Coolant overflow

Hey everyone I had a weird thing just happen with my cooling system and I couldnt seem to find anything online. I'll start with some background info.. 2004 2rz

6 months ago the radiator, hoses, and thermostat were replaced by a shop. The lower radiator hose they installed was some universal junk and kept dripping overnight. I ended up replacing that lower hose but of course drained my radiator out. After replacing the house and replaced the coolant and it was drip free. (same coolant because it was less than 1 month old) I then went to burp the system by letting the engine come up to full operating temp and let it idle for 10-15 mins and gave it some revs to help the water pump move coolant faster.
heres where i'm confused on some stuff...
When I put the coolant back in and burped it I realized it wasn't up to the top of the radiator. so I added distilled water to the mix on a hot system (yes i know its a little less than 50/50 now). Re-capped it and didnt look again.

a few weeks later i open the hood to look around and check the oil and realized the coolant reservoir bottle was at the very top. (likely due to adding additional distilled). again. didnt think anything of it just assumed i had extra now.

now today i wanted to peek into the radiator and see what the level was. when i opened the cap i had coolant gush out of the overflow. it skipped the reservoir and went right overboard. mind you this is a cold system, truck hasn't run in over 24 hours... so now im like what the heck.. did it overflow because my reservoir/system is overfilled?
coolant reservoir was full, 1/4"-1/2" from the cap.

so i just ran the truck up to operating temp with the cap off. scangauge said temp was 184 and i let it idle at that temp for about 7 mins. i put the cap back on and let it cool. it appears the reservoir level is a little lower... im hoping the original cold system gush was because it was overfilled? any experts on the matter? thanks! will edit to include photos.

in the photo you should be able to see the old reservoir line and the new level its currently at after cooling. (its only been 20 mins cooling)

 

Pic attached

 

Off the wall guess is that radiator cap or the return tube out of the reservoir are not flowing correctly..

As engine gets hot, it sends overflow into the overflow res....

When it cools, its supposed to draw it back into the radiator......

If that's interrupted, the coolant overflow, will overflow, and the volume in the radiator will slowly draw down.....empty.



check those little tubes first....ability to draw back......and maybe a new radiator cap.....

 

Thanks for the reply. The cap is also new. I woke up this morning and the coolant reservoir is a little lower after the truck continued to cool overnight. (After getting it hot with the cap open last night) the cooling effect must have pulled the coolant back in the system. The current level is where it was when the shop returned it to me about 70% full on the reservoir. So it seems the tubes are all working properly.
I honestly think my issue was when I overfilled it on a hot system a few months ago when I changed the hose and burped it. I’ll report back with any oddities. Gonna drive it about 2.5 hours today all highway.

 

Sounds like you had some air in the system and it's working it's way out.

 

Toyota pressure cap I hope.

Easy to understand explanation if you are curious…

https://www.freeasestudyguides.com/engine-radiator-cap.html

 

Haha uh oh. They installed some aftermarket cap that has a red pressure release handle before it can be spun off. Should I go get me a genuine Toyota or nicer one?? I’ll try and attach a pic

 

They cheaped out on my lower radiator hose let’s hope this cap isn’t garbage?

 

this is my thought as well. open cap, see that it is full. level off reservoir to correct level at the temp you happen to be at and watch it?

I would change that cap, even if only so the TW crowd won't lynch my ass verbally when they see it

 

Yeah, I have owned a lot of Toyotas that had picky cooling systems (many 1st Gen MR2s) and a factory cap was always the way. Whenever I see an aftermarket radiator cap on *any* make of car it's the first thing I would replace if it has cooling issues. The Toyota cap is perfect for stock engines. Toyotas are reliable only as long as all the parts are Toyota in most cases.

 

I have a little more info. I'm trying to figure out why the system has positive pressure when stone cold. Lets back up to the radiator replacement back in the summer, the valve that allows coolant to flow into the core hasn't worked all year (not an issue in florida). so when those mechanics did a flush on my new rad and hoses, the heater core was never open even if they thought they opened it with the climate control knob. Today I manually turned the heat on by opening the valve by the firewall. No heat. maybe 2 degrees higher in air temperature from vent (measured with IR gun) and all the hoses near the valve were hot.

The old radiator had stop leak in it from previous owner.. could the heater core be all clogged up and have a bunch of trapped air pockets? Would trapped air in the core cause my system to remain pressurized after cooling overnight? Really concerned about this being the onset of a head gasket issue.
oil looks fine, coolant looks....okay. it has a darker color to it i'm assuming they didnt flush it enough times and that stop leak crap is probably still floating around. i'll try to attach a video or 2.

 

https://youtu.be/8nP_UHf9dxY?si=WN3J5z_hDb_yJYH3

https://youtube.com/shorts/frRO3FTpmvo?si=KH7EsnXR1a2e9wa5



Anybody see anything to be concerned about here? i dont really like the color of the coolant very much but I'm guessing its from the stop leak the old owner put in there.. the stuff seems to be persistent in staying in the system even after multiple flushes when the new rad was installed. do i have a ticking time bomb here with a potential head gasket issue? or am i just over reacting

 

as far as the flush(s) go......i wished i saw this thread b4 i flushed my system

https://www.tacomaworld.com/threads...the-block-drain-to-3-4l.818760/#post-29382407

as far as potential HG
pull plugs and inspect.....if look rusty or smell like coolant....HG
IF you have access to a bore-a-scope....if top of piston looks steam cleaned....HG

im not feeling good about prior owner putting stop leak in coolant system

 

I'm taking it to a new shop in a week. totally baffled on what to do and this has become pretty frustrating. There is no heat in the truck. both pipes for the heater core are hot as hell. After driving to operating temp across town the coolant does not expand into the reservoir but if you release the rad cap pressure valve it will expel air into the res then it will suck coolant back to radiator after cooling. Then after another drive of about 35 minutes i got home and decided to check the radiator + hoses, the top 2-3 inches of the radiator are hot and the bottom 95% of the rad is cold. bottom pipe is cold. totally lost. these are all new parts. thermostat was new with radiator too. just gonna have a different, reputable shop look into it.

what's extra weird is the coolant reservoir... it doesn't seem to expand into it when hot.. but if you crack the release valve, air comes out and then eventually the coolant will contract back into the rad when it cools... No bubbles from radiator with the cap off + running. Im gonna have the shop run all the head gasket tests as well as check for any clogs in the system. which would be infuriating because the shop 6 months ago should've flushed the whole block like they said and make it squeaky clean in there.. just complaining into the void and recording symptoms. will be back with an update in a week or so.

 

Get rid of that radiator cap, it's likely keeping the overflow system from working properly. Those things are not designed for modern vehicles

Just the fact that they chose to install a pre-historic cap like that makes me wonder about the skill and experience of the shop..

 

just called the local toyota dealer and they have a cap in stock 33 plus tax.. going now. will report back in a few days or next week.

 

A radiator cap for $33? That's absolutely obscene.

 

For real I guess they don't call it the stealership for nothing! I opened the system once since the new cap. System was stone cold. No positive pressure like before. Still gonna take it in to have the heater core diagnosed and see what else they find on the first week of New year.