Temp spike and new radiator

[FC50]

I have a strange problem with my bog standard VT (2000), which is well maintained and in very good condition, lowish k's and not driven hard.

It had a gurgling from behind the dash when cold, leading me to believe that the system needed a bleed.

The main issue
Occasionally when pulling up at lights, the temp alarm will go off and gauge would go from below 1/2 and roar up to full (red line) in about 5 seconds, sit there for 30 seconds or so and just as rapidly drop back to below half again.
It always had water in it and never felt overly hot and never smelt but a couple of weeks ago it did it again and something didnt feel right so I shut it down and found it was actually hot and smelt hot this time and the radiator had shat itself.

RACQ to the rescue and towed it to the mechanic I had used for years and replaced the radiator, thermostat and cap and he said that he had great difficulty filling it up with fluids having to raise the front considerably to do so (seems odd), but eventually all was good, had it sitting there running for an hour or so and no problems.

Over the last few start ups, the gurgle seems to be back and today, the temp spiked again.
Motor did not feel overly hot, no smell, but I was surprised that the radiator cap was cold, as in stone motherless cold to the touch, while top and bottom hoses felt hot, as they should.

Suggestions?

Add:
Yes, I have searched the forum http://forums.justcommodores.com.au/...%23post1891661 when I first had these issues previously but found nothing conclusive.

[Killr6]

get a pressure test and see if there are more leaks? like maybe a faulty water pump.

[])R@G()N]

The rapid jump in temp and down again suggests a loss of presser in the system, get it pressure tested as DanLusas stated,
Good chance its your water pump, have a look at the top of the sump near the Harmonic balancer if your waterpump is leaking there will be coolant on there or traces that its been there.

[blueV8vl]

thats def got air in system need to be bleed.

[Hot-Rod]

All the symptons you are having could be the above suggested, also possible a split hot tank side in the radiator also does the above symptons.

[Killr6]

All the symptons you are having could be the above suggested, also possible a split hot tank side in the radiator also does the above symptons.

he said only just got a new one? and deffs bleed the system

[Hot-Rod]

Others on this forum have received defective radiators from New. Its possible.

[FC50]

Thanks for the replies
back to the mechanic this morning and I'll update when I know more.

[FC50]

In the mechanics shop now, couldn't see it yesterday

Yes, it did have air in the system again and they have no idea how as they reckon they spent hours bleeding it so must have got rid of it all, right?
But at least today, the temp spiked while they drove it.
It has been pressure tested and dye checked? -- all OK
It has had the water pump out and checked -- all OK
It has had yet another thermostat fitted.
The system has been bled, yet again.

They say that one of the fans does not cut in when the ac is running, but it is winter and it should not cause a spike in temp, but they'll fix that as well.

Lets hope that its fixed.

[Hot-Rod]

Sounds like they didn't bleed it properly. I had the radiator flushed not to long ago. Took them 1 hr to do everything. No issues at all. How do u spend hours bleeding Holden cooling systems?? All the coolant would come out the bleed valve.