I went back and re-read your orignial post. Somehow I've misunderstood that you took readings from both heater core pipes and from the radiator hoses. If the system was bled properly, then it seems more and more likely that you have a plugged heater core. This is especially likely due to the fact that your main radiator was bad (plugged). You really down to two choices - replace the heater core, or do the acid flush of the cooling system. The problem with the flush is this - since you have low flow of coolant though the heater core, there is no guarantee that it will move enough coolant through there to make necessary reaction and to clear the blockage. On the other hand it it works, it will save you lots of $$ not having to tear out the dash and the heater core.

One question: did the shops that back flushed the heater core and later tested flow did so by disconnecting the hoses to it? My concern is the same as yours - the temp of the coolant going to the core is way too low. 130-140 is barely lukewarm. You should be getting full high temps there.

Looking at the diagrams of the hoses going to/from he heater core, I'm starting to wonder if you may have an obstruction in one of the smaller pipes in the engine compartment feeding the heater core? Take a look at the attached PDF. Perhaps it would be worth checking the pipes #12 and #15 for flow obstruction? Run it by your mechanic see what he thinks. This would be definitely worth checking if the heater core was tested independently from the system and flow was OK.

 

I was told they disconnected the hoses at the firewall when they did the back flush. If that's the case and the flow was acceptable, you might be right. The smaller water pipes might have an obstruction. After a dozen phone calls I located a small shop (with good reviews) and they said it would cost about $500 labor to replace the front heater core (I already have the replacement core). I'm inclined to let them replace it, but I would still like to be 90% certain that is the issue. I'll contact them this week and see what they say about the water pipes #12, #15, etc.

Thanks again for the advice and the file. Kind of surprised nobody else is posting on this topic.

 

I've been offline a while, and just saw your thread. Any updates?

I've been experiencing the same issue. A little history first ... the heat in my 2002 Limited was working great in July of this year. I had flushed the cooling system and burped all the air out of the front and rear heater cores myself, mostly due to ruptured heater hoses at both the throttle body, and under the car going to the rear heater core. These were probably due to an overheating condition.

In October, I took it to a local shop to have both heads and the radiator replaced. When I got it back, the Monty was running great, but the heater never got more than lukewarm. It gets down to the 30's here in my area, and on some mornings my hands get numb by the time I get to the office. At least the heated seats still work. I've taken it back to the shop, and they flushed the front heater core, but that was a very marginal improvement.

I've googled up and down and found nothing except possibly a disconnected cable linkage that seems to be a common issue on Pajeros. However, I don't think that issue applies to climate control. I looked under the driver's side console, and didn't see the cable linkage that was described.

After reading through your post, I might flush my cooling system and fill it myself, being careful to bleed all the air out of it to see if that works. I will update you if I do.

 

Ematulac,

Like you, I googled for a few hours and really didn't learn anything. Seems like a lot of information on overheating--but nothing on the coolant not heating enough. I made several phone calls and they all said basically the same thing--bad thermostat, inverted thermostat or air pocket. I'm fairly comfortable that those have been eliminated. One mechanic that builds engines says it sounds like the coolant is running backwards. I can't quite visualize that, though I'm not a mechanic. If the top radiator hose is hot, it seems that the water would be flowing correctly--into the top of the radiator. The water temp gauge gets to about the center mark after 15 minutes of driving--but the top radiator hose is only about 160-170 degrees and the lower hose is much cooler. I don't think the temp ever gets hot enough to open the thermostat (180 degree). Next week I am going to try one more time and take it to another shop. After the lower end rebuild, it runs real nice--just no heat. I also rely on the seat heaters--but my feet are freezing. Let me know what you find out and I'll do the same. Good luck.

 

The last repair shop thought the issue was the thermostat--since the aftermarket thermostat is different in length than the OEM. They put in the two-stage OEM thermostat, charged me $200 and, presto, I still have no heat. I wish there was a Mitsu dealer closer than 2+ hours away. They might be able to diagnose it. Most of the shops I've taken it say that the coolant flow seems to be reversed in the Montero from most other vehicles.

 

Since your Mitsu dealer is far away, you can try to call them and ask to talk to one of the mechanics who works with Monteros. Preferably the oldest guy out there. Ask him about this. I an in the same situation (over 1.5 hours to nearest Mitsu dealer) and had talked to the actual Mitsubishi mechanic about how to remove/replace certain components or to troubleshoot things.

 

I actually phoned 3 different Mitsubishi dealers--one in Oregon and two in Washington. They did not want to volunteer much information--they just encouraged me to make an appointment. Still trying to figure it out.

 

Bummer.

 

Can anybody enlighten me as to the flow direction for the coolant in a '05 Montero? I'm pretty sure that in all of the previous vehicles I've owned the hot water/coolant from the engine goes through the upper radiator hose and cooler, denser coolant flows from the bottom radiator hose back to the block. Several mechanics have commented that it is the reverse in the Montero with the hot water going into the bottom of the radiator and the cooler water exiting through the upper radiator hose. Can anybody check their Monty and let me know how theirs is flowing?

Thanks

 

I had the same issue (see the other thread with heat. I ended up disabling the rear heat and realized after all the flushing and burping I had done, not much coolant was flowing through the rear heater core. But now I had heat.

The symptoms before I did that were that I had hot water at the inlet and outlet of the heater core, but it wasn't really flowing through. Since I got rid of the Ts going to the rear core, I now have double the flow through the front heater core and the heater works fine. It also made it easier to burp now, so there isn't a bubble in the front core.

I know that not much coolant was flowing through the heater system because when I disconnected the rear core, I blew it out with my air compressor and the coolant that was still in the lines going to the rear was not the nice green flushed coolant that was flowing through the rest of the system, it was still old coolant.

I debating between fixing it correctly and getting the rear heat working, or going all the way and eliminating the long hard lines that go across the engine bay and having the lines from then engine connect directly to the front core.