Think this is a heater core problem?

[malik641]

When the motor is cold and I turn it on the car normally warms up to the "A" on Normal but I turn the heat on and there is no heat....all of a sudden (whether i attempt to turn the heat on or not) the temp shoots up to the "N" (this is very hot) and after a few seconds of driving it shoots back down and my heat comes through. My guess is that something is getting stuck in the heater core and causing the pressure to build and causing it to overheat. I think that after it overheats and builds pressure it pushes whatever is in the way and operates normally....i have a brand new water pump so i doubt the pump is clogged.
I also put a new thermostat in because i thought THAT was the problem but its still doing it...I don't think I installed it incorrectly (the spring is going toward the rear of the car). When I was testing the hoses to see which ones were hot, though, the one coming from the water pump going to (i think) tee 1 wasnt getting warm (this hose went to the metal fitting that goes towards the firewall met by another hose going to the heater core). .......Sooooooo
Waterpump/Heater Core/waterpump/heater core/waterpump/heater core??????????
Please help me....

 

[kn7671]

Nope, not a heater core problem. The heater core has engine coolant running through it all the time just like the radiatior, not just when you turn on the heater.

If you are not losing coolant, and the levels and overflow are correct, it really sounds like a pressure problem. Usually this is caused by the radiator cap, so as I stated, if you aren't losing coolant, replace the radiator cap. Even if pressure builds in the upper radiator hose, the pressure could be too low, allowing the coolant to boil. Caps are cheap, so replace it and let us know.

Back to the heater core, the only problems people have with heater cores is that they spring a leak, usually allowing coolant to leak into the car. It is usually very noticeable from the smell in the car/ventilation system, coolant or water appearing on the passenger floor, and fogging windows/windshield for little to no reason.

 

[malik641]

Yeah i know about the heater cores leaking and causing the windows to fog when the defrosters are on and you'd smell the antifreeze in the car, but i thought maybe there was some kind of corrosion or something.
Yeah ill try the cap thing tonight, i work at napa and i get parts 10% over cost !!!
I let ya know tonight/tomorrow.

 

[88stangmangt]

bouncing temps could be the cause of a weak/bad therm.........................therms sticking will cause the temp to rise then shoot back down once it opens.........happened on my GMC work truck................

 

[malik641]

bouncing temps could be the cause of a weak/bad therm.........................therms sticking will cause the temp to rise then shoot back down once it opens.........happened on my GMC work truck................

Yeah but i replaced the thermostat twice already (and im a damn pro replacing these things now) and i dont think its the thermostat

 

[malik641]

you know......what if the coolant temp sensor has anything to do with it?

 

[kn7671]

Forgot to mention something about that gauge, yes, it could be the gauge or sending unit.

If you have recently done any work to the engine or intake, you may have disconnected a ground strap that went from the engine to firewall. Many things in the electrical system can be affected from this, so if the radiator cap does not fix it, you may want to start looking at grounds before replacing the temp sending unit.

 

[malik641]

The cap seems to help, but then again i havent put it to the test like i normally drive it. I forgot to mention that i dont let it warm up fully before i drive. Ill let it get to 130 and drive it....that's when the temp gets all screwy. This morning after replacing the cap i let it warm up and it went between the R and M in "Normal", then when i drove it i turned on the heat and again no heat....then the temp dropped after driving it for a little and it went between M and A...that's when i got heat.
I'm gonna return the temp sensor for now...i need lunch money

 

[malik641]

Alright, this morning i started up my car and went to work and the temp rose sharply, then fell again...except this time NO HEAT....WTF!!!!!
I dont care anymore, im replacing the heater core, the thermostat w/gasket AND the housing cause i think it might be warped, and any coinciding hoses....i cant live without heat.

anybody have a part number for a thermostat they used and had no problem with....maybe the number my comp at NAPA is giving me is wrong

thanks,
Joe