Need help; Crazy coolant blockage

[fowljesse]

So, the car over heats, and the lower filler neck stays cold. I opened the cap, and cold water shot out, due to th pressure in the system. We tested, and the thermostat works. I drilled hols in it, just to be dure. When the engine is cold, and running, the coolant moves through the upper filler neck. I put pressure to everywhere I could, and ran the car for a second with the thermostat out, and that part open. I can't find any blockage, but the lower filler stays cold, and the pressure builds so much that I have leaks in a couple places.
What the heck?

[mikeinaus]

heater core maybe? you could try bypassing the interior part of the system and see if it helps. disconnect the 2 coolant lines going to the firewall and join them somehow...

[Newfie_dan]

Have you ever ran rad stop leak in the car? as an option you could attempt running a strong clr mix through it to see if its scale buildup. I once ran into a waterpump that had rotted away and clogged the cooling system a few years ago on another car but it ran and sounded fine aside from the overheating issue.

[davmac]

Sounds like a clog somewhere - but if the car overheats you will get excessive pressure and may even force some leaks.
- If heater core was clogged you get no heat in the interior of the car, but would not cause overheating of the engine
I hope it is not the case, but overheating and excessive pressure in the cooling system could be a bad head gasket leaking combustion gas into the cooling system.

The place to start is to pressure test and look for leaks. Air in the system will cause overheating. Assuming there are no external leaks there could be an internal one. I haven't done it but understand there is a test for exhaust gas in the coolant.

Good luck. Overheating especially in winter sucks - as do repairs in the cold.

[mikeinaus]

Sounds like a clog somewhere - but if the car overheats you will get excessive pressure and may even force some leaks.
- If heater core was clogged you get no heat in the interior of the car, but would not cause overheating of the engine
I hope it is not the case, but overheating and excessive pressure in the cooling system could be a bad head gasket leaking combustion gas into the cooling system.

The place to start is to pressure test and look for leaks. Air in the system will cause overheating. Assuming there are no external leaks there could be an internal one. I haven't done it but understand there is a test for exhaust gas in the coolant.

Good luck. Overheating especially in winter sucks - as do repairs in the cold.

how would a clogged heater core not cause the car to overheat? the cooling system is one big closed loop. there isnt a second water pump and coolant system for the heater core. a clog anywhere could cause the entire system to stop circulating, the motor to overheat and the heater to not work. depending where the clog is, it also may not build excessive pressure. the thermostat is rigged to pop open and drain excess coolant when the cooling system reaches a certain temp and the coolant has expanded. if the clog is after the thermostat it would open normally and vent off excess pressure. i would also highly suggest against overheating the car on purpose to try and free the blockage. warping your cylinders or killing your head gasket is going to be much more expensive to fix then a clog.

before you can really try and fix the system you need to find where the blockage is. whether it be the thermostat, radiator, heatercore or inside the engine somewhere. eliminating one piece at a time and seeing when its fixed is probably your best bet. although you cant do that with everything. you can however bypass the thermostat, radiator and heatercore quite easily. if you have access to an air compressor, you could probably rig something up to shoot compressed air threw your rad/ heatercore and thermostat (individually) when there full of water, if the water shoots out the other end you know its not clogged.

someone may correct me on this, and id even look into it yourself before id even consider trying this, but you could try some household drain cleaner. its designed to be safe to use with metal and plastic piping so it MAY be ok for your coolant system. the only thing id be worried about is your gaskets. i really have no idea how bad it could be for your motor, it could be bad enough to completely destroy your gaskets and need a rebuild, or it could be harmless. either way if you do decide to give it a try i highly suggest you fill and drain your coolant system atleast 3 or 4 times after youve cleared the leak.

[davmac]

mikinaus: I hope it is a clog too, but the cooling system is designed so the heater core is not important for cooling the engine. There are 2 hard pipes that run from the right side off the coolant filler cap. The heater core gets coolant feed separately from the smaller pipe - basically a bypass pipe. In some cars there is a heater valve that shuts off coolant to the heater core when heat isn't needed inside the car. A clogged heater core = no heat inside the car but your engine doesn't care. Although if your engine is overheating you might delay it a bit by turning up the heat and using the heater core as a tiny radiator. What can cause overheating?
- Low coolant level or air from a leak (including all pipes, hoses, water pump, heater core or radiator)
- thermostat stuck closed
- problem with radiator fans
- radiator clogged
- bad water pump (sometimes not obvious because the impeller can spin on the shaft or be damaged by corrosion leading to poor or no circulation)
- Bad head gasket or cracked / warped heads or block that either act like any other leak or allow combustion gas to enter coolant passages

Don't use any drain cleaners with an aluminum radiator and engine. There are flush products but they are only good as maintenance to prevent clogs. Replace a radiator that does not flow well enough to prevent overheating.

[Daninski]

Your car is simply punishing you for spending too much time on Facebook and neglecting the car. Fill the system, install the coolant caps and squeeze the heck out of the top hose to make sure you don't have an air lock.