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Old 03-12-2012, 11:28 AM   #1
C15_Sierra
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Bleeding cooling system

I'm running a stock '80 cooling system in my 5.3 swap, and I'm thinking over my lack of coolant flow issue. I thought it might be a new water pump, but now I'm doubting that and thinking that it's air-locked somehow.

I used '00 Silverado radiator hoses (my 5.3 is from a '00 Silverado), and the upper radiator hose runs up and across to the radiator inlet on the drivers side. I moved it down since it was the highest point in the system, but I'm still not getting any flow. It does seem like there's any coolant in there, so how can I bleed that hose so I can figure out if its indeed my water pump.

Previously, I replaced the thermostat, so I know that's good. Any other tips?
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1980 GMC C15 Sierra LWB
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Old 03-12-2012, 02:32 PM   #2
SeventyOne
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Re: Bleeding cooling system

Did you run the engine w/o a thermostat and the radiator cap removed?
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Old 03-12-2012, 05:32 PM   #3
68gmsee
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Re: Bleeding cooling system

Is it running hot or above normal or you just can't feel water moving?

What I usually do is turn the heater to hot and run the vehicle with the cap off while I top off the radiator. Then I'll put the cap on, run it to operating temp (thermostat opens) and after it cools off check it and top it off again if it needs it and make sure the overflow container has coolant in it.

I'll say that in some vehicles you can't always feel water going through the upper hose. I guess I should say, I haven't always felt it but I know it's going through there cause it does get hot..
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Old 03-12-2012, 06:12 PM   #4
C15_Sierra
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Re: Bleeding cooling system

Couldn't run w/o a thermostat because it's built into the water pump inlet housing, low in the system (so replacing it would defeat the purpose)

I didn't feel any heat in the heater hose or in the upper radiator hose...that shoulda told me something

What I DID forget was to back-feed coolant into the block via the upper radiator hose. Did just that, and lo and behold, she ran a steady 197 degrees according to the scan tool. Heater hoses had heat and so did the upper rad hose

Thanks guys!
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1980 GMC C15 Sierra LWB
Dark Carmine Red/Carmine Int
Was: 250/3spd (1980-88), then a 305/TH350 (1988-2011)
Now: 5.3/4L60E, 2.73 12-bolt open rear
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Old 03-12-2012, 06:38 PM   #5
cableguy0
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Re: Bleeding cooling system

The easiest way to bleed a cooling system is with a funnel like this one Amazon.com: Lisle 24610 Spill-Free Funnel:... Amazon.com: Lisle 24610 Spill-Free Funnel:... . It stops you from making a mess and having coolant blow all over the place from running the vehicle with the radiator cap off.
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No more truck for now. Parted it out and sold everything to fund buying a house.Next truck will be another 67-72 most likely LS powered. Shortly I will be looking for preferably a 71 or 72 in decent condition on the cheap as long as it isn't a basket case I don't care about condition. Its the first time since I have had my license I havent had something fun to drive and I dont like it
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Old 03-12-2012, 08:48 PM   #6
68gmsee
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Re: Bleeding cooling system

Quote:
Originally Posted by C15_Sierra View Post
..... lo and behold, she ran a steady 197 degrees according to the scan tool. Heater hoses had heat and so did the upper rad hose
Thanks guys!
Great going!

Quote:
Originally Posted by cableguy0 View Post
The easiest way to bleed a cooling system is with a funnel like this one Amazon.com: Lisle 24610 Spill-Free Funnel: Automotive . It stops you from making a mess and having coolant blow all over the place from running the vehicle with the radiator cap off.
Good idea. I usually use a funnel but it never seems to want to stay in place. Might have to order one of these since my yearly coolant change is due on my vehicles... Thanks.
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Old 03-12-2012, 10:10 PM   #7
truckdude239
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Re: Bleeding cooling system

i got the same funnel at work not quite figured it out yet
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Old 03-12-2012, 10:40 PM   #8
cableguy0
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Re: Bleeding cooling system

The trick is to not fill funnel to the top. The coolant needs room in the funnel to expand. Also when it first starts pushing the air out while its running it will push the coolant upward. I keep the funnel filled to about when it goes from the large cone to round area right on the line. That way it doesnt overflow.
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No more truck for now. Parted it out and sold everything to fund buying a house.Next truck will be another 67-72 most likely LS powered. Shortly I will be looking for preferably a 71 or 72 in decent condition on the cheap as long as it isn't a basket case I don't care about condition. Its the first time since I have had my license I havent had something fun to drive and I dont like it
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Old 03-13-2012, 01:58 PM   #9
fastwillie 696969
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Re: Bleeding cooling system

have you tried to jack the rear of the truck up
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