Help no heat

[260zCaliCar]

Coolant drop is only from the engine block to the heater core.

The only way I can imagine the coolant dropping this much in such a short distance is if your connecting hose(s), heater core, or valve is like 90% blocked. You would still get some flow, so it would heat up a little bit, but it would take much longer for the coolant to get through giving it enough time to cool down. With a reasonable rate of flow, it should eventually heat up. How are you measuring temperatures at the different points?

[IdahoKidd]

I just came back in from the shop. Using a laser digital thermometer, temp readings are:

Thermostat housing 132

top of radiator 120

Midpoint of radiator through fan 96

Head temp above/at sparkplugs 162

Head temp at back of block 162

Upper heater hose at fire wall 91

Lower heater hose at fire wall 91

Temp at water temp sensor at block 132

Exhaust temp at collector 475

Temp at Y at water pump inlet 92

Temp gauge shows about 160. Has known good 190 thermostat.

The only conclusion is that the water is bypassing the thermostat and getting back to the radiator to cool. I simply can't figure out how that can be possible. A non circulating water pump would cause the engine to heat. Been to two shops now and still no idea of where to even start.

Someone needs to make a little icon of a white surrender flag so I can wave it .........

[70 Cam Guy]

Are you certain your heater core is not plugged? If anyone ever used stop leak or any of that cooling system leak stop stuff (Bars), that could have easily plugged or restricted heater core flow. Age and/or lack of coolant changes can contribute to that too if I recall

260CaliZ also makes a good point about the control valve being restricted internally.

[IdahoKidd]

Coolant flows freely the through the core, I just put in new lines from the block to the core. Both lines. Double checked two other cars to be sure they were in the right place. The repair shop says something inside the the head, the block, or the water pump is allowing water to get to the radiator by going around the thermostat. We are going to completely block off the water neck at the thermostat housing and see if we can get the temp to come up. It will clearly confirm the suspecion but may not confirm the culprit. It is already 8 degrees this morning and I am starting to get tough. It isn't as big an issue as it was

[FastWoman]

I know you've tried multiple thermostats, but have you confirmed their operation with a thermometer in a pot of water on the stove?

Does your thermostat housing have pits or voids that would somehow allow water to flow around the thermostat?

(Running out of ideas...)

[Pomorza]

Have you ever done a flush of the block and or the heater core? I had the same kind of issue with my friends ford. The previous owner used "something" to fix the radiator and it got stuck in the block. Took us literally hours to get it out and get it back working.

Anyhow from what your saying the coolant hose from the top of the thermostat is cold. I'm nearly positive it should be at least warm to the touch. I don't see how the waterpump or something can cause water to bypass the thermostat. From every image of the cooling system on Z's that I've seen water goes from the thermostat to the top of the radiator down to the opening around block and back up after going through the coolant lines.(I'm sure this is right...right?). So I just don't see that happening that your coolant goes around your thermostat unless there are so voids or something there.

Where did you get your thermostats from? It is possible that both are bad and stuck open I would test them in hot water. I'm with fastwoman on this one as I'm running out of ideas. Unless your 280z is completely different than my 76' I can't see how it runs this cold. Do you have a working temp sensor(s)? It is possible that they are telling the computer that it warm when its not causing it to lean out the mixture. (just throwing ideas out there now).

Hope this at least gives you some ideas.

Jan

Edited December 10, 2009 by Pomorza

[geezer]

I have never heard of an air lock in the system occurring in one of these cars, but it is a common problem with some other cars when the coolant in the system has been run down too low or changed, especially vehicles with rear auxillary heat. To check for an air lock, disconnect the water outlet hose so it can vent to the atmosphere.To keep things clean it is best to put the hose ends into a empty jug or bucket. You may have to rig up an extended hose to do this. Make sure the rad cap is on, the heat controls are on and let the vehicle run, watching what happens. This will rule in or out the heater core being the problem and if there is an air lock, it will be purged. Just a thought I had reading this thread.

[cheney119]

My heater didn't work and it was a bad thermastat. What does your temperture guage read?

[IdahoKidd]

Hey guys, I am still plugging along. Woke up to a basement full of water from a frozen/broken water line so no Z activity today. Perhaps tomorrow I'll try some of the things mentioned (purging for air, etc.)

[kzim81]

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

I had the same problem on my 1978. Check the Vaccum lines on the right shock tower. I had my whole dash apart to find it was a vaccum line split open, 10 minute fix

[IdahoKidd]

Geezer, I followed your suggestions about the purge. I also bypassed the heater core completely by looping right back off the back of the block to the Y at the water pump. I added nearly a gallon of coolant after that. I know I didn't loose that much. In the shop, I was able to get the engine temp up to 190 (had upper hose off with thermometer stuck in open end) and the temp gauge also came up to 200. Hooked the upper hose back to the radiator and when the thermostat fully opened, the gauge dropped back to 150 or so. But, it is better than it was. Now I have to figure out what I did to the temp control switch. Moved it back and forth with enough frustration I either bent the lever or the wire came off or something. The outside temp is up 30 degrees as well. I still don't believe it is fixed, but........... perhaps a drive tomorrow in the new snow will tell me.

[geezer]

If you were able to add a gallon of coolant that means you did purge some air from the system. I think you misunderstood which hose to remove though. By removing the outlet hose coming from the heater core you would allow all air to escape from the core. You would also be able to tell if there was a blockage. I think the problem you have now is with the controls, no matter if they are cable or vacuum actuated. Another thing to remember; you should allow the coolant to cool before adding any, in order to take advantage of thermal expansion. Glad to hear it has warmed up in your area some.

Edited December 13, 2009 by geezer