How to replace the heater core?

Hi,

The idea that the engine temp lowers with the heater on and the hoses only get warm is odd. Based on the hose temperature, it sounds like there is a restriction slowing the flow down. I'm not sure why that would cause the engine to cool.

I attached the directions below from my manual. Additionally, here is a link that explains the general process. I'm adding this because the manual is somewhat vague.

https://www.2carpros.com/articles/replace-heater-core

When you flushed the heater core, did the water go through it easily or did it seem to be restricted?

Let me know and let me know if this helps.

Take care,

Joe

See pics below.

Hi,

Based on what you are indicating, it sounds like the core is the issue. If you removed both the supply and return hoses from it and tried flushing it directly from one of those hoses, coolant should flow freely through the core and out the other side.

Also, since it isn't overheating, I don't feel the flow is weak.

Let me know.

Joe.

Hi,

If that is the case, the core isn't the problem. It sounds like the coolant thermostat is opening too soon and delaying the warm-up time.

Have you replaced the thermostat? If not, that is absolutely where I would start.

Here is a link that explains how in general it is replaced:

https://www.2carpros.com/articles/replace-thermostat

Note, it appears that the thermostat used is different between TBI fuel Injection and CPI. Make sure you get the correct one.

Here are the OEM part numbers based on the fuel system used.

TBI === 10190925

CPI === 24505924

Let me know if this helps or if you have other questions.

Taka care,

Joe

See pic below.

You may want to consider replacing the thermostat. It isn't working properly. On the other hand, if it takes 212°F (boiling point) to open, that should cause the vehicle to warm up faster.

Regardless, it should open slowly as it heats up and at 195°F, it should be fully open.

Let me know.

Joe