Battling cooling issues

mitchely03 · August 17, 2020

Hey all, just wanting some guidance on where I should look for a problem, or if I am in the clear and these are normal situations...\

Recently on my 2015 5.3L with 77k I am noticing coolant issues and trans temp not only in towing, but almost in normal driving...

It has been hot in here in Socal lately. I was towing my car back from the track yesterday and my coolant hit 230... Trans temps got to 207. I think that is extremely high... for the given scenario. I am towing about 9500lbs, and it was 100* yesterday.

Am I crazy to think that this should be happening? Is this normal? If not normal, where do I need to look to help with this. I have a track day at the end of the month and its a 4+ hour drive... I DO NOT want to take it if my truck is getting temps like this.

Any thoughts?

P.S. I have NOT done the thermostat mod for the trans. I am considering it...

CamGTP · August 18, 2020

I'd say 230 on the coolant temp isn't that abnormal.

I've hit 228-230 many times when I hot rod my truck around or when I went to the track. Doesn't take much for it to go from 210-215 cruising temps to 230 when I'm putting a ton of heat into the engine going wide open throttle. When you are towing it's doing the same thing at less rpm but the load is way higher.

They sell lower temp thermostats that may help you. I would go too low, maybe a 185 or 190ish if they make one like that.

The transmission thermostat mod for the 6L80e should be done, it's easy and drops temps.

mitchely03 · August 18, 2020

16 hours ago, CamGTP said:

I'd say 230 on the coolant temp isn't that abnormal.

I've hit 228-230 many times when I hot rod my truck around or when I went to the track. Doesn't take much for it to go from 210-215 cruising temps to 230 when I'm putting a ton of heat into the engine going wide open throttle. When you are towing it's doing the same thing at less rpm but the load is way higher.

They sell lower temp thermostats that may help you. I would go too low, maybe a 185 or 190ish if they make one like that.

The transmission thermostat mod for the 6L80e should be done, it's easy and drops temps.

Thank you for the insight. Makes me feel better about the temps.

I will do that thermostat mod for the trans.

Lsgun1 · August 19, 2020

I agree, doesn't seem out of whack especially for 100 day and I'm guessing the A/C was on.

mitchely03 · August 19, 2020

1 hour ago, Lsgun1 said:

I agree, doesn't seem out of whack especially for 100 day and I'm guessing the A/C was on.

Yup ac was on too

mitchely03 · September 1, 2020

So after doing the thermostat "flip pill" mod..

Towing last weekend to the race track. Was a 4 hour drive. In about 100 degree weather.

Going up hill my highest recorded coolant temp was exactly 233.60 would not get higher than that.

Highest trans temp was 223.

Coming back home going up the grapevine 5 freeway. Highest coolant temp was 233.60 and trans temp was 243...

How ****ed is my engine and trans?

Grumpy Bear · September 1, 2020

I've run a Reisch Racing 170 F stat for years without issues. The 160 stats will need a tune and are too cold of a street motor that isn't supercharged or turbo'd

This one below from Katech is a drop in and the gasket stays on unlike the one Jon and I both used before. This one is MUCH better.

https://store.katechengines.com/174-degree-gen-5-lt-thermostat-p729.aspx

Here's some data and his methods. Lives in California. Note he also lowered fan settings and runs Red Line D-6, a PAO/POE blend with a higher temperature resistance. That does not help prevent seal damage and and you are getting close on that point. Your oil temperature will be running hotter than you water (see his gauge pack). This sort of heat..to me....Either change oil like you change socks OR use either AMSOIL SS, or Red Line HP, both Ester based oils with more heat tolerance.

If this doesn't get her done then the next step would be to separate the trans cooler from the radiator and use a fanned stacked plate exchanger. Derale trans cooler. Followed by a NHT radiator. But one step at a time.

CamGTP · September 1, 2020

Well, I mean you are pulling basically the max weight for that truck with the AC on and in 100 degree weather. I'm not sure you can expect a whole lot less when it's kinda the worst case scenario right now.

I bet if the temps were 10-15 degrees cooler the temps would be much less.

What are your temps with the thermostat mod when not towing 9,500 lbs??

Epsilon Plus · September 2, 2020

Unfortunately, normal.

I got about the same results pulling 6350#s in the flats but in 116F ambient. Thats WITH a trans thermo delete and a 174 stat and modded fan settings in the tune. It's all within the parameters of the modern fluids but I still don't like it either.

I'm considering adding more power with an intake/exhaust combo to lessen the load of the engine but I think the right answer is eventually diesel. Too bad GM currently makes the most hideously ugly full size trucks in the business.

Edited September 2, 2020 by Epsilon Plus

mitchely03 · September 2, 2020

16 hours ago, CamGTP said:

Well, I mean you are pulling basically the max weight for that truck with the AC on and in 100 degree weather. I'm not sure you can expect a whole lot less when it's kinda the worst case scenario right now.

I bet if the temps were 10-15 degrees cooler the temps would be much less.

What are your temps with the thermostat mod when not towing 9,500 lbs??

I was scared so I turned the ac off when I was pulling up the hills, but when i was back on flat ground AC was on, but temps were looking better like 210-212 on coolant and 167-170 trans.

NOT towing, i actually noticed my coolant temps got to around 220 yesterday... not dead stop traffic, but just moving at like 20mph. AC wasn't on, it was about 87 degrees outside.

I should NEVER be seeing anything above 210 normal grandpa driving no???

Whats odd to me is ill see 210 temps, then i look away and I will look back and they dropped down to like 186... then climb back up, then drop.

Grumpy Bear · September 2, 2020

1 hour ago, mitchely03 said:

I was scared so I turned the ac off when I was pulling up the hills, but when i was back on flat ground AC was on, but temps were looking better like 210-212 on coolant and 167-170 trans.

NOT towing, i actually noticed my coolant temps got to around 220 yesterday... not dead stop traffic, but just moving at like 20mph. AC wasn't on, it was about 87 degrees outside.

I should NEVER be seeing anything above 210 normal grandpa driving no???

Whats odd to me is ill see 210 temps, then i look away and I will look back and they dropped down to like 186... then climb back up, then drop.

That's your fan cycling as it should. A radiator needs air flow to exchange heat. In 20 mph traffic you don't have enough. So the fan does the work. So yea, in normal grandpa driving at such a low speed and on such hot days...yea...pretty normal. Even mine does it in 'wreck' traffic on a hot day.

Your non tow numbers look good. Could look better with a lower water thermostat as pointed out earlier.

Your towing numbers are going to need the help of more cooler in that climate. Your truck, I take it, is not NHT. The RPO code in the glove box.

Grumpy Bear · September 2, 2020

Note that cooling is highest between 50 and 55 mph? Heat exchange is a compromise between area, flow and TIME. Time in the case of an exchanger is measured in air speed and density. In engineering calculations its 25 meters per second.

IMHO your system is operating normally BUT it is operating at it's maximum capacity and then some.

It will not get better without some help.

flyingfool · September 2, 2020

if it's a 6 speed ...he could have a mechanic install the deep SS camaro pan for more heat resistance...

what are the temp cycling points on the grill shutters? open/close temp? and how does one modify these points? was toying with the idea of removing the motor T-stat for an experiment, and just use the grill shutters and fans as my thermostat

Edited September 2, 2020 by flyingfool

mitchely03 · September 2, 2020

40 minutes ago, Grumpy Bear said:

That's your fan cycling as it should. A radiator needs air flow to exchange heat. In 20 mph traffic you don't have enough. So the fan does the work. So yea, in normal grandpa driving at such a low speed and on such hot days...yea...pretty normal. Even mine does it in 'wreck' traffic on a hot day.

Your non tow numbers look good. Could look better with a lower water thermostat as pointed out earlier.

Your towing numbers are going to need the help of more cooler in that climate. Your truck, I take it, is not NHT. The RPO code in the glove box.

Okay, thank you for the reassurance again. I think I am going to get the lower thermostat... seems cheap enough and easy to install.

I am not seeing the NHT code. What does that indicate again?

mitchely03 · September 2, 2020

36 minutes ago, flyingfool said:

if it's a 6 speed ...he could have a mechanic install the deep SS camaro pan for more heat resistance...

what are the temp cycling points on the grill shutters? open/close temp? and how does one modify these points? was toying with the idea of removing the motor T-stat for an experiment, and just use the grill shutters and fans as my thermostat

Mines a 6 speed. I have heard of people installing those deeper pans. I think morosso makes one? My grille doesn't have the shutters.