VZ V6 running hot for no apparent reason

[SKNOT9]

Hi there. I have a 2005 VZ V6 and just recently it will overheat (little picture comes up on screen saying its overheating) and the guage is just about at the top. Im not quite sure that it is actually hot, because i pulled the car over and opened the bonnet and could rest my hand comfortably on the top of the engine, and couldnt feel much heat rising from the engine. It was a cool morning, i don't have any coolant leaks, the coolant has been full every month that i check it, there is not frothing on the engine cap which would indicate something was wrong. Im thinking it may be a temperature sensor just saying that it is hot? or maybe it is really hot and i just cant tell. the thermo fans are coming on when the guage is just above half so that seems normal. Im just wondering if this is common or if anyone knows what could be wrong? This has happened randomly 4 or 5 times over the last month or so.

[richardpalinkas]

i heard the radiator cap or thermo may cause it?

[SKNOT9]

do you mean thermostat?

what could the radiator cap have to do with it?

[richardpalinkas]

yea the thermostat.

i dunno, just what i 'think' i read somewhere on here

[impulsive]

Thermostat could be the problem, Radiator caps have known to fall apart which causes the car to over heat, happened to me, check the spring underneath radiator cap it could be broken, if so replace it.

Generally with simple stuff like this it pays to inspect components of the individual system, check other things while your there, belt tension etc

[bulldog79]

my sister had the same problem there was a falty batch of thermostats

[Sean880]

You should have had it professionally checked out the first time it occurred. Overheating problems do not fix themselves. Running the engine hot like that can easily result in blown head gaskets and damaged heads. ( Expensive damage).

2. If it is intermittent, it sounds to me like it might be a thermostat that is intermittently sticking. When the coolant is heated in the engine, the thermostat is sometimes not opening to allow the coolant to freely flow from the radiator through the engine. Hence a hot engine condition. I don't think you have a problem with a failed water pump because in that case the overheating condition would usually be a continuous problem.

3. The culprit might also be an intermittent blockage in coolant flow through the engine due to debris build up in one or more of the coolant passages in the engine.

4. Air in the cooling system, from inadequate bleeding of the system, can cause an air lock and consequential high temperature condition. It does not sound like that is the problem though.

Problems occur in cooling systems because they are often neglected. People often wait until they have a problem before servicing them and in the process risk engine damage.

Cooling systems need flushing at least every 2 years and refilled with the recommended coolant mix. Thermostats need to be working properly (plenty get replaced) and water pumps fail periodically and need replacing.

You will need to take the car to a competent mechanic to have the problem properly diagnosed and addressed before you do major damage to the engine by overheating it again.

[Torquative]

alloytecs are known for having failing theromostats and as mentioned radiator caps

[SKNOT9]

thanks for all your help guys it is great!! i will replace the thermostat and check the radiator cap and if that is not the problem i will take it to a mechanic and get the system flushed and get other things checked out. Normally I would be on this sort of thing straight away but I have had overheating VS and VN and you could really tell it was overheating by the feel of the engine and when you opened the bonnet just a wave of heat hit you, but with this car it just seems like its running fine so i figured it is a gauge error or something. Another thing i forgot to mention is that when it says it gets really hot, just sitting at lights, sometimes it will just drop back down to half temp in about 5 seconds, so it seems like a "glitch" if you get me. What temperature should my coolant be running at?? I appreciate all the suggestions

[alex2_s]

what could the radiator cap have to do with it?

Radiator caps are rated to a certain pressure which it will hold pressure too until it allows the coolant to expand into the expansion tank. If the radiator cap cant hold pressure (or you just simply take it off) the car will almost certainly overheat straight away as the system wont be able to pressurise (coolant has a higher boiling point when pressurized)

[SKNOT9]

ok well i dont think that is the problem, because i put the car into diagnostic mode or whatever and it happened this morning it said my coolant was at 119 degrees so if it was the radiator cap it wouldnt be able to get that hot if it wasnt pressurised and i got out and my top hose was hotter than bottom hose, ive heard that that means thermostat

[Sabbath']

Could be an air lock in the system causing innefficient cooling. Have you rebled the cooling system at all during your diagnosis?

[Scaf_man]

Im not shore if this will help be helped with me,

Take your rad cap off and start the car, see if you can see anywater swashing around down the cap. If not top it up until u see it bubble and settle. This happend to me and for some reason my reservoir said was full but was hardly anything in the block.

[SKNOT9]

ill try that scaf-man, cheers, and also how do u bleed it sabbath? ive only ever done that with an ecotech

[MissSV6]

have had overheating problem, replaced thermostat and radiator cap.

[SKNOT9]

well i replaced the radiater cap the other day and it hasnt done it for about 3 half hour drives, so i think the problem is fixed. Thanks everyone! when i took the other radiator cap off i noticed that i could only push the spring in about 2-3mm and then it stuck and wouldnt push in anymore so i believe it was a dodgy one.

[Longy188]

gday, this is the exact problem my sv6 is doing it only does it occasionaly, so by the sounds of it ill be up for a new thermo or cap, how hard is it to change the thermo ? and how do u bleed the system ??

[SKNOT9]

apparently its a pretty big job to do the thermostat, either have to drop out the gearbox or take the inlet manifold off as the housing is at the back of the engine. But give a radiator cap a go to start with it was only 13 bucks. Not sure how to bleed the system sorry

[Torquative]

yeh, it is a fairly large job to do the thermostat for that reason /\

Ive heard gearbox out is easiest

[impulsive]

its not hard to take the manifold off though

[Kernal]

Digging up an old thread.

My sisters VZ has been running hot latley. Went into the red once. I filled 3L of coolant this morning. There seems to only be water in the system so im planning to flush it over the weekend.

How many liters does the VZ V6 cooling system hold?
The radiator cap does not have any spring thing in it. Do VZs not have it? And should i replace the cap as well?
Lastly, because the radiator cap is at the highest point of the cooling system, do i need to bleed the system?

[azazeldeath]

The radiator car does have a spring on it, if request I will show you a picture of a new one. If it is getting hot and there is no spring in the cap I can almost garentee thats your problem.

EDIT:
Decided to put one up anyway. My old one had a yellow top, this one is black. Got it from Holden for about $30 if I remember correctly (can check that too if you want).

[Kernal]

Thanks mate, that helped heaps. The one she has doesnt have a spring in it. Some shitty plastic thing, looks more like an oil cap. I buy a new cap for her.

[Phillshz]

yeh, it is a fairly large job to do the thermostat for that reason /\

Ive heard gearbox out is easiest

It`s a major pain to change the thermostat and would try that last. Id look into the cap first as they are well known to fail,they simply fall apart.

[Giant]

If the spring etc has fallen apart then it maybe rattling around inside the radiator you may need to remove the radiator turn it upside down and give it a good flush with the hose.