Hi

I bought 2003 montero sport es 3.0L which has overheating problem. Replaced thermostat with fail safe. Flushed cooling system. It seemed as it was working when I was flushing it ( heater was blowing hot in cabin ) since I filled it up with coolant heater does not blow in cabin and engine overheats realy bad. I had it tested at pepboys and engine block is fine. They said that thermostat does not open. There are no leaks from water pump. Radiator looks brand new, hoses are fine. Both hoses to the heater core are hot. I had it burped and bled. The only thing I can think of is water pump but not sure since there are no leaks from water pump area.
Could clogged heater core cause that ? My friend sugested bypassing heater core. Please help - I have 3 kids and need the car working.
How do I test radiator? Noone seems to tell me what is wrong with it. I spent already over 100$ for mechanics to tell me " it might be the pump "
I was thinking about taking the whole cooling system apart but than I have no clue what to look for. Any ideas ?

 

First off, welcome to the forums!

Let's see if we can't cool off your ride; it's hot enough driving around with a bunch of kids in back, IMHO.

First off, you can tell if the thermostat is opening because you can feel an increase in pressure in the upper hose once it does. It might be hot so you may want gloves, but if the engine's warmed up you should be able to feel an increase in pressure in that upper hose. If not, then maybe your thermostat isn't opening and needs replacing.

You said it was burped and bled. By whom? And are you rock solid certain bet your life on it sure that this is so, because your problem sounds exactly like a big old air bubble in there. Would that it be something so simple, huh?

But if you're sure it isn't, then we'll have to look elsewhere. There is a bleed nut on top of the thermostat housing. It may behoove you if there is any doubt in your mind to slowly loosen this nut and see if any air escapes before any coolant does. It wouldn't be the first time in the History of Man that a shop had neglected the obvious.

Question time: How many miles? How long have you had it? Did you buy it knowing it had this overheating problem? If so, what were you told about it? Are there any other issues with it that could possible be related? What does "replaced thermostat with fail safe" mean, exactly? The old film with Henry Fonda? I thought of this one: Is it actually overheating of is this just something the dial on the dashboard is telling you? Does your fan engage as your engine heats up? Are your belts at their proper tension? Have you checked your radiator cap for proper sealing; if it leaks, the coolant will "boil" sooner at a lower temperature. Sorry, but like a doctor, I've got to cover the patient's history and I don't ever mean to insult you by asking things which you may feel are obvious...

You could have an air bubble in your heater core from what you're describing. I know of no easy way to access the core, as the manual indicates removing the console and instrument panel to gain access to it. There are 2 small coolant hoses which attach to the rear of the throttle body in the engine compartment; it might be possible to remove these and attempt to flush the core from there, although I've never done this.

Maybe someone in the peanut gallery who owns a similar model will have something more to add which can help.

Keep us posted....

 

Thanx for reply. It all makes sense. Anyways I replaced radiator today since somewhere in the process of asking different mechanics one of them mentioned that there is little wet spot at the bottom of the radiator. When car idles it jumps to 75% on gage and now after replacing radiator it drops down to half ( very good sign )
As to pressure in the upper hose - YES - the hose has a lot of pressure when hot. The lover hose is just slightly warm. I am almost certain that there is air in heater core - I was thinking of bypassing heater core since we live in Texas and don't really need it untill winter. I ran the car with radiator cap off and all bunch of bubbles came out than coolant shot out. The only thing coming out of the bleeder hole is coolant. I know what you talking about because before I replaced radiator it would bubble a lot.
I'm gonna take it for test drive later tonight to see if it made any difference. I was told that if what I did so far : flushing system, replacing thermostat and hoses, replacing radiator the only thing left is water pump. I hope that is not the case.
I am guessing that it's really hard to get to that heater core and the only way is from the inside through the dash.
I will keep you posted and once again thanx for help !
Mike

 

Oh yeah - I bought the car 5 days ago. I was told that it runs little hot but that all it is just thermostat. The guy I bought it from running a scam but I found out about it after I bought the car. I was told by the seller that mass air flow sensor needs to be replaced because rpm's are high with a/c on and thermostat needs to be replaced.
I'm sure I left something out - can't think straight - spent whole day trying to figer it out. Sorry for mistakes - english is not my first language.

 

That's OK, Lakomy. I'm gonna call the lower hose the lover hose from now on!

Yeah, sometimes a new radiator can work wonders. I wonder, though, if you know if the vehicle had been sitting a long time without being driven? That's when gunk in the system can settle down for a long Winter's nap and end up plugging up the works.

Well it sounds like you know what you're doing. I hope for your sake that you come back here with some good news, because both a new water pump and cleaning the heater core are both PITA jobs considering everything you've got to remove just to get to the good stuff.

Keep us posted, Amigo...

 

Hi I have been struggling with my 2003 Montero sports heating problem for a while now too and has been spending a lot to try and fix the problem. It overheats when it is idling during the day. To bring back the temperature gauge needle back down I have to give it a constant rev'. I have flushed the radiator, change the fan clutch, removed the thermostat, change the water pump recently and I am still having the problem. Any ideas?

 

Lakomy, I had the same issues a while back. What fixed it for me was fan clutch. Just adding to the list of things to consider.
Good luck.

 

Hi, I did change that as well but the problem persist