling then what you describe in your original post is normal behaviour.

The overflow bottle is there to allow for the expansion and contraction of the coolant.

Yes, water does expand quite a lot when heated.

Rob

Hopefully, 10 months after he posted this he has fixed the problem

by the sounds of it, your cooling system is doing its job :D have fun

Thread mine!!!!!!!!!!!!!!!!!

The problem was the overflow bottle cap. It had gone porous allowing the bottle to fill up but wouldn't letter water suck back into the rad.

haha yeah... once on mine the rubber pipe between radiator & overflow got chewed
by the alternator pulley/fan... only a slight gash but even the smallest crack will
destroy the vacuum needed to suck the water back

Guys, this thread is a year old, please take note of what you are replying to, this member stopped posting long time ago, no need to bring this back up again