Cooling system problem

[aj_vmax]

Hey guys and girls. I have an issue I just can't work out. A few weeks ago my patrol smelt hot so I removed the thermostat and it was stuck shut, replaced that but after I run in to town and back 100 klms round trip, when it cools down there is 1/2 ltr of coolant missing from radiator but it's in the over flow. So I thought it was the over flow hose so replaced it and gasket glued it so now leaks. Still missing water in radiator and in the overflow. After a run for 200klms today and waited for it to cool and went to check the water level in radiator and it was pressurised. I have purchased a new radiator cap but do u think I may have a bigger problem. There is no water in oil and no oil in water. Thanks in advance

[nissannewby]

So its not recovering the coolant?

[aj_vmax]

Yeah it wasn't. But now the radiator has pressure in it and when open it sprays water everywhere like it would if it was hot

[nissannewby]

Ok. So its pressurised even when not running. Try the cap first as normally if its something more sinister it will only be pressurised when running. Of course it is still possible it could be something worse but caps are very cheap. Stick to genuine if you can.

[aj_vmax]

Thanks I got a cap today waiting for to cool will put new cap on in morning. It wouldn't be a crack in head and exhaust gasses getting in cooling system would it

[nissannewby]

It could be but I would wait and see if the cap fixes it.

[the evil twin]

... most of that sounds normal and it sounds as if there was a fair bit of air left in the system after you replaced the thermostat

A modern cooling system in good nick will often have a bit of pressure in it at the radiator cap.
Remember that the cap seals at 10 to 14 PSI or so depending on rating and above its pressure setting the cap releases and ports coolant to the overflow.

After shutdown any residual pressure has nowhere to go unless you crack the cap albeit it will slowly leak down over time

Any decent amount of air in the system means the the air volume will reduce significantly as it cools (much more so than coolant) and draw coolant from the overflow tank.

If the rad is spurting some coolant (not heaps and heaps tho) when you crack the cap when cool...and... there is no coolant getting blown overboard... and you aren't having to top up the overflow at all IE it is staying between the marks in the overflow then everything should be OK

If in doubt you can 'burp' the cooling system and that new cap sure won't hurt anything

[aj_vmax]

Thanks guys how do u burp the system

[the evil twin]

Thanks guys how do u burp the system

Not sure that you will need to but if you do...

Find a bit of a hill/ramp/jump up and park so the top tank of the rad is higher than the motor as much as is practical,
cut the neck off a coke bottle or whatever,
take the rad cap off,
put the heater on full hot
hold the coke bottle neck down in the rad filler,
kick it in the guts at idle, should only need a minute or two...
Any air bubbles etc should collect and escape via the bottle without a heap of coolant going everywhere

[dom14]

If you are not losing water, then it should be ok. If you are losing water and can't find any leaks anywhere around the engine, then you got a big problem.
Little bit of gas inside the radiator that hisses out as you open the cap(cold engine) is ok. If it spurts out lot of gas and coolant along with it(when cold), then
that can't be a good thing.
Exhaust gas test at the the radiator is a very good idea.
If you want, you can buy a kit with the liquid off fleabay and do the test yourself.
I'm developing my own test atm.
I'll post the details, once I've perfected it.

[trainman]

If it helps, I'm having exactly the same issue. So far cap has been replaced, thermostat got done a while ago, engine and radiator have had a good flush.
I find that removing the overflow, opening the vent and returning the excess to the radiator about every 2-300km is enough to keep it happy. Clearly not a good long term option though, especially as the weather warms up.
I can't say I'm convinced in the merits of horizontal flow radiators either.

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