heating questions from a novice....

[dapperdan7]

hi there.

thanks for the help with my emission issues. two new denso 02 sensors and $200 later, i passed smog.

my newest issue:

my 2000 safari awd van (230,000 miles) has never had decent heating and i have decided to deal with it.
symptoms:

--the blower works (i can hear it) but little air comes out of vents (besides on defrost mode)

--the top hose is warm but not hot

--i have enough coolant and the temp gauge registers the engine getting hot but never getting anywhere near red (it gets up to 215 degrees at top). i assume my thermostat works.

***** so, would you recommend a full flush first to see if there might be an obstruction in heater core etc?

***** does the fluid always run thru the heater core or is there a sensor for the core that opens when the temp get to a certain level?

***** what steps would any of you do in terms of diagnosis? I'm a rank amateur at figuring things out but willing and able to do the hellish grunt work of replacing when i know what the problem is?

***** and one more dumb one: does the fluid run through the water pump?

thank you
dan

[chevymaher]

The water control valve would be why the hose only warm.Here is a thread showing your valve.Read thread and decide fix or eliminate.They work better with out them.

viewtopic.php?f=34&t=10216&start=20#p143256

[dapperdan7]

i don't believe i have a rear heater...

[redfury]

If you look at your heater core from the hood and look straight down, you are going to find a heater hose going down to a vacuum controlled valve..it's next to the vacuum reserve ball way down there. You can pull the hoses and bypass that valve and see if you get better heat.

However, I'd have to say that the first thing I'd do is reverse flush the heater core, check your vacuum lines to make sure your heater controls are working properly, and most importantly, with the doghouse off, you can see the heat control which is electrically operated. It's a triangular box with a silver circle with a slot cut in it..that part rotates the blend door open and closed depending on the position of the heat level switch. You can watch it rotate. I've seen them get screwed up and bind up from bad limit switches, causing them to stay in one position.

So in summary, the two things that control the actual heat coming into your van are the vacuum operated valve and the blend door actuator. However, with that many miles, I'd suspect your heater core is fouled up and you'd need to have it backflushed. This is something that works very well and avoids the costly repair bill of a heater core replacement. Look on Youtube for heater core backflushing videos and you'll see what I mean.

[dapperdan7]

thank you redfury. should i also change the thermostat while I'm at it?

[redfury]

Wouldn't hurt, they are really easy as they use a rubber gasket around the thermostat instead of the old flat gasket. I was surprised to see that on my 2001 5.7L in my van... I'd assume yours would be the same as mine.

[Lumpy]

Backflushing the heater core is really simple. You can do it in like an hour.

Under the hood, look at the firewall on the passenger side, up high farthest thing to the passenger side of the
engine compartment. Find two 3/4" ID hoses that are connected to metal nipples that run through the firewall.
Those are the heater hoses. The metal nipples are connected to the heater core inside the cabin.

Unscrew and/or cut off the rubber hoses that are connected to those nipples. The hoses are typically
only about six inches long. They are connected at both ends to similar metal pipe nipples.

Get those hoses off and you'll lose a tiny bit of coolant. Be sure it doesn't drain onto a spot
where cats and dogs will lick it up. You won't lose much, that is the highest point in the system.

Now simply stick a garden hose nozzle on one of the nipples that run IN to the core and a small bit
of coolant, rust, bug poop, hidden contraband, whatever, will squirt out the other nipple. Do that
to both nipples to work it both ways. When it runs clear, you're done. You can flush your entire
system that way. Just stick your garden hose in to every opening and hose in the system and wait
for clear water to come out the other side.

Typically, the rubber/foam seal around those heater core nipples on the firewall aren't very water tight.
Hold a bunch of rags around there while you're doing the garden hose thing to avoid getting water into
the passenger cabin floor. I dried mine really well and sealed it really well with RTV.

If you cut the old hoses off, naturally replace them with new hoses. New 3/4 heater hose is
about a dollar per foot at Peppercheckzone. Put on new hose clamps if the old ones are wonky.

If you decide to flush the entire system, try and drain all the old coolant you can into a container
and take it to an appropriate recycle place (most auto parts stores). Again, use caution around
doggies and kitties. It's toxic for them.

Replace coolant, obviously, with 50/50 green stuff or whatever you feel is correct.


Lump