Radiator cap cold/overheating

[Glaze]

There’s hundreds of threads with most likely a similar situation I’m dealing with. I’ve scoured the forum for anything almost mirror copy of my issue but can’t find an exact complaint. It’s a 3.8 auto

Trouble is past couple months temp gauge has been fluctuating, going up and down as it pleases. The conditions are: even while driving/accelerating gauge rises, heater on full blast gauge rises, gauge rises at idle (common) but goes to H, sometimes with heater on and driving gauge will drop. I’ve noticed the cap is very cold and overflow tank is at a high level, both hoses are hot to touch so thermostat seems to work properly.

Since the beginning of this I’ve replaced the cap twice with genuine item, genuine radiator twice, genuine thermostat, Mackay hoses, flush and bled coolant excessively. Fans do kick in but doesn’t help. I’ve owned this Ute for 3 years and never changed the water pump no signs of leaking etc I’m beginning to think the impeller has deteriorated in the pump since it isn’t pushing coolant because when I accelerate it tends to drop in temp.

No signs of oil in coolant, cap is clean, oil dipstick is clean, occasionally white smoke on a cold day at idle but goes away when operating temp is achieved. Most of the time car sits at under half always. I’ve ordered a pump and see how I’ll go but any advise or experience would be appreciated cheers

 

[krusing]

"white smoke on a cold day at idle but goes away when operating temp is achieved."
Sounds very familiar/common
How many K's ?
Any modifications ?
Any Water Leaks ?
Any smell of coolant in the car ?

I am tipping -
Replace the LIM Gaskets,
Replace the Thermostat,
Bleed the cooling system correctly,
I reckon that will possibly eliminate the over-heating issue.

 

[Glaze]

"white smoke on a cold day at idle but goes away when operating temp is achieved."
Sounds very familiar/common
How many K's ?
Any modifications ?
Any Water Leaks ?
Any smell of coolant in the car ?

I am tipping -
Replace the LIM Gaskets,
Replace the Thermostat,
Bleed the cooling system correctly,
I reckon that will possibly eliminate the over-heating issue.

It’s at about 380xxx kms
Only has growler intake, pacemaker extractors and aftermarket exhaust
No coolant leaks at all and no smell radiator and cap is pretty clean been monitoring for a while without flushing and almost no build up of oil

I’ve replaced the thermostat once it has a genuine Holden one not sure if it’s failed and this was about 20,000kms ago

 

[Deuce]

Water pump sounds fine to me.
It sounds like a steam pocket issue to me.
Give it another try bleeding the system as per the manual and see if it improves.

Well if you have already ordered the pump, swap that in and bleed it.

 

[Immortality]

Doing the pump seems like the only major item left.

 

[greenacc]

Impellers can corrode, break, Fall off among other issues. Change the pump and while you're at it I would flush the engine block to make sure it's not blocked. Was the car in good condition when you bought it or was the radiator full of rust and sludge?
The cap should not be cold. You need to work out why it's cold. If hot coolant was circulating properly the cap would be hot like everything else.

 

[Immortality]

Have you run an engine flush through it? Might pay to do that before doing the pump so there is less risk of damaging a new pump with debris from within the block.

 

[Glaze]

So I used enyvous customs scan tool program and found these faults. I’ve replaced the temp sensor with a genuine one so I’m stumped.
Today when driving home from work car warmed up quite quickly to normal temp then about 5mins later shot up to H, kept driving and gauge dropped back. Car kept doing that whole way home rising and dropping. When I got home bled the car through the bleeder water came out fine but occasionally was spitting air but it always did that whenever I bled the car multiple times I even bled the car for over an hour to point where there was no coolant left and heater became cold. The cap was always cold whole way home as I pulled over twice to check for leaks. I’m thinking the radiator is probably blocked somewhere

 

[Glaze]

Bit of an update since last post

Been filling coolant every 2 days about 1-1.5L so coolant is being lost somewhere. No overheating because I’ve been regularly topping up. Before I started topping up temp started to rise so the loss of coolant obviously caused temp rising. Haven’t noticed white smoke from exhaust early in the morning when I drive so I’m unsure whether it could be water pump or inlet manifold gaskets. I’ve had a look around the water pump no signs of leaking but can never really tell since the coolant will just evaporate. Radiator cap has always stayed cold since I made this post. Any ideas?

 

[Immortality]

The most common place for these cars to loose coolant internally is via the LIM gaskets but 1 to 1.5 litres is a lot.