I took my 92 t4r 3.0 to toyota for a radiator flush because I noticed that there was green antifreeze in the radiator and I know that that is bad for these motors.

The service adviser called me back today around noon and told me that the thermostat (ts) was gutted out and when they put the new oem ts in and filled her back up, the truck was overheating.

I have NEVER had any issues with this truck with overheating (albeit I just acquired it on April 6th), but I digress. Not a drop of oil leaks, and no coolant leaks. It's also important to know that the truck had the top end of the motor and the cam replaced about a year ago. I talked to the tech who did the work around 3 pm at the other dealership across town.

I seriously doubt the headgasket is bad... I have read all over on these forums that these trucks (3.0 in particular) are real difficult to get the coolant and all of the air out - thus causing overheating... but I am at a loss at what to do next.

They told me that they will attempt to put the old gutted ts back in tomorrow and see if that works... but that's not a solution!

Why won't a toyota dealership know how to fix this? I mean really!

I asked if they checked the water pump, radiator cap etc and they told me that all of those were good to go. Any ideas?

This is what I found out about "how" to do this:

• open radiator cap

• set air temp to heat

• dont turn heater on

• start the truck

• let it run till operating temp

• while topping off the coolant

• once it has been warmed up and ran a few mins after that

• install cap

• turn truck off

• top of reservoir tank a little past full

• lower front end up and let it cool down.

• done

Any advice? I need this truck for a road trip next Tuesday and now I am very concerned.....

PS - they told me that they RARELY see 90-95 Toyota 4Runners in their shop - could it be that this Toyota dealership has no clue???

please help - thanks!

Always turn the heater on full. Also, some t-stats have a very small hole drilled in them to let steam pockets pass, otherwise the stat will not sense the correct water temp to open.

Sounds like they're jerking you around. I just did my water pump, thermostat, and radiator so i had all of the coolant drained and didn't have nay issues filling it up or having it overheat. The way i filled was, I disconnected to upper radiator hose from the radiator and lured coolant into the hose and let it fill the block until it started to overflow out of the upper hose. Then I reconnected the upper hose and filled the radiator and reservoir. I then started the vehicle and turned the heat on and let it heat up with the radiator cap off. The system burped itself and I haven't had any issues.

That's pretty much how I do it, and I've never had any problems.

they put the gutted thermostat back in and gave it back to me. I don't know what to do.... I noticed that the A/C heater was all the way over on heat and the fan was on high when I got into the truck. I read in that the fan doesn't even need to be on, just the lever needs to be over to the highest heat setting. Not sure about the rear seat heater switch.

I want to try to purge this myself over the weekend, but I need to understand the steps better on how to do this.

I'll have a couple gallons of distilled water ready in case I lose some fluid.

If I swap out the TS with the new one, I will lose a ton of coolant right? so... before I swap it back to the new TS, do I need to drain the coolant first?

Yes, when you remove the lower hose, TS and the TS cover you will basically be draining the whole system. All of the coolant in the radiator will drain out as well as the coolant from the block. I would replace the old TS and gasket then refill the cooling system with 50/50 antifreeze and go from there. You're looking at $20 total cost roughly. Its the cheapest part to replace to start your troubleshooting.
As far as steps to draining and filling the system, Just remove the lower radiator hose and let it all drain into a bucket. I've already explained how i filled my system earlier, give that a go. If its still overheating you may want to check you head gasket as these motors are know for their HG issues from everything that I've read.

oh... forgot to mention.... I have ZERO white smoke coming out of my tail pipe. I have no leaks... so... for the stock TS to just fail (cause the motor to overheat) with no symptoms of any HG warning signs... I find it very hard to believe that I have a HG issue (even though they are common)

I would have 'other' warning signs. also, I changed my plugs last week - they were NOT wet they all were light brown, some had a little white tint to them, but remember, I was chasing a vacuum leak for a while in my other posts.

I don't understand the whole premise of needing a coolant flush because you have green coolant. When Toyota rebuilt my engine 12+ years and 80,000 miles ago they used green coolant. It wasn't until recently replacing the thermostat and upper hose that I put in fresh stuff.

But right after replacing the coolant, I did have trouble getting all of the air out. I drove it up a mountain road, so uphill with several sharp turns in each direction. It started to overheat, so then I drove it down that same hill. Finally just before home (maybe 4 miles total) it "burped" when going around a corner.

When I switched out the thermostat a second time, I let it heat up a while first, and then just drove it in the neighborhood but taking the corners sharp. I didn't have a problem.

Good luck. But if nothing was wrong in the first place, why did you worry much about it?

... because I am restoring this vehicle. This is not a daily driver - this is a project. I saw green, and I know it needs red. Any fan who will purchase this from me would know that as well. .... plus, I has a slight case of OCD when it comes to restoring and after 22 flips, and lots of profit, so that's a good thing....

back to this issue... I had a compression check over the weekend by my suspension crew and my suspicions were right. My numbers are FINE. lowest number was about 139, highest number was 152. With 184k miles, that's isn't bad. This was a dry test, not the wet one with oil to check valves. This was a general health check of the motor - remember, I have no issues leaking oil, or coolant, and no white smoke in the exhaust.

that being said... I am not confident that I have a bad hg. so what would cause a new thermostat to cause overheating (besides the burping process?)

anyone?

It is completely possible that a new out of the box thermostat can be bad. to test it put it in a pot of water on your stove top. use a thermometer to keep track of the temp, and watch to see at what temp it opens.

good point! that would be crazy huh?

Toyota didn't have toyota red coolant when our trucks were made. I believe that the came out with it in 95/96? But I do think it's better than green and I've had no problems getting air out of mg truck. I've drained coolant 3+ times and every time I just fill the radiator and overflow. Start the truck add coolant till the radiator is full put the cap on and drive. Haven't had an issue. Your radiator could be part of it plugged and a good t-stat slows it just enough to over heat. But this is the time of year for hg it seems like. At work we've done 2 subarus and a 22re in less than 2 weeks

Yep, my '92 FSM says to use ethylene-glycol (page CO-12).

At the same time, if the new red stuff is backwards compatible and better in some or several ways (less corrosive, less poisonous, better temp range, longer lasting, etc) and doesn't have limitations, then it would be better to use. Mine's doing ok, and when Toyota did the 3.0 rebuild on it back in '97 or so they still put in the green stuff.

But it's similar to engine oil. There's been a lot of improvements in the past 40 years, with longer life and consistency of synthetics, better ranges in all, and then improved testing with new specs. One could continue to put the exact spec of oil it called for on an older call (say the 1960's Mercedes my grandma used to drive), just as one could continue to legally drive in that car without seat belts since it didn't come with them. But neither would make much sense.

I just don't know about the improvements and backwards compatibility of the red coolant, while I do know that the 2nd gens definitely called for the green coolant originally. If someone has a link to a good thread or article on it, can you post it? Thanks!

^^ yea, I'd be interested in this as well. So.... for the older 3.0's (3vze) it's the green stuff.... hmmm. I guess the only good thing about me being proactive in doing the radiator flush in the first place was that I found out that I had a gutted TS. Had I *not* done the flush, I would have driven it up to TN (from FL) in the mountains - I would have overheated for sure....... now that I know what I do... more work needs to be done to make sure this rig is reliable, and unfortunately, more money out of the budget.... smh

A 3VZ-E with a gutted ( but not totally missing) thermostat is an old trick to keep it from overheating. That means the seller knew that there was a problem and it probably the #6 spot on the driver side head gasket.
I ran my previous 3VZ-E for quite a while with a leaky HG before replacing the entire engine... and it never blew white smoke or leaked either.