Cooling System

[djtlaz]

I have a quick ? for you guys. When should I be able to see the water pumping through my radiator. I can start my truck and remove the radiator cap and my coolant is motionless. Also it seems that when I put my cap on the coolant comes out the reserve hose. There aren't any signs of water pump malfunction. Nor does the truck seem to be running out. I'm just tired of having to put water in every morning cause I indicated when the cap is on the coolant is coming out.

[Longhorn Man]

you are overfilling the rad. The coolant level is supposed to be 1 to 2 inches BELOW the cap.
Coolant movement should start when the T-stat opens. If y9our pump wasn't working, you'd know it.

Everything sounds fine to me.

[fastwillie 696969]

change your thermostat first and see if it open up before you replace the water pump what condition is the water in ? rusty? green how many miles on the truck or engine ?

[djtlaz]

It is a 1971 chevy 4x4 shorty. It has a 350 generation 1 vortec for a 1988-1995. Don't know miles think is fairly new but I just bought the truck and that was what was in it. It is clear water that is coming out cause until I resolve this problem i'm not going to keep putting anti-freeze in it.

[Bill72BB]

I always like to start with the easy thing first , I would get a new radiator cap , then change the thermostat next .

[A.P.]

djtlaz, I use to have the same problem with my truck. What I did was to install a Coolant Recovery Tank and problem solved.

[meathead95]

you probably have the wrong radiator cap

[Longhorn Man]

wrong rad cap won't cause exsesive coolant to come out. It'll just come out sooner.

How low does the water level drop?

[meathead95]

thats strange, because somehow i lost my radiator cap. so i went and bought a new stant for my 2wd blazer (daily driver) and it kept running low on coolant. everytime i would shut it off it would run out of the overflow hose as they gave me the wrong cap (vato zone). because when i went to get another figuring that was the only thong that was changed they gave me a different part number for a stant cap at parts america and it is all good now

[mocwon]

Originally Posted by Bill72BB

I always like to start with the easy thing first , I would get a new radiator cap , then change the thermostat next .

Ditto this.... radiator caps are frequestly over looked as a culprit for cooling system problems.

[cdowns]

i too am of the opinion that nothing is wrong and you're just overfilling the rad when it's cold// buy a dozen caps and as many pumps and hoses as you care to if you overfill it it will still run out on the ground

with the rad cap off let the truck run for a minimum half hour then adjust level to about 1inch below the filler put the cap on and you won't have the problem anymore

[BubbaGreen]

no chance it has the wrong water pump...ie, reverse rotation vs standard rotation. I dont know if this is even possible on that motor, someone might chime in.

[djtlaz]

Thanks guys! I will do all that was suggested once I get time. But just to add another note. If the radiator is only suppose to be filled to a inch below the cap then when it drains it should only drain to that level. So times I have to put a cup(32oz) or more in. It was low enough one time that it didn't have enough flow through the heater hose that my heater was blowing cold. I'll start with a radiator cap this weekend. Then I'll try a thermostat that opens fully at a lower temp. Is there a thermostat that is always open? And if not why wouldn't you wan't water flowing through the motor constantly? Thanks for all the help.

[Longhorn Man]

you want the water in the engine long enough to absorb the heat, then in the rad long enough to disapate the heat.
Running with constant flow will keep the engine way below optimum operating temps...then eventually, it'll run hot and overheat.

[FormerMember]

So, the TBI motor you have (not a Vortec) should have a 180 degree thermostat in it. It should be a fully closed system, meaning the overflow bottle is crucial, as is the radiator cap.

[nevada70chev]

i am having about the same problem, the rad cap is a Stant 330 16lbs with the lever pressure release (Lev R Vent), i fill the rad so i can see the green coolant when the cap is off. when it is completely full (i can see the coolant) the heater seems to work better. am i just being stupid or could i have the wrong cap? if i install an overflow bottle will the system fluctuate the amount that is in the bottle as the system heats then cools down? thanks guys i always learn something from the board.

[76bonanza]

The only part of the cap that can be wrong is how many pounds it takes to push it open and let water out of the overflow not sure what you are suppose to use but 14-18lps would be good I would think? Any cap in this range designed for a closed system should work. And unless you have a system set up to recover overflow the bottle will only catch what comes out of the overflow. The overflow is there to let pressure and or fluid bleed off if the radiator builds to much pressure. And one cup is not alot it should be about 1-2 inches below the top. Fill it, get air out, run it let it belch any out it dont want then check it should be a few inches below top then leave it alone.

[76bonanza]

And if someone can confirm these radiators from our era were never designed to draw overflow back in to the radiator. And if you buy a cap off the shelf or a nice chrome or billit one it is not design to draw over flow back in you would have to get one from a newer style truck right? Not sure how you can tell but it would have to have somekind of vaccum deal. So does such a cap exsits for our radiators?? I just always here people talk about pulling overflow back in and it takes more than just a bottle to do it. With the closed system cap like ours it only lets pressure bleed out to stop the radiator from bursting. nothing goes in? Anyway can someone confirm or enlighten me?

thanks