I recently purchased a 91 Xtra cab V6 4x4 Auto 31" BFG's from a friend of mine. There are a couple issues that I need help with and I believe they are related. Let's start with the cooling system... I just installed my second thermostat. The truck takes forever to warm up after it has been sitting, say overnight or 8 hours at work. Tonight when I left work it was 62 degrees and the truck had been sitting for 9 hours. It took 11 miles on the freeway for it to reach about 1/4 on the temp gauge. Now here is where I get confused/concerned. The truck will not shift into overdrive when the temp gauge is reading cold. Once the temp reaches close to the 1/4 mark the overdrive kicks in and possibly a torque converter lock up? it does this every time. I do get some warm air from the heater when reading cold so I thought it might be the CTS. Installed a new one and did not change things. My friend has had this problem since he bought the truck a year or so ago. He went as far as dropping 2300 on a rebuilt tranny and transfer case. Hes sick of it so now I got it. The truck also seems to lack the power that my 4runner has. So here is a quick overview of what I have done. I look forward to your advice.

Water pump, timing belt, cap, rotor, wires, plugs, set timing, radiator cap, (2) thermostats thinking the first was sticking open, coolant temp sensor, fan clutch, Egr transducer, and a bunch of head scratchin'

What I am mainly trying to accomplish is the truck warming up in a decent time frame and having overdrive. I have lots of freeway time. I believe that I have overlooked something that hopefully one of you will have run across.

Thank you in advance

 

Are you using a Toyota thermostat? Aftermarket thermostats cause the same problem on my 92 pickup.

 

My truck warms up in less than a minute; two minutes if very cold. I don't know where to point you, but obviously there's too much water flow when the engine is cold.

 

Thanks for the info. I purchased the factory Toyota T-stat and gasket... Installed it at lunch today. I still had the same issue. It was just over 11 miles before the temp gauge read normal. At that point tho the overdrive kicked in and everything seemed normal.

Another thought, there is warm air from the heater prior to the truck fully warming up. Could the ECU be faulty? I have a temp gun that I am going to bring with me in the morning and I will check temp at the top and bottom of the radiator and see what I get.

Anymore advise would be very helpful.

 

I am thinking faulty sensor, corroded connections the trans ecu is not seeing the correct temp.

your not putting the thermostat in upside down???

Spring side towards the engine.

 

I agree; probably a faulty sensor or connection.

 

Have you purged all of the air from the system? Those trucks absolutely need to be bled by having the front end as high as possible, where the cap it the highest part of the whole system. On mine, I had to park the front of the truck on ramps on my elevated driveway, to where the front end was probably 4-5 feet above the back. That's the only way to get all of the air out.

 

I have installed the thermostat with the spring side towards the engine block. I have replaced the coolant temp sensor and the connector for it. I pulled the harness off the ECT and checked all connections there, i didnt see any corrosion or loose pins. Any particular sensors I should be looking at?

As far as bleeding the system, I have not raised the front end. I will do so today and see. Thank all of you for your help.

 

Make sure you have the heater on hot, too, to get whatever air might be in the heater core. I wish you luck.

 

Do the 3.0 also have the air pocket issues like the 22 r series engines??

i don`t have one so I don`t know.

Just because you can`t see corrosion on a connector does not mean it is not there.

i had a brand new stereo that drove me nuts took like 4 hours to get it working the female plug did not look corroded but it was at wits end sprayed some contact cleaner it worked.

You did use a conductive sealer when you installed your new sensor??

By new you do mean out of the box new.

How did you splice the new connector ?? Solder and Heat shrink??

I still say bad connection or sensor or even the wrong one.

In any case good luck.

 

"Warm"? The air from the heater should be pretty hot. If your thermostat is staying open, the coolant may never heat up far enough for the heater to get "hot." And if the coolant hasn't heated up then overdrive is not supposed to work.

You could try just putting your hand on the upper radiator hose when you start and idle. It should stay cold then heat up very quickly when the thermostat opens. If, instead, it starts cold but immediately starts to slowly get warmer, that suggests the thermostat is not closing.

 

I installed a new from the box sensor. I soldered the connector and used weather tight shrink wrap. I went wheelin a bit today until I found a great hill. Parked on it blocked the wheels and let it run. With my temp gun the engine is not warming up. After 5 mins of idling there was still no flow in the radiator. The idler/water pipe was 140 degrees. More than 15 mins of running. This is the 4th t-stat I believe... This one from toyota so I have pretty much ruled it out. I don't believe it's a computer issue because the physical temp of the engine is low. I don't know where else the water can be flowing if its not in the radiator.

20 minutes idling with the nose of the truck pointed skyward the t-stat opened. Very little air. I added maybe a cup or 2 of water.

Oh by the way I removed the fan just to make sure.

Is it time for 5 gallons of gas and a match?

Just to be clear the t-stat does go in with the spring side toward the engine right?

 

Crap...sorry, dude. I was hoping it was going to be something simple like an air pocket.

 

This is total BS, I flushed mine and it was on level grpund, and no burping or any of that amateur stuff, If you turn the upper hose upwards and fill the engine thru that, there will be no air in the system, the air will rise to the highest point and purge itself, these motors aren't any different than any other motor, you'll never see a professional mechanic filling a cooling system standing on a ladder because the front of the vehicle is 4 feet in the air. Air rises even in a 3VZE!!!

 

913micks,this may sound dumb but give it a try {had the same issue for a year} reach down to the bottom of the heater core, you will find a heater control cable. unhook the cable and open the valve. { should open counterclock wise} I tried everything and stumbled across that the other day by luck. hope it helps

 

Thank you everyone for your thoughts and ideas. I have traced every wire from the sensor to the computer, no resistance to corrosion etc. Replaced both Coolant sensors with factory stuff. Swapped computers. burped, bled and reburped and bled the cooling system. Factory thermostat. opened the heater valve manualy. Tonight was the real test after all this work. the trucksat for 10 hours and was stone cold. Started it up at work and let it idle for about a minute. Took off and hit the freeway. Same old thing. I just dont get it...AT ALL! My 4 runner same vintage and drivetrain does not do this. Its just gonna be on of those things I guess.

I really do apreciate everyone advice!

 

so you have heat but the tranny isn't kicking in like it's warm? I'd start looking at the transmission itself, as well as it's connections to the ECU.

 

Sorry I didn't reply the cure!! There was silicone in the small u shaped coolant line by the sensors. I assume not allowing coolant flow. Removed it and blew out the system. Works like a charm. Thanks again for all your help.