Radiator and coolant

[cdt]

Had my radiator cap replaced at my last service. The car has been running okay for the last few days, but today I had steam coming out of the swan neck cap. Once it had cooled it was obvious the cap wasn't tight. I presume it must have been before otherwise I'd have had steam coming out far sooner.

Can the cap loosen itself? Is it easy to get a replacement cap for the swan neck? (not sure if this is the problem)

Is there any advantage to using a higher than 25% anti-freeze mix, to raise the boling point?

How much coolant does the radiator hold?

The expansion tank was empty when I checked it. Took 2 litres of coolant to get it full at the swan neck. Still seemed to run a hot on the way home tonight. I presume it will need topping up again, will have a look in the morning. Might have to try the trick of filling it on a slope to get rid of any airlocks.

[adam quantrill]

I put the swan neck cap on with blue hylomar and leave it well alone. Just make sure you do use antifreeze or inhibitor when you top up or you'll be looking at a new head gasket shortly (Eh, Jim?)

[jchase]

a-hem, yes, er put antifreeze in, it takes around 20 hours to replace head gaskets the first time you do it - the tin head gaskets on mine had suffered cathodic corrosion - presumably due to lack of corrosion inhibitor. TVR recommend 45% mix which just happens to be a 5 litre bottle into the 11 litre system capacity. IMHO 25% is not going to help.

-Jim

[toltec]

I found using a big whetstone to make sure the spigot has a flat seal all the way around helped. Just make sure you put some rag in the opening to catch the grit.

[rev-erend]

Make sure it's a flat cap with no pressure spring on the swan neck..

Some people mix the two caps up - this would cause the symptoms you describe.

So : Flat cap on the swan nech
and pressure cap on the expansion tank.

Also - do not over fill the expansion tank : it needs to be to the level marker inside the tank and not up to the top !

[leorest]

rev-erend said:

Also - do not over fill the expansion tank : it needs to be to the level marker inside the tank and not up to the top !

Doesn't it just find it's own level by blowing excesses out the overflow?

[rev-erend]

leorest said:

rev-erend said:

Also - do not over fill the expansion tank : it needs to be to the level marker inside the tank and not up to the top !

Doesn't it just find it's own level by blowing excesses out the overflow?

Yes - true but then the owner thinks it's loosing water and that they have a problem !

[cdt]

Thanks for all the replies.

I thought you shouldn't fill the expansion tank, always fill at the swan neck?

Caps were on the right way. It was just loose, not sure how, but it is tight now.

So 25% isn't good, most of what I put in previously was 50% anyway due to a memory lapse, is there any advantage to going over 45%?

Have filled it up with the cap off and engine and heater running and after every attempt to get it to overheat it won't now. It took another litre or so of coolant to get it full, I hadn't driven far yesterday, so I hope no damage has been caused.

Edited by cdt on Tuesday 25th July 21:12

[GV]

What about fitting an alternative - say a screw type fitting. I'm there must be out there somewhere?

[bobble350]

cdt said:

It was just loose, not sure how, but it is tight now.

So 25% isn't good, most of what I put in previously was 50% anyway due to a memory lapse, is there any advantage to going over 45%?

The swan neck filler is a crap design, the neck will bend soft as chit and the caps tend to be useless and can't be reused once the rubber has compressed to the shape of the neck - i.e. after the first run. Scrap it and solder in a screw in plug boss.

Water has better heat transfer properties than anti freeze. The increased viscocity of anti freeze can also slow the circulation if too much is used. It does however raise the boiling point.

Mark.

[adam quantrill]

You used to be able to get corrosion inhibitor on its own but I haven't seen that for a while though. I think 25% mix is reasonable, I have used that ratio for many years with no problems. Just make sure you _never_ put plain water in. _Ever_. Also I use water out of the hot tap for topping up, as this has already dropped some of its hardness and/or reacted with some metal in the hot water cylinder.

[cdt]

adam quantrill said:

You used to be able to get corrosion inhibitor on its own but I haven't seen that for a while though. I think 25% mix is reasonable, I have used that ratio for many years with no problems. Just make sure you _never_ put plain water in. _Ever_. Also I use water out of the hot tap for topping up, as this has already dropped some of its hardness and/or reacted with some metal in the hot water cylinder.

The water I use is always from the hot tap and then put through a filter.

Presumably water wetter is the ideal thing, as it is a corrosion inhibitor and helps with cooling. Would just be a little expensive to fill the radiator with it, would need about 30 bottles ...

[gwood]

by adding more anti freeze doesnt raise the boiling point of the coolant, only a higher pressure of the rad cap does that.(the rating should be printed on the top)but i wouldnt recomend that might blow something!! i would check your thermostat maybe its sticking.( my 350i had that prob)also it took some time to get the air out of the system. plus coolants today are a good anti corrosive and also a good summer lubricant too.

[cdt]

gwood said:

by adding more anti freeze doesnt raise the boiling point of the coolant, only a higher pressure of the rad cap does that.(the rating should be printed on the top)but i wouldnt recomend that might blow something!! i would check your thermostat maybe its sticking.( my 350i had that prob)also it took some time to get the air out of the system. plus coolants today are a good anti corrosive and also a good summer lubricant too.

Anti-freeze has a higher boiling point than water. The higher the percentage of anti-freeze, the higher the boiling point.

[TVR 3X]

quote gwood

by adding more anti freeze doesnt raise the boiling point of the coolant, only a higher pressure of the rad cap does that.(the rating should be printed on the top)but i wouldnt recomend that might blow something!! i would check your thermostat maybe its sticking.( my 350i had that prob)also it took some time to get the air out of the system

endquote

This sounds as though your thermostat was not fitted correctly. In most cases there is a little hole (usually with a jiggle pin in it) this hole must be at the top so that any air can circulate through it. If it isn't the thermostat bulb may just be sitting in air - not water and won't open.

Russ

[gwood]

i bought my car just recentlty but it had been stood for about 12 months without any use so there was alot of things that had seized. it overheated a few times so it fitted a thermostat and its been fine since.(fingers crossed)