93 4Runner/V6 will not go into O/D

[gdlathey]

Just purchased a 93 4Runner with 177K. Looking for some help. It would not go into overdrive unless you drove it for quite awhile. I have read many a post in this forum and I am trying the thermostat route first. Couple things...prior to putting in the new thermostat, the temp ran about midpoint on the gauge. I bought a new one today from Toyota and put it in. When I pulled the old one out, it had 7 holes drilled in it. Why would someone do that? Are they notorious for running hot? I did not drill any holes in the new one. I put close to 2.5 gal of 60/40 antifreeze in it and let it warm up, yada yada. Took it out for a ride and it pegged hot really fast. My first guess is I got a bad thermostat. I know, I know, I should have tested it prior to putting it in. I am going to pull it out tomorrow and test it. Is there something else I should be checking? The antifreeze capacity is something like 2.35 gallons according to the manual. If I got that much in there to begin with, the stat must have opened at some point, no? Any help you can provide would be greatly appreciated.

[Brian R.]

Did you install it like in this picture?

[gdlathey]

Yes...exactly like that.

[gdlathey]

I tested the thermostat, it works fine. Could there be some blockage in the system somewhere? It is running with green coolant. Not sure what was in there from the beginning. I have heard the red stuff will crystalize in places. Is a flush in order? Would a flush get rid of any blockage in the system? i.e crystalization deposits?

[gdlathey]

Maybe....I am not filling it back up right? Am I just supposed to put the stat back in and fill it up from the radiator cap? Is there some reason that maybe it's not getting enough coolant into the engine and it is all sitting in the radiator?

[4Wheel]

Once it got hot did you recheck the level? (careful)
How did you test the thermostat?
At exactly what temp did it open?

[gdlathey]

I did add a little more coolant to it....not much though, maybe 1/2 a quart. Didn't seem to make much of a difference. I just boiled a pan of water and stuck the thing in there after the water boiled. It opened up pretty quickly.

[gdlathey]

Just got off the phone with a tech at my local toyota dealer...he states that it is probably an air pocket in the system somewhere. He said should fill the block up as much as I can through the top radiator hose, all the while have the front end lifted up several feet so the incoming coolant will force the air out. Also ensuring that when I have enough of the coolant in to start it up, make sure that the interior heat is on high as that and the water pump should be the only things restricting the flow through the enigne. He also said to cycle the engine a few times with the coolant jug filled about 3/4 to the top. His reasons for that are if you do have remaining air in the system, if it burps, the level needs to be well above the bottom of the drop down hose in the jug so it doesn't suck any more air in. He did say these are the worst for getting the air out of them. I'll try that tonite and let you know what happens. Thanks for the help so far.

[gdlathey]

Well...not working...It seems to stay mid-remp range but then as soon as I back it out of the garage and take it for a spin, it gets hot again. I had it idling in there for awhile and it didn't get too hot. Why would it get hot when you drive it? ARGH!!! Side note, it does shift into overdrive now. The tranny seems to shift better all around. Please help!

[4Wheel]

If you still have the old one put it back in.
Make SURE it is installed correctly. this really sounds like it is installed backwards.
There is a small hole to allow just enough flow to get the hot water to the thermostat to open it.
Have either the top or bottom radiator hose been compromised?
To test properly the thermostat should open at the specified temperature, this will be stamped on the thermostat.
If it only opens at 100 degrees Celsius it will over heat.
Make sure it is the correct temperature thermostat. 80 - 84 degrees Celsius

Sticky post at top of forum:
1993 FSM
http://personal.utulsa.edu/~nathan-buchanan/93fsm/

Thermostat:
http://personal.utulsa.edu/~nathan-b...10thermost.pdf

[gdlathey]

Dropped it off at the dealer today....they said the top of the radiator is HOT when it overheats, yet the bottom of the radiator is cold. Plugged radiator. Stopped at Napa and got one today...will do swap tonite and let you know. Kinda looks like we'll have a fix tonite....stay tuned

[4Wheel]

If there is no flow because the thermostat is malfunctioning the radiator will do the same thing.
Interesting. Hope it fixes it, what did it cost you?
I paid $9.00 for a 1988 3 row core on ebay it cost me $19 S&H and $50 to have it cleaned and tested.
Good Luck and do let us know.

[gdlathey]

Well, same thing...new radiator and is still overheating. Bottom radiator hose is cold and top is hot. Flow of water should go from top hose to water pump, what possible obstructions would be between the top hose of the radiator and the thermostat to block flow or quit working? Should I hook up a hose to the top hose and pull the thermostat and see if there is any flow? Not sure what else to do?

[Brian R.]

Originally Posted by gdlathey

Well, same thing...new radiator and is still overheating. Bottom radiator hose is cold and top is hot. Flow of water should go from top hose to water pump, what possible obstructions would be between the top hose of the radiator and the thermostat to block flow or quit working? Should I hook up a hose to the top hose and pull the thermostat and see if there is any flow? Not sure what else to do?

The coolant goes from the bottom radiator hose to the water pump into the engine, then from the thermostat into the radiator through the top radiator hose. Think about it. If the top hose fed the pump, you'd kill your engine everytime you ran even a little low on water.

That's why the top is hot, bottom is cold. It's natural. The engine overheating and the high termperature gradient in the radiator are both signs of insufficient flow through the engine/radiator. Sounds to me like you have either a bad water pump (corroded fins), plugged up cooling jacket, or a bad bottom hose that's collapsing under suction.

Check the bottom hose first and replace if it is not strong to squeezing it. If that doesn't fix it, then flush the engine. Then, last of all, replace the water pump.

[4RUNNER_RIDER]

it should be your water pump or your fan clutch. the top one is the outlet and the bottom one is the inlet were the cold will start giong inside the block.. you should just change both the water pump and the fan clutch..