Coolant overflow tank cap seeps

[ahtoxa11]

Any of you guys have this issue? Easy fixes?

The cap on the overflow tank seeps where I see pink crusty dried coolant around it. It's minor - just a few spots now and again. It's low enough that it doesn't make it down the side of the tank or anything.

My 19 did that when new and dealer replaced the rez tank and cap both. Problem solved for almost two years and now I've noticed it again.

I'm sure this happens because the coolant is splashing around in the tank, especially when wheeling, but it's a small annoyance and I've noticed that for 2020, Toyota changed the design of this cap slightly.

Thoughts? I was thinking about trying teflon tape around the opening of the rez to see if that creates a better seal. Maybe I'll just replace the cap itself with the newer design.

 

[rdruss]

I'm getting same thing on my 4th gen.

 

[ahtoxa11]

I have a theory that the minor amount of coolant between seal and cap dies and over time crusty residue forces a small gap to open and seep more.

Cleaned up the neck of the tank to remove all crust as well as inside the cap and seal. Will test. The seep definitely isn’t coming from the hose on top of the cap - no residue there at all - just around the seal of the cap.

Ordered a new cap just in case.

Edit. I keep my coolant level pretty full - it’s maybe a 1/2” below the full mark and stable. Perhaps when it’s that full the splashing and tilt of the rig when wheeling forces coolant against it. Might not happen if coolant level was lower in the tank - not sure.

 

[2021nightshade4x4]

You know back in the early 2000s and before, companies like Dodge and Jeep didn’t see a need for pressurized overflow tanks - they had a flip cap and that’s it.


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[ElectroBoy]

I have a theory that the minor amount of coolant between seal and cap dies and over time crusty residue forces a small gap to open and seep more.

Cleaned up the neck of the tank to remove all crust as well as inside the cap and seal. Will test. The seep definitely isn’t coming from the hose on top of the cap - no residue there at all - just around the seal of the cap.

Ordered a new cap just in case.

Edit. I keep my coolant level pretty full - it’s maybe a 1/2” below the full mark and stable. Perhaps when it’s that full the splashing and tilt of the rig when wheeling forces coolant against it. Might not happen if coolant level was lower in the tank - not sure.

Probably the rubber gasket under the cap has compressed. If you can, try flipping it over. I’ve done that with other similar gaskets to get a better seal for a while.

 

[1000MPH]

I tend to get this only when I keep the coolant near the full mark. When the truck was new, it happened quite a bit, as it aged I let the coolant hover about halfway between the marks and didn’t see it happening. Now after replacing the coolant about 18mos ago, and filling it to the full mark, it’s back.
Same with our RAV4, only it makes a little more of a mess because there’s no drain hose.

 

[Jeremy556]

Mine has done this for many years, I don't worry about it.

 

[Rocko9999]

So the caps don't come with a gasket?

 

[MAXISTYLES]

My 2013 has done this since New. Never changed the cap and never had any issues, just maybe add a little coolant once a year or so.

 

[Rocko9999]

My 2013 has done this since New. Never changed the cap and never had any issues, just maybe add a little coolant once a year or so.

Yeah, just annoys me more than anything wiping it off. Might make a gasket.

 

[seatia]

This is not a coolant expansion tank which is pressurized with a sealed pressure cap like most radiators. The radiator itself has the expansion tanks and pressure cap you can see if you take off the plastic cover.

This is a coolant reservoir (tank)
It is open to atmosphere which means it is vented and does not have or need a sealed cap.
The hose on the cap is sealed to the tube that runs inside to the bottom of the cap. When the engine cools down some coolant is drawn back into the radiator thru this tube and hose.

As long as the level is above the low line when the engine is cold you are golden. If above the full line when hot, the excess will be puked overboard and is of no concern.

EPA didn't like puking this expansion on the ground hence the introduction of these fancy catch cans.

 

[skag1T]

Last summer i went to Chicago to visit the Car Care Nut guy and asked him this question.

He said it's normal and should not worry about it.

Just clean the crust from time to time.

My SR5 did this from new.

 

[1000MPH]

When owners see the coolant level like the pic below, I bet they think it’s low. Dealers overfill so the customer doesn’t complain about taking their truck in for “overpriced service and they didn’t even fill the radiator”. My res burps a lot less when I set my level here vs. the full mark