grandmasterE

Living in Canada I know how important heat can be, and my 96 Runner doesn't dissapoint.

In my 91 pickup, the control cable for the heater temperature came out of it's end once, and it caused the same symptoms. If nothing is holding the housing of the control cable, moving the lever back and forth isn't really doing anything. With my pickup, I noticed that the temperature control lever was a little bit easier than normal to move back and forth, and that's what tipped me off that something was up with the cable.

Here's what I would suggest to trouble shoot your problem before you drop the $$$ for a new rad:

Check the rear heat. If it gets 'hot', then obviously you have good enough coolant temperature, you must just have a blockage/restriction in the coolant line to the front heater. My guess is the collant control valve isn't in the full open position. If you have no rear heat, then your coolant temp isn't quite up to snuff. Take your Runner into a rad shop and have them check out your rad. If you do have rear heat, the next step would be to figure out exactly why you're not getting enough coolant through your front heat exchanger. Did you get a visual of the control valve? Take the hoses to it off, and function it full open and full close. Is it working properly? If not, why not? Control cable end off? Vavle jammed/corroded?

I wouldn't rush out to drop the big bucks on a rad quite yet. Hopefully you can get this thing figured out.

MTL_4runner

I found this link which might be helpful to others overheating but mine seems to be the opposite situation:
http://www.troubleshooters.com/tprom...204/200204.htm

Anyone tried any cooling system cleaners like these?

"Prestone and Zerex sell liquids that are supposed to be much better
than their 10-minute cleaners. They come in quart jugs (not smaller)
and are meant to be kept in the cooling system for 6-8 hours of engine
run time (doesn't have to be continuous but can be spread out over a
week), and they'll even remove calcium deposits and solder bloom (only
brass radiators are soldered, and all factory radiators are aluminum
or plastic). Prestone's is called Super Radiator Cleaner, and while I
don't know what Zerex's is called, it Prestone implied that it may be
slightly better because it contains EDTA.

The strongest fairly safe cleaner may be oxalic acid, usually found in
powder form. You run the cooling system with nothing but water and a
cup of oxalic acid for 45 minutes, then drain and refill with water
and 2 oz of baking soda and run for 5 minutes to neutralize the acid.
I don't know where you can buy oxalic acid powder by itself, but
Prestone sells it as their Heavy Duty Cleaner.


I've heard of people using vinegar (acetic acid), lemon juice, or even
phosphoric acid to clean out cooling systems, but I don't know how
safe these are for the seals and gaskets, but with any cleaner you
have to watch out for bad leaks developing, especially around the
water pump shaft (don't use a strong cleaner unless you plan on
changing the pump). "

CynicX

can you run a hose through the radiator to see if its blocked or clear it out?.....

How many miles is on the rig? Might want to do the timing belt if you havent already and do the water pump at the same time. Most people do this anyway while replacing the timing belt so at least you could eliminate it as a problem. Even though I would think the engine would overheat with a faulty water pump obvisiously.....

MTL_4runner

I did the timing belt at about 90k and I am at like 140k now. I was thinking of just doing the waterpump anyway this spring but I get the feeling there are alot of deposits in the system (this relates back to my old confrontation I had between a service manager at a dealership in AZ, they drained my coolant after I refused to do the headgasket recall and I have a feeling they may have done some other "dirty stuff" too because very shortly after that I saw some serious rust appearing in my cooling system....not worth going into in detail, just sucks). Soon after that I flushed the entire system and thought that was the end of it. The heater was never and issue in AZ so I had no reason to ever suspect anything was wrong. After moving back to where I needed a heater, it is now an issue and I am trying to figure out what is going on and where the issue really lies without taking the entire system apart to find it.

MTL_4runner

I just cut out the center of the old thermostat (to remove the thermostat as a possible restriction) so I am going to try replacing the new one to see if I feel any effect on the heat moving through the radiator. With no thermostat in there the heat should be almost uniform (although perhaps not as hot) then I can see if there is a flow issue or not.

02SE

With no thermostat you will run cooler, not hotter.

The thermostats purpose, is to allow the engine to reach operating temperature, and to maintain operating temperature by regulating the coolant flow.

If you aren't getting sufficient heat now, it will be just be worse with no thermostat.

MTL_4runner

Hehehe, yes, I do know exactly what a thermostat does (no offense), but I don't think the issue is that I am actually running "too cold" (you can feel the top radiator hose is getting hot, while the lower is still cool).....I do think there may be a blockage in there which is artificially slowing heat transfer so opening up the thermostat and allowing the system to freeflow may create enough coolant movement to dislodge any cooling system deposits if they are there. The lack of heat transfer is just a symptom of the real issue.

I will test it again tonight and see if it makes any difference getting it out on the highway.

02SE

Well, I wasn't being condescending. Just trying to help.

MTL_4runner

Of course not.....and I appreciate all the help I can get.

MTL_4runner

Has anyone ever used CLR or another mild acid to flush their cooling system?

MTL_4runner

Can someone with a 3rd gen 3.4L in a cold climate (ie below freezing) check the bottom of their radiator and the lower radiator hose for me?
I wanted to see if the engine ever gets hot enough to warm up that hose or if it stays cool most of the time.
I drove mine on the highway quite a bit this morning and I still didn't feel it getting warm at all.

BADLNDS

I'll check for you MTL_4runner...I am on my way home (and its pretty cold in Montreal today).

I'll let you know tomorrow morning if it was hot or not.

-B

MTL_4runner

Cool, thanks!

It seems like the heat in the cabin actually came back quite a bit after the thermostat (it was hard to tell before because temps were well above freezing but now we are back into the 10s now and heat is decent) but the bottom hose is still staying quite cool. I still think it could do better (since it is still not hot enough to need to disrobe or anything) so I will try removing the tranny cooler to see if that may add heat back to the system. I will also be flushing the system with those radiator flush additives (I may have to try a few before I find one that really works unless someone can share their experience on these) come spring.

marreque

dont waste your time with the tranny cooler idea. if that lower hose is cool you have a blockage. and i think you can rule the t-stat out of the equation.

BADLNDS

okay...i checked both the 2 small hoses at the bottom of radiator and the large one in back.

-large hose: was cold
-2 small hoses underneath: warm to the touch (not hot) i could keep my hand on them and they were just warm.

Hope this helps.
-B

MTL_4runner

That helps a ton, thanks!!!
So coolant hose should be cold and the tranny lines should be warm (makes sense).

So it sounds like mine is coming back into the normal range finally. There may still be some rust deposits in there preventing optomum heat transfer, but overall I should be pointed in the right direction. I'll keep posting if I get any more improvements.

grandmasterE

Do you have good rear heat?

I think you might be completely missing the problem here. With the symptoms you're suggesting there's a good chance your coolant control valve for your front heater isn't working properly.

MTL_4runner

Yep, heat in back was not amazing, but it worked much better than the front.
The heater control valve had a garden hose run though it already.....no blockages or partial opening that I could see.

SLC97SR5

Jamie, good luck on this. I'm interested to hear your experience with the coolant cleaners. Could be the new SeaFoam!! Have you pulled the petcock on the bottom of the radiator? They rarely get used and will usually be plugged with the deposits on the inside so much that although the drain is removed the layers hold the coolant in. You could break this up and try to look inside your radiator for further blockage. *This is for everyone...always use your heat in the summer to cycle coolant through the core and heater hoses to help limit corrosion.*

farmerj

Just a thought,

Look into your waterpump. Saw this one other time and it drove us batty.

When we finally pulled the pump, the vanes were almost gone, effectively making the pump useless.