bleeding air out of cooling system (radiator) - The 1947 - Present Chevrolet & GMC Truck Message Board Network

salazar44 · 05-04-2008, 06:04 PM

OK... I have an issue with my truck running hot after about 5-10 minutes. I think it may be due to the fact that I never bled air out of the cooling system. Can somebody please explain this process? There are supposed to be some bleeder valves somewhere but I dont know where. I know there is a drain cock... but i dont want to drain it!

drbyrdman · 05-04-2008, 06:07 PM

squeeze the upper rad. hose with the cap off slowly and the air should come out. your thermo stat might be stuck to. tap on it also when it warms up

greg64 · 05-04-2008, 08:21 PM

One trick that might help you is to drill a small hole in the flange of the thermostat (NOT through the thermostat). This allows a small amount of coolant (and more importantly, air) to bypass the thermostat even when it's closed.

The problem is that if air is trapped against the backside of the thermostat (low side), the coolant can't reach the thermo to actually open it.

You can also try warming the engine while parked with the rad cap off completely. This eliminates the pressure that might otherwise build up, and will allow you to verify that the thermostat is opening (since you can see the coolant circulating).

salazar44 · 05-04-2008, 08:30 PM

Ive tested my thermostat for opening on my stove. then Ive let it run and had the cap open and didnt ever see the fluid move much. I think you might be right about the air trapped under the thermostat not allowing it to recognize temperature is reached. Hmmm...

joe231 · 05-04-2008, 10:56 PM

hey salazar, get you one of these, should be able to get on at your local parts store.
linky
they come in very handy!

**ChiefRocka** · 05-05-2008, 12:59 AM

Quote:

Originally Posted by joe231

hey salazar, get you one of these, should be able to get on at your local parts store.
linky
they come in very handy!

That is a cool little tool.

**Chevy Fleetside** · 05-05-2008, 04:18 AM

Acually all you have to do is remove the heater hose that in connected to the intake manifold and fill up the coolant untill it comes out of the hole then put the heater hose back on and fill the rest. It allows the air to come out through the top instead of being trapped.

05-04-2008, 06:04 PM	#1
salazar44 65 - Chevy C10 Join Date: Jun 2006 Location: Los Angeles, CA Posts: 625	bleeding air out of cooling system (radiator) OK... I have an issue with my truck running hot after about 5-10 minutes. I think it may be due to the fact that I never bled air out of the cooling system. Can somebody please explain this process? There are supposed to be some bleeder valves somewhere but I dont know where. I know there is a drain cock... but i dont want to drain it! __________________ VIC One Repair Leads to Another! http://vix65chevyc10.blogspot.com

05-04-2008, 06:07 PM	#2
drbyrdman Registered User Join Date: Feb 2006 Location: San Diego Posts: 631	Re: bleeding air out of cooling system (radiator) squeeze the upper rad. hose with the cap off slowly and the air should come out. your thermo stat might be stuck to. tap on it also when it warms up

05-04-2008, 08:21 PM	#3
greg64 Registered User Join Date: Dec 2007 Location: Kimberley, BC, Canada Posts: 799	Re: bleeding air out of cooling system (radiator) One trick that might help you is to drill a small hole in the flange of the thermostat (NOT through the thermostat). This allows a small amount of coolant (and more importantly, air) to bypass the thermostat even when it's closed. The problem is that if air is trapped against the backside of the thermostat (low side), the coolant can't reach the thermo to actually open it. You can also try warming the engine while parked with the rad cap off completely. This eliminates the pressure that might otherwise build up, and will allow you to verify that the thermostat is opening (since you can see the coolant circulating). __________________ Greg 64 GMC Suburban - 283, NV3500, 14 bolt 77 C10 swb - 292, SM465, 12 bolt

05-04-2008, 08:30 PM	#4
salazar44 65 - Chevy C10 Join Date: Jun 2006 Location: Los Angeles, CA Posts: 625	Re: bleeding air out of cooling system (radiator) Ive tested my thermostat for opening on my stove. then Ive let it run and had the cap open and didnt ever see the fluid move much. I think you might be right about the air trapped under the thermostat not allowing it to recognize temperature is reached. Hmmm... __________________ VIC One Repair Leads to Another! http://vix65chevyc10.blogspot.com

05-04-2008, 10:56 PM	#5
joe231 Registered User Join Date: Dec 2007 Location: Palmer, Alaska Posts: 13,821	Re: bleeding air out of cooling system (radiator) hey salazar, get you one of these, should be able to get on at your local parts store. linky they come in very handy! __________________ *CHEVY ONLY*

05-05-2008, 04:18 AM	#7
Chevy Fleetside Registered User Join Date: Sep 2006 Location: San Francisco Posts: 4,782	Re: bleeding air out of cooling system (radiator) Acually all you have to do is remove the heater hose that in connected to the intake manifold and fill up the coolant untill it comes out of the hole then put the heater hose back on and fill the rest. It allows the air to come out through the top instead of being trapped. __________________ "A man and his truck, what a beautiful thing" 65 Short Fleetside BBC 65 Long Fleetside 283 3 on the tree for now. my build thread http://www.67-72chevytrucks.com/vboa...d.php?t=259536

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