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coolant won't drain back into radiator from reservoir

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Old 05-15-2008, 10:44 AM   #1
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coolant won't drain back into radiator from reservoir

I've been having a mild overheating problem the past couple weeks. What will happen is.....everything will be fine for a couple days, then it'll try to heat on me (210-220 degrees) alittle. I'll let it completely cool down, and check the radiator to find out it's low. I'll fill it back up, everything will be fine for a few days, then the same cycle again.

This happened yesterday. The day before, I had flushed the whole system and put new antifreeze in. I have a 40 mile trip home from work; everything was fine driving to work and going to lunch. On the way home, after about 30 miles, the temp started slowly climbing to the 210-220 range. I got home, raised the hood,but didn't attempt to open the radiator. But I checked the reservoir and it was completely full of my new antifreeze. I waited about 3-4 more hours and let it completely cool, so that antifreeze would go back into the radiator. Not a drop had drained back in.

There are two hoses on the reservoir; a hose from the radiator neck to the bottom of the reservoir, and a hose from the top/side of the reservoir that drains out underneath the truck. I took the cap off the radiator, pulled the reservoir drain hose out from the bottom, and literally blew into it with my mouth and slowly blew the antifreeze back into my radiator through the neck until it filled back up. So that tells me my antifreeze isn't leaking out anywhere.

What the hell is making the overflow not drain back into the radiator???
Old 05-15-2008, 11:00 AM   #2
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Re: coolant won't drain back into radiator from reservoir

Did you replace your radiator cap lately. It acts like a valve...if it sticks or anything it wont suck back in. That would be the first thing I would look at.
Old 05-15-2008, 11:29 AM   #3
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Re: coolant won't drain back into radiator from reservoir

Quote: Originally Posted by jhankinson
Did you replace your radiator cap lately. It acts like a valve...if it sticks or anything it wont suck back in. That would be the first thing I would look at.
+1
Old 05-16-2008, 09:48 AM   #4
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Re: coolant won't drain back into radiator from reservoir

Well it's the waterpump.

Got home and let it cool down, then topped the radiator off and got the temp back up. Some of you may have seen my other thread about having a pulley somewhere making a screeching noise, that's the waterpump too. I put the new cap on, yet was still low of water when i finally got home. After looking the topside over real good, I pulled it up on some ramps and looked at the bottom. There is actually a trail that has been washed clean from the diaphram hole in the bottom of the waterpump, down the water pump and dripping on the harmonic balancer. It's a slow weep, not pouring. It actually doesn't leak at all while running, but it starts a couple minutes after shutting it off. I guess it's from the pressure buildup. I shut it off and got back under the truck, and watched it weep, drop after drop, from the diaphram hole onto the harmonic balancer.

Mine is a 95' TBI. Looking closely from the frontside, it really doesn't appear that I'll need to take the alternator or AC loose to get the pump off. I know I'll have to remove the top of the shroud and the fan, obviously. Have any of you changed a pump that's the same setup as mine? What all did you have to take off?
Old 05-16-2008, 09:54 AM   #5
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Re: coolant won't drain back into radiator from reservoir

Quote: Originally Posted by SD44
Well it's the waterpump.

Got home and let it cool down, then topped the radiator off and got the temp back up. Some of you may have seen my other thread about having a pulley somewhere making a screeching noise, that's the waterpump too. I put the new cap on, yet was still low of water when i finally got home. After looking the topside over real good, I pulled it up on some ramps and looked at the bottom. There is actually a trail that has been washed clean from the diaphram hole in the bottom of the waterpump, down the water pump and dripping on the harmonic balancer. It's a slow weep, not pouring. It actually doesn't leak at all while running, but it starts a couple minutes after shutting it off. I guess it's from the pressure buildup. I shut it off and got back under the truck, and watched it weep, drop after drop, from the diaphram hole onto the harmonic balancer.

Mine is a 95' TBI. Looking closely from the frontside, it really doesn't appear that I'll need to take the alternator or AC loose to get the pump off. I know I'll have to remove the top of the shroud and the fan, obviously. Have any of you changed a pump that's the same setup as mine? What all did you have to take off?
I'm all too familiar with this problem. You won't need to pull the AC or Alternator. The only thing you'll really need to pull is everything connected to the pump itself. It's really straightforward, just make sure not to fudge up the gaskets when you put it all back together.
Old 05-16-2008, 10:22 AM   #6
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Re: coolant won't drain back into radiator from reservoir

Quote: Originally Posted by cardboardbox
I'm all too familiar with this problem. You won't need to pull the AC or Alternator. The only thing you'll really need to pull is everything connected to the pump itself. It's really straightforward, just make sure not to fudge up the gaskets when you put it all back together.
Thanks, I was hoping i wouldn't have to pull those two. Looking at the water pump bolts, it looked like I could get to all of them with a swivel on my socket. Still gonna get my hands scuffed up, though.
Old 05-16-2008, 09:36 PM   #7
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Re: coolant won't drain back into radiator from reservoir

Ill be replacing my waterpump and my p/s pump etc...on my truck on the 25th of this month. My p/s pump is leaking a slowly, so figured id replace my waterpump at the sametime b/c i dont think it was ever replaced. Would of replaced it when i put my new head on but didnt have it at the time...ill try to get some pics up of the replacement. Ill obviously have to take of the shroud and the shitty clutch fan to pull the water pump pulley off and replace the pump. Cant wait to get an efan, it will be so much easier to replace belts etc...!
Old 05-28-2008, 03:58 PM   #8
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Re: coolant won't drain back into radiator from reservoir

Sounds like your overflow reservoir problem might be Dex-Cool related. Did yours come with Dex-Cool from the factory?
Old 05-28-2008, 04:04 PM   #9
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Re: coolant won't drain back into radiator from reservoir

Quote: Originally Posted by Norwood
Sounds like your overflow reservoir problem might be Dex-Cool related. Did yours come with Dex-Cool from the factory?
Uhm... They all did.
Old 05-28-2008, 04:57 PM   #10
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Re: coolant won't drain back into radiator from reservoir

When I flushed all the dex cool crap out of my system, most of the hoses were caked with junk on the inside and my hoses to my reservoir were almost completely clogged.
Old 05-28-2008, 05:04 PM   #11
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Re: coolant won't drain back into radiator from reservoir

I had posted in another thread that it was my water pump, which has been replaced and I have no more problems.


But yes, I have a gummy substance all over everything, like jello. Is that from the factory anti-freeze that it came with?
Old 05-28-2008, 06:55 PM   #12
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Re: coolant won't drain back into radiator from reservoir

Quote: Originally Posted by SD44
I had posted in another thread that it was my water pump, which has been replaced and I have no more problems.


But yes, I have a gummy substance all over everything, like jello. Is that from the factory anti-freeze that it came with?
Did you mix the factory coolant with anything from the aftermarket?
Old 05-29-2008, 09:16 AM   #13
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Re: coolant won't drain back into radiator from reservoir

If you put regular anti-freeze in your truck, you must flush out all the dex-cool. they do not mix well. With just the dex-cool in my truck, everything looked like it was coated in mud. I flushed it 2 times before i put anti-freeze and water back in it.
Old 06-03-2008, 10:31 PM   #14
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Re: coolant won't drain back into radiator from reservoir

Dex-Cool if im not mistaken, are for 96' or 97 and later model chevys or gmc cars/trucks..i have a 95 Noma and learned that it would f' up the coolant system or something; It was a really good reason, just cant remember what kind of problems they say it causes, enlighten me anyone if you can remember, b/c i know that dex-cool isnt recommend for 95-earlier model GM Vehicles. i obviously just use prediluted 50/50 Prestone.

Last edited by GmcNoma95; 06-03-2008 at 10:33 PM.
Old 06-03-2008, 10:52 PM   #15
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Re: coolant won't drain back into radiator from reservoir

Quote: Originally Posted by GmcNoma95
Dex-Cool if im not mistaken, are for 96' or 97 and later model chevys or gmc cars/trucks..i have a 95 Noma and learned that it would f' up the coolant system or something; It was a really good reason, just cant remember what kind of problems they say it causes, enlighten me anyone if you can remember, b/c i know that dex-cool isnt recommend for 95-earlier model GM Vehicles. i obviously just use prediluted 50/50 Prestone.
Yeah my '95 Cavi was green coolant.
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