My heater core was taken off and by passed with a kit Have a new radiator 3 years old and new hoses Now I'm over heating could it be the thermostat?

Bad coolant flow. check for low coolant, also a thermostat could be restricting proper coolant flow. If coolant is full in the radiator than touch your upper radiator hose to see if it is hot. If their is proper coolant level and engine is warmed up to temp and radiator hose is cold replace your thermostat.

There are a couple of possibilities....

1. The heater core has been bypassed. If the core was leaking someone may have looped the heater hose back on itself. Check to ensure that the supply and return heater hoses are in place and properly routed to the firewall.

2. The heater core may be clogged. Age does a lot as does old coolant to clog up a heater core. To check the core disconnect the heater hoses at the block. Blow through one hose and see if you can get coolant/air to pass through the core. You can raise one hose higher than the other and pour water through or use low-pressure air as well. If the core is clogged, it may be possible to unclog it using a diluted drain cleaner. Pour the diluted cleaner into both hoses and let sit for a time, then flush with clear water. This may take several attempts. If it works it will save much time and expense. The unfortunate downside is that there is also the possibility of generating a core leak this way. But considering that if you hadn't tried you would have to replace the core anyway, you have nothing really to lose.

3. The blend door in the heater control box may be stuck and not letting air pass thru the core to heat the cabin. This one is hardder to verify.

drain coolant system locate heater cores hoses going through firewall you need to buy the radiator flush kit at any auto parts stores. remove heater cores hoses from one end or buy extra long heater hoses same size as heater core hoses in vechicle at auto parts store use the flush kit when you flush through one of the heater core hoses let the other hose drain in a drain pan when you use home garden hose use low water pressure dont use garden hose to the max or you will rupture heater core. your best bet let radiator shop flush whole coolant system. because heater cores hoses are in a tight spot.make sure engine off if you just going to flush out heater core only .after flushing heater core good time to replace heater core hoses.if job too hard or complicated let radiator shop flush out radiator the engine block and heater core because if radiator stopped up or engine block stopped up the gunk and rust will reenter plug up heater core.if you tight on money you can flush out your own radiator.drain out radiator using large drain pan. remove top radiator hose and remove bottom radiator hoses connect to water pump.use garden hose with flush kit part with water pressure not too high put garden hose to top radiator hose run water until clear water run out bottom radiator hose in drain pan,the flush out engine block remove thermostat.if you had another spare thermostat housing with RTV SILICONE SEALANT THAT HAS SET UP INSTALL THERMOSTAT HOUSING BACK TO ENGINE WITHOUT THERMOSTAT FLUSH OUT THE ENGINE BLOCK, WHEN DONE INSTALL NEW THERMOSTAT THEN INSTALL ORIGINAL THERMOSTAT HOUSING WITH NEW ORING WHICH YOU BUY AT DEALERSHIP.IF ALL SOUND COMPLICATED LET RADIATOR SHOP FLUSH OUT COOLANT SYSTEM.

It sounds like the heater control valve may be stuck. This valve allows heated water from the engine to pass through the heater core which in turn heats the inside of your car. If this valve is stuck, only a small portion of heated water will pass through. If this is the case, you should have the control valve replace.

You should be able to find it by following the heater hoses coming from the radiator leading back to the firewall. These hoses will about 1/2 - 3/4 of an inch in diameter so you shouldn't get them confused with the normal radiator hoses.

You can probably purchase a new valve at an auto parts store but I'm sure the dealer will have one.

If that's not the problem, it could be that the core itself is clogged up. That's a little more expensive and more of a pain to replace. if this is helpful please dont forget to give rateing thank you

LOOKING AT HEATER CORE TOP HOSE COOLANT FLOW IN BACK OUT THROUGH THE BOTTOM HEATER CORE HOSE CHECK WATER PUMP BYPASS HOSE SEE IF IT GETS HOT.IF NOT COULD BE BLOCKAGE AT BYPASS HOSE FROM WATER PUMP OR WATER COULD BE FAULTY GETTING TOO WEAK PUMP COOLANT THROUGH SYSTEM.IF COOLANT GETTING HOT GOING TO HEATER CORE THE HEATER CORE AND COOLANT SYSTEM NEED FLUSHING OUT.

Read all of these instructions before starting this job.
First test your heater core for flow by disconnecting both heater core hoses from motor and forcing air from an air compressor into one of them watching for flow from the other. If you have no flow then you may need to backflush your heater core - it is possible you have blockage in it. Your local auto parts store has a backflush kit you can buy that will have a backflush valve ( to be added to your supply heater core hose ) and an additive to put in your coolant system. The kit will not include new coolant so you will need to get that too. Install valve and connect a garden hose.Run motor specified time in the kit. Remove lower hose from your radiator and turn on the water from the hose full blast. Watch the coolant coming out from your radiator to see if any chunky stuff comes out - also watch for the color of the flow. Run water until it comes out clear, then shut off water and disconnect garden hose. Allow system to drain, reconnect radiator hose and cap flush valve. Refill coolant system, turn heat on high and run motor until it is warm. Top off coolant in radiator ( be careful - the pressure may cause coolant to spray out when you remove cap - put a rag over the cap before you remove slowly). If you do not have warm air at this point you may have a bubble in the heater core and may need to block rear wheels then raise the front of the vehicle until the radiator cap is higher than the heater core. Restart vehicle and turn heater on high . Check coolant level in radiator and top off, then cap radiator and shut off motor. Lower vehicle and start again with heater on high. If you still have no heat then your heater core may be plugged. To check, remove both heater hoses from motor and force air from an air compressor into one of the hoses, watching for flow from the other hose - if no flow then core is plugged and needs to be replaced, but if you have flow then you still have an air bubble in the system and need to purge using the above steps until you have heat.
Hope this helps and please rate my solution - good luck!!

common problem is the water resivor cracks up at the bottom... it appears that your water level is fine because the car doesnt over heat but i am willing to bet that resivor doesnt have water to the top. The radiator will hold just enough water to keep it cool. I replaced mine 3 times the sulution is doing to sound weird but go to the junk yard and get one off a murcury sable. dont know why but the sables res doesnt crack like that

No, you just won't have water flow through the heater core, Coolant flows through the engine through the lower radiator hose as the water pump sucks it out of the radiator and pushes it through the engine. It then flows out the top radiator hose when the thermostat opens. It then flows into the radiator to cool off.

Is your heater core leaking?

if you got heat when its running and almost nothing iddling the heater core inside the car has rectriction idle circulation not enough prestone pass thrue the radiator because of scale when our driving way more circulation more prestone go thrue ¸=more heat you need to flush the radiator inside the car normally i put a radiator flush leave it running longer then what they say go for a drive remove the heater core hose be carefull not to break the pipe use garden hose pass hose water pressure o n both side do it a few time each side flush all the prestone add new prestone you shoul have way more heat good luck p.s some shop might tell you change the heater core that perfect but very big money do it right its cheap and gonna work pierre

Sounds like the heater core (a small radiator of sorts under the dash) is leaking or a hose going to it is leaking. If in a warm climate, you could bypass or block the heater hoses temporarily. Their only purpose is to make heat avail to interior of car. The 2 heater hoses either connect to feedthru's at the firewall or simply pass thru the firewall to the heater core. Every car I've seen has it on passenger side.

Peer up under the dash, it should be clear where it's coming from.