car not blowing hot

[Greg]

My girlfriend's 86 LXI (which I'm having trouble with) blows only luke-warm.

The temp gauge reads in the middle, but w/the heater on the hot setting, it's not blowing very hot.

The heater cable to the valve is busted, so I manually set the valve to the hot position under the hood. I pulled it UP as far as it would go, which I know is hot, and I really jerked it. I don't think it's at half-way or anything.

And after like 40 minutes of driving it starts to get hot, but it takes that long.

I put a cheap aftermarket thermostat in the thing when I changed the radiator a couple months ago. Is it maybe stuck open?

And, in general, does the coolant circulate between the engine and the heater core ALL the time or only after the thermostat opens? I've always wondered about this. It's ALL the time, right?

If you guys think I have a bad thermostat, what kind would you recommend?

ALSO, the car runs shitty for like 1/2 an hour, but as it starts to blow hotter, the idle smooths out. I think that whatever makes the car go on fast idle doesn't work long enough because the idle drops to 900 after only a couple minutes, but it stutters at idle until like 30 minutes of driving.

You think it's just because the engine doesn't reach operating temp in freezing-ass Chicago since the t-stat is maybe always open and the RPM's don't stay high enough...???

Could there be another reason for being luke-warm (the coolant has been full for a while -- it's not leaking any anywhere)/

[smufguy]

if the car is in normal operating temp, then the heater should blow really hot air like 15 secs into heater operation. ur heater valve under the hood could be clogged or blocked and even in full open, it can be lettin in small amounts of coolent. u could be havin a vaccum leak if the car is sputtering.

The coolent flows thru the heater core and the block ALL the time like u said. The thermostat controls only the coolent going to the radiator and the fast idle valve if u look closly at it. The heater core is directly on the block. Thats why the heater core acts as a (which technically is) a secondary radiator to cool down ur engine.

do u warm up ur car befor u drive? cause for a carb u GOTTA warm up the car before u pull out of the driveway.

[Greg]

My girlfriend's car is EFI. Mine is carb.

She warms it up for like 30 seconds @ idle cuz it dies otherwise and then she takes off.

Yeah, I think either there's a blocked valve to the heater core or the thing is not warming up right (stuck thermostat...?)

I flushed the coolant recently, and it's SUPER CLEAN. I don't know if the valve could be blocked yet the stuff be really clean. Has anyone seen a blocked valve on a 3G that does this?

I've thought about the vacuum leak causing stutter but I can't find one. A stuck-open EGR would do this too, no? I can't find a leaky hose so maybe there's a valve that's leaking somewhere.

But the stutter mostly goes away after the thing gets a little hotter. I was thinking that maybe because it doesn't run @ fast idle and MAYBE has a constantly open t-stat, it takes forever to warm up so it misses a little. Then on top of that I have this feeling that my spark might be a bit weak (resistance on my primary field of ignition coil is a little higher than spec) and it misses a little until it gets warm enough to burn the mix more easily.

OR maybe I just have some leak I can't find.

But then why would it smooth out when warm?

[mowery]

I had similar heating issues with my 94 EX. I was thinking it was a blocked core also.

It turned out that the cable from the control panel had become unclipped under the dash at the turnbuckle. That turnbuckle thing had two cables attached to it: One controls the heater control valve on the engine side of the firewall, and the other controls the heater box damper door.

So as you move the heater knob, it opens/closes the heater valve and open/shuts the damper door simultaneously.

If you say the heater cable is busted, the door to the heater box may be in the closed position. Therefore, the core is getting hot but no air is being allowed out of the blower.

Let us know what you find out!

[Greg]

I don't know what the damper door is??? What is it and where is it?

Are you sure that on a 3G it's not that switch that has the picture with the blue arrow for cool and the white for hot -- like, the one that routes where the air is coming in from...

Is that what you're talking about (but I've never taken this stuff apart and I only vaguely understand it).

-Greg

[Greg]

OK, I just looked at a diagram from Paul's online shop manual. I had no idea that the shit was this complicated. I thought that there was just one cable from the temp-mix slider to the valve by the firewall.

So it looks like there is one cable from the slider to a lever that is attached to another cable that goes to the valve (air mix cable).

Then there is another cable from the cool vent switch (that's what I was talking about in my above post), and I guess THAT cable is what controls the damper door that you were talking about.

Maybe this got detached too.

I swear the previous owner of this car busted so much shit on the dash -- I don't understand. The arm that controls the wipers is all loose and out of wack too.

Driving hard, I understand. But these people who operate their heater and wiper controls hard... I don't understand

They also obliterated the clutch @ 160,000 while the one on my LX (which my dad owned before I did) lasted to like 210,000.

Maybe I'll take the dash apart some time and check this stuff out.l

thanks!

[mgirl69]

does it blow very hot when the front defroster is on full blast?

[Greg]

No, actually I tested this today, and the defroster blew cold. Why? What does this tell me?

I felt around under the glove box and felt the rod thing go up and down as I flipped the hot/cold air lever that's above the buttons (w/the person sitting and either the blue or white arrow pointing at the face).

So I think the cable to that is working.

But does the cable going to the temp slider actually change anything other than the heater valve?

[shepherd79]

ok,
i had this problem last winter. my heater core was cloged. here is what i did. i disconnected both heater core hoses from the engine. i took water hose and showed into the hose that doesn't connect to the valve. it should flow in reverse. make sure the valve it open. and turn the water on. i had a junks of metal flying out. and it was nasty. it works like a charm now.