Ouch. Not the outcome I wanted to hear. Glad you have heat though.

I have similar temps to what HunterD recorded, but my lower radiator hose is showing about 75F. Also, I'm only seeing a 10 degree differential on the heater hoses at the firewall.

My latest observation is that if I don't turn on the front blower, and leave the fresh air vent open, I actually get good heat from the front vents. Laser thermometer was reading 120F when I was parked in the driveway and had the fan blowing, but the air felt cold.

I'm going to put a T-valve in the bottom heater hoses going to the rear and flush / back-flush from there. The rear heater is still ice cold.

 

My montero is back to no heat... I had a big debacle where the timing belt tensioner went back and the car was out of town so I took it to a shop and I think they ended up bending the valves, so now it has new heads, etc... so... they didn't burp the cooling system good and now it doesn't have heat again. The last time I did this, I ended uptaking the rear heater out of the system. Now the ports from the engine go directly to the front core, so theoretically, it should be mush easier to burp, My next step is to put put something like this in the top heater hose and bleed it from there.

 

jstecz, won't the two bleeder screws near the thermostat accomplish the same thing as what you are adding?

When decent weather arrives, I'm going to tackle the rear heater core. I had to order a replacement from China, since I could not locate one anywhere else. Also, when replacing the front heater core, I wanted to have a replacement blend door actuator handy, just in case. I was not able to locate a new one anywhere. I spent a lot of time online and calling Mitsu dealers, but the actuator does not seem to exist. I hope that's not anybody's issue. One more setback and I'm selling the Montero for something that has a better part supply chain.

 

The hoses going from the engine to the heater have to go down to the bottom of the engine and then back up to the heater core, that gives the opportunity for air to get trapped in the core. Also, the coolant is not forces through the heater pipes, that is, you can block off the heater hoses and then engine will still cool normally. So, I want to put a bleeder at the heater cores to allow the air in the core and the pipes that go down to the engine to get cleared of air.

That's the idea at least. We'll see if it works.

 

I finally have heat again from both heater cores.

I had to flush each core individually from under the car. I tried putting a T-valve in the inlet hose and flushing the cores, but in hindsight it did nothing. What worked was disconnecting both the inlet and outlet hoses going to the hard lines that go to the heater core under the car. I did one heater core at a time. Using clear vinyl hoses and my garden hose, I flushed each core multiple times in both directions until I could get it as clear as possible. The first flush to the front car was really, really, bad. I could reach my hand into the bottom of the bucket and get a handful of crap out.

I didn't do anything special to refill the system with coolant. I opened the 2 air bleed valves and filled the system as normal. I keep checking the reserve tank thinking I would need to top it off, but so far I haven't needed to.

Too bad our daytime temps are in the 80's now. But I'll be ready come fall.

 

I am curious to find out if anyone else has had any luck getting their heat back to normal. I have a 2003 Montero and I have had the system flushed and backflushed multiple times now and still very little heat. Mechanics are scratching their heads - I can do the heater core if it comes to that, but I want to be sure that is the problem before going that route.

 

I know this thread is 6 years old but I have the time to try to revive it! Lol

I have a 2003 Montero Limited 3.8L that I bought and the heater settings blow air in all the right places and without clicking or noises, but the air in the front and back doesn't get hot. The A/C works fine in all settings.

Is there any sort of coolant valve that reatricts/allows coolant to flow through the heater core? How about a door that retricts air from blowing through the heater core? I want to rule these out first.

I want to narrow this down to a dirty heater core needing flush, or perhaps a very bad air gap in the heater core (unlikely). I can't find if there is anything like the above mentioned control functions of the Heater operation. Do you know?

Also, when you flushed your core, did you access it through the hoses on the bottom of the truck (exterior) passenger side? That looks to be the easiest. That's what I'm looking at. I'd like to be able to flush it, and then pump white vinegar thru it with 12 hour soaks, and repeat for 3 or 4 iterations over 3 days. But I'm scratching my head how to get the vinegar from the bottle into the heater core via a small hand or electric pump. Any ideas or good experiences with this?

Thanks!

 

wilde,
I had the radiator flushed twice and eventually there was good flow. Still very little heat. I pulled the dash apart to get to the front heater core and replaced it with a new core (it had been flushed a couple of times via access to hoses on outside of firewall. So now I had a new core and a radiator with great flow--but the hose temps (discussed earlier in the thread) were still insufficient to produce decent heat. The Montero I purchased had a lot of sand in the cargo area, so I decided to remove all the plastic panels and replace speakers, place sound insulation and replace the rear heater core at the same time. The Montero was quieter, the sound system was better and the rear heater core was new. I still had little heat and after $1200 of wasted time and money, I sold it. Got an '05 4Runner and had to replace the head gasket 500 miles later. Good luck. I still have a 'Word' document that I copied from an Australian site that walked me through the disassembly of the dash and console. It was real helpful. Let me know if you want it.

 

Yes. I would appreciate that. I'll message you my email. Thanks!

It makes no sense that both cores would be replaced but still no heat. I know some report air bubbles get trapped but I've never experienced that myself and I've opened and drained the coolant systems on my Limiteds several times over 10 years.

Did you come across any sort of air duct control part under the dash that would have allowed air to come out of all vents when temp was turned to hot, but not allow it to first flow through the heater core?

From what I understand on the Limiteds, the water always flows through the heater cores (no heater core control valve) but the air flow control I can't get a clear answer on. Thanks again!

 

20 or so years ago, a friend had a heating problem in his truck. I wasn't there when he tried this to help diagnose the problem.

Using adapters he inserted a temp gauge in the RETURN line. Don't recall what the final diagnosis was but this thread got me thinking.
Could one use an infrared thermometer to capture temps from the original setup and then slave a used/junkyard core in the engine compartment and check the temps?
Would this be enough to confirm where the problem is hiding?
Maybe avoid the Dash dive.

Just thinking out loud sorta...
jc