1st gen Tundra overheating

I'm not really new but new to posting, my name is Ahki with a 2003 Tundra access cab 4x4 with a 4.7 engine. I have been reading for awhile now and would like to thank everybody for the knowledge on this site. My problem is my truck overheated on the highway which it has never done before. I had the truck towed to the yard and looked at the engine which was wet pretty much everywhere. I replaced the thermostat with a premium thermostat from Advance Auto. Started up the truck and idled it for at least 15 min., the gauge went up about halfway like it always did and I saw no leaks. There was some bubbling up in the overflow tank but stopped after a few minutes. Took it for a test drive and within about 100 yards the temp gauge went all the way up. I got back to the yard quick as possible and shut it down. I still saw no leaks, the upper radiator hose was hot and there was no heat either on the road or in the yard. i always thought a vehicle would overheat more while idling than driving. I do my own mantainance but am definitely not an engine tear down skill level guy. I would appreciate any ideas from the panel of experts for this strange (to me) issue. Also no water in the oil and the transmission fluid looked fine.

 

Sounds like the new thermostat is either stuck in the closed position or you still have an air bubble to get rid of in the system. Two things:
1. Thermostat needs to be “clocked” correctly for proper operation
2. You need to burp the system to get all the air out

 

I just had a strange heating issue at work, basically no movement of heat or water because it had air in the lines.

 

^^^
This

 

Somehow I pictured on your job it was those old school boilers since schools never to seem to update from the original system.

 

I think I saw this when I was researching here before, so I made sure to clock it at 12:00, I don't remember the burping procedure.

 

Hahah I wish we had cool shit like that, one building has a 6’ blower wheel from the 50s that’s still trucking.
This building actually got overhauled over the summer, but our “project managers” aren’t worth a shit, found like 4 other missed issues while taking care of this call.

 

I found the burping procedure on Tundra2 reply if anyone else is looking.

 

I can't remember if we need radiator cap off or not since I haven't had to do it myself and we have the overflow reservoir. (Mechanic last changed T-stat with timing belt and water pump)

1. Turn heater all the way on (don't need the fan on)
2. Park the car on an incline
3. Run the truck in idle
4. Rev it to 2K RPM for 10-15 seconds
5. Repeat step 4 a few times with breaks in between
6. Once complete, top off the radiator (when coolant is cold)

Step 1 is the most important; Steps 2 & 4 are to help it along

Maybe someone else can chime in whether the radiator cap off is important or if it just needs to be off on the overflow tank; it would definitely let you see the bubbling and fluid level fall to let you know the air is out

 

Thanks Jack, I'm gonna go try it now.

 

The overflow tank is not, and is never sealed so cap on or off, it doesn't matter.

With the RADIATOR cap on, air, can only escape under pressure, 15 PSI if memory serves. You want it off while purging air, at least until you get enough out to stop overheating.

In the normal operation, any air collects at the top of the radiator, and is pushed out into the overflow tank when the system heats up and pressurizes, and then when it cools, new fluid is pulled in from the bottom of the overflow tank, progressively removing any air during each thermo cycle.

This would eventually work to purge the system too, but it would take many start, heat, cool, cycles to do so, which is why you try to get as much out as possible by burping the system.

The important thing when running the system hot, with the cap off, is to make sure to get the cap back on, and have the overflow filled, when you shut off the engine, otherwise when it cools, it will just pull more air back in.

 

Thanks for the detailed explanation @Aerindel

 

I followed burping instructions from Jack and drove my truck my home, checked the coolant level, no loss, gauge was just above halfway the few miles to my house. hopefully that's the end to this chapter. Thanks again Jack, also for the details from Aerindel, nice to see my Tundra in its proper parking spot. Love this site.

 

The main thing you want to check, once you have all the air out, if for any bubbling in the overflow tank.

You do this with a fully warmed up engine, with the engine running and someone lightly holding down the gas pedal to get the RPM up to 2-3K. Pop the cap of the overflow tank so you can get a good look down it, but make sure the tube is in and under the level of the fluid and look for any bubbling. If there isn't any, you're fine and can probably forget about the issue.

If there is any kind of constant stream of bubbles, you're looking at blown headgasket.

Don't bother doing this until you've purged the system and driven a few times, or right after it warms up. Its normal to get a couple bubbles when the pressure comes up and the valve first opens during warm up.

There is usually a little air in the system, which is why it designed with a check valve in the cap so it automatically purges any air each time you run the vehicle.

It's only if you get a constant stream, or series of bubbles that you need to worry about it.

 

I bought this funnel for burping my system,mine took about 2 drives to get the coolant perfect

$23 EPAuto Spill Proof Radiator Coolant Filling Funnel Kit

EPAUTO Spill Proof Radiator...

 

Those are great. Used them when I was a mechanic and Ive used it 2 other times working on my junior squids vehicles. Makes for a "cleaner" mess!

 

So once this process has been completed should the fluid level in the reservoir move? My fluid level on some days will be high and other days close to the low level why is that?

 

The level should be high after driving for a while and the truck is warm, and low after it has cooled down.

The system is designed so essential once its hit normal temperature, its over pressurized and dumps extra fluid or any air that has worked its way to the top of the radiator, into the reservoir, (raising the level) and then when it cools down, pulls that fluid (but no air because the tube is under the level of the fluid, back into the radiator, lowering the level in the reservoir. It's a great system in that as long as you have fluid in the reservoir, it will top itself off every time your engine cools down.

 

@Aerindel great explanation thank you!