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Merry Christmas...

So here's what happened. Since I was over my quota, I went thru the list and tried to delete multiple entries. So in other words, there will be many instances where someone will look for information and it will be G O N E !!!!!!!!!!!
 

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Re: Heater Valve Repair

Awesome write-up. I didn't realize the valve sold by Nissan had been redesigned. Thanks! :)
 

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Re: Heater Valve Repair

An additional reason to pull the dash is to replace that short section of heater hose that connects the valve with the heater core. That hose in my 79ZX was hard as a rock. I had to carefully use a Dremel tool with a small cut off wheel to remove it from the heater core pipe, very slowly so I did not nick or cut the pipe. The original Nissan hose for that spot is molded with a slight bend, rather than being a straight piece of normal hose, but you can find slightly bent hose sections and any parts store, just using your calibrated eyeball to pick the right one. It is only about a 15 degree bend. The problem is that the hose is so short that bending a straight piece can place too much stress and cause early failure and leaks.

And just like that valve, if the hose leaks, it is a miserable chore trying to replace it without taking out the dash and moving the heater box.
 

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Discussion Starter #5
Re: Heater Valve Repair

Mind if I insert this into the document. It would be a good preemptive fix.
 

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Discussion Starter #7
Re: Heater Valve Repair

If you already downloaded the above document. It has now been revised to show Bob's suggestion.
 

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Re: Heater Valve Repair

EXCELLENT picto-instructions! Thanx for taking the time!!!
 

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Re: Heater Valve Repair

Sorry this might but a dumb question but would that new heater valve available through Nissan work for a 77 280z?
 

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Discussion Starter #10
Re: Heater Valve Repair

Don't know. You'd have to know what yours looks like. Z-store does not show one for the 77. Go here

http://www.thezstore.com/page/TZS/CTGY/SHC03

and compare yours with the 75 and 79/83. You may just have to rebuild it.
 

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You should change the title of the Sticky to "280ZX Heater Vavle Repair" since it deals specifically with that model.
 

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has anyone tried this in a older z like a 76? the Nissan part that is i ordered one today any info would be great thanks
 

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1982 280ZX NonT Heater bypass??

Hey y'all. I would like to know, Is it crucial to the non-overheat of my car to fix the heater by-pass job that the POs did. I say yes:rolleyes: but the Mercedes mechanic doing some work on my car says it makes no difference it has nothing to do with overheat. So.....????
 

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It's been shown that the heater passages should be blocked if the heater core is not in-line, not connected together as a bypass. The bypass lets coolant that would normally travel through the head go straight back to the water pump, reducing flow through the head, especially the rear cylinders. Tony D actually did some work and took measurements to show this (search Tony D and heater core bypass and you might find it, I think he posted results on this forum). Blocking the passages forces the coolant through the head, bypassing lets it avoid the head.

I don't know if it's crucial but it could be a factor.

Also, the impellers on the old water pumps have been known to corrode away, something to check.
 

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Merry Christmas...
Another trick I thought I would share with you ZXT owners. If you vacuum pump goes bad, as my did twice...just old from running all those years, go to your Ford Dealer or order the replacement part for a Ford 250 Superduty vacuum pump. That is if you want you AC and heat when you floor your car. Plumb it in the same as the old. Its quiet and will do the job. You cannot use the original location for the old pump but it bolts up nice and clear below on the fender.
 

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It's been shown that the heater passages should be blocked if the heater core is not in-line, not connected together as a bypass. The bypass lets coolant that would normally travel through the head go straight back to the water pump, reducing flow through the head, especially the rear cylinders. Tony D actually did some work and took measurements to show this (search Tony D and heater core bypass and you might find it, I think he posted results on this forum). Blocking the passages forces the coolant through the head, bypassing lets it avoid the head.

I don't know if it's crucial but it could be a factor.

Also, the impellers on the old water pumps have been known to corrode away, something to check.
Looking at my words here, they're not quite right. Bypassing the heater core doesn't actually bypass the head, it just allows more coolant to pass through the back-bottom portion of the head, instead of flowing evenly through the head cooling channels and up to the thermostat. Changes the flow rates and paths through the head. Just to be literally correct, for any future readers.
 

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how to check heater core valve

Re: the water **** valve.
Car is 1979 base model five speed.
Water **** is manual, no vacuum lines attached to it. It does have copper wire that goes to a copper coil temperature sensor under the heating unit.

While in my hand it seems that the valve lets air flow pass in either direction when the actuator is in both the extreme open and closed positions. Yes, that means I'm blowing on one tube and attempting to observe outflow on the other end.

Q1: Should this valve pass water (air in my manual test) in both the "open" position and the closed position?

I see no water passing through the main seal (as Palladin has written up) when I tested it with a garden hose while it was still installed in the car.

Q2: What exactly does this thing do if it doesn't seem to restrict water flow while in either position? I do see the tie-in to a vent control flap (directly above the heater coil).

I think I've read over 20 posts on water cocks aka heater core valve, plus Paladin's write up, plus TonyD's posts on the matter. FSM (AC) skims over this part.

I just don't seem to grasp what the valve's purpose in the A/C system is since I'm not seeing a total open or close.

I'm not trouble shooting any specific issue. I'm on a preventive maintenance kick before we drop the rebuilt engine back in the car. I want 100% new rubber hoses in the cooling system so I've put in the effort to get the hoses going to the heater control valve / watercock as well.

I've pulled the heater core and the heater core valve. Heading to the radiator shop tomorrow to have the gas tank cleaned and I'm taking the radiator and the heater core with me to have them inspected.
 

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Discussion Starter #20
Don't know how we missed this, so I apologize for the delay. There is a plunger in the tube, not shown, that blocks off the water to the heater core. I considered replacing it and the only thing that came close was those round rubber valves you find in faucet repair kits. Mine wasn't that bad so I did nothing.

But it is possible that if the plunger has deteriorated, then you will get water though even in the closed position.

The leak occurred when you moved the selector to cold, closing the valve. This pulled that plunger and expanded the round rubber washer type seal. Over time, it split right in the center. When it was pulled, it allowed water out of the system onto the floor.

The replacement are a much better design. Not too long ago they were available thru Nissan for about $30, though that one now is on ebay for $128.

They claim it is for AC and non AC, but I think they really mean auto air and manual air. There were only 2, count them 2, different types heater valves. This one and the one for auto air which was vacuum operated.
 
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