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No heat - Thermostat or Hose Assembly Inlet?

14K views 79 replies 10 participants last post by  spta97 
#1 ·
I have a 2007 Armada;140k miles. The heat is not blowing hot air.

I did some research on the forum and originally thought it could be the common hose assembly inlet valve (plastic gear breaks). However, after getting the truck up to operating temp, both hoses on the inlet and outlet side were roughy the same luke-warm temp.

It got me thinking perhaps the thermostat is stuck open not allowing the coolant to get hot enough. I also noticed there was no coolant in the overflow tank (I do not see any leaks).

The temperature gauge reads normal and I have no other HVAC issues other than the no heat.

Thoughts? Should I try topping off with coolant? Bleeding air? Replacing thermostat? Anything else?
 
#2 ·
Unhook the heater valve from the firewall then open it take the top two gears out and take a flat head and turn the valve to straight up and down. You will have heat then. Buy a piece of fuel line hose for a push mower engine cut a piece about 2/8’s and put on the white gear at the bottom that gear likely slid up out of position very very common


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#8 ·
"not allowing the coolant to get hot enough"

I have an inexpensive bluetooth BAFX OBDI dongle that pairs with my Android phone. It doesn't do everything, but it does read coolant temp. Mine runs around 190 F after warming up. I just replaced everything (2004 with 132K miles): thermostat, radiator, water pump (the oem water pump gasket was leaking), radiator cap, reservoir cap, fan clutch, upper and lower hoses, serpentine belt, pressure tested and refilled with Uview Airlift (no trapped air).

"there was no coolant in the overflow tank"

Check very carefully for leaks with a bright light. Look for coolant spray and deposits around hose connections, the water pump and on the radiator. I think some of them can be intermittent and only happen under very specific conditions: Hot day, A/C running, idling in heavy traffic. Then air eventually gets in and turns the aluminum radiator into a flash boiler. (which is when I noticed the problem).
 
#9 ·
It could be your vent door actuator which is a common problem. Have you had any clicking sounds under the dash? Is your AC working as it should? When you move the hot and cold wheel is it working as it should? When you move the vent selector, is it working as it should? There are many videos and other threads on this issue.
 
#12 ·
I had looked into the blend door but I don’t hear any unusual clicking under the dash (I recall hearing some movement noise though). My AC works great and all the vents operate as they should. The only issue is the heat comes out cold or not so hot.

I’ll see if I can get my hand up there to feel if anything is broken without taking the dash completely apart.

Interestingly, in auto mode the fan stays at low until the truck is warmed up so I guess the function is reading the temp from elsewhere.
 
#13 ·
Any progress on this yet? I replaced the control valve earlier this year while it was warm out but the wife says it's still luke warm at best... I don't have the clicking and I can hear the difference in the air when the knob is turned .... I'll be replacing the cap, thermostat (Nissan parts, not stant crap) and drive belt this weekend to see if that's an issue... coolant is full in the radiator and about half way full in the overflow.... so no clue what is going on... I tried the 'raise the front end' deal to burp it and managed to spit coolant out of the radiator sooooo... then I leveled it out checked coolant and all was well after I put a little bit back in.... I'll keep going after the problems but pretty sure it's not in the cab unless the heater core is going.... I'm probably going to buy one of those little heat reading guns too just to ensure the hoses are really getting hot, I have another thread on here with the part #'s .. one is a Gates that I got off Amazon, https://www.amazon.com/Gates-23797-...440------------&vehicleName=2010+Nissan+Titan

Gates 23797 ... I think Rock Auto was out of stock when I ordered it from Amazon....

Hope this helps when people want to replace those... And I'll tell you now.. go get the hose clamp pliers from Auto zone or O'Reillys... they will save you a lot of headache...
 
#14 ·
Any progress on this yet? I replaced the control valve earlier this year while it was warm out but the wife says it's still luke warm at best... I don't have the clicking and I can hear the difference in the air when the knob is turned .... I'll be replacing the cap, thermostat (Nissan parts, not stant crap) and drive belt this weekend to see if that's an issue... coolant is full in the radiator and about half way full in the overflow.... so no clue what is going on... I tried the 'raise the front end' deal to burp it and managed to spit coolant out of the radiator sooooo... then I leveled it out checked coolant and all was well after I put a little bit back in.... I'll keep going after the problems but pretty sure it's not in the cab unless the heater core is going.... I'm probably going to buy one of those little heat reading guns too just to ensure the hoses are really getting hot, I have another thread on here with the part #'s .. one is a Gates that I got off Amazon, https://www.amazon.com/Gates-23797-Coolant-Hose/dp/B009HL6GCY/ref=sr_1_3?crid=1UWN3RAD8XT4V&keywords=2010+nissan+titan+heater+control+valve&qid=1570566985&replacementKeywords=heater+control+valve&sprefix=2010+nissan+titan+heater+contro,aps,336&sr=8-3&vehicle=2010-67-2440------------&vehicleName=2010+Nissan+Titan

Gates 23797 ... I think Rock Auto was out of stock when I ordered it from Amazon....

Hope this helps when people want to replace those... And I'll tell you now.. go get the hose clamp pliers from Auto zone or O'Reillys... they will save you a lot of headache...
Not yet as I leave early for work and get home late so it will likely be this weekend.

My overflow tank is empty so my first task is to get the Nissan coolant and top things off. Then I have to look for a leak if that fixes the issue (perhaps get the dye).

If not I’ll replace the thermostat. I am also going to look at the valve mentioned to see if it is broken.

I recall thermostats can lock open or lock shut. In the case of the former, the fluid is never captured in the engine so it doesn’t get hot enough to produce heat. I’m wondering if that is the case with yours (and mine).

As I’ve got 140k, I’m tempted to replace it anyway. I should probably do the fluid change since I never have, but often I’ve found it causes more problems.

Thanks for the link, I’ll check out your thread as well.
 
#15 · (Edited)
Yeah.... I'm going to get this all sorted out this weekend and I'll post up some pics if I can.... I think my 2010 Titan has about 125K on it now... the wife wanted it instead of her craptastic Impala, which we traded in on our 19 XD Cummins Pro4X..... and the heat is sort of an issue up here in northern Utah on some days.. LOL...

Most of the time, the leak is on the bottom of the radiator because of the plastic trying to mate to the metal bottomside of the radiator..... I'll be dropping the skidplate to check mine this weekend... Which reminds me, check to see if all your bolts are there if you have a skidplate... stupid people at the oil changing place the wife took it to (jiffylube I think) lost one of the bolts so it has 3 now.... 6mm I think was the size....

If you are going to swap the thermostat go to the dealer or use Tasca, https://www.tascaparts.com/auto-par...oling-system-cat/radiator-and-components-scat , to order the cap and thermostat at the very least... that link is for my 2010 but you get the jist ....I've heard way too many horro stories about the stant stuff sold through Auto Zone and O'Reillies and those type stores....

As far as a fluid change... just don't do a power flush.... I'd just drain it and add back in.. like the transmission deal... just time consuming i would think... I had that done way back in 2014 to the orange coolant because I worked in North Dakota... it might be time for me to do it again....We shall see but it looks fine right now...
 
#16 ·
Last night I popped off the radiator cap and inspected the inside of the radiator as well as looked for leaks. The fluid had a “mean green” (i.e., new) look to it as we used to say when we were teens and had time lol. bit It did appear low as it wasn’t right at the top and as stated the overflow is below the min. The only thing I can think is there must be a leak. I am going to get the antifreeze at the dealer ($5 cheaper than amazon surprisingly) as well as an OEM thermostat (I agree with you on aftermarket).

My plan is to fill it up first but I’m curious if I should fill via the radiator or overflow tank. At that point I’ll check for leaks and take it from there.

So you have a confirmed leak? What do you mean the plastic/metal mating? Are you referencing the radiator drain plug? I noticed on my skid plate (engine side) from the top I saw what looked like evidence of residue which could line up with the drain plug but I didn’t have time to dig deeper at that time. I think I’ll get the drain plug as welll.

One other idea, on the Armada forum many had complained about the spring hose clamps and replaced them with screw band clamps as the spring ones were prone to leaking (some had the transmission cooler line leak). Might be a good idea but get stainless steel. I love those things - they last forever.

I’ll post back as well once o get a chance to work on it this weekend.
 
#17 ·
You can fill it via the overflow, just make sure that the radiator is at least full to the bottom of the neck where you take the cap off. From what I understand, the radiator has a plastic type bottom piece where it's prone to leak from where it mates to the bottom of the radiator. If mine is leaking from that spot, I'll probably order a new all aluminum radiator.... Check to see if your drain plug is tight, if it is, you should be fine... reason many people complain about those clamps is because they don't have the right tool to take them off and try to use pliers and end up messing them up.... I like worm drive clamps too but sometimes its a pain to get a screwdriver, wrench or rachet to them and i have pretty big hands.... the spring clamp tool I'm talking about is flexible to a point... you'll see what I mean if you get one... it came in very handy.....

I hope it warms up a bit here in Utah... low 20's is not the ideal environment to be trying to swap out parts... LOL...
 
#18 ·
Ah yes. I’m in denial it can be a radiator crack. I’m really hoping it is not :). One trick I saw on YouTube was to spray with WD40 to help slide the clamp. I’ll have to check out that tool you referenced.

I hopefully will know more this weekend. My work day is 13 hours with commutimg so no time during the week.
 
#20 ·
#21 ·
"the spring hose clamps"

The theory is that they maintain dynamic clamping tension through many thermal cycles. Until they don't. Then they leak.

"replaced them with screw band clamps"

Some of the coolant hose clamps are difficult to reach. Like the heater hose clamps against the firewall and the hose clamp low down toward the back of the block on the driver side.

"some had the transmission cooler line leak"

I'm on the second attempt with those. I used screw type injector clamps the first time, but they eventually started seeping. This time, I removed all the short hard lines, used Gates transmission hose and doubled clamped with single ear stepless stainless steel crimp on clamps (supposed to withstand thermal cycles), except for the lower connection on the oem atf cooler, which I couldn't reach with crimp pliers. So now there's only six clamped connections: hard lines from tranny that end under the front of the engine, oem atf cooler, aftermarket atf cooler.
 
#22 ·
Yes.. That second one is really close to what I have... you'll need that flexability when you try to get to the back clamp between the firewall and the intake... this is only for when you replace that water valve assembly... I went that route first because everything else seemed good... now I'll be swapping the thermostat and cap.. see if anything happens.. then on to the overflow cap... until I get some heat... I may pop the cover off the valve and see if its still working too...
 
#23 ·
I am now experiencing the no heat issue. I opened the valve co we and turned it with a flat head so I have heat. My white gear was not out of place and my + gear at the top is not broken so I am at a loss for why it’s not working except for internal electrical issue. I’ll have to test the plug for current but I had turned the valve the wrong way and put it back together only to get a hard clicking sound when I shut the truck off so I am pretty positive it is working to some degree. Any idea what else could be causing it both hoses are hot once I corrected the valve opening


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#27 ·
I was having the no heat problem last year and also noticed, like you said, I had no coolant in the overflow tank.

I could not find a leak.

I bypassed the flow valve and that did not help. However, I noticed again that I still had to add coolant to the overflow tank.

I looked all over for the leak. Could not find it. Then one day, while I was doing something else under the hood and had the engine running and the truck up to full temp, I had some wet nead the overflow tank.

I found that the little nipple that the overflow hose connects to had a crack in it. It was not large enough to be noticable and nothing came out when the truck was off and/or cool.

Seems the overflow tank is part of the pressurized cooling system - that is why it has a pressure cap on it and the radiator does not. When the truck was fully warmed up and the cooling system had pressure, that is when it leaked. It leaked slow enough that the truck did not overheat but, there was not enough coolant in the system to send any through the heater hoses.

I replaced the overflow tank with a new one and my heater has worked correctly ever since - I even removed my valve bypass.
 
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#28 ·
I was having the no heat problem last year and also noticed, like you said, I had no coolant in the overflow tank.

I could not find a leak.

I bypassed the flow valve and that did not help. However, I noticed again that I still had to add coolant to the overflow tank.

I looked all over for the leak. Could not find it. Then one day, while I was doing something else under the hood and had the engine running and the truck up to full temp, I had some wet nead the overflow tank.

I found that the little nipple that the overflow hose connects to had a crack in it. It was not large enough to be noticable and nothing came out when the truck was off and/or cool.

Seems the overflow tank is part of the pressurized cooling system - that is why it has a pressure cap on it and the radiator does not. When the truck was fully warmed up and the cooling system had pressure, that is when it leaked. It leaked slow enough that the truck did not overheat but, there was not enough coolant in the system to send any through the heater hoses.

I replaced the overflow tank with a new one and my heater has worked correctly ever since - I even removed my valve bypass.
Thanks for the idea - I will check that as well!
 
#30 ·
It does not have a vacuum when it is running ... it is under pressure

When it cools down a bit, it can pull a vacuum when it is low on coolant since the hose was covering the crack. When it was hot it could push the coolant out but when it cooled it did not leak
 
#32 ·
Hmmmmmm.... I may have to check the overflow tomorrow when I start pulling it apart for the thermostat.... I think when I pick up my 19 from getting its radiator replaced, under warranty, I'll pick up the overflow cap as well... just to be safe... I have a new nissan cap for the radiator soooo... lol
 
#33 ·
Well I'm back from the dealer for parts. They only had the antifreeze so I ordered the thermostat from Amazon. I also got a new radiator cap for the hell of it.

Tonight I am going to fill with antifreeze and check for leaks. If it is leaking, I will address it when I get the thermostat and do a flush at that point.

I will report back results later.
 
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