Weird experience changing coolant today

This was an odd one for me. I've replaced coolant in a number of different vehicles over the years. Most are fairly straightforward; some have a specific procedure to ensure it is properly bled. This was my first time changing coolant on a Tundra, and seems like it should have been in the straightforward camp.

I got about 2.5 gallons drained out of the system (including expansion tank)... just over 1 gal. from the passenger side block the rest from the radiator + expansion tank.

The radiator took 2 full gallons to refill; I topped up the expansion tank to Full, added quart or so to the no-spill funnel (2.5 Qt capacity). In total, this was just a bit more than the quantity removed from the system, leaving plenty of room for purging/expansion into the funnel. Set the HVAC to full hot, let it run to bleed.

Up to this point, everything was normal. Some squeezes on the radiator hose to encourage purging, 5 mins or so, Temp gauge was reading at operating temp, got some air out but no indication that the T-stat opened (fluid level drop) and no warm air from HVAC.

Then it got weird... fluid level in funnel started going up. Brought the idle up to 1500-2000 to encourage the T-stat; typically, the fluid level would go down, then come back up at normal idle. In this case, the fluid continued up, overfilling the funnel. All liquid, no air... more than a quart puked back up from somewhere. It took a LONG time to get coolant to the heater core... probably 15-20 mins or so.

Does the service procedure call out draining the block as part of the coolant service? I hope there was enough bypass through the T-stat housing to refill the water jacket. All I know is there was a bunch of coolant not getting to where is should have be for some time. Going forward, I think I'm just going to forego draining the block and just drain/fill radiator.

 

Had similar thing happened when we did my buddy’s 2016 during the bleeding step the fluid came up high. We had to shut the motor down. Empty out the funnel a little and restart the bleeding. Once we did it again the t stat finally open up fully and we could feel the heat from inside the cabin. The fluid did not rise anymore after that. Just went on about another 15-20 mins watching for more air bubbles. Kept an eye on the temp needle, when no changes occur we call it good. It was weird. That did not happen to my ‘21 when i did the coolant change two wks prior.

 

I have a 17 and a co worker has a 14. Both did the exact same thing. It simply took far longer for the stat to open than we thought.

 

I can see engine parameters on my Kenwood headunit. With that being said, when I did my coolant change, at idle, it took about 15 mins for the truck to warm up to around 190-195, where the thermostat opens up. If you’re driving, this obviously happens sooner. But at idle the motor warms up very slow.

 

Put the truck on an incline, nose up it will help bleed the system.

 

I drained both side of the block and did not experience this. One difference, I did not turn the heat on. I could be wrong but by turning on the heat, your pulling heat away from the engine, causing the engine to take longer to heat up. I've actually seen leaving the heat on high as a way to keep a vehicle with a coolant leak from overheating. I would suggest not turning on the heat when doing a coolant change and trying to get the engine up to temp.

 

I drained everything when replacing coolant. Filled up with new into the radiator, left cap off and let engine run with heater on. There were bubbles coming out but nothing as you're describing. You probably got a freak airibble in there that was stubborn at coming out and was pushing coolant along with it.

 

It was

 

Weird, how steep of an angle? I’ve drained my tundra twice and didn’t have an issue either time. Mine was probably 20 or so degrees pointed up

 

Heat on is standard practice for coolant flow through the heater core. Not sure if Tundra has a heater valve or not; I didn’t see it called out on the cooling system diagram.

I’ve just never seen that volume of coolant come back up during the purging process. I’ll try to look up the FSM procedure. I’m guessing they call for a vacuum purge with a service tool.

 

Same. I didn't use the heater when I did our Sequoia. No issues.

 

not that much… whatever my driveway slope is probably 3-4” over the length of the truck. Drained nose down, purged nose up.

 

Here's the procedure.

 

Thank you for that.

My only deviation from that procedure was HVAC heat on and I used a no-spill funnel where the procedure calls for the radiator cap to be replaced. Noted for next time.