VZ V8 Cooling problems

[MorganVZ]

Been reading for a few hours trying to find some advice but haven't really found anything that applies to my problem (its a L76 V8). For some reason my car keeps overheating as I can hear it bubbling away into the overflow. These problems started a couple of weeks ago when it blew the back of one of the side tanks on (note: Didn't crack, blew it off). I replaced the radiator and kept having problems. I took off to a Radiator specialist a couple of weeks ago and thought it was fixed but yesterday it dropped a lot of water. It get's hot but for some reason the Thermo Fans won't kick in, however with aircon on the fans do kick in and everything's fine.

So far replaced;
Radiator
Radiator Cap (seal was knackered)
Thermostat (seal was knackered)
One of the lower hoses (looked knackered)
And after all that it then blew the heater tap which was replaced.

After that it pressure tested fine and no problems until yesterday.

Anyone got any ideas? AS far as i can tell there are no leaks (pressure tested fine and not dropping coolant apart from yesterday) was gonna run some chemiweld through the system to fix any cracks in the head but while heating the engine up it started blowing water out of the Radiator (Cap off)...

 

[lowandslow]

Checked your fan relays?

 

[CONROD]

Gidday mate, when I flushed and changed my coolant in mine, make sure the heater is on full hot (as you have replaced yours make certain it is actually going all the way),park the car on an incline so the front is elevated or run it up on ramps as that will help to let all the trapped air to rise to the top, or use the cut coke bottle set up.
I found it easier to raise the front of the car up because it is lowered I wanted the neck of the radiator higher than the heater core.
The L76 is self bleeding, but if you feel you have to use chemi-weld for a cracked head no amount of bleeding will suffice.
Take your time topping up as it will drop and rise constantly until all air is expelled, once you feel the top radiator hose get hot too touch you know the thermostat has opened.

 

[petern64]

is your engine oil clear or milky in colour ?

 

[iChris]

by the sounds of it you should be finding out why your engine fans are failing to come on as they should. see if that fixes the overheating problem.

are you sure it's a cracked head? if so, should that not make itself known when pressure testing?

 

[MorganVZ]

Thanks for the quick replies, the radiator guy swapped the relays around and everything still worked. The fans do come on, just not for long enough. It doesn't even show it's overheating on the dash as the needle doesn't go past halfway, but it boils.

@ Conrod I had the car on a massive incline but the problems is I can't fill it up as it literally blows the entire coolant out of the radiator like a hose.

I'm thinking it's either a blockage somewhere (which would be why it passed the pressure test and it doesn't show the car overheating on the temp gauge) or the water pump is shitting itself. Does that sound right?

 

[99notout]

You haven't got LPG have you??

 

[MorganVZ]

Nah, only run it on 98

 

[99notout]

Ok, it was just that if you had LPG, it can enter your cooling system and cause similar symptoms.

 

[XioiX1983]

Split top/bottom tank? tried pressure test?