Low engine temp after radiator flush

1SLOW1500 · February 22, 2019

So the lt is the evolution of the ls and the coolant system has a auto purge setup that said I hate it. So we start truck and Un plug the highest vent port at the radiator. If I remember right there is a disconnect in the middle so hold hose high. Other wise there is just the over flow tank.

Sent from my SM-N960U using Tapatalk

njs2247 · February 22, 2019

8 minutes ago, SS502 said:

So are you or are you not seeing the fluid level dropping? Obviously we missed the fluctuations in your original post...but if you’re not losing fluid you shouldn’t have a leak, maybe air in the system but no fluid loss equals no leak.

No, fluid level has been normal.

Sierra Dan · February 22, 2019

18 hours ago, njs2247 said:

Dan, where about on radiator are the cracks happening? I've yet to smell any coolant, but I'll take a look and see if I see anything.

Up at the top on both driver and passenger sides. Or on one side or another.

The cracks are where the aluminum meets the composite plastic. Where they are fused together.

Here is the thread to the problem:

TSB

#15829: Special Coverage - Radiator Leak - (Nov 9, 2016)

Subject: 15829 — Radiator Leak

TSB #1513 is on 2014

In my case I kept smelling coolant around the front grille area of the truck.

It was slowly evaporating thru the cracks and no visible sign of dripping onto the floor or ground.

I had also noticed my coolant level dropping about 1/8-3/16" from the full fill mark in the reservoir.

Sierra Dan · February 22, 2019

15 hours ago, SS502 said:

So are you or are you not seeing the fluid level dropping? Obviously we missed the fluctuations in your original post...but if you’re not losing fluid you shouldn’t have a leak, maybe air in the system but no fluid loss equals no leak.

Depending on the size of the radiator crack, air can get in without necessarily allowing coolant to fizzle or leak out.

At least this is what my dealer explained. My level drop only occurred In the warmer summer months and again about 1/8" or about 2 cups of coolant over the course of 3-4 months or a few thousand miles.

Again because the OP has a 2014 Model I brought up this TSB radiator problem so he can check that out and possibly have it fixed free now without having to buck up down the road.

Dealers are usually favorable to taking care of TSB issues on early models because they know there were definite problems early on.

SS502 · February 22, 2019

Just now, Sierra Dan said:

Depending on the size of the radiator crack, air can get in without necessarily allowing coolant to fizzle or leak out.

At least this is what my dealer explained. My level drop only occurred In the warmer summer months and again about 1/8" or about 2 cups of coolant over the course of 3-4 months or a few thousand miles.

Again because the OP has a 2014 Model I brought up this TSB radiator problem so he can check that out and possibly have it fixed free now without having to buck up down the road.

Dealers are usually favorable to taking care of TSB issues on early models because they know there were definite problems early on.

I don't think you can ever have too much information! I won't even pretend to know or be an expert in the cooling system but my brain is trying to understand how a pressurized (when hot) system can allow air in but no fluid out? Not saying it can't happen, I am a visual learner and can't always see things as they are. I guess when the system is cold it could allow air to enter the system and as it heats up and things expand maybe that somehow seals the crack/leak point?? No argument here, just a wondering (some would say wandering) mind at work LOL

njs2247 · February 22, 2019

I have 117k miles on my truck, so I seriously doubt the dealer will work with me, even if I show him the TSB. I guess it's worth a shot. The weird thing is that this all started right after I got the system flushed. I noticed it when driving it home from the shop. I know for a fact that it didn't do this before the flush. I always glance at my gauges while driving (something my dad drilled in my head when I was younger).

I'll definitely check for leaks when I get though.

1SLOW1500 · February 22, 2019

I don't think you can ever have too much information! I won't even pretend to know or be an expert in the cooling system but my brain is trying to understand how a pressurized (when hot) system can allow air in but no fluid out? Not saying it can't happen, I am a visual learner and can't always see things as they are. I guess when the system is cold it could allow air to enter the system and as it heats up and things expand maybe that somehow seals the crack/leak point?? No argument here, just a wondering (some would say wandering) mind at work LOL

You are mostly correct a leak works both ways. However if you look at a over flow tank. When it is low it sucks air in. I have a aluminum tank. With hole at the bottom and welded inside is a breather/overflow. So I keep a eye on it as it took a long time to purg all the air out of the system. Now I have a radiator cap on the upper hose. So I can use a full funnel. Mounts to a special cap and allow the engine to warm up and burp out the air. My cap has no internal rubber so it can expand the water and suck it back.
So to answer your question air pockets in the top of the radiator will suck air in as other than the termostatw closed it isn't a pressurized system. Look at the lower hose and see it goes to a over flow or fill tank that breaths and releases pressure.
That my understanding of it. The disign has pockets in the very top of radiators that is why we vent the top steam line also. But there are also pressure vacuum fill tools out there.

Sent from my SM-N960U using Tapatalk

MRW412 · March 5, 2019

Did you figure out the what was causing the temp to fluctuate?

njs2247 · March 5, 2019

I've ordered the thermostat but have not had time to switch it out yet. I've been keeping a close eye on coolant level and it has been normal this whole time.

The engine temps haven't really been fluctuating, it just stays below 210 all the time. Hovers around 190 for the most part. I'm going to dealership to get recall work done on Friday, so I might have them do a pressure test to make sure there's not a small leak or crack I'm missing.

I read on a Corvette forum from a guy that had a situation like mine and it turned out to be a hairline crack on radiator just before the water pump that was sucking in air causing low engine temps. His coolant level also showed normal.

Anyone have some tips on how to burp the coolant system? Maybe the shop that flushed my system left some air in there?

MegaCode360 · March 5, 2019

I have a similar situation. Granted it's been cold here, but my temp drops to 195 or so when cruising down a hill off the gas, but goes back up to 210 when I get back on the gas. Is everyone else's right at 210 all the time?

njs2247 · March 5, 2019

Every other GM truck I've had has run at 210. Plus this didn't start happening until I got coolant system flushed. Before then, it was running at 210 when warmed up. My truck will get to 210 if I'm driving very aggressively, but for the most part it stays around 190-195.

diyer2 · March 5, 2019

My 2012 will drop in temp on a cold day going down hill.

Goes back up to 210 once under load again.

Grumpy Bear · March 5, 2019

3 hours ago, diyer2 said:

My 2012 will drop in temp on a cold day going down hill.

Goes back up to 210 once under load again.

My 2016 is just like diyer2's. Always has been. Even after thermostat swaps.

MRW412 · February 6, 2020

Finally replaced my thermostat. It fixed the issue. Engine stays at 210°.

Roger906 · February 28, 2021

Drill tiny, 1/32 " hole in t stat in between the center hole and the gasket flange. It will allow a tiny amount of coolant thru,(and air!) , not enough coolant to matter, but the air will eventually get purged at the reservoir tank