90toy4x4

1990 4x4 pickup, auto. stock engine.

Previous owner has replaced waterpump, timing chain and gears, timing cover.

Radiator is topped off, overflow tank is topped off. no leaks from the coolant system, no other issues with the engine.

When the HVAC is set to heat, i can hear coolant gurgling and the air from the vents get hot. The engine temp keeps rising though. untill HVAC temp is set all the way to cold, then engine temp will start to drop back to where it normally rests. Temp gauge usually rests about 1/4" into from the left side of the "normal" range.

I am at a loss of what to check/do next. anyone have any ideas?

90toy4x4

Bump. Anyone?

SoCal4Running

If its gurgiling then their has to be air in the heater core.

I wonder that when you turn the heater on that when the valve opens to circulate water thru the core that the air in it is not somehow stalling the water pump from flowing.

Park on a steep incline and let motor cool.
Remove radiator cap when cold and turn heater on and then start motor.
Let run until either the water level in radiator drops so you can add more or raises and starts to overflow and then put cap on.

stanz

iTrader: (1)

I agree. Sounds like you need to burp the system of air in the coolant. Tons of videos on Youtube as well on how to do it.

90toy4x4

Thanks for the help. Ill try it and let you know

SoCal4Running

The issue is that there is no vent at the highest point, which is where air will get trapped.

It can be a big problem with cars since the aerodynamics require the radiator at the front to be lower down compared to the engine and the passenger compartment.

Most modern cooling systems will have removable plugs at these high point to allow the air to escape until water flows out of them.

Our trucks are not one of these vehicles hence the steep hill will help the bubble rise and the engine running with the valve open (heater on hot) will help with pushing it down to the motor and then out the radiator.

My theory anyways

98_3RZ

i had the same issue on my 94 22re. it would run hot when the temp was set to warm. i replaced the thremostat with the toyota TSB thermostat from the 80's, haven't had that problem since, i put in a call to my dealership and get a part number

BMcEL

Yep, OEM two-stage thermostat. Problem solved.

98_3RZ

got the part number, its 90916-03070. now i'm going to warn you, it will be more expensive than a standard thermostat for the 22re. and the dealership probably won't have it in stock, so it will have to be ordered. but from the symptoms your truck seems to be having, this thermostat should fix it. its kinda stupid that the TSB only applies to some 84' trucks, and 83'-84' celica's with the 22re. my 94' 22re had the exact symptoms, i put this thermostat in, and it hasn't acted up since, that was a year and a half ago

90toy4x4

thanks for the P/N. I tried the uphill burping to no avail. coolant rose an inch when temp got to about half way, but it didnt move. I would figure once the thermostat opened, you would be able to see the coolant move to one side or the other.
I first thought that there wasnt a thermostat in it because the temp reads so low, but if there wasnt one in it you would be able to see coolant moving in the radiator, right?
I will have to pull the thermostat here soon and see what it looks like.

98_3RZ

i'm about 90% sure about that part number, double check it at the dealership

BMcEL

90916-03070 is correct. More info here:

http://www.4crawler.com/4x4/CheapTri...tml#Thermostat

SoCal4Running

The Dual Stage Thermostat was a fix for Temperature Gauge Overshoot that Toyota was experiencing a lot of service returns for.

As far as I know the engine was not and would not overheat. This thermostat (which I do also use) was only designed to allow a small amount of heated water thru so the gauge would not spike high and freak the driver out.

I dont think it will fix any gurgling in the heater core.

Inferno451

These guys are absolutely right. Just put in my 2 stage thermostat. Expensive at about $35, but nice to not have my temp gauge go into the red every time i start it cold!

BMcEL

Correct...that's air (or worst case, exhaust) in the coolant.

If the coolant passes an exhaust contamination test, it's probably just air trapped in there. It can be a pain to burp all the air out sometimes.