Diagnosing no heat
 

My car has little to no heat. I opened up the heater box today and felt the heater core, it was just barely warm to the touch with the engine at ~200*. Is there anything else I should check before I slap a new one in there? Could the old one be flushed effectively? I was looking at a diagram of the cooling system and I noticed there is a part on the hose leading to the core called a "flow restrictor", is that a mechanical part that could fail? Or just a fixed restrictor?

Hook up a garden hose to one of the rubber coolant hoses going into it and flush it out. You will have to pull the other rubber hose off and let it drain under the car.

What Brad said dexcool gets very sludgy

^x3

all of the above! except i use air. never really liked the idea of using 40+PSI into a system designed for 16.

Yeah if I flush it with a hose I will turn the water way down, don't want to blow anything open. Might change some of the hoses while I got it drained. Probably makes sense to flush it in reverse right?

Correct

i did it both ways when i did it on the s10 figured it couldnt hurt

Did a lot of crud come out when you flushed it?

you wanna go backwards first. if you were to flush in the normal direction of flow you can plug it up worse. then you mine as well change the heater core!

yesssss.. it was pretty gross lol my heat didnt work for shit for the second half of last winter...thought i was going to have to replace the heater core but we tried flushing it out and now it works ALMOST as good as new

Cool I will do this soon. Once I have heat again then I can worry about getting A/C back

Just make sure you dont put a ton of coolant all over the ground.

Update: Did the heater core flush today and it worked pretty well. I'll have to wait until a cool night to know for sure but the heat felt nice and hot, and it was basically nothing before. It didn't seem like a lot of crud came out of it, just some murky looking coolant and a few tiny little chunks.

Since I had the coolant drained I also cleaned the coolant level sensor (works now) and did the throttle body bypass. Don't know what it's really worth but after driving the car around I could rest my hand on the TB, before it would have been too hot to do that.

I drove the car around for a while and it didn't overheat so I must have managed to get all the air out, I always hear about people having problems so I was a little bit worried. I just followed the instructions in the manual: crack bleeders, fill until bleeders are weeping, shut bleeders, fill to top of radiator, run engine for four minutes, refill. After driving it a few miles I had to top it off again (which I knew since my low coolant light works now) and I'm letting it cool now and then I'll check it again. Nice to kill three birds with one stone. Most of the remaining projects will probably be a lot more labor intensive.