Hi,
I have a 1994 4runner with the fabulous 3vze!
I have installed a rebuilt long block and have done the following:

Most hoses replaced
Waterpump replaced
Timing belt replaced
New oem thermostat (tested in boiling water)
Radiator cleaned and pressure tested at radiator shop
Engine has been timed correctly with light

So the problem is that after it runs for 10 minutes or so the temperature gauge goes all the way to hot and coolant blows through the radiator cap to the overflow bottle. The strange thing is that the top radiator hose is hot, the top of the radiator is hot but the bottom of the radiator and bottom hose is not hot its actually kind of cool. I removed the thermostat and tested it to make sure that it works and it does. I know the coolant makes it into the motor through the top radiator hose because I forgot tighten the coolant drain plugs when I transfered everything from the old block and found out when I went to fill it up with coolant.
I am stumped, do I have a rebuilt long block with a crack in it that heats up the top end of the motor and coolant.
Do I have some sort of air bubble that is keeping the water pump from doing its job.
I am not sure that I see water cycling through the radiator when its runnning with the rad cap off.
Is the new water pump not working correctly, its driven off of the timing belt.
HELP!

 

Abecedarian are you out there!

 

Sounds like a stopped up radiator

 

The radiator shop tested it and cleaned it out, it was only a year or two old. It looked brand new.

 

Well considering those motors are NOTORIOUS for blowing head gaskets have you had any thoughts that maybe when you put the heads back on you dinged one? and/or maybe they were cheap and one blew already? although they're brand new and most likely wouldnt blow i have seen it happen.... but maybe it blew and and its pushing compression into the cooling system? start the truck with the cap off and check for lots of bubbles.

 

You can buy a test kit to check for combustion gases in the coolant. Using a vacuum to draw fumes from the top your radiator through a fluid provided with the kit. If the fluid changes color, you have a problem.

NAPA sells a kit (~ $40.00) and probably other FLAPS. NAPA calls theirs a "combustion gas block tester", or something close to that.

I've not used one or seen it used, but maybe some others can chime in. A guy I knew many years ago never bought a used car without doing the test.

Harry

 

Sounds like the typical air in the system problem. It needs to be bled properly, or it will not operate correctly.

Easiest way to make sure its not a head gasket, is to completely remove the thermostat, then fill it, then run it. Removing the thermostat eliminates the chance of an air pocket. If all runs well, you know the air pocket is the problem.

 

Just the fact that the top of the rad is hot and the lower is cold when this happens suggests to me that coolant isn't moving around.
Like DC suggested, have you tried running it without the thermostat to verify coolant is actually circulating?

oh... and you didn't install the thermostat backwards did you?

 

t-stat or what you don't want head gaskets installed wrong

 

Nope, coolant goes from the upper radiator hose to the radiator, then out the bottom of the radiator though the lower hose and passed the t-stat and into the water pump. http://personal.utulsa.edu/~nathan-b...05descript.pdf

 

ok so heres what happened, when I went to fill her up with coolant I only put enough to fill the radiator (1 gallon) it looked full so I started it and I guess there was some sort of air pocket that would not allow the water pump to work correctly. The temp gauge pegged and blew coolant past the cap to the overflow bottle. I let it cool took the thermostat out and checked it (it worked) then I added an additional gallon of coolant because the radiator was mostly empty, when it was almost full I squeezed the top radiator hose and essentiially burped all the air out of it. I have let it run for extended periods and it has not overheated. Another side note after putting the second gallon of coolant in, the idle dropped from about 1500 at idle to 800. That must have had something to do with the coolant circulating through the intake because it was now full?
All is well, I am now trying to register it with dmv and will get her smogged and I am done.

 

Death Cougar...... You are correct!

 

the idle is controlled by the coolant level, and temp.

Glad i could be of assitance

 

I'm having this EXACT same problem with an air-pocket. How do you get rid of it ???

I overheat at any rpm under about 3500. 4000 rpm will cool it quickly and this is accompanied with a sloshing sound in the dash area (Intake manifold ?). I know there's air in the system as the car ran fine when we bought it with no thermostat installed... It just ran a bit cold is all, so we put in a thermostat.

Does it need to be a Toyota (drilled with a bleed-hole) thermostat ??

HELLLLLPPP !!!!

Thanks in advance guys...

 

search: cooling system burp

 

to bleed the system just keep your t-stat in and jack up the front end as high as you can. thenstart pouring it in till its full while it is running so that the t-stat opens and in the mwan time keep squeezing the upper hose like a bulb on a fuel line. keep doing this till it is full then try to add a little more and your problem should be solved.

 

I've done this and the thermostat won't open due to air next to it's bulb. Somehow I have to burp the air out OR ELSE the thermostat will never open. I've determined to remove my NAPA thermostat and drill a small bypass hole at the top like toyota originally did and put it at the 12-oclock position. Maybe that will let the air go around the thermostat so the hot water will contact the bulb and open the darned thing...

Thanks !

 

What engine do you have?

 

3.0 V6 (3VZ-E ?), mines a 1991. I feel it can not be the head gaskets because it did not overheat when we bought it just a few weeks ago after which we found a 'gutted' thermostat installed (no thermostat). Also no smell or steam in the exhaust, it runs great. No water in oil.

With all the 'sloshing' sound up around 3000 rpm or higher it just sounds like air trapped in the system to me...

Brad

 

Yeah drill a small hole and put it at 12:00.