90 s13, heater occasionally gets hot - come check what I've done

[lbrowne]

Only now that its -25 that I notice how well the heater is working in the car, which is sporatic for it's heat output. She has 168k miles on the clock.

I've replaced the t-stat about 1.5 months ago, because she would run a good while and the temp needle wouldn't move and even when it did it wasn;t much and then drop back down. Everything is fine there now.

About a week ago I replaced the coolant temp sensor, in hopes of getting a few more mpg.

The last few days the outside temps have gotten REALLY cold. My car warms up fine according to the gauge, and runs fine. but the temps out of the vents are not hot. It gets luke warm, to barely warmer than whats outside, to short stints of really good heat. All the while the temp gauge is pegged where its suppose to be.

I just put in some more coolant, because I may not have put in enough to replace what came out when I did the t-stat. I'm starting to lean towards a air pocket in the system, unless someone can tell me otherwise.

It seems if the car is in motion with a few revs on the tach it throws out warmer air...not hot but warmer than if it were sitting idle. But I have to diagnose that further to be absolutely sure.

My t-stat isn't faulty, and the cts I replaced doesn't affect the heat for the cabin. My heat switch vent works because if I swipe it to cold, I get the loud thunk and whoa, that air is cold.

Any ideas? Theres no coolant leaking out onto the ground or anything, what else can I eliminate? I've read a couple of archives, not too much on this subject beyond faulty t-stats. I'm thinking air pocket....

cheers,

lbrowne

edit: oh yeah, my oil isn't milky, nor was my coolant before the t-stat change look bad. Nice and bright green!

[nuts510]

this sounds a little strange but it's very true, try using a thermostat from Nissan I have had several instances where the car would be warm but not produce good heat for the passenger compartment your compare the thermostats and see some minor differences in the aftermarket unit when you compare it to the Nissan thermostat but for some reason the Nissan OEM thermostats work much better than aftermarket thermostats.

[lbrowne]

this sounds a little strange but it's very true, try using a thermostat from Nissan I have had several instances where the car would be warm but not produce good heat for the passenger compartment your compare the thermostats and see some minor differences in the aftermarket unit when you compare it to the Nissan thermostat but for some reason the Nissan OEM thermostats work much better than aftermarket thermostats.

Thanks, but I'm not going to swap that back out. I have the same temp rating as a Nissan one, the option was there to go with a different spec and I never. I've only ever used these t-stats on my now 3 nissans I've owned over the years.

[180fan]

my initial guess would have been thermostat as well. I have seen thermos be bad before, unless you boil test the thermo before install with a thermometer, you can't be 100%, even then they can also clog up with overzealous use of rtv.

Another possibility is a chunk of stuff moving through your cooling system that's blocking the passage of coolant through the heater core. This is also where the pocket of air comes in too.

Definitely check for bubbles first. Cheapest and easiest to check for. Personally I like changing my coolant in winter, it lets me pack in more coolant than I would be able to any other time of the year. Elevate the front of the car, if you've got ramps or a hill around, now's the best time to use em. Pop that heater core to full HOT and burp the hell out of it.

[lbrowne]

I can't curse enough. Now that is a balmy -40 for the last almost week this is happening. Too cold for me to swap it out.

In bumper to bumper traffic this morning, it took 30 minutes for my needle to move off of below C. The auir never got hot, enough to keep the windows defrosted, but not enough to make you want to unzip your coat.

Pissed, I clearly have to take it to a shop to get another one in there. Too cold out there now.

[lbrowne]

Oh yeah and the needle never started climbing until I started moving along after because for my first 1/2 hour I was crawling at like 10-15 kph, and then once I was going 80 the needle climbed up at least a 1/3 of the way.

Wish I had ym garage done, I'd be doing a complete flush and new t-stat. grrr

[ricebike]

i'm lucky then...

i've got an aftermarket STANT since back then, i didn't have time to get OEM...

i did tested the stant before putting it in...

& i made DAYUM SURE to bleed the system from air pockets & running full blast on heater while on an incline, idling, rad cap open to make sure no air is in the system...

[lbrowne]

I'm going to give the system a good flush I think within the next week. This t-stat did have stiffling hot air coming through when I first replaced it.

[sliders]

if it took 30 minutes for the gauge to move and you still didnt have hot air your t-stat is stuck open buddy not allowing the coolant to heat up and you said its cold as hell out side....change to an OEM t-stat your nissan will love you for it

[180fan]

well most thermos are made to open at the same temp an oem thermo is set to. So that's probably not the problem. A possibility is with the fan and fan clutch if you're 100% sure all the air is out.

[lbrowne]

It can't be stuck open, my car actually reaches normal operating temps if you are going a constant speed - say 70 kph. If it was stuck open the gauge wouldn't move much wouldn't it?

How would the fan and fan clutch which is for cooling the motor affect the car's heater not blowing hot air? With this weather, -39 today, I'll probably just get the t-stat and the coolant done just to be sure.

[Acecool]

Make sure your RADIATOR HOSES ARE NOT LEAKING...

One of my hoses busted on me, in cold weather.. Instant death to hot air...

Make sure you have the proper anti freeze / water or coolant ratio in your car..

[lbrowne]

Theres no coolant smell being burned off, nothing left for stains on fresh white snow.

I'll take a closer look maybe the weekend for sure thought to be positive, its -42 out there now. I have a -35 or -38 ratio coolant, which is good enough for some degrees beyond. This is not the first time I've experienced these temps.

[Acecool]

Yeah, that is my suggestion though, checking for leaks in places, radiator etc etc...

[lbrowne]

So today on the way home in -39 temps I tried what I read in another thread... and stuck the system on recirculate. If the heater was that warm off of the recirc - I wouldn't have wrote this post. So does that mean the heater core is good?

[sliders]

sounds like you have two problems one your car doesnt reach temp until like 30 mins-change your tsat, and two your get hot air when on recirc but not otherwise problem with your blend door/.

[lbrowne]

I don't touch the blend lever, and the temp changes drastically from recirc to regular.

If I flick the blend over to cold the temp is so cold - its straight from outside trust me. The lever is kinda stiff when trying to move it off the hotest setting...also I had a prob before it caught cold that the push button blower directional controls weren't working all the way. But that has nothing to do with the blend door right?

So maybe coincidental probs...hrmm.

[180fan]

yeah it could be sticking through the cable that's a good point out

[itsnever2fast]

the stock temp gauge is VERY inaccurate, it will sit in the middle of the range from 65 celcius up to about about 95 celcius so my suggestion is let your car run for a LONG time without moving and see if you have heat

warm up the engine, if one heater hose is warm, and the other is not, your core may be clogged, just b/c the coolant was clean doesn't mean the system is. if you have a heated space to work in, disconnect the heater hoses and test flow the heater core with some water or coolant...

i have an aftermarket tstat and it stays open to long, when i am on the freeway in near zero weather i can tell when it opens b/c my heat stops.... then comes back about a half mile down the road. btw how hot is the engine really running? see if you can get a laser temp gun on it

[H8tred]

I have the same issue. I myself am leaning towards my fan clutch. I'm pretty sure mine is bad, and the fan runs all the time. I have the stock 92 Ka24de with 121k miles on the clock. I'm not going to fuss with the clutch though, I intend to put an electric fan in there as soon as funds and time permits. Either way, something else for you to look into. Keep us updated on your findings, and good luck.

[lbrowne]

What does the fan clutch have to do with it? The fan is for cooling not heating....or are you saying the fan stays on all the time not allowing the car to heat up? I thought the fan on the ka24e always stayed on anyways?

I was beginning to think the clutch must have something to do with the waterpump but noone elaborated earlier when I asked.

Either way I'm getting some good info here guys, thanks a bunch!

[H8tred]

What does the fan clutch have to do with it? The fan is for cooling not heating....or are you saying the fan stays on all the time not allowing the car to heat up? I thought the fan on the ka24e always stayed on anyways?

People say that it's worthless at speeds above 25mph. If it was supposed to stay on all the time, it wouldn't have the clutch at all.Another clue that it's staying on at all times is there are cracks between the blades. Nothing serious, but a good sign that there is more stress than there should be.I think it would be enough to keep the engine on the low end of the inaccurate reading in colder weather. As someone above stated, the only real way to know would be to get a more accurate temp gauge, which would be a marginal improvement at best, or use a infrared temperature gun.

Someone chime in and correct me if I'm wrong, but if memory serves me right, normal temps for us should be between 70f and 120f. That's to say that an electric fan controller would cut on at around 120ish, maybe 115, and cut off at 70. Either way, this isn't a set in stone solution to your problem, but what I have deduced my issue to be.

[Defiant]

Okay, a few things.A thermostat doesn't cool an engine, the radiator does. The thermostat regulates the flow of coolant to keep an engine's temperature up.When the thermostat was failing to close by 1/16 of an inch, it wouldn't heat up my 200SX Turbo in our grisly 45°F winters down here. I don't even want to think about the icy hell of northern Canada. But if that new thermostat is leaking in the slightest, you'd have cold engine issues.However, what I think you should check for is that the heat control door is moving through its full range. Datsuns (and, most foreign cars) used to regulate their heaters by means of a water valve. Ask a mechanic about replacing the one on a 240Z. Best to duck after asking, as things may be thrown.In the eighties, even Datsun realized it was a much better scheme to regulate heating with a door between outside, ambient and cabin air, and let the driver (or, climate control) open the flap to steer the air. This did away with the irritating delay you used to have when you opened the water valve and waited for it to heat up the cold heater core, and then for the next fifteen miles argued with it being too hot/too cold/too hot/etc.So, easy things first: make sure the control cable's not slipped, not off the flapper control, that the flapper lever isn't bent, and that a rodent's nest hasn't bound up its path of travel. Also make sure the cable's not come adrift from the control lever or knob.As for a stuck fan clutch, a correctly-functioning thermostat should make up for that attempt at over-cooling. You may suffer some mileage penalty from the extra load, and you'll have to turn up the stereo to make up for the hideous wind roar. And some more wear and tear on the waterpump.

[lbrowne]

The drive home from work, which is about 25 km, with the controls on recirc it gets hot enough i can open the windows. If I switch to regular the temps immediately start to cool off to luke warm air.

Maybe it is the blend door...somehow. I don't even want to know how to check that.

[Defiant]

Eh, you just stick your snoot down there and listen while you cycle the controls, and look for the arms to move. Feel for any binding, or any movement that's too loose.

[H8tred]

Mine gets hot after about 15 to 20 miles, but at idle gets cool again. I normally don't turn on my heat unless it's raining, or below 45F outside... For those first miles, if I allow it to idle about 10-15 minutes, I can get fairly warm air by leaving the fan on 1 or 2, but that does nothing when it's like 28ish outside. Like I said, his may differ, but I'm fairly certain that my problem lies in my mechanical fan...

[lbrowne]

Right after this thread the weather got warmer - and my heater was working great. (not hot out, but warmer than the minus -30 temps)

Everything was fine and dandy, and now we're into another cold snap - it appears the luke warm heat comes when its at least -20. If its warmer than that it gets hot enough I have to shut the heater off.

The previous owner had a sheet of cardboard in front of the radiator...wonder if this is why?

[180fan]

Probably. The heater is getting it's heat from the coolant that's running through the system. If the weather is seriously cold like anything - you've listed, the engine's gonna have a hard time keeping warm, aka you'll be cold as hell in your cabin.

[lbrowne]

It must be a KA thing then, or maybe just mine - because the 93 Explorer does just fine. It got to -39 Celcius last night when I was going to hockey.

[H8tred]

I don't know. I would think that a 2.4 wouldn't have any problem getting and staying in the operating temperature range. It could only be a handful of issues that would cause it. Low coolant, thermostat stuck open, clogged heater core, and/or the fan staying on at all times obviously increasing in rpm with the engine.

I realize the fan seems odd, but if it only gets warm after you have surpassed the wind speed at which the fan actually pushes air, and it is running all the time, it seems logical.

I haven't looked into it any further, all I did was check the radiator hoses, and have a look at the fan. It could be my thermostat, but I doubt it. In my opinion, it would take a longer time to get warm than it currently does.

I guess the best bet would be to flush the cooling system, and use some sort of cleaner in it. Then inspect the other areas of the cooling system mostly the fan, waterpump, and thermostat.