SEE PICTURES ON PAGE TWO OF THE THREAD.SEE PICTURES ON PAGE TWO OF THE THREAD.2016 Toyota Sienna with 15,000 miles. Coolant has appeared on TOP of the overflow tank since the van was new. It has never overheated or been on long trips. I took it to two different dealers. The dealers said they couldn't find anything wrong. All they did was replace the coolant bottle cap and radiator tank cap. The level of coolant in the overflow tank and radiator is always proper when the engine is cold. There is a drain tube in the cap of the overflow tank so I don't understand why coolant ends up on top of the tank. I come home from a drive and there is wet/fresh coolant on top of the tank. In my experience the only time you would have coolant overflowing the coolant bottle is if you had a pressure issue of some kind and/or a blown or damaged head gasket. There is no white smoke coming from the tail pipe and the vehicle drives perfect. The oil is the correct color without any coolant in it.I want to give the dealer more ideas of what to check or I will have to trade this van in before the warranty is over. I don't want a $3,000 head gasket repair out of warranty. I would like to keep this van for more than 10 years so I really would like to figure this out.Questions:1. Has this happened to your van?2. Any ideas of what to check to diagnose this problem?3. Why would coolant end up on the tank instead of flowing out the hose connected to the coolant overflow tank?Thanks guys.Jeff Fox

Is the reservoir itself cracked near the cap allowing coolant out and not a bad pressure cap? Is the drain plug clogged with a spider web or something?

No. They are also both new and I rechecked them. Thank you for the idea.

Exhausting into the water jacket.

Could you please clarify your statement sir? Thank you.

Hes referring to a blown head gasket. It will allow exhaust gasses ro pressurize the cooling system pushing coolant out of the overflow. I have experienced this on a dirtbike before.

Coolant overflowing the overflow container. | Good Sam Community

Grit_dog
Navigator
Dec 27, 2017
Well, good luck with the repair. At least it's under warranty still.
jefffoxsr
Explorer
Dec 26, 2017
Last time it was at the dealer I asked the dealer to do a leakdown test and they wouldn't. I will take it back to the dealer in a few weeks and ask them to do the leakdown test and also an analysis of the coolant to see if there are exhaust gasses present. Hopefully they have the machine to do the coolant analysis.

I have said to them all along that it is very likely the head gasket but they don't want to discuss that idea.
Grit_dog
Navigator
Dec 26, 2017
jeffo, unfortunately, I think you just answered your question.
Under normal use, especially an easy drive in cold weather, there should be zero coolant overflow into the overflow tank.
Remember when vehicles just p!issed antifreeze when they overheated? Now it goes to a tank.
That level should not chmage unless it's blowing past the rad cap, or somewhere else the cooling system is not holding design pressure, OR something is over pressurizing the system.
My money says the Yota dealer tried a couple bandaids and didn't check for other more serious causes.
Dave_H_M
Explorer II
Dec 26, 2017
Hunting dog. I think you are on a back track if you know what I mean. :W

I did not say that the tank is sposed to be sealed.

It will take a seal between the cap and the tank for the system to work properly. the overflow tube on the tank is above the level of the top of the tank. So if the top lip of the tank is dorked up or the hose is plugged, therein lies the problem.

Regardless of the problem, the crapola should be flowing or blowing out the hose unless there would be enough transfer of air into the cooling system to overload the capability of the inside diameter of the overflow spout on the tank and/or the inside diameter of the over flow hose.
Huntindog
Explorer
Dec 26, 2017
It is really pretty simple. The coolant is getting pushed into the tank. The cap on the tank is not supposed to seal. It is vented, so the fit of the cap etc, is not important.

Something is causing the coolant to get pushed into the tank.
The most likely cause is a head gasket.
Dave_H_M
Explorer II
Dec 24, 2017
jefffoxsr wrote:
The dealer already replaced the cap and also the radiator cap.

I would a been hands on a long time ago. What about the fit of the cap on the tank? Maybe the rim of the tank where the cap attaches warped or something. What about the drain hose? i just replaced the funky ole rotten hose on the daughter's toyo and all is now well. :h
garyemunson
Explorer II
Dec 24, 2017
Best bet is to go to a local radiator shop. They will have the chemical test kit that checks for combustion gases in the coolant.
jefffoxsr
Explorer
Dec 24, 2017
Thank you for all the great information.
thomasmnile
Explorer
Dec 24, 2017
TakingThe5th wrote:
thomasmnile wrote:
I have a 17 year old Camry that has crystallized coolant on the reservoir neck just like your photo shows liquid there. Coolant level is never low. Done it since we bought it new. Perhaps a Toyota oddity.

That container should not be under pressure yet the leak looks like a pressure leak. So sometimes the container DOES build pressure?? gets shaken while in transit, some of the coolant under pressure leaks past the cap which is not designed for pressure.

Replace the cap and discharge hose on the overflow container. Cheap fix. See if it works. The inside of a rubber hose can deteriorate, or cap might have debris in it or some defect - either can cause pressure to develop. Might also want to check out the radiator cap.

Radiator and radiator cap, top and bottom hoses all replaced in 2015. Like I wrote did it before replacement did it after. I knock off the crust, add distilled water if level is low and drive on.
TakingThe5th
Explorer
Dec 23, 2017
jefffoxsr wrote:
The dealer already replaced the cap and also the radiator cap.

Sorry, I missed the your comment saying it was not pressurized.