1990 4runner 3.0

I've searched and see periodic mention of burping after a flush, but haven't found advice for how-to.

I've idled for 10 minutes with a loose cap, and did have some overflow out of the cap.

What other methods of burping are there?

What are the symptoms of trapped air? How do you know when you've fully burped it?

Thermostat is new, OEM. Old thermostat was also OEM and looked very new and shiny, but I replaced it anyway.

My temp gauge never quite reaches the middle.

When it's 30 or lower outside, this thing barely runs hot enough to heat the car, and won't stay in overdrive on the interstate.

I don't want to switch to a hotter t-stat just to band-aid a trapped air problem if that's what I have. I want to eliminate the trapped air possibility before progressing.

Any suggestions?

Thx.

 

If you've done it and its burped and nothing is changing (engine temp), you should be good to go. Symptoms would be increase engine temp. Keep a eye on the temp and if you see it start to go up, theres a possibility of more air in the lines.

 

I guess my problem is that my temperature is almost always too low.

My concern is a bubble in the temp sensor console on the back of the motor, causing the sensors to read too low, so that the dash gauge and the ECM think the car is cooler than it really is, therefore limited access to overdrive and a confused driver.

How do you know if it burps? When I tried idling with the loose cap, I never really saw or heard anything other than some coolant slopping out.

 

The way I always do it is before I refill the system, I jack the front of the vehicle up as high as I can (compared to the rear). That makes the rad cap the highest point of the system, and encourages air bubbles to make their way out the fill opening. Also, turn the temperature knobs for the front and rear heat to "full hot", to ensure the control valves for the heat are fully open.

Re-fill the system slowly, to allow air pockets to be displaces through the pipework as the system level is rising. With the system filled, start the truck with the rad cap off. Let it idle while gently and repeatedly squeezing on the upper rad hose. You'll see bubbles coming out of the rad fill opening (don't squeeze too hard, or you'll get a facefull of coolant). As the air comes out, the level in the radiator will drop. Keep re-filling it as you're burping the system. Try to get this done under 5 to 7 minutes or so with the truck idling, otherwise, the coolant will start overflowing out of the fill hole as the truck warms up.

Once you're confident the air is out. Put the rad cap back on and you're done.

 

I have a '91 4R... had a similar problem only to find that a water passage was clogged with gasket maker from when the dealer did the HG recall. It's the tube that runs from the intake on the rear passenger side. A PITA to replace but I had the exact same symptoms. I replaced everything easy including the temp sensor, thermo, only to find the same problem... never would heat up. Finally, found the cause fixed it and never looked back. Will take a full day to find and fix. Might consider changing out the knock sensor while you're in there. Good luck!

 

I have air trapped in mine too after I changed my w.p. I have never owned a vehicle that is so hard to bleed air out of the cooling system.

I parked on an incline yesterday so steep the runner didn't want to climb it & had to add in another half gallon of coolant when I got it home. I didn't hear the typical air bubble rushing sound from the heater core this morning but I'm sure the tricky little girl is just TOYing with me lol

Oh, b.t.w. I never had any temperature problems even with all that air in the system.

Edit: one tip is to make sure you have the jiggle valve at the 12 o'clock position when installing a thermostat!

 

What's the jiggle valve? I don't remember my FSM mentioning anything about having to position anything when reinstalling the thermostat.

 

The jiggle valve is a 2mm hole in the face of the t-stat that's occupied by a loose (jiggly) brass grommet. It lets air through the t-stat when filling system, and it let's coolant weep through as well. You see it on oem t-stats, and some Beck Arnleys, but not on most aftermarket t-stats.

Mine's at 12. Thx.

 

I will try this! Lot's of steep hills close by. I may even try it both ways: nose up, and tail up.

I'd love to get a burp worth a 1/2 gallon. Then i'd know it burped!

 

Elevate the front, pour water in upper hose until its full then put it on radiator that is full and top off, full heat, and start with cap off topping off squeezing upper hose as stated above. I have done this twice now with no problems at all.

 

I have read about this. With dread, fear, anxiety, and nausea.

Another guy reported he found a gasket-maker plug near the u-shaped hose on the temp sensor console behind the motor. He discovered it by blowing 70psi air into the temp sensor console, and had a rtv booger shoot out of the t-stat orifice. Kind of like a snot rocket when you think about it...

I'm holding on to (fading) hope for a burp miracle.

If that doesn't happen, I guess I'll spend a Saturday pulling coolant hoses and passages until I find the blockage. Thanks for the tip on the knock sensor.

Was yours a job that required pulling the intake plenum?

 

You'll never get your system filled if you park the rear of your vehicle much higher than the front. Nose up it what you want.

 

Thats funny,... when I did my motor swap, and went to clean out my oil cooler, I found a chunk of a red taillight lens jammed in the oil cooler antifreeze input port. Had to use some hemostats to yank it out. Amazing what people will pour into their radiators!

 

what's the capacity of the anti-freeze/water mix in the v6 engine?

 

Pasted from the service manual, 3.O engine:
****
NOTICE:
• Do not use an alcohol type engine coolant.
• The engine coolant should be mixed with deminer–
alized water or distilled water.
Engine coolant capacity (w/ heater or air conditioner):
2WD
M/T 9.9 liters (10.5 US qts, 8.7 Imp. qts)
A/T 9.7 liters (10.3 US qts, 8.5 Imp. qts)
4WD
M/T 10.0 liters (10.6 US qts, 8.8 Imp. qts)
A/T 9.8 liters (10.4 US qts, 8.6 Imp. qts)
****

 

I am having simillar temp issues. My truck will shift into OD when warm, but after about 5 mins of highway cruising it will downshift out of OD, and i will have to go back into city driving before it will even think about going back into OD. I was suggested to do the thermostat, but reading these posts, I think I may take a weekend and check for any blockages, replace the thermostat and temp sensor. I can see there is some RVT squeezing out at the water pump, so chances are some squeezed inside aswell.

 

Easiest way to get most of the air out is to remove the heater hose from the heater control valve on the firewall. Put a funnel in the radiator(lisle tools makes one specifically for filling radiators) and fill untill a good stream comes out of the hose and reconnect.

 

Yes... I'm still trying to recover from that job! It runs better than new now so it was worth the effort. I truly hope it's an air issue for you. There is a coolant line on the drivers side front corner area coming off the intake. It is a metal line that has a rubber hose connected to it going under the throttle body. A Toyota tech advised me to remove the rubber hose as the metal line is the highest point on the engine. When re-filling the cooling system with the rubber off, the antifreeze pushes the air out this line and bleeds the system automatically. I've been doing it this way for years and never had an issue with air being trapped in the system. There are probably a lot of ways to do it... this works best for me, besides, this tech gets paid to do it!

 

Oh yeah that's a good idea, the coolant line going to the TB is the highest point. Does coolant ever actually flow out of that line while you're filling?

BTW if an aftermarket T-stat doesn't have a jiggle valve you can just drill a small hole near the edge and put the hole at 12:00.

 

It's looking like this weekend is going to involve the removal of all coolant lines. What should I replace while I have the intake off and all that fancy jazz?