Help no heat

[Greg Galotta]

My 1977 280Z Heater blows out cold air any suggestions?

[Zs-ondabrain]

If it's got vaccum operated valves to move the doors in the heater system? I would start checking vaccum lines under the dash.

[preith]

Have you made any changes recently, like maybe remove the AC? There's a vacuum operated coolant valve on the inside of the firewall opposite of the coolant inlet. You could put a mightyvac or something on that, it worked for me

[Weasel73240Z]

My 1977 280Z Heater blows out cold air any suggestions?

Fix it.

Seriously, there's lots of things that could be happening. Has it ever worked, is this a new thing? Is the heater core old or new? Does it leak at all? What temp. cap are you using? Have you checked all the connections behind the dash that operate the system? Has the car operating temp. changed at all?

You won't get quality feedback if you don't take the time, and put in the effort, to write a detailed question.

[240Z-Fan]

Things to that can cause this

1) Low coolant

2) Thermostat stuck open (what is the engine temp after driving it for 10 minutes? Does the needle ever move?)

3) Loose or cracked vacuum line. Under dash or under hood on right side fender, IIRC

Al

[IdahoKidd]

My 77 often blows cold air. Oddly, after a second start up, it will blow warm. (ie, drive to store, air is cold. Drive back home with warm air). When it doesn't blow warm, engine temp shows warm. I am curious what you come up with for a solution. I simply haven't taken the time to track it down. I too will have a look at the vacuum lines.

[FastWoman]

If your '77 is like my '78, there are two stopcocks. One is vacuum actuated and simply turns the water flow on and off. The other is variable and is controlled by wire with the temperature lever. If you have absolutely NO heat, I'm guessing the vacuum actuated stopcock isn't working or doesn't get vacuum. The little vacuum tubes can rot, and they can also come apart rather easily.

[Greg Galotta]

Thanks for all your help, the car is in the body shop, so as soon as it gets out I will check all the vacuum lines. Snd I will post what the problem is.

[IdahoKidd]

I've searched and this thread came back up and since it is recent, I hope still relavent. My 77 280z has never run much in the way of a temperature according to the gauge. 140 ish. Now that it gets frosty, that isn't enough of a temp to defrost the windows. I swapped out the thermostat, which was a 200, and put in a new 190 and lost about 10 degrees on the gauge, but there isn't enough heat to defrost the windows, heat the cabin, etc. The radiator is cold to the touch. The thermostat housing is warm to the touch but definately not hot. The hoses from the block to the heater through the fire wall are barely warm. The hose from the thermostat housing to the radiator is cold to the touch.

I just checked, cardboard over the radiator for 20 minutes idling brought the temp up on the gauge to about midway, 180ish. Could both thermostats have been bad? They should hold the water in the block until the specified temp and release it only when that temp is exceded and close up again when the temp falls below, right? Am I missing something or is there another issue?

Thanks guys (and gals)

Leonard

[IdahoKidd]

Nope, the cardboard didn't work. Drove it about 6 miles and was able to take the radiator cap off and literally stick my fingers in the water. Barely bathtub warm. It makes no sense to me at all.

[FastWoman]

I just checked your weather. Wow, it's COLD in Moscow! It sounds as though you're losing all your heat just from the engine block to the air.

You're right that the thermostat lets the water flow when the engine temp rises above the set point; however, it might not completely shut off flow when the engine is below temp. Often thermostats will have a hole that allows a very small amount of water flow. I think it might be to ensure there is actually water flow, so that the thermostat will actually heat up and open.

You might be getting a lot of air blowing through the engine compartment if your fan clutch is frozen up or sluggish. Does it sound a bit like a hovercraft when you rev the engine? Is there quite a wind blowing in your face when you've got the hood popped and are standing over the engine? The fan clutch is supposed to slip, and the coupling is supposed to slip more when the air through the radiator is cool and less when it is hot. The clutch is filled with a silicone oil that gets as thick as honey as it ages. Alternatively, the oil can leak out, and you'll either get inadequate torque to the fan, or the clutch can seize up entirely. If the clutch still turns (if you can turn the fan by hand), you can remove it, open it up, wash out all the silicone oil with brake cleaner, dry it completely, refill the deeper half with 90 wt gear oil, and reassemble. That solved the hovercraft effect in my own clutch. Don't worry about exploding springs or hard to match up parts. It's a pretty easy operation.

[IdahoKidd]

Hey Fastwoman, it is cold here but it has warmed up to 22 this morning. I thought about the fan but it seems to be just fine. I know exactly how they work and sound when they lock up. I took the car to the Toyota shop yesterday (no nissan dealer here for 100 miles) and the tech looked it over and determined "that motor doesn't make heat) and scratched his head then added "that ain't possible". I am going back on Monday and he has a thermal imaging gun that he will shoot the whole block with. I've got 11 cars and have had a hundred through the years, this has really got me stumped.

PS, I have tried thermostats with and without the "bleed" hole. No difference.