Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.

New Posts Contact us

Just Commodores Forum Community

It takes just a moment to join our fantastic community

Register

Overheating in traffic

glenncol

New Member
Joined
Jul 29, 2009
Messages
5
Reaction score
0
Points
1
Members Ride
VE SSV Sports Wagon
Hi all

We have a VX commodore and have come across a strange issue, when is heavy traffic the temp gauge will climb into the red and beep but then 30 seconds later it will drop back to normal temp and another 5 or to 10 minutes in the same traffic it will do it again.

To me it seems like the thermostat might not be operating correctly or an issue with the radiator cap?

What are you thoughts?
 
J

JohnW

Guest
Sounds to me like possibly a thermo fan issue. If it was things like the thermostat or radiator cap I doubt it would drop back to normal like you describe.

My thinking is it may drop back to normal when the fans eventually turn on (and overheating in traffic because they are not turning on at the appropriate temperature level).

Possibilities......

- Faulty temperature sensor (this is my best bet). I'd start by replacing it (easily done). Even if its not it, at least you'll know for certain that not the problem.
- Low speed fan not turning on

A completely failed temperature sender will throw an error code, not sure if it turns on the engine fault light. But an inaccurate one may do neither.

I've just written a procedure to easily verify both the low and high speed fan circuits in post #16 in the following thread ..... https://forums.justcommodores.com.au/threads/code-92-low-speed-radiator-fan-response-signal.81344/
 

glenncol

New Member
Joined
Jul 29, 2009
Messages
5
Reaction score
0
Points
1
Members Ride
VE SSV Sports Wagon
Sounds to me like possibly a thermo fan issue. If it was things like the thermostat or radiator cap I doubt it would drop back to normal like you describe.

My thinking is it may drop back to normal when the fans eventually turn on (and overheating in traffic because they are not turning on at the appropriate temperature level).

Possibilities......

- Faulty temperature sensor (this is my best bet). I'd start by replacing it (easily done). Even if its not it, at least you'll know for certain that not the problem.
- Low speed fan not turning on

A completely failed temperature sender will throw an error code, not sure if it turns on the engine fault light. But an inaccurate one may do neither.

I've just written a procedure to easily verify both the low and high speed fan circuits in post #16 in the following thread ..... https://forums.justcommodores.com.au/threads/code-92-low-speed-radiator-fan-response-signal.81344/

Hi John, thank you very much for he replay


I hear you with the thermo fan, i have noticed when in traffic but have not taken notice of how fast they were spinning, I will replace the temp sender tomorrow as a great start.

I went into the Vic market this morning and traffic was fairly light and the temp went up after being stuck at only 2 sets of lights, but again after 45 secs to a minute temp went back down to below half

Thank you for the link i will give that a good read right now
 
J

JohnW

Guest
Hi John, thank you very much for he replay


I hear you with the thermo fan, i have noticed when in traffic but have not taken notice of how fast they were spinning, I will replace the temp sender tomorrow as a great start.

I went into the Vic market this morning and traffic was fairly light and the temp went up after being stuck at only 2 sets of lights, but again after 45 secs to a minute temp went back down to below half

Thank you for the link i will give that a good read right now
Another thought ......

Turn the air-conditioner on (if the car doesn't have Climate Control), or if the vehicle has climate control, set the temperature to the minimum setting to force the air-conditioner on. The high-speed fans are wired to activate whenever the air con is running no matter the engine temperature, even with the engine clay cold when you first start it. Lift the bonnet and check. If they aren't on with the air-conditioner running, straight away you know you have a problem there.

Now drive around for a while with the air-con set like this (and high speed fans engaged) in the conditions you know the car overheats. If it still overheats before falling back you've just eliminated 'thermo fans' as a potential cause (because they are operating at 'full steam').
 

glenncol

New Member
Joined
Jul 29, 2009
Messages
5
Reaction score
0
Points
1
Members Ride
VE SSV Sports Wagon
Another thought ......

Turn the air-conditioner on (if the car doesn't have Climate Control), or if the vehicle has climate control, set the temperature to the minimum setting to force the air-conditioner on. The high-speed fans are wired to activate whenever the air con is running no matter the engine temperature, even with the engine clay cold when you first start it. Lift the bonnet and check. If they aren't on with the air-conditioner running, straight away you know you have a problem there.

Now drive around for a while with the air-con set like this (and high speed fans engaged) in the conditions you know the car overheats. If it still overheats before falling back you've just eliminated 'thermo fans' as a potential cause (because they are operating at 'full steam').
Cool man thank you

To replace the temp sensor does any of the belt need to come off or can you get to it without touching the belts?
 

mpower

Well-Known Member
Joined
Jan 22, 2007
Messages
4,856
Reaction score
1,390
Points
113
Location
Brisbane
Members Ride
V2 CV8 Monaro and VF SSV Redline
i'm thinking that the cooling system may also need to be bled.
 

Aussie Trev

Active Member
Joined
Feb 3, 2019
Messages
169
Reaction score
110
Points
43
Age
70
Location
Queensland
Members Ride
2 by VX Acclaim Wagon Series II 2001 & 2002
i'm thinking that the cooling system may also need to be bled.
I've had that in a VX when the coolant was just a little down in the radiator even though it was showing okay when checking on the overflow dip stick. Check the radiator when it is cool and see if it is down at all.
 
J

JohnW

Guest
Cool man thank you

To replace the temp sensor does any of the belt need to come off or can you get to it without touching the belts?
Without walking out and looking at the car, I'll say no its easily accessible without remove the serpentine belt. I certainly was able to easily undo the electrical plug from the sensor the other day to test the slow/high speed fan circuits.

Even if you find removing the belt necessary, no big deal. Just make a front on drawing of the way it goes around each of the pulleys before you remove it. That's the only hard part, figuring out how it goes around the various pulleys when you go to refit it. To remove it is just a matter of fitting an appropriate size ring spanner on the tensioner pulley nut and levering it back to remove the belt tension, then just lift off. Refitting the same procedure. Just make sure the belt sits centered on all grooved pulleys when it is refitted.

And you will need to bleed the cooling system from the bleeder in the top of thermostat housing after changing the sensor. Just need to remove the plastic engine cover (4 nuts) to get access to it.

P.S. And the reason I think its most likely the temperature sensor, or if not the thermostat, rather than some of the other suggestions, is because the engine temperature returns back to normal quite quickly. The only reasons I can think off for that happening are the fans finally kick it, or a faulty thermostat finally opens. Every other reason for overheating that I can think off e.g. blocked radiator, low coolant level, cracked head, etc, etc, .... this wouldn't happen. It'd just get hotter or stay hot. That it quickly returns to normal tells me the 'bones' of the cooling system are fine. It's just something not kicking in early enough before the temperature gets high e.g temperature sensor, thermostat.

PP.SS. Maybe just replace the thermostat while you have the engine cover off anyhow. What are they $25? Only one coolant top-up. Downside, you'll never know which it was if changing both fixes the problem, perhaps you don't care.
 

mpower

Well-Known Member
Joined
Jan 22, 2007
Messages
4,856
Reaction score
1,390
Points
113
Location
Brisbane
Members Ride
V2 CV8 Monaro and VF SSV Redline
returning quickly is also a symptom of an air pocket, thus the bleeding suggestion.

and that's a free thing to try over a sensor or anything else.
 
Last edited:
J

JohnW

Guest
returning quickly is also a symptom of an air pocket, thus the bleeding suggesting.

and that's a free thing to try over a sensor or anything else.
Ok I'm genuinely interested in how an 'air pocket' comes and goes in making the engine overheat, then drop quickly back to normal, time and time again. You may be right, but honestly I don't see how. Anytime I haven't bleed a cooling system (or more correctly didn't realise it had to be done or how, Toyota Prado) the damn thing just plain olde overheated due to a low coolant level.

And how does an 'air pocket' enter the block without a serious leak that would show up as an unexplained low coolant level, that needs fixing?

P.S. A couple weeks ago I went and retrieved the old VT wagon from Newcastle where the son had for the past several years. Don't think he's ever checked the radiator or overflow bottle in that time. The bottle was bone dry and I had to tip about 3 liters of water into the radiator to bring it up to the cap. No tools to bleed it, and just drove it back to Sydney (hot day 3 hours on the Motorway and across town in peak hour). Kept a careful eye on the gauges all the way, and it ran with the temperature gauge stuck like glue just below the half-way mark. And this was with no slow speed fan functioning (later discovered as one of the reasons for the endless display of warning lights. WTF has the airbag light ABS/TC etc lights got to do with fan, key, and cam angle sensor problems.)
 
Last edited by a moderator:
Top