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

mpower

Well-Known Member
Joined
Jan 22, 2007
Messages
5,078
Reaction score
1,713
Points
113
Location
Brisbane
Members Ride
V2 CV8 Monaro and VF SSV Redline
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.

*source - I had this happen to me when i was a know nothing noob and I changed my coolant (VT V6) not realising I had to bleed the system.
 
J

JohnW

Guest
*source - I had this happen to me when i was a know nothing noob and I changed my coolant (VT V6) not realising I had to bleed the system.

But the OP hasn't changed the coolant or been experiencing loss of coolant (well not that he stated and would have expect he'd have said so if he was, being important points).

I've also changed the coolant in the VT (it was originally the family car) and not bled the system, without a problem. The reason being go back before a certain time and no vehicle of any kind has a coolant bleeder. You simply refilled the complete dry system after say an engine rebuild, started it up, and kept a close eye on the coolant topping it up till it came up to operating temperature. Stick the cap on, go for a test drive, and then recheck everything one more time, job done. Any trapped air just had to make its way out of the system all on its own.
 

Aussie Trev

Active Member
Joined
Feb 3, 2019
Messages
169
Reaction score
111
Points
43
Age
72
Location
Queensland
Members Ride
2 by VX Acclaim Wagon Series II 2001 & 2002
But the OP hasn't changed the coolant or been experiencing loss of coolant (well not that he stated and would have expect he'd have said so if he was, being important points).

I've also changed the coolant in the VT (it was originally the family car) and not bled the system, without a problem. The reason being go back before a certain time and no vehicle of any kind has a coolant bleeder. You simply refilled the complete dry system after say an engine rebuild, started it up, and kept a close eye on the coolant topping it up till it came up to operating temperature. Stick the cap on, go for a test drive, and then recheck everything one more time, job done. Any trapped air just had to make its way out of the system all on its own.
Older cars didn't have the situation where the radiator cap was not the high point in the system as is the case with the V6 hence air would move to the cap and be pushed out by fluid. as to how air gets in there without an obvious leak, those inlet manifold gaskets start to leak and instead of pulling liquid back from the overflow bottle they suck air in.
 

mpower

Well-Known Member
Joined
Jan 22, 2007
Messages
5,078
Reaction score
1,713
Points
113
Location
Brisbane
Members Ride
V2 CV8 Monaro and VF SSV Redline
hey it's just a suggestion, and a free one at that. all things being equal it's not the issue but you don't know until you check it.
 
J

JohnW

Guest
Older cars didn't have the situation where the radiator cap was not the high point in the system as is the case with the V6 hence air would move to the cap and be pushed out by fluid. as to how air gets in there without an obvious leak, those inlet manifold gaskets start to leak and instead of pulling liquid back from the overflow bottle they suck air in.

IF, (and I stress if) your theory of how air might get into the system is correct, then you've actually saying 'bleeding the system' is not a fix. At best its just diagnosing a VERY expensive repair. So expensive for most that its most likely they'll flick the car because they'll see it as not financially viable to throw that sort of money at a car of this age.

And the reason I say 'if' your theory is correct, I find in impossible to comprehend that if the intake manifolds are such a poor seal to allow air to re-enter the system as the engine cools to the point of a vacuum, then they would leak coolant like a sieve under the constant pressure of the cooling system at operating temperature.

The irony of 'air in the system' is that we've gone from starting with the simple and relatively inexpensive task of replacing the temperature sensor and thermostat to potentially junking the car due to the expense of a major repair.

I'm aware of why they put the bleeder where it is.

Still waiting for an explanation of how an air blockage in the cooling system results in the temperature rising and then suddenly and rapidly falling back to normal temperature, time after time. I believe it would create poor circulation and/or low coolant level so the engine will get hot, and just stay hot.

If the OP changes the temperature sensor, thermostat, replaces the coolant in the process if due, and in the process bleeds the cooling system and it works then everyone is happy. I'd certainly be doing a simple inexpensive task like this, total cost of about $40, before considering pulling the intake manifolds off.
 
Last edited by a moderator:
J

JohnW

Guest
hey it's just a suggestion, and a free one at that. all things being equal it's not the issue but you don't know until you check it.

See my post above explaining why it is neither 'free' and not a fix. Well not unless your suggesting the OP pull the engine cover and bleed the cooling system every morning before heading to work (or whatever fills his day).

If air is entering the system and causing the problem, then unless the cause is rectified it'll just return. So far its been suggested this could be from leaking intake manifolds. That's a VERY big and expensive problem to most people.

I recall a doctor telling me one day how they were trained to diagnose health problems. Basically look for the common and simple reasons first and eliminate them first before considering the exotic. At the time I thought to myself, no different to a motor mechanic.
 
Last edited by a moderator:

Aussie Trev

Active Member
Joined
Feb 3, 2019
Messages
169
Reaction score
111
Points
43
Age
72
Location
Queensland
Members Ride
2 by VX Acclaim Wagon Series II 2001 & 2002
Doing the intake manifold gaskets is not expensive or complicated and anyone with a moderate skill level should be able to do them in a couple of hours. You only need a 3/8 spanner and some silicone sealant for the ends of the valley seals where they meet the intake gaskets. Undo all the bolts, lift the manifold up, get a mate to hold it up, pull out the old gaskets and place the new ones, silicon the ends of the valley seals, put the manifold back down and replace the bolts in sequence and torque to spec. It is not inconceivable that a system can leak under vacuum but not leak under pressure. as to why the temperature shoots up and down if there is air in the system I don't know, I just know it does and keeping the coolant topped right up stops it from happening from my personal experience.
 

mpower

Well-Known Member
Joined
Jan 22, 2007
Messages
5,078
Reaction score
1,713
Points
113
Location
Brisbane
Members Ride
V2 CV8 Monaro and VF SSV Redline
Still waiting for an explanation of how an air blockage in the cooling system results in the temperature rising and then suddenly and rapidly falling back to normal temperature, time after time. I believe it would create poor circulation and/or low coolant level so the engine will get hot, and just stay hot.

crikey mate, could you be more argumentative??

Also it's an air pocket, not an air blockage.

i stated that i literally had the same behaviour and i had to just bleed the system. bleeding the system once you know how is quick and easy.

dear OP, hope you get your issue sorted, regardless of who has gotten you the correct advice.
 
J

JohnW

Guest
crikey mate, could you be more argumentative??

Also it's an air pocket, not an air blockage.

i stated that i literally had the same behaviour and i had to just bleed the system. bleeding the system once you know how is quick and easy.

dear OP, hope you get your issue sorted, regardless of who has gotten you the correct advice.

An argument takes two people. All I've see you describe so far is a completely different scenario, you forgot to bleed the system after changing the coolant.
 

mpower

Well-Known Member
Joined
Jan 22, 2007
Messages
5,078
Reaction score
1,713
Points
113
Location
Brisbane
Members Ride
V2 CV8 Monaro and VF SSV Redline
An argument takes two people. All I've see you describe so far is a completely different scenario, you forgot to bleed the system after changing the coolant.

it does, OP don't check your coolant since you didn't mention it we can assume it's perfect.
 
Top