[MrRocky]

It seems my overflow bottle is refusing to drain back into the radiator.
So far replaced rad cap, heater hoses, pipe into rear of water pump, overflow bottle (and hoses), genuine thermostat, radiator

Before you say head gasket, im wondering if the heater tap could be loosing me some pressure. There is no coolant loss, no bubbles or overheating. Quite simply it just refuses to drain back.
It is a reconditioned engine

[Gwagensteve]

I vote you have an air pocket somewhere.

[Jack jr]

G'day MrRocky don't know about the heater tap but my sierra was doing this and i replaced the head gasket and it started reterning back to the radiator, sorry i cant be more help.
Cheers Jack.

[MrRocky]

Jacked the front and gave the rad a good burping as well as cracking a few hoses. Will see how that goes

[alien]

Smell the coolant in the overflow... mine managed to bridge the head gasket between cyl 2 & 3 from a coolant valley to an exhaust one. So the coolant was getting pressurised with exhaust and smelt like fumes.

[fordem]

A leak anywhere in the system can cause it not to develop the vacuum needed to draw the coolant back - in my case, the leak was a hairline crack in the overflow bottle cap.

[MrRocky]

Bypassed heater tap and heater core.
Issue is now sorted. Well at least for the summer.
Mind boggling there was zero coolant leaks but still enough of a pressure leak to empty the top rad tank and fill the overflow then not drain back.

[MrRocky]

Well after blocking off the heater core/tap the coolant drains back but pushes a heap of coolant out the overflow even when car is below operating temp after cold start. Im thinking maybe radiator is blocked? Car has sat for a long time.

[bumstein]

Got a spare to try? I’ve got a good one here if you need it

I’m still suspicious of head gasket.

[Gwagensteve]

Head gasket.

[MrRocky]

Ok so i pulled out my new genuine thermostat and the toggle/hole was letting next to nothing through when cold, really was miniscule. Maybe i got the wrong genuine item. Ive removed the toggle and drilled out the hole to 3mm. Seems to have made a substantial difference, need more seat time to confirm

[MrRocky]

Ugggghhhh

[krat]

Bugger.
"Well there's your problem"

Hope all goes well.

[Gwagensteve]

Next time people give me a hard time when I say g motors don’t recondition well.....

[MrRocky]

Motor was rebuilt 10yrs ago with new head/rockers ect...
Only done a couple thousand kms but gasket was toast. Cleaned up and added some extra ft lbs on the tighten up so should last a few more years.

[MrRocky]

Running much better now

[303zuke]

Running much better *for* now.

Fixed it for you.

[MrRocky]

[markmo]

303zuke wrote:

Running much better *for* now.

Fixed it for you.

Isn't this the standard response for anything G series?

[MrRocky]

Ahhh but if a 1.3 sierra and a jimny had a race would jimnys still be shit offroad...

[markmo]

MrRocky wrote:

Ahhh but if a 1.3 sierra and a jimny had a race would jimnys still be shit offroad...

of course