Simple coolant/radiator cap question

[citizenerased]

Hi All

Dead easy question for y'all. I know basics but am definitely not a car person.

The coolant expansion reservior process on my VT only half works. The expansion part seems to work fine (hot engine forces excess coolant into reservoir), but for some reason the coolant is not sucked back into radiator once engine cooled. As a result, an air void develops in the radiator (which I have managed for a while by topping up radiator coolant).

From what I've read, the radiator cap might be the issue? Spring not working properly to allow coolant suction back in? My radiator cap is in rather shitty condition.

Any other problems it could be?

Cheers in advance for replies.

[Catchy]

Had the exact same problem, radiator cap wasn't allowing fluid from the overflow tank back in. Replaced it and all is good. I'd try that first.

[jonboy]

hi
mine does the same thing sometimes, i should get a new cap as well

[accentstencil]

hi
mine does the same thing sometimes, i should get a new cap as well

Yes you should, they are not expensive.

[holden_calais_VT_1999]

I got one for free from the wreckers socked in degreser over night and washed and cleaned in the morning and polished her up looks brand new

[nzBrowny]

yeh man replace that cap. i had the same issue but same as the others got a replacement and no more problems. check that the hose which goes into the reserve tank is long enough as well. it might be that it cant pick up the coolant to suck it back into the radiator?

[citizenerased]

Cheers for the replies, legends!

I'll get a cap from a wrecker and give that a try.

nzBrowny - haven't got the reservoir out to have a look, will check that everything with the hose is as it should be.

[wortus]

I had the same problem, replaced the cap and it worked for a month or so now it's doing the same thing.

[Giant]

Yeah best to buy a new cap they don't cost much.

[Dayvo]

yeh man replace that cap. i had the same issue but same as the others got a replacement and no more problems. check that the hose which goes into the reserve tank is long enough as well. it might be that it cant pick up the coolant to suck it back into the radiator?

Also check to see that the hose doesn't have a hole in it and is not sucking air instead of fluid . The hose does tend to swell with age too

[Tree cutter]

Try replacing the cap first. If it still doesnt suck coolant out of the overflow bottle, then you have a leak in your cooling system somewhere. Air will be sucked in from anywhere that leaks instead of sucking the coolant back out of the overflow bottle because air is easier to suck in than coolant. It could be a leaking waterpump front seal or heater tap or any of your hoses.

[Catchy]

It could be a leaking waterpump front seal or heater tap or any of your hoses.

Could also be leaking from your radiator tanks.