Heater core & radiator core obstructed with crud?

When the radiator is obstructed, the flow through it is too small. But what little water gets through has plenty of time to cool off. So the lower hose is cool.

Same kind of thing with the heater core, and it can happen for the same reason. Crusty crud from old anti-freeze builds up.

If you don't get any success from other tests, you may have to resort to disconnecting the heater hoses so you can use a garden hose to flush water through. If the water doesn't go through easily, then you know its blocked.

I checked the radiator hoses this morning after arriving at work and they were both hot. So I guess that rules out the thermostat. I'll take a look the other suggestions. Will I need to drain the coolant before disconnecting the heater hoses?

You don't HAVE to drain it. Just makes it easier & less messy.

If you don't drain the coolant, it'll spill out from the heater hoses. If you want to catch it that way (messy) then you'll probably not want to put THAT fluid back in.

If you drain it, you'll have to guess just how much to drain. Still might not be clean enough to re-use. I would just use this as an excuse to drain it all & fill with fresh.

make sure that the cable opens the heater valve fully ..
you stated that it moves it but does it open it all the way ??

No, I'm not sure if it is opening fully. I haven't been able to confirm that. Can I tell w/o disassembling anything, or do I have to take the glove box out or something?

Jim,
You said, "If you don't get any success from other tests, you may have to resort to disconnecting the heater hoses so you can use a garden hose to flush water through. If the water doesn't go through easily, then you know its blocked."

If it is blocked, what is the cure? Can the crud be flushed out, or does the heater core have to be replaced?

I think the heater might be fixed. This morning I drained the coolant. I tested the thermostat for kicks and it seems to work fine. I examined the core valve, and that works right. I then put a garden hose to the hose going to the heater core. Initially only a trickle came out the other end, but eventually I had a good flow. Could it be that I flushed out a clog?

Now I get heat out of the heater. It's perhaps not has hot as it could be, but it is definitely an improvement. The temperature gauge on the dash still only rises to about 1/4. Can the engine be made to run hotter so that this approaches half way? Would a hotter engine mean hotter air coming out of the heater?

Thanks to all of you who have offered advice.
Richard

Great Information About this Thread..Read It Members
 

Good information for anyone to check if they are having Heat Control Problems..

Thanks Jim and Bill , good information...:)

My temperature gauge only goes to 1/4 or maybe 1/3.

The gauge is only relative scale. The actual temperature of the coolant is at 190F when the thermostat is fully open.

It sounds like you DID get something flushed out. If that were not successful, you could have tried some clean/flush product but the last resort would be dismantle the dash & get a new heater core (PITA).

Temperature gauge is not real accurate. Probably it's repeatable, so once you know where the normal operating temperature is for YOUR car, you can trust that. All my Hondas have been around 1/4 to 1/3 on that scale.

If you're worried about the actual temperature, it's better to measure it vs. trusting that gauge.