What have I missed? Rad swap, new switch - fan now not kicking in

[GTXTRA]

As per my Mk1 project thread.

Have fitted a new radiator - done this sort of thing many times including on this very car a week ago...

However - today there's an issue with the fan not kicking in when bleeding the system...

Fan works with the switch wires engaged together.

I've tried with the new switch and even the old one - the temp gauge shoots up and coolant flows out - no warning light, no fan.


What have I missed folks?

[mr.brown]

Exactly what happened to me. It turns out I didn't run it long enough with the cap off and it must caused an airlock at/near the switch. I ran it for an few minutes with the cap off and all was well.

[james butler]

Exactly what happened to me. It turns out I didn't run it long enough with the cap off and it must caused an airlock at/near the switch. I ran it for an few minutes with the cap off and all was well.

this is why after a coolant change i always run the car up to temp untill the fan cuts in with the cap off.
still yet to work out why it causes the strangest of issues if you dont do it.

[GTXTRA]

Yes - that's exactly what i do.

FB advice point to blocked return hose/pipe or failed thermostat.

[GTXTRA]

I've changed thermostat.

Flushed system with hose.

Refilled, bleeding, car goes to overheat, no warning light, gauge shoots up.

Fan still not kicking in.

Top hose hot

Rad cold.

Bottom hose cold.

At a loss.

[mr.brown]

Reverse flush rad? Possible some old crud got caught in there.

Failing that, run without a thermostat to make sure there's flow.

[unknownmale]

Maybe the rad is blocked?

[GTXTRA]

Brand new rad.

[GTXTRA]

Ok.
Now I’ve got
Top hose and bottom hose hot, rad hot.
No flow at 8mm outlet hose to bottle.

No fan kick in

[james butler]

sounds like a manufacturing defect if coolant isnt coming out.
you could run a drill bit through the 8mm hose into the rad and see if its blocked.
or take the rad back and get it exchanged.
alternatively the pumps packed in?

[GTXTRA]

JAMES - I wish I'd read this answer properly when you posted it.

Turns out this rad DID have some sort of plug built in to the outlet for some bizarre reason.

Now sorted.

Phew.