Mysterious Coolant Loss (1 Viewer)

[Daskoff]

Hey Folks - I have a very strange coolant loss situation. First off this truck is new to me - about 1.5 months ownership it's a 2012 with 109k miles. I have records from two Lex dealers since new. Only coolant related work was a radiator swap in 2019. No record of replacing the water pump.

I was taking a trip to Houston from DFW and checked all fluids and noticed that the expansion tank was empty. I checked for leaks and having found none, i added coolant to the appropriate level and headed to Houston. I kept an eye on the level driving down there and back. No movement except for the heat expansion but always back to the level mark I originally filled it to. So I thought no big deal and went on my merry way driving around Dallas with some highway and some bumper to bumper traffic (about 2 weeks). This weekend I went down to Houston again and i checked all fluid levels and lo and behold, my coolant tank was empty. I filled it to the proper level again (engine was warm) and checked it in the morning before the trip. It went down a little since it cooled and drew fluid from the tank. With great trepidation I took the truck to Houston and checked every time I filled up and morning and night. The level did not move (except for the normal expansion/contraction based on engine temp.

This is driving me crazy. How can you have an intermittent leak? I checked the oil level and it is fine, I checked the water pump as well as I can and did not see any leak but to be fair I have not used a mirror for a close look. I know about the prone leak under the intake manifold but no way I can check that. I do not have any leaks under the truck either. There is no black soot in the expansion tank either. But the craziest thing is the intermittent nature of the leak. If there is a leak would it not always leak (slow or fast)?

Anyone have any ideas what else I can check? I have an appointment with the dealer on Friday to perform a pressure test but it's gonna cost me about $160 (which they say is more than just pressure test).

Thanks!

 

[re_guderian]

Have you gotten under the truck back by the tranny and looked back up towards the front for pink crusty evidence of leaks?

 

[re_guderian]

...How can you have an intermittent leak? ...

Lots of theoretical ways. Time at temperature, leak from heater cores that aren't always open and circulating, etc. Start simple first. You have a relatively new radiator, any reason why? Are hoses leaking? The nice thing about the Toyota pink coolant is it leaves a cotton-candy trace when it leaks. Consider a cheap bore scope camera to inspect the underside of things, and places you can't readily see. Head gasket failures aren't too common, so don't leap to that yet. Rule out the more common, less expensive possibilities first. My valley plate leak started soon after I purchased mine, and showed clear evidence when viewed from the bottom of the truck.

 

[Daskoff]

Have you gotten under the truck back by the tranny and looked back up towards the front for pink crusty evidence of leaks?

Looks clean, no residue. I assume the coolant would leave some sort of pink residue. Although I did not remove the stock skid plate to see what it looks like on the inside. Next on my list.

 

[Bang Bang]

I had the coolant valley leak and it was very evident like @re_guderian is referring to. But there have been a few on here who have said they didn't see any evidence of the leak and when they finally pulled it apart it was apparent that the gasket had failed in the rear. Plausible ideas for how the leak would not present itself as the pink crusties have been that it was such a slow leak that the coolant burned off before it could make it's way down to be seen. Do you smell burnt coolant after driving it and opening the hood?

 

[Acrad]

Yep... a few have had just small enough leak for it to contain itself in the valley before evaporating

 

[Daskoff]

Yep... a few have had just small enough leak for it to contain itself in the valley before evaporating

This makes sense but wouldn't I see a steady decrease in coolant in the expansion tank? That's what is weird to me in that 1 week passed after the first topping of coolant there was a complete loss from the expansion tank and now 4 days since last topping - no perceptible drop in level. I think it will be off to the dealer for pressure test. Worst feeling is not having confidence in your ride...I got to get that back.

 

[Daskoff]

I had the coolant valley leak and it was very evident like @re_guderian is referring to. But there have been a few on here who have said they didn't see any evidence of the leak and when they finally pulled it apart it was apparent that the gasket had failed in the rear. Plausible ideas for how the leak would not present itself as the pink crusties have been that it was such a slow leak that the coolant burned off before it could make it's way down to be seen. Do you smell burnt coolant after driving it and opening the hood?

Nope no smells, although I still need to pull skid plate from under engine to take a peek.

 

[MrTorgue]

Yep... a few have had just small enough leak for it to contain itself in the valley before evaporating

^ This is likely my situation. After a bit of highway driving (over an hour) I can slightly smell coolant. But only because my sense of smell is superhuman.