help pls 1st gen 3.4

Hey taco fam i have a 1997 tacoma base model with the 3.4 in it i bought it about 7 months ago when i took this tacoma to get smogged the shop told me she wasn’t running at operating temp and that either the thermostat was faulty or something else to do with my water system was faulty after looking around i notice the truck didn’t have a thermostat to begin with so i thought easy fix. i threw a thermostat in there and started the truck went to drive it to warm up the cats for a smog and overheated within two blocks of my house so i thought faulty thermostat tried 2 different thermostats neither worked (all purchased from oreileys). from there I replaced the water pump the radiator both hoses and the radiator cap the truck still overheated with a thermostat in it. after explaining all this to a shop they said for sure i have a blown head gasket. when pressure checking the block the test came back negative for a blown head gasket after explaining this to the shop they said they don’t know and would need to tear things apart to see what’s going on does anyone know what the problem could be?????

 

I read that the air bleeder valve in the thermostat is to be at the top when replacing the thermostat for the air to bleed out of the system.

 

i’ve also seen that method to bleed the block. Ive also heard of drilling a 1/8 inch hole at the very top on the thermostat for air to bleed out easier when bleeding the block. neither have seemed to work for me in this case.

 

I also read a horror story of a thermostat center section breaking and disappearing somewhere and causing a overheating condition.
You can boil a thermostat to watch it open.
With other cars iv had success with the vehicle on a incline, nose up, for bleeding out trapped air.
A radiator cap with a faulty valve can have a effect on Temps.
If it has a headgasket superheated coolant issue, a spark plug usually will be steam cleaned. And a corresponding coolant loss.

 

the coolant stays in the radiator so i don’t figure it to be the head gasket. the incline is such a good idea i will definitely have to try that next time i try to bleed it that’s so smart . when bleeding the block i just attach a air tight funnel to the where the cap would be and leave it half full with radiator fluid and then start the truck the engine knocks bubbles come up and it seems to have no effect the truck still overheats does it vaguely sound like i’m bleeding the engine correctly ?

 

Does the heat work in your cab?

You can bypass the heater core and the throttle body by connecting the hoses going to each and then you’ll be working with a pretty small system - just the rad, rad hoses, oil cooler, and engine block. How high did the temp gauge go when you overheated? Will it overheat at an idle standing still?

 

I have a small leak in my heater core on my 2000. I purchased a new heater core then read about the nightmare that is changing the heater core on my truck. Sounds nothing short of absolutely ridiculous what needs to be done to do it right. Is doing this bypass you mentio, at least untilI can do the heater core, ultimately a bad idea, or will it not hurt anything?

 

Are you sure you are putting the thermostat in the right way?
https://youtu.be/N3DNaSZmHvc?si=08v9t9n-WrDwxnSq

 

I actually had two faulty aftermarket thermostats, they are cheap and poorly made.
I bought an OEM and everything was good and a week of being frustrated

 

The orientation of the jiggle valve shouldn’t lead to overheating - maybe just another 10* hotter or so as @1997tacomav6 had measured before and after temps with his at 12 o’clock and 6 o’clock with a scanguage. Some thermostats don’t even have one and if OP got his from Oreillys they may not have one. The 170* Stant thermostat I put in my 3.4 for my supercharger didn’t have one and had not overheating issues even when running at 1500-2000 rpm for long periods of time at a stand still while I was figuring out why it was idling so high (no afr gauge connected haha).

To bypass the heater core you just connect the hoses that go to the heater core valve with a solid piece of metal tubing @Mpstickers - but if that plastic valve is original, be prepared for it to possibly break and need to be replaced when you replace your heater system with the new heater core and want to hook it all back up again.

 

so i’ll try to bleed the block with the jiggle valve at 12 aclock with a oem thermostat at an incline with all advice considered i believe this to be my best route to get it to not overheat unless someone else has more advice to give

 

There’s also a coolant drain plug on the passenger side of the block (yours won’t have the tube, it will most likely just be a bolt blocking it off) that you might be able to fish a magnet on a stick through to see if you’re picking anything metallic that shouldn’t be there.



Ignore the hole in the block. It sounds suspicious that you bought the truck without a thermostat - sounds like it was a preexisting condition the previous seller didn’t know about or didn’t tell you about with overheating with a thermostat in it. And just to confirm your coolant isn’t getting an oil slick on it of any kind?

 

that is 100% the case i am trying to justify this purchase by fixing it myself and not having to spend bank to fix it through a shop i am aware to an extent i got scammed but also picked up a sick ride that runs great everything works perfectly without the thermo but with it is another story. it’s also metallic purple stock which is the rarest color a 1st gen could come in i believe there were as little as 300 released in california in 97 and i haven’t seen another anywhere. but yes definitely fishy

 

so after watching that yt vid the guy states that the jiggle valve needs to be at 6 aclock not 12 aclock would that not affect the air coming out of the block????

 

The 6 o’clock position of the jiggle veces been exhaustively discussed and John @1997tacomav6 recorded temperatures with it in each position and got about 10* cooler operating temp with it in the 6 o’clock position. It has to do with the flow coming into the thermostat. Bottom line it should work in either position on a truck that doesn’t have any other cooling problems.