S14SEAN

I have a 2000 4runner with auto trans and 3.4l 5VZFE. Over the summer i rebuilt the motor entirely. It was a victim to the "Pink Milkshake" and melted 5 pistons. I finished the rebuild in September of 2011 and since then it has overheated. Because of the cold weather in the winter the problem has not been as noticeable, but it is warming up and i need to address the issue. no matter what temp it is outside if i turn the heater knob to cold on the inside after a few minuets of driving the temp gauge goes up just under the red mark. then if you turn the knob back to hot to run the heater, it goes back down to about 1/2. Lately, in cold weather cooler than 40 degrees on my short drive to work (4 miles) or around town (10miles) the temp gauge never goes past half, it stays right where it should be. On the freeway the temp stays right around half until you get off an exit and it shoots up to about 3/4 until you keep moving and get the revs up. Usually if the revs are up above idle or 2k it will cool down until the gauge is back to 1/2. I have replaced the radiator with a "Spectra Premium" brand. The water pump is NOT Toyota (a mistake) it is from "Parts for Imports" not sure what brand it is, BUT the water pump is my #1 suspect. Looking at the stock water pump that was pulled it had flat angled aluminum fins. The unknown brand water pump that replaced it is cast iron looking fins that do not resemble the stock unit what so ever. I had a feeling that I should have used genuine Toyota for such a crucial component. But what is done is done. I need to problem solve before I do any replacing of parts. I also tested and installed a Toyota OEM thermostat. All hoses front of the firewall have been replaced. When filling the motor with coolant I forgot to flush the heater core of what was left of the "Pink Milkshake" Juice so some NOT much was circulated into the radiator. After i found oils from the Milkshake in the radiator I drained and flushed the system 3or 4 times with radiator flush and Potable water. Finally I filled up the radiator with 100% coolant ( I run 100% green coolant on all my vehicles with great results). Once again It has no problems overheating as long as the temp outside is under 40 ish degrees and the cabin heater knob is in the hot position. Any help is greatly appreciated. Thanks S14SEAN

FogRunner

First off running 100% coolant is a BIG mistake.

Antifreeze/coolant is a chemical modifier and actually has poor heat transfer properties. It's only for changing the boiling and freezing points of water and includes anti-rust agents, lubricants for the water pump and an anti-foaming agent. It must be mixed with water .... no exceptions. It is water that does the work and antifreeze/coolant is there to help the water work better.

First off i would start by running a 60% water and 40% coolant and re-evaluating your problems.

After that I would make sure you jack the front end up as high as possible to "burp" the air out of the system. Air pockets can cause intermittent overheating issues.

If the above doesn't fix it then I would look at the water pump, but first and foremost you NEED to run WATER/anti-freeze mix in your cooling system.


FOG

rworegon

Fog gives good advice above regarding coolant mix and burping. I would only add to use distilled water in the coolant mix.

The temp issue sounds like a fan clutch is going/gone out. Also, be sure the jiggle valve on the t-stat is at the 6 o'clock position.

An option for down the road...head gaskets were installed upside down and are blocking a water port. Yes, it recently happened here on another member's rebuild.

FogRunner

That or because the pure coolant is thicker than water the pump isn't able to move enough volume at low RPMs

rworegon

...I also wonder about the design of the aftermarket waterpump impeller not being as efficient moving the volume.

S14SEAN

Thank you FogRunner. I as of your post yesterday I drained a little over a gallon of coolant from the radiator drain then filled it back full to the top with water, then filled the overflow to the full mark with water. I drove about 4 miles yesterday and found that It helped quite a bit. Today I drove 10 miles and I was able to turn the heater knob to cool and drive without the temp gauge shooting right up to below the hot mark. now it gradually goes up to just under 3/4 on the temp gauge and if I turn the knob to heat it will go back down to half. This is a good improvement. I am wondering if i need to add more water or drive some more so that it can circulate the water from the radiator back into the cooling system. Im not sure how long it takes for the coolant to fully cycle from front of the radiator to the heater core and back. I just looked at the coolant from under the radiator cap and it looks quite clear so It may not be fully mixed with the rest of the coolant.

Also how important is it to have the "jiggle" valve on the thermostat in the 6 o'clock position ?

Thank you much S14SEAN

rworegon

Ten miles of driving with a warmed up engine should be enough to mix the coolant, IMO.

Jiggle valve impact on temps (post 10 and end of thread):
https://www.yotatech.com/forums/f2/5...easure-249481/

Headgaskets mounted wrong:
https://www.yotatech.com/forums/f2/9...tumped-245391/

enapa

Doesnt sound like the hg is backwards to me, thats me the retard that did that lol. However, easy way to check is to lay down behind front drivers side tire and look up to see if the corner of hg has an L on it. If it doesnt and you used oem hg then they are backwards. Another harder way to check is taking intake manifold off. Youll see coolant sitting in water jackets which there shouldnt be. To me it sounds as if you need correct coolant mixture and really get that air out. Try that first but at least try to do the visual hg check. Then if you cant confirm i would take off intake manifold before doing water pump. Also double check that the throttle body coolant lines are in right spot.

S14SEAN

Okay so let me update. Today I drained to coolant and pulled the thermostat, tested the thermostat and it functions just the way it should opens up at 180 degrees. The giggle valve was in the 4 o'clock position when I pulled out the thermostat. I put it back in with the jiggle valve in the 6 o'clock position. I filled the radiator back up with 50/50 water coolant mix and ran the motor for a couple min. Topped it off again. Ran the motor for another 2 min then topped off one last time, also filling the over flow to full. I went for a drive about 10 miles. During the drive when the heater knob was in the hot position the gauge was in the middle rock steady. when I turned the knob to cool the temp gauge when up to just under 3/4 ( it seems like an improvement). when I got home I popped the hood and the overflow bottle was close to the top and I could hear and feel the coolant boiling in the top of the radiator . I also felt the bottom radiator hose and was just warm cool enough to hold my hand bare on it with no discomfort. In contrast to the top hose that I could not even touch for a sec with my fingers.

I looked at my head gasket and I did not see any marks. I KNOW that they are not on backwards, I triple checked it before I put it on. the front has a square hole for the coolant and the head gasket has a hole with orange bead RTV silicone to match it. And all the holes lined up. Im not sure what brand gasket I used. I checked the hoses on the top of the motor and there is no other way the could fit.

For some reason I still think the cast fin water pump is the issue.....

enapa

The problem is the hg will go on either side and a lot of holes do line up, not all though. What youre describing is very similar to how my 4runner acted with backwards hg. Would not overheat with heater on full blast. Im not saying that im 100% thats your issue just very very similar symptoms. If youre gonna replace water pump i would pull intake manifold just to eliminate the backwards hg possibility.