Coolant Boil / Bubble

[endless]

Ok i have done a search, sounds like my cooling system may not be bled correctly.

Recently installed a new waterpump & fresh tested / cleaned radiator for my 26.

The car does not overheat at all when driving, however after stopping the overflow bottle starts to boil after a little while.

I filled up the coolant correctly (removed bleed screw etc) however to get the remaining air out it sounds like i may have to undo this bolt again when the car is hot / boiling after i stop? Just want to make sure this is safe enough to do.. or perhaps there is another way?

[J'z-R33]

Cut the base off a coke bottle and tape the smaller side opening to your radiator filler (when cold). start the car then start tipping water into the coke bottle till its half way full and let it idle for a while.. it should bubble up releasing the air..

Cheers

Johno

[FrangaR33]

Cut the base off a coke bottle and tape the smaller side opening to your radiator filler (when cold). start the car then start tipping water into the coke bottle till its half way full and let it idle for a while.. it should bubble up releasing the air..

Cheers

Johno

+1 thats the way to do it, just keeping filling till you get water coming out of the bleed screw.

[endless]

OK just did this again incase of any bubbles but i filled it originally this way - definitely no bubbles coming out with this method!

Can anyone answer my original question about the upper bleed screw?

[mad082]

probably not best to do when fully up to temp if you aren't confident. if you do decide to do it, have a rag wrapped around the area, or at least sitting over the top of the spanner. also you don't want to remove the bolt the whole way. you just want to loosen it enough that any air can escape, so you probably only need to loosen it a few turns. you will be able to tell once you are starting to get close to having it completely undone as the last few turns the bolt will be a bit wobbly in the thread, and also you will get coolant making it's way past the thread. the moment you get coolant starting to seep out then you don't need to loosen it off any further.

however i would do it when the car is only just coming up to temp. i wouldn't be doing after driving the car round for half an hour.

[endless]

Cheers for the help. I bled it with this method this evening, took it for a drive - problem is still there when turned off!?

It doesn't go above 82 degrees whilst driving, even when giving some boot.

I am thinking that it might be corrosion in the cooling system? The radiator is clean as a whistle but inside the radiator pipes on motor side doesn't look too healthy. I have some cooling system flush on the way so will give this a whirl and see how i go.

I suppose the only other thing could be air getting into the system somewhere... in another thread someone mentioned the turbo water supply/return hoses.

Could it be anything else?

[mad082]

it is very hard for air to get into the system, because the system becomes pressurised when hot, so any places air could get in will have water squirting out of them. only real cause of air bubbles can be a dodgy water pump causing cavitation resulting in bubbles, or a blown head gasket.

it may be worth replacing your radiator cap and see if that makes any difference. just go a standard cap with the same pressure rating.

[endless]

Yeah was also thinking the radiator cap. Always easy to overlook the simple things!

Replaced it last night - boil is gone

I heard a couple bubbles when it was cooling down. Probably just crap left over in system, getting engine flush next week.