1999 QX4 No heat Flush Help

[PROVISIONCOLOR]

Hello everyone! I have read a ton of posts here about my heating issue with my good old QX4. I get no heat from the vents. I have decided to try flushing the heater core as many here have recommended but I wanted to make sure I was doing it right. So I have a few questions for you.

1. Do I just unhook the hoses leading to the heater (through the firewall) and put a garden hose up to one of the hoses and let the water run?
2. A few people mentioned that I don't need to worry about draining the coolant because the hoses are at the top of the system so I won't loose any, is that true? Or do I need to drain the coolant?
3. After I've flushed the water through in hopes of getting any air pockets out, do I just reconnect the hoses and that's it? Does the water in the core matter?
4. Anything else to do before I turn the engine on and hope to get hot air blowing?

Here's a picture of what I THINK are the heater hoses, if someone could take a look and let me know if those are the right ones, that would be great. I would REALLY hate to send water into something I wasn't supposed to!

Thanks a ton!
PVC

[Towncivilian]

Those are the heater hoses, yes.

I believe you can stick a garden hose through one, then the other to thoroughly flush the core. You shouldn't need to drain the coolant, and you'll only lose a small amount (whatever's in the hoses). Ideally you would use distilled water to flush it somehow since tap water contains impurities, but I don't think this would matter given it's just the small amount being introduced to the system through the heater core's capacity. If you can, use an air compressor to blow out as much water as you can (obviously don't set the pressure ridiculously high). Top off as required with distilled water. As far as I know, you don't need to do anything prior or after the core flush. I've never done this, YMMV.

You should also inspect your radiator cap. Examine this TSB for details.

[Chuck Tribolet]

I'd be looking for a problem other than water circulation through the heater core. If the heater core is corked up, so is the radiator.

And if you have a radiator cap problem, you'll be loosing coolant into the catch tank.

You will need to drain the coolant, otherwise it will all end up in the driveway. But use a clean bucket and you can put it back.

[PROVISIONCOLOR]

Hmmm. Okay. Thank you both. Sounds like some conflicting opinions. What I'm reading in some other posts is that there may be a possibility of an air bubble in the core and that running water through it would fix that problem. Does that sound correct?

[ARKQX33V6]

Engine gets hot radiator gets hot as well as coolant.
Your cabin temperature for heat takes what you allow through the heat control.
Hot engine, variable cabin room temp as you modulate the required temperature.
If your engine is too hot or too cold the temp gauge will indicate
The cabin temp needs the engine temp but the heat exchanger in the cabin can only get heat from the engine.

As Chuck has said, if engine heat problems so cabin heat problems.

Where to look.
Feel the input line of the cabin heat exchanger, feel the output lines. If both are hot the same temperature, the exchanger is likely OK, but if in is hot and out is not a problem if heat is demanded.

Check the air flow controls, vent to feet to windows, as you move the control does major air circulation move, try it with cold air, then try with heated air at high flow.

If no heat the valve or the controls that regulate cabin temp is faulty.

Verify controls, verify heat no heat.

With answers return with your results

Do not disassemble anything, but do your diagnostics first.

A vent or primary heat control is likely but if you have never changed the coolant that complete system could be now complaining. By the way flushing the system with soft, distilled water is a total waste of money because as a DIY you do not have the pumps nor the quantity of distilled water. Use a garden hose, flush out while checking for blockages, crud etc, then install only distilled water test your rad heater and run at temperature for a 1/2 hour, let cool dump everything then install new anti freeze at a 50/50 with distilled water and be sure to use long life, stuff, aluminum compatible and no silicates .

If you can test the rad while at temp with an IR gauge all the better, looking for hot and cooler spots on the complete radiator surface, then spot check the cabin heat exchanger.

All this will keep you clean and clear for 5 years, but if neglected the rad is possibly plugged and the cabin heat exchanger could be also. If that is the case a chemical wash is needed.

[yeldogt]

First ........ you need to look into the operation of the system. You have the Auto Climate Control system ...correct?

Do the hose get hot? What is the maintenance of the system? Does any heat come out?


I don't know it the heater core on the ACC system cars is hot all the time and then controlled by flaps or if it has a water control valve like most auto systems have.. If it has a valve then that is what I would look into.


If you are getting weak heat then a clogged core may be an issue -- if the system has had regular maintenance then the core should be fine.

I would do some research prior to flushing anything ---- also, if the core is indeed clogged -- you have other problems and the whole system should be done and then properly filled with the correct coolant and distilled water.

[PROVISIONCOLOR]

Okay, thanks for the replies. Here's what I know.
I checked the temps on the hoses and one is hot and the other is only warm.
I was able to locate the Air Mix Door motor (using the service manual) and watch it move when I switch the temp from cold to hot, so it appears that is working ok.

I do have the auto-climate control system. When I push the temp all the way up (85 degrees) I get air that is barely warm, if at all. All the gates seem to be working when I cycle through the different settings (foot, vent, defrost, etc.).

I will look into a water control valve and see if that may be the issue.

Some of the other posts have mentioned that there could be an air bubble in the core when these same symptoms occur. Does that make sense to you guys?

Thanks for all your help!!

[yeldogt]

Have you done any maintenance to the system recently?

If you have ---- look over the service manuals available here on the forum --- check how to properly fill the system. Basically you fill the system and let it run with the cap off and then topped it up. I think something else is up. How is the temperature of the engine.

The nissan engine is a bit strange since it has an internal water pump and the engine uses two thermostats --- although all of these are very reliable and very few have problems with them with proper maintenance to the coolant. I have never touched any of mine.

[PROVISIONCOLOR]

I did have the thermostat replaced last year because the service manual lead me to that conclusion. I guess we replaced only one of the thermostats though as I was not aware there were two. That didn't change anything however, I still wasn't getting anything more than just luke-warm air.

The engine temp runs just fine. It gets up to operating temp pretty quickly and then never really fluctuates. I have really had zero problems with this vehicle outside of the heat. I tell you, I'm an Infiniti fan for life.

I will look into the coolant level thing as well. Maybe it didn't get refilled properly (my wife's little brother did it for me and he's just learning, but still knows more than me! Ha!). I will check it. All the levels look full to me, but I'm a total novice.

I'm striking out on the water control valve. Can't seem to find any references to one in the service manual. Any ideas where it would be if there was one?

Thanks again!

[yeldogt]

Unfortunately -- both of the Pathfinders are at a different location -- so I can't go out and take a look. I don't know if the system has a valve -- some do and some don't --- so I don't want you to think you have one when maybe you don't. The cooling system has another thermostat in the back of the engine along the crossover tube between the two head of the V6 -- it is an unusual setup. Since I have never touched any part of mine I don't know what it looks like.

[PROVISIONCOLOR]

Alright folks, here's an update for you. I took it in and had the entire coolant system flushed, cleaned, and re-filled via vacuum (no air bubbles) and... voila! Heat! The technician measured the temperature of the heat coming out of the vents at about 105 degrees (f)! Needless to say, I was VERY pleased. This was Monday afternoon.

However...

Tuesday morning, I jumped in to head to work and... no heat. Back to the same old problem. Very confusing.

I actually ended up taking the vehicle into the Infiniti dealer that day for a separate recall issue and they informed me that they noticed coolant leaking from the area of the timing belt. Ugh.

So after chatting with some friends, it sounds like I need a new water pump. This was one of the possible solutions I had read about last year actually. Someone mentioned that if the water pump was failing, it may not have enough strength to push the coolant through the core. Who knows. It needs to be replaced and at this point I'm hoping for some miracle that it will fix the heater problem as well.

So, looks like I'm sending it in to have the timing belt and water pump replaced. Fun, huh?

Thanks for all your help. I will keep you posted. If you have any opinions on the water pump theory, I'd love to hear them!

[Towncivilian]

Depending on the mileage on the vehicle, you may be due for a timing belt anyway (unless you already had one done within the maintenance interval, then that sucks ). I believe it's common to replace the water pump during a timing belt job due to convenience. The coolant flush was unfortunately a waste of money, as the coolant will need to be drained obviously. Are you having the work done at a dealer?

[PROVISIONCOLOR]

Yeah, it's time for the timing belt to be done anyway. I'm about 125,000 miles, luckily. I'm a bit frustrated that I wasted the money on the coolant flush, but it's done now, right?

I'll have it done at my local mechanic. I only went to the dealer for the recall issue. They charge WAY too much for my blood...

[Towncivilian]

Yeah, sounds good. I'd suggest having your mechanic order an OEM water pump (and thermostat if that's going to be replaced) - after all, your presumably original one lasted about 12 years As for the timing belt and assorted hardware, I'm sure any name-brand kit will work fine (otherwise we'd have a lot more reports of snapped timing belts with brand x, etc).

[NocturnalQX4]

Where is the thermostat even located I'm having the same issues

[Towncivilian]

Where is the thermostat even located I'm having the same issues

See page LC-16.