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Tips
Tips

it's cold outside

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The tstat does not impede flow through the heater. How is your short heater hose? It makes a sharp angle. Is yours kinked?
 
I have bypassed the shutoff valve and have the lines going direct to the heater, I wanted that out of the equation so I don't have to wonder about it.
 
Rick;
after running it for awhile, it is best to check the level again.
This may not be the problem, but I find they, sometimes are low on antifreeze. (air pockets and all that)

Let it run without doing the cap up tight and after about 5 minutes, check the level.

Hope this helps.

Dave :savewave:
 
Ha, if you don't open the vents in the footwells it will never blow hot air.

Do you have a valve on the hot water line from the engine to the heater?
 
I had the valve, but I took it out and ran the hot directly from the engine to the heater.

With the vents below closed I get air out the top defroster vents. Sometimes warm air even! :wink:
 
Chilly ride this morning.
The temp gauge reads about 190F while driving now (up from 165F).

After getting off the freeway I commonly have to sit at a red light & idle a couple minutes. Pretty much always I do get heat after leaving that spot.
This morning there was heat from the time I left the freeway offramp to the parking lot (about 1/2 mile). Plenty of heat coming out, temp gauge read a bit above 190F.
Just no heat when running on the freeway.
 
Where does your heater feed from and where does your temp gauge feed from. You do have a different engine in this, right?
 
Right - Nissan A15 (1500).
The heater hoses - one runs to the back of the engine and I believe the other goes to the water connection on the intake manifold.
The Temp gauge is connected to a sensor on the front passenger side of the head.
 
Do you know which way the water runs. ie rear of engine to the heater or the other way around.

Take the input to the heater free and add enough hose to allow you to hold over a bucket and crank it. Sounds to me that you are not getting enough water through the heater to really warm it up. Could this be?? The way you say it is set up if your therostat says 190 you have 190 in the heater also, or you should. Stoped up hose??

this is an intresting problem because the answer is going to be really simple and dumb. Is the heater radiator unpluged. Take off both hoses and blow through it with your mouth or hook the end of a water hose to one side and a dump hose to the other.
 
I did the "blow" test when I removed the valve. It blew freely.
I don't know about flow from the motor, but I assume since this is a Nissan copy of the British 1500 it flows the same way.
I do have a book at home on the Nissan motor so I'll check that tonight.
 
Rick, great to hear the new thermostat fixed most of your problems.

could it be when you're on the highway, the increased cold airflow it simply too much for the car to handle? if you are getting heat at lower speeds, that tells me your heating system is working fine, at least you know coolant is flowing through the heater box, right?
 
Does not make any difference which way it is going but it should go, and quite fast.

I think you have a stopage someplace, not 100% of course but something.
 
It really does seem to me like there's simply not enough flow.
If the water in the motor is above 180F the heat ought to be flowing.
I don't get heat until the car has sat & idled without the cooling fan running.
Then I get heat.
I'm going to simplify the system more and do like Jack suggested and run a hose to a bucket to see if there is enough flow. If there is a blockage that would answer this, reduced flow would make it so that what water does get to the heater cools off too quickly. That's something to check.

Another thing could be the heater is partially plugged so water only gets to a small area. I don't really know how the water flows through it but if it enters and exits from the same end that could be a problem.
 
And Rick, we got to know the outcome. It is such an intresting question.
 
I'm betting on a partially blocked heater core. Coolant is going in but circulating around top or sides and not ppassing through the heater core itself. Could that be a possibility?
 
Sounds plausible to me, I just can't get over how easy it is to access a Spridget heater core, I had to get at mine on my Opel GT and it involved dropping the steering column, pulling the whole dash board AND taking out the windshield!
 
jvandyke said:
Sounds plausible to me, I just can't get over how easy it is to access a Spridget heater core, I had to get at mine on my Opel GT and it involved dropping the steering column, pulling the whole dash board AND taking out the windshield!
Click to expand...

Good point - so what's involved?
I've never taken one of these heaters apart before.
 
Sure could, I bet on a blockage some place and of course the core is the most common spot. Not too hard to check though.
 
This afternoon's experiment:

Bypass water circuit through intake manifold.
Where the top heater hose connects down by the water pump there was a T and one side went to the heater while the other went to the intake manifold then out another hose goes back to the back of the block.

Working on the theory that less water going through the intake might result in more water going through the heater.

Result: No difference.

Drove around, temp gauge went up to 190F but no heat.
Both heater hoses feel very hot to the touch.
If I let it sit and idle for 60 seconds I start getting heat. What's up with that? :crazyeyes:
 
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