88c4vette

Hey guys,

Had great help from you all with my leaking cold start injector issue just a while back and thought I'd lay out another issue I have and see what we can figure out.

My heat will not blow hot air or even remotely warm air. I've checked the heater core and there's no leaks. The hoses to and from the core are warm but seem to be empty, with no coolant in them. I flushed it out not too long ago and it flushed fine. The a/c is good and cold, but when the temp is raised and switched to heater or defrost, the temp of the air stays cold. There's also a horrible noise coming from the blower occasionally, and the light for the digital display on the climate control only comes on every once in a while. Not sure if the blend door clip is broke or what, but switching from air to heat never makes a noise like the door is opening. If that's it, tell me the easiest way to get to it and fix it, please.


Thanks in advance!

hooked073

first thing to check is your colleant level. after that it would help to know what your engine temps are

88c4vette

Coolant is full and engine temps run about 170. I have a 160 thermostat in it, when I bought it there wasn't one in it for some dumb reason. But I had a third gen camaro in the low temps of winter with the same stat in it and it still produced heat.

DanielRicany

Did you bleed out the system?

If you did then look into your heater control valve.

dlee425

Had the same problem. Found the heater control valve was clogged. I deleted it flushed the core and run new heater hoses in place of it. Look inside and see if the valve movea when you pull some vac on it.

88c4vette

dlee425, where is the heater control valve located and what does it look like?

dlee425

It is on passanger side going to the firewall. 2 rubber hoses to heater core. Its a metal valve on mine. Have someone move the hot/cold temp and see if the valve lever moves. If not you could have a bad temp control. If so it may be clogged.

SunCr

I don't think the '88 had a valve so if you don't see one, you can quit looking for it - nor should there be one with Electronic Air.

Clogged cores flow coolant over the top but not through it. If it's plugged up, good possibility that the Radiator, Heads and everything else is full of crap too.

Pull the Blower Module on the Evaporator Case and look inside to see what the Temp Door does while someone diddles with the Controls.

dlee425

I was going by my 86. it has a manual slide control. Had no heat and the valve moved. Pulled the control valve off and clogged to the point of not moving and the core was clogged. But the engine and rad was clean as a whistle. Someone must have flushed the system before I got the car.

Vetteoramma11

Is is blowing out anything? Is it only coming out of the defrost vent?

88c4vette

it was coming out of everywhere, now my electronic control is being intermittent, so I can't test it. I changed the stat to a 180, flushed the system, put new antifreeze in it and still no heat. replaced the 2 way check valve that runs behind the distributor (one side was broken off) and hooked all those vacuum lines back up, still blowing everywhere, just cold. I'm beginning to think the blend door isn't opening or that my electronic climate control has dirty contacts. I'm going to take it out tonight and clean it up and see where we get from there.

hcbph

I've had 2 cars that after working on the radiator had no heat. What I did with both that worked for me was:
1 Get the car hot
2 Open the heater control to the max
3 Run up a parking ramp (steeper the better) in low with rpms up
4 Go all the way to the top, come down and do it again.
After 2 or 3 loops, I had the air out and heat came on.

88c4vette

I will have to see if I can find somewhere to do that at. Not really many steep drives here and definitely no parking ramps. I just took apart the ECC and cleaned it and it's blowing out all the correct orifices, just no heat. The blend door is moving though, because I watched it while I had the vents out. I'm pretty clueless why this is happening.

dspayne

I am having the same issue and did a lot of searching on the forum. I think my issue is the hose coming off the manifold by the thermostat and connects under the valve body is clogged and possibly this pre-heater box as well.

I flushed my heater core and it is clear and flows well. I then pulled the hose heater core hose off the intake plenum under the valve body (passenger side). I was told this is to preheat intake air in cold weather for emissions control. After I pulled it off and with car running, nothing came out from the intake even though the car was hot. After it cooled down, it tried inserting a wire into the tube that the hose connects to and to clean it and could not, it is clogged solid. I haven't had time to disassemble and clean it, this pre-heater or the hose running down to the manifold. I read where some people by pass the intake preheater box as it really doesn't hurt it. Evidently the heater core hose is 1 size and the hose off of the manifold is a different size. Hope this helps.

Cliff Harris

The fitting that the hose attaches to (on the front of the intake manifold) has a restriction in it to limit the flow. The hole is about 1/4" diameter. Check that out.

88c4vette

I will check these things when I get off work today, though I'm pretty positive I pulled those hoses before and had coolant come out of them.

88c4vette

Hey guys. This past weekend, I pulled off the throttle body, cleaned up where the coolant runs through to heat the intake air, even unscrewed it and no obstructions. I reverse flushed the heater core and flushed the opposite way as well, and flushed the motor and radiator. I added new coolant, topped off until the whole system was full and changed the coolant sensor under the throttle body. Had a small leak of coolant I've been noticing for a while but could never trace it, it was always at the back of the motor. Discovered last night it was a small hose with 5/16 threading screwed into the back of the intake near the distributor ran from the heater core and it had a small rusted hole in it. When I removed it, the hole that coolant was supposed to flow through into the intake (I assume) was clogged with a rusty looking matter that wasn't letting anything flow through. I cleaned it out and hooked it back up and it flows fine, but still no heat.

(Sorry this was a novel)

-Brad

SunCr

As long as the Temp door is blocking air flow to the a/c Evaporator, the Core is plugged. As posted earlier, coolant is simply flowing over the top, but not through the Core. If it wasn't it'd blow a hole in something. You can apply some compressed air, but that can also blow it up. I unplugged mine years ago - once it was out of the car, by putting my thumb over one end and hitting the other with 100 psi. When I remove my thumb, there was a loud pop and after I hooked it up to hot water, the core got nice and toasty. I still trashed it and put in a new one. Cruddy cores, radiators and that bypass hose being plugged up, are an unfortunate sign of galvanic corrosion caused by a leaking head gasket. I'd see what the plug at number 7 looks like.

ghr4news

Don't know if this will help. Mine is an 86 and recently did a major restore which required me taking the entire dash apart. If the blend door is not opening, it could be the vacuum hose has a leak or has become disconnected from the air mix valve actuator or the outside air valve actuator is defective. These are connected to the door arm. Now you may also want to check the other actuators. One is the A/C vacuum actuator. In mine it is positioned way up on the driver's side under the dash and is screwed on to the central air duct that sits in the center of the dash. The other one sits just below it and is called the front mode vacuum actuator. The vacuum for the hoses which operate the doors is controlled by the heater and A/C programmer. That module is also bolted to the inside firewall on the drivers side. Make sure all the hoses are in good condition because if any one of them has a leak it will prevent the various heater/AC doors from opening.

Good luck.