Coolant reservoir keeps dropping - do I have a leak?

Cliff notes version:

Radiator broke so I changed it out last friday with a TYC brand and re-used factory clamps. (no factory OEM ones are available ANYWHERE!)

I filled the radiator and the reservoir

After running it a while at full temp I filled the reservoir to 1/2 way again

I marked the top coolant level in the tank while hot and I marked the low coolant level when cold.

On Monday the tank level dropped about an inch when cold so I filled it up again. This was probably due to the air working its way out and cooler weather here.

On Tues evening the levels were right at the marks both hot and cold and no visible leaks in the bottom shield.

This morning (Wed.) I checked the coolant tank levels and it was about 2 inches below the cool level mark. It was a bit cooler weather last evening by about 20 degrees. This drop happened in one evening.

I am concerned the new radiator might be leaking somewhere but where? This is a 2019 SR5 so I would think the heater core and water pump are OK. I have crawled all around and under looking for any signs of a leak and nothing. Maybe this is all normal and it was just more air working itself out and the cooler temps?

 

If you don't see any leaks or smell any coolant outside the truck or inside I wouldn't worry about it.

 

Give it some time to settle. My other car has a coolant reservoir that can be used as a thermometer it fluctuates so much with temperature changes.

 

Check the passenger floor for coolant? Youd smell it for sure. It probably burped

 

When you first refilled your radiator, did you run the truck with the radiator cap off for a while to let all the air escape?

 

Burp the system and see if the trend continues.

 

Only for a short while. I figured it would burp into the reserve tank. The first time the reserve tank dropped in level I thought that was the burp and only one but maybe not. It runs fine and the temp gauge stays just under 1/2.

 

My truck sits low and after it warms up the resi is back to normal. Just checked right now and it’s in the middle.

 

Whenever I refill coolant, I fill at a slight slope and I use a lisle funnel to let it burp. If you don't see any leaks, it's possible that all the air was just being released. The reservoir is doing its job by allowing the system to be replaced with coolant.

If there was a leak, you'd smell it, or see it. Check your connections and block for dried pink residue. Check your crank case to see if its mixing with the oil. Check the smoke coming from the tailpipe, etc. If you don't see or smell anything out of the ordinary, I wouldn't worry about it.

 

The reservoir tank dropped about another inch today in 9 hours. I have crawled in, around, under, over and all around that thing and cannot find any trace of a leak. I would think if it were leaking that much it would show up somewhere. Tonight I replaced the aftermarket cap with the factory one. I am also thinking about putting some UV coolant trace dye into it and see if it shows up anywhere.

 

I had the same issue, and found that coolant hose above radiator fan, was seeping through a bit, and coolant traces were on the fan shroud itself.

 

Is it going into the combustion chamber?

 

You need something like the OEM Radiator Funnel kit that does a great job of getting the air out when you refill. And have your heater set to hot and the fan on.

https://www.summitracing.com/parts/...AuibPZiqKkglJwqtByZarLK_Z64AorsoaAh-uEALw_wcB

 

Does that model have the transmission cooler built into the radiator. I saw a post where it failed and water mixed with the transmission fluid. I suppose that if that were the case you would have noticed transmission troubles by now. Just a thought.

 

I am pretty sure it doesn't as I only had to disconnect the top and bottom hoses in order to remove it.

 

Did you ever find the culprit? Currently experiencing a similar thing with my ‘21 CM. I didn’t replace anything, just finished a road trip from PHX to LA and noticed the coolant level dropped about a quarter inch. I filled the reservoir about 4 or 5 weeks ago to the full line because it had dropped down to below the low mark. I don’t see ANY pink crusties anywhere in the engine bay or near the transmission cooler, I looked in the intake valley as much as I could for any signs of leak and nothing, and have never seen any drops on the skid plate or in the driveway. This one has me scratching my head.

 

Yea I’m experiencing NO symptoms besides dropping coolant reservoir levels. Oil is clean, no smoke, and no leaks. I’m guessing the fluctuations could be due to the change of location (PHX—> LA)

 

I have a 2016 and my water pump was leaking causing a drop in coolant. The pump was replaced around 75,000 miles. No issues in coolant levels dropping since that was all fixed over 35,000 miles ago.