air in coolant system

[Bubba Stanley]

have a 95 pontiac grand am se 3.1L CAN't BLEED OUT ALL THE AIR out of my coolant system ?

[bryan]

Can't you just loosen the bleeder screw while the car's running to allow any bubbles/air out ?

[angrysk8r]

Can't you just loosen the bleeder screw while the car's running to allow any bubbles/air out ?

Yep that's how you bleed it. Just keep running the engine with the bleeder screw undone until you see a solid stream of coolant coming out. If that doesn't happen or you still have bubbles in your coolant try uncapping the coolant reservoir and repeating the bleeding process.

[doobiess]

acutally doing it while its running isnt a great way since with the water pump flowing coolant past the bleeder it will naturally bleed and bubbles could be through the whole system

Actually have all things closed and then get to full temp... run for a bit and shut off engine for a few min.. then open since air raises to the top (bleeder valve) then you try and get air out.. and bam its done..

[angrysk8r]

acutally doing it while its running isnt a great way since with the water pump flowing coolant past the bleeder it will naturally bleed and bubbles could be through the whole system

Actually have all things closed and then get to full temp... run for a bit and shut off engine for a few min.. then open since air raises to the top (bleeder valve) then you try and get air out.. and bam its done..

The coolant system should be under pressure while the car is running so I'm not sure how air would have a chance to get in. If you do it with they system off, wouldn't there not be any pressure and nothing to displace the air in the bleeder?

[doobiess]

actually if shut the engine off pressure will remain for quite some time and if it dont you have a different prob your rad cap is fried.... thats its job hold pressure

[angrysk8r]

I still don't see how not having the engine on then would make any difference. I'm just going by what I've always been told to do.

[rixGAphx]

Wow.

Just, 'WOW.'

The 3.1/3.4 engine in the GA is goofy relative to bleed procedure, compared to most all other engines and cars.
Becasue fo the veeeerrryy low hod, the radiator sin't very tall, and he reservoir is mounted low.
The highest part of the coolant system in nearly all 'V' engines is the intake manifold; such is true also for the 3.1 and 3.4.
But with the GA's reseroir mounted so low, air becomes trapped in the intake manifold, and must be circulated-out.
Doobiess is correct, that the coolant must warm-up sufficiently for the t-stat to open to allow circulation to occur; this circulation will move the trapped air (from the op of the radiator into the reservoir via the 'y'-hose, and from the top of the manifold down to the t-stat housing whence it travels back to the waterpump/bleed pipe via the cross-over pipe).
But he isn't correct that the coolant should be topped-off 'warm', nor that the 'bleed' should be performed 'warm' with the engine running as Sk8r states.
If you do it this way, then as the coolant cools and shrinks, the level of the reservoir will drop and a suction will develop within the system.
The 'suction' will usually just draw air into the top of the reservoir thru the pressure cap (its pressure-valve is one-way), but it *might* allow air to be drawn into the coolant system thru a faulty gasket (head or LIM, usually) that otherwsie seals well when under pressure.

Rather, perform the bleed twice: Once after filling everything cold; then warm the engine, allow full circulation, shut off, and allow to fully cool; then repeat the bleed.
See Item 3 at: http://www.gaownersclub.com/forum/faq.php?faq=maint_repair#faq_cooling_serv
* * *

Now, as to Bubba's specific question:
If you have done the 'bleed' properly, NO AIR will ever enter the cooling system; ever.
Unless there's a leak: Usually a headgasket, since only cylinder pressure is strong enough to overcome the cooling system's 14 psi pressure cap (assuming it's good).

So if you bled it properly last weekend, and you check it this weekend and it needs bleeding again, then there is obviously some kind of leak; it should be repaired.
First, make sure the cap holds pressure.
Next, find out where coolant is leaking out (if air is getting in, then some coolant is being lost; find out where).
Check the tailpipe for smell of antifreeze, and for excessive water after the exhaust pipe and muffler have warmed.

There are also about 9 more common leakage points on a GA 3.1, including the infamous LIM gasket:
* Radiator plastic side tanks - Cracks.
* Heater core plastic side tank hose nipples - Cracks.
* Heater or radiator hoses.
* Plastic reservoir - Crack.
* Reservoir pressure cap - Fails to seal, and allows coolant to escape as vapor.
* Waterpump weep hole.
* T-stat housing gasket.
* Various other gaskets, especially the timing case-to-block gasket.
* Freeze plugs.
Identify which one, and repair accordingly.

Hope this helps,
-Rick

[angrysk8r]

Thanks for the clear up, I wasn't very specific as to the complete process with warming up the engine and everything.