How much coolant loss is normal?

[royalkangaroo]

I’ve got a 2015 Sierra with 62k miles.  Been meticulously maintaining since day one, however over the past year or so I’ve been topping off the coolant tank maybe once every 6 months.  10-12oz at a time I’d say (almost an inch below “full cold” mark).  Is this normal? 

[Mike GMC]

Unfortunately, no that's not normal.  Look around the radiator and all the hose connections for evidence of a small leak.  If you don't see anything, you may need to get a pressure tester so you can put pressure on the system and then look around for leaks.  Do you see any chocolate milky looking good under the oil fill cap?

[royalkangaroo]

18 minutes ago, Mike GMC said:

Unfortunately, no that's not normal.  Look around the radiator and all the hose connections for evidence of a small leak.  If you don't see anything, you may need to get a pressure tester so you can put pressure on the system and then look around for leaks.  Do you see any chocolate milky looking good under the oil fill cap?

No visible leaks or seeping from what I can see.  Oil fill cap is clean as well.  Coolant tank cap seems to seal fine.  I’m not quite sure, pressure test will probably have to be next.

[JimCost2014]

1 hour ago, royalkangaroo said:

No visible leaks or seeping from what I can see.  Oil fill cap is clean as well.  Coolant tank cap seems to seal fine.  I’m not quite sure, pressure test will probably have to be next.

Depends on who you ask, I have added coolant to each of my K2"s (14, 16, and once on my 18) and the wife's 16 Tahoe.

 

This is something I notice a lot when members post pictures of their engine bays, some are right the top full mark, and others are well below as you described. 

 

I could be wrong, but I think you do loose some due to evaporation, it is a "sealed" system, but with the engines running at 200 plus degrees, IMO, it happens.

[2018GMC]

Mine has been over full since day 1. 2 years later it hasn’t moved.

[NWI Denali]

I was literally just going to post this thread. My 2017 with 36k is down about an inch. No visible leaks. Wasn't there something about cracked tabs on the radiator?

[davester]

If the water pump seal is failing, water can come out it's weep hole and run down the front of the engine, and evaporate before it hits the ground.  You may be able to see a streak on the front of the engine, looking up the front of it when lying on the ground.

[JimCost2014]

4 hours ago, 2018GMC said:

Mine has been over full since day 1. 2 years later it hasn’t moved.

Thanks for the reply, my friend.

 

That is kind of my point, have not added a drop to the Tahoe after the AC condenser replacement, and it is the same way.

I was always told that too much is not a good thing either, much like oil, but with all the trucks I have had (exception on my 99 when the water pump failed), it seems they get to a "happy point" after a while and you do not add any more.

[JimCost2014]

3 hours ago, NWI Denali said:

I was literally just going to post this thread. My 2017 with 36k is down about an inch. No visible leaks. Wasn't there something about cracked tabs on the radiator?

On 14 and 15's, thermostat caused too much pressure in the system and cracked the radiator.

[MannyE]

Radiator caps can leak releasing fluid that immediately evaporate. With the coolant escaping as steam,  no leak is visible.

Edited April 12, 2020 by MannyE

[tlaw91]

On 14 and 15's, thermostat caused too much pressure in the system and cracked the radiator.

Yes this one. Probably a leaking radiator. Put one in anyways with updated thermostat. if not today then it’ll be cracked tomorrow.


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[beetle]

I have to add a few ounces every few months on my '14 since new. No leaks, I'm not worried.

[royalkangaroo]

I did a little more reading and took another look under the hood this morning.

One of the top radiator clips is cracked. One side of the top of the radiator looks very clean from what I can see, the other is brown and dirty. Not sure if this indicates a slow leak over there or not.

I’m going to make an appointment this week. Seems like this could be the issue: https://static.nhtsa.gov/odi/tsbs/2016/MC-10138004-9999.pdf


Cracked clip (clean side)





Dirty side






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[mookdoc6]

A good rule of THUMB?  If your putting more than a 12oz or about the same amount of can of soda into the reservoir prior to year of cycling something is off and you need to look into it further.  Could be as simple as your Coolant dilution is off.  If your concerned after inspecting like others posted as where to look...I would replace coolant with spec coolant to 50/50 exactly replace T-Stat and meticulous run/add new mixture until you get it land at about the same level every time in Reservoir.  Now, Mark the Reservoir with SHARPIE remember that every hot cold cycle will result in different levels settled in Reservoir tank they will differ maybe up/down 1/4" MAX that is expected.  If you get out that Sharpie line area markedly and in fairly quick fashion you have something going on no doubt! 

 

Or you could do what 95% of JOE PUBLIC would do...just keep pouring it in there SON!

[mookdoc6]

9 minutes ago, royalkangaroo said:

I did a little more reading and took another look under the hood this morning.

One of the top radiator clips is cracked. One side of the top of the radiator looks very clean from what I can see, the other is brown and dirty. Not sure if this indicates a slow leak over there or not.

I’m going to make an appointment this week. Seems like this could be the issue: https://static.nhtsa.gov/odi/tsbs/2016/MC-10138004-9999.pdf


Cracked clip (clean side)





Dirty side






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Almost everyone of these trucks will have the "CRACKED" clips both sides...means nothing other than CHEAP.  Look up into your corners for the very subtle weeping on the cooler.