Finished rebuilding my 02 montero ls 3.5 and am having over heating issues again.

I bought it used about a year ago, and the person who sold it to me knew it had overheating issues so they removed the thermostat so it wouldn't overheat during test drive.
So needless to say i drove it home and it over heated and ended up warping the valves. I took it in and had the valves re machined about a year ago. I have been working on putting the engine back together over time.

I replaced a lot of stuff while i had the engine open. Like the timing belt, water pump, thermostat etc.

So I Just finished putting the 3.5 back together the engine was smoking a bit from around the oil cap which i shrugged it off thinking it was just older stuff burning off. I opend the oil cap to make sure it was slinging oil and it was.

However its still doing the over heating crap even though i replaced all of the cooling system.

This issue is what caused the valves to become warped before and i am worried it may do it again if i don't find the issue and fix it.

I am wondering about the temp gauge. It shows it as warmed up but never rises past the middle of the gauge. I am wondering why it is not working and showing it as over heating.

So what alerted me to the issue returning was driving it around the other day. It started to make boiling noise from the middle of the engine by where the water line goes through( i am hoping it was just the water line and not something in the engine internally), and the over flow was completely full to the point where it was above to start going out the over flow hose and the radiator was hot!

i replaced the water pump, thermostat, all of the o rings/gaskets, and OEM Mitsubishi radiator cap(which was outrageously expensive however i was told that if not an oem one it could cause over heating issues).

I am going to try and see if it is just air in the cooling system today however i bled it while filling.


Any ideas of what could cause the over heating issue?

Thanks all.

JP

 

Do you have heat coming thru the cab vents while at idle or only if you rev the rpm's? Mine had an air bubble in the system and it would make gurgling sloshing sounds like it was boiling. I found there is a bleed screw up top and was able to get mine fully purged and working properly (that is until it spun two rod bearings).

There are also known issues with the instrument cluster that causes the temperature gage to not read properly (search and you will find it). A resistor needs to be soldered.

Good luck!

 

Upon pressure testing it to check for leaks i found one of and hopefully the only issue.

It is the water coolant pipe. It is leaking from the very back of itself. It is a bad leak and causes pressure to drop drastically and fast. Unfortunately it is not just an o-ring on it .

It is magnetic so my friend said just take it out and he would run a weld bead over it for me. Another friend said to just pull one from a wrecked one the only issue i could see from that would be if it also leaked.

I am not sure i want to do that but I figure it couldn't hurt to try that first to save $ on buying the 100$ coolant pipe.

That was why I heard the bubbling coming from the middle of the engine.
I really hope this is the only leak issue, but will pressure test it again once I put the pipe back on.

If the gauge did not register it as over heating would that be caused from the leak and it just wasn't getting to it? Hopefully that's the issue with it.

Going to fix the pipe issue whether I get it welded, pull one, or buy it new. I will report back after doing that and running a new pressure test.

 

Keep us posted on your progress.

Attached are some pictures of the water pipe from my 3.5L engine.

I think (no guaranty) the part number might be MD324680. If you search that part number at the link below, it is $32.10. I have bought parts from them and have been very pleased. Eric in the parts department was very good to talk with and used the VIN to confirm parts would fit.

https://www.mitsubishiparts.com/oe_parts_catalog.html

The manual shows a "jiggle valve" on the thermostat and says it needs to be straight up. I assume this has something to do with removing air pockets in the system. Pictures of my thermostat are attached (no clue if mine is OEM or not. It is stamped "MotoRad" on one side and "Germany" on the other).