Thread: cooling system blocked?

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  1. #1 cooling system blocked? 
    GrandPrix Junkie
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    The low coolant light has been on again lately. Was fine for a few months after the new rad. and cleaning the sensor. I checked the rad. and it's been full. No leaks anywhere. I fired it up tonight with the cap off so I could wait for it to heat up and open the thermostat. About 3 min. in at idle it started to puke coolant out the rad. I pulled the RPM's up some and it belched a few times. Got to the point where I couldn't raise the RPM's much more to keep it from puking coolant so I stuck the cap back on it.

    Before I shut it down I noticed I had heat in the cabin but the top hose was stone cold still. Temp gauge didn't hardly move. This is a new rad., thermostat and coolant. Water pump is newer as well. Is this a sign that the system is plugged up somewhere? Never had an issue like this one.
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  2. #2 Re: cooling system blocked? 
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    Stuck thermostat?


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  3. #3 Re: cooling system blocked? 
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    if its not overheating id assume there is no clog in the system could be the level sensor can be had for a few bucks from the junkyard or like $40 for the new ones. or maybe the new thermostat you put in dosent have a small bleeder hole in it. I know when I went back from 180 to stock the stock thermostat didn't have a bleeder hole made the car much harder and longer to bleed and I drove off and thinking it was fully bleed and shot up from 200 to 240 deg real quick lol
    2004 gtp SD headers, e85, #60 injectors, Walbroh 255lph, junkyard custom fender well intake, lq4 MAF, 2.8 Pulley, 1.95 rockers, l76 springs, ssic w/ vw rad shift kit and tranny cooler 275/45r17. BMR trailing and rear control arms, zzp STB's, tubular control arms, Dorman and Addoco sway bars, intense coilovers, all poly. avid av-20s
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  4. #4 Re: cooling system blocked? 
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    also when you say the top hose I assume your talking about the hose going into the radiator not the heater core right?
    2004 gtp SD headers, e85, #60 injectors, Walbroh 255lph, junkyard custom fender well intake, lq4 MAF, 2.8 Pulley, 1.95 rockers, l76 springs, ssic w/ vw rad shift kit and tranny cooler 275/45r17. BMR trailing and rear control arms, zzp STB's, tubular control arms, Dorman and Addoco sway bars, intense coilovers, all poly. avid av-20s
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  5. #5 Re: cooling system blocked? 
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    I thought thermostat, but when it's cold it should be shut, which it seems to be. Just seems strange that it wanted to puke that much coolant while it was warming up. I wanted to leave the cap off and let the thermostat open so I could verify/top off the coolant if it was really indeed low. I know the coolant sensor issue. I actually had it unplugged for years and just cleaned it up when I installed the new rad. and reconnected it. It seemed to be working fine for a while, then ocassionally it would flash, then it just stayed on, hence why I thought it may actually be low on coolant.

    When it's fully hot the gauge reads normal and I have heat that will roast you out of the cabin, so maybe the sensor is just done and I'll disconnect it again and move on. I'm not wrestling that stupid thing out of the sidetank to change it with the rad. in car.
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  6. #6 Re: cooling system blocked? 
    SE Level Member chrisrexmandie's Avatar
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    You can try changing the sensor but i would also check to see if maybe the thermostat is bad or even you mistakenly installed it backwards. The fact that you have heat wont give you much information about the thermostat as the heater core will be circulating hot coolant well before the thermostat ever opens. I guess engineers design cars for creature comforts before engine reliability. That's why if you leave the heat turned off in the winter the engine will warm up quicker.
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  7. #7 Re: cooling system blocked? 
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    I just gave it another shot. Left the cap off fired it up and just let it puke coolant until it decided to stop. Then just topped it off until it reached the bottom of the neck and let it run until it wasn't going to hold it. Shoved the cap on it and let it keep running. Thermostat opened and the low speed fan cycled on/off as it should. Temp gauge isn't doing anything odd and the low coolant light stayed off so far. Cracked the bleeder on the housing and got a steady stream of coolant.

    I'll let it cool off overnight and check it in the am. Beginning to think I had a massive air pocket in the system somewhere.
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  9. #8 Re: cooling system blocked? 
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    Well it looks like it might have been air bound somehow. I didn't drive it this morning but I pulled the cap before I left to check it out and only had to add about 2 cups of water to top off the rad. Probably drive it next week and then see what I get.

    Still going to clean/flush the system. There is some rust colored junk settling in the coolant bottle.
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  10. #9 Re: cooling system blocked? 
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    Check here for a worst case scenario. I know it's an old video, but it's a scary one. Pontiac Grand Prix 3.8 - Water Pump Replacement - YouTube
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