Thermostat temp '77 280z

[Jennys280Z]

No, this is what accumulates after i drive the car round trip to work. i called around to find the nearest radiator shop that stays open long enough for me to make it into town before they close. i should find out something next week Tuesday. I took a picture of the temp gauge on my way home ( condition o/s temp 58 deg. @ 70 mph ) does this look normal ?

Not to me, it looks too low.

That's lower than it normally reads (has read) for you, right?

I guess the gauge reading low is a possibility, but

Are there any other symptoms? Changes in the way the motor's running?

If it gets cold outside at night there you might take it out around the neighborhood to warm it up and see if the heater can blow hot air out the vents. It'll be more obvious if you're very lightly dressed. At least that's what I'd do. :classic:

Or if you have a cooking or candy thermometer, it's also easy to take the coolant's temperature under the radiator cap. Being careful opening it when hot, as always.

Edited January 29, 2011 by Jennys280Z

[kjphilippona]

This is the first winter that i have had the car running good enough to drive it all the way to work. The engine does hot run great but for a car with 400k+ miles i guess it gets down the road good. It starts up with just a bump of the starter and idles with a slight lope. The temp will climb up to ctr of the gage when sitting at a light but will drop back down as soon as you start driving. When it was very cold in the morning, the gage would barley be off of the 120 mark and i had no hot air coming out of the heater vents.

[ozconnection]

What worries me is that you've got no hot air coming out of your heater vents when the fan is on. They're hooked up and the hoses aren't blocked up with corrosion or kinked or anything?

Other than that, it suggests to me that your thermostat isn't working correctly.

Let's look at what a thermostat does. Understanding its job will help you assess the situation more thoroughly.

At start up with a cold engine, the thermostat is closed. The engine runs and the coolant gets hotter as it absorbs the heat. Depending on which model you have, some water is allowed to circulate via the internal bypass passage in the block. Some engines also have a small hose that runs from the thermostat housing to the water pump inlet side, the external bypass passage.

Now, as the engine coolant temperature reaches the thermostat temp. setting, the thermostat opens and allows coolant to flow through the radiator, to cool things down but as the coolant renters the engine head and block it mixes with hotter water and the overall temp drops a little. When it gets back to the thermostat, if too cool, the thermostat will close a little to reduce flow out of the engine and into the radiator. This will have the effect of raising or stabilizing the coolant temperature to a point close to the thermostat temp setting. Make sense?

Your thermostat, if stuck wide open all the time, will allow too much coolant to be cooled...thus your condition as you describe it. At idle with the car not moving, the coolant guage will come up to halfway.....yes, that fits in as well.

Don't forget that the heater is a mini radiator too, so it will make matters worse by cooling things down even more. (You can use this fact as an emergency "extra" cooler in the summer months if things are getting too hot...I did when I was towing a really heavy load a few years back in the middle of summer....an engine saver. I just wound down the windows a bit more to cool the cabin down a bit!)

Get a warm(ish) thermostat ie 180 degree (hell even 190 for the cold months, swap it over when the warmer months arrive), your engine will run more crisply with the oil temperature closer to optimum as well, Cold oil robs power and doesn't work as well when cold. The cold outside air will be dense and that will keep your engine running strong.

Cold engines wear more quickly so get things sorted man....change that thermostat, sort the leak and let us know how you go.

Cheers from OZ!

[Jetaway]

No, this is what accumulates after i drive the car round trip to work. i called around to find the nearest radiator shop that stays open long enough for me to make it into town before they close. i should find out something next week Tuesday. I took a picture of the temp gauge on my way home ( condition o/s temp 58 deg. @ 70 mph ) does this look normal ?

I'm thinking two problems. The first is engine temp. and the second is heating system. Yes, the reading on the gauge seems low to me also. Thermostats are cheap and easy to replace, so I'd just go ahead and replace the old one. And check for leaks. When it cooled down here, my 1972 began running a needle width cooler than normal (which has been dead center), so I swapped out the 180 for a 195. Now it runs one and a half / two widths above. "Cool" being relative, of course. We've had a cold winter, which means it does get below freezing on clear nights-- not much but a little. Hazarding a driving time outisde temp average guess, let's say 50 this winter. The 195 does keep the cabin toastier, but I probably won't run the 195 next winter. You're probably warmer than we are, so I'd stick with a 180.

You wrote that this is the first winter that you've driven the Z to work. A couple of questions:

Have you ever used the heater before?

By "no hot air" do you mean no warming, no heat, nada? Or a lukewarmish kind of heat?

If yes, and lukewarmish, replacing the thermostat will (hopefully) solve both the engine temp and cabin heating problem.

If either no or yes and nada, sounds like you've caught a clog in the heat exchanger or one of the hoses going to and fro. Hopefully a clog, because another possibility is the heat exchanger is getting ready to drench your feet and carpeting in coolant.

Best of luck figuring it out.

Chris

[Walter Moore]

Here is a really basic question: His profile says he has a 1977 280Z. On that version do the "vents" in the dash connect to the heater box? I know that on the early cars "vent" and "heat" are separate airflow paths, and it isn't possible to get heated air from the dash vents.

By the early 80's that was no longer the case, so I suppose that on a 77, it may be possible to heat the vent air.

Generally there are three causes of "no heat"

1. Low coolant level. (Generally associated with overheating, but not always)

2. Plugged heater core.

3. Thermostat stuck open.

Another possibility is that since he is in Alabama, a previous owner may have bypassed or plugged the heater hoses.

[kjphilippona]

Yes this is the first time i have driven the car and had to use the heater, the air is only warm. Yes this is a possibility that the heater core has been plugged off, my Dad was the PO and he was known to some of the strangest things. I replaced the thermostat (180 degree) as usual had problems, the bolts looked like the had not been removed in some time and were heavily crusted up, washers were added to get good threads. I tapped the holes and used new bolts, have not tried it out because of another problem, screwed up the plastic drain plug and had to order another :mad:

[FastWoman]

So to be clear, you replaced the thermostat, and the engine STILL won't heat up to 180? And when you drive it, vs. idling it, the temp will STILL fall? Maybe you got a defective thermostat. (It wouldn't be the first time this has happened.) What you describe are classic symptoms of a thermostat stuck open.

With regard to heater core issues:

Your '77 and my '78 are very similar designs. My '78 has two stopcocks on the heater core. One is vacuum-controlled and turns the coolant flow on and off, depending on the mode switch setting. The second opens and closes variably and is controlled by a wire from the temp lever. You should check to see that both function correctly. (You can reach up and feel these stopcocks with your hand, and you can feel them operate when you turn the levers.) In my '78, the mode selector switch was gummed and crudded up and didn't hold a vacuum. You can take it apart and lubricate it with dielectric grease to get it operating again. It's a simple part, and nothing will explode. However, you have to be certain to correctly align the gear teeth when you R&R. You can read about it here:

http://www.classiczcars.com/forums/showthread.php?t=35521

Also make certain you have vacuum to the selector switch, It's very easy for someone to pull the little vacuum line off it. Leaks and breaks are also commonplace.

Edited January 30, 2011 by FastWoman

[sblake01]

EDIT: Disreagard post, I just looked in Kim's photos and it does have factory air which makes moot the questions I deleted from this post.

Edited January 30, 2011 by sblake01

[kjphilippona]

FastWoman, i have not driven the since replacing the thermostat, i screwed up the drain plug and it seem that no one had one, so one had to be ordered. I did not think about it until i had returned home after running all over town looking for a replacement, the radiator in this car is not the OEM, it was replaced a few years back by my Dad, so i am not sure what plug i even need. I don't understand why some things cant be generic. it's only a stupid plastic plug :mad:

[Jetaway]

Yes this is the first time i have driven the car and had to use the heater, the air is only warm. Yes this is a possibility that the heater core has been plugged off, my Dad was the PO and he was known to some of the strangest things. I replaced the thermostat (180 degree) as usual had problems, the bolts looked like the had not been removed in some time and were heavily crusted up, washers were added to get good threads. I tapped the holes and used new bolts, have not tried it out because of another problem, screwed up the plastic drain plug and had to order another :mad:

OK, so as far as you know, the heater has never worked properly since you got the car. That's ... good, I think. At least closer to good than bad because a sudden change for the worse is never a good thing and is usually quite bad.

Walter asked if hot air is supposed to come out the "vent." I'm curious myself, because as he wrote, the three dash vents on the 240Zs (at least through 1972) were fresh air (i.e. not heated) only. Maybe you shouldn't expect hot air from the dash vents. Or by "vent" did you mean the defrost or floor vents?

If the 180 thermostat has solved the engine temperature problem but still no heat, I would:

1) Check for clogged hoses.

2) I get the suggestion from your post that your dad had an ... ingenious mind, let's say. While my dad wasn't the P.O. a P.O. had rerouted the coolant hoses so that the flow from the heater core went back to a hose that led directly from the water pump. (Don't ask.) I reasoned that this may well slow down the flow through the heater core because the return from the core was trying to merge into a high pressure stream. I rerouted the hoses and got more heat inside the car. Manuals aren't of much use in this type of thing, but you should have one to make sure that "in" and "out" connections of the heater core are correct. Then trace the coolant flow in and out of the heater core and its return to the engine. Maybe your dad did something as equally creative as my P.O. did with the hoses.

3) Marry Fastwoman.

4) If #3 proves not possible, and you've followed all mine, and Walter's and Ozconnections, I'd bet money that Fastwoman's stopcock diagnosis is either right on the money or very damned close to where your problem lies. And I'd also bet that if it isn't the stopcock, Fastwoman will have a couple more excellent diagnostic suggestions.

5) I'm ignorant of how the venting is arranged in a 280Z, but even after rerouting the coolant hoses (going from cold to lukewarm) my Zs heater was none too impressive. And I could never get the fresh air vents fully off. The problem (Did I mention the misrouted control cables? No? They were, but #5 has nothing to do with control cables) was that the foam that sealed off the fresh air vent duct when the control flap was in the "heat" position was but sad little crusts. Using one of those "grab small items when they fall behind something" tools and cursing freely I managed to place one sided adhesive household foam door seal pretty much all around the duct. Still leaks a bit, but until I gin up the courage to dissemble the console, it'll do. My foam hack was enough to change a couple hour drive at 45 degrees from, uh, I think I'll take the other car, to being able to turn the fan down to one and have the window cracked a bit.

I have to admit I chuckled (with you, not at you) when you reported "screwing up" the radiator drain plug. Ain't that the truth, brother. I don't think there is one first time repair that I've done on the Z that didn't result in my breaking, jamming, misadjusting, or losing some other damn part whose only crime was being physically close to or tangentially related to the problem I was attempting to fix in the first place.

Now that my experience level has risen to, oh, novice, I offer a piece of generic advice.

Penetrant.

Drip it on, spray it on if gravity won't cooperate, but use, use, use penetrant. If you can plan work a day in advance, put penetrant on the day before, then again when it comes time to twist the nut. And don't forget to rap (gently) the parts a couple of times with a hammer after putting the penetrant on.

Chris

[kjphilippona]

Well if its not not one thing another, i was not able to find a replacement pet **** at any of the part stores for my radiator due the fact that this is the third radiator including the OEM that my dad had in this car. I some how lost the plug gasket but was able to chase the threads so that the plug would screw in tight. Filed her up with water only to check for leaks and test the heating system. I will drive the car until i find a replacement plug at a radiator shop. Started it up and let it warm up, temp gage came right up to almost center gage. Turned the heater on high, i only had cold air coming out of the ac vents and nothing out of the heater vents at your feet. I think i have some big problems that will take some time to figure. I also noticed that my lower radiator hose has a good ware mark from the alternator rubbing against it, new hose time. My dad had this problem when he got the radiator replaced, he made it half way home before the alternator wore a hole in the hose and poof giant cloud of smoke, i remember his saying he thought the car was on fire, scorched the underside of the hood. My guess is that i should stay away from aftermarket hoses and get OEM.

[FastWoman]

3) Marry Fastwoman.

4) If #3 proves not possible...

I forgot to mention that the vacuum control hose runs from the vacuum switches on the righthand side of the engine compartment, through a grommet in the passenger firewall. Pull the hose off and try blowing through it. If you can freely blow air through it, either it's leaking, you have a hose pulled off somewhere, or that vacuum switch is crudded up -- in which case you'll need to pull your center console and go diving into your HVAC control stuff. (Have fun.)