L76 getting a "contact dealer" after 160* stat?

[Silver09GT]

I searched and couldn't find any related issues from others running a 160-stat

I’m getting a “X contact dealer” and it is related to the coolant temperature sending unit, since the temperature sending unit has bottomed out and the air conditioner cuts off. Have you all seen problems like that with running a 160-degree thermostat with these L76 engines?

The reason I ask if it is stat related is that it doesn’t seem to happen in stop and go traffic,, only cooler morning when I catch all the traffic lights,, or late evening temperatures when I go directly to the interstate. Could it be the coolant temperature is not rising fast enough? Data logs show temps dropping to 160 degrees when the car is rolling, climbing to around 190 in stop and go traffic. The times this has happened are when the engine may have never gotten over 160 for the first 10 minutes or so of driving.

Then again, it just might be a bad sending unit,,, stranger things have happened.

[Sneakyws6]

YOu have to edit the P0128 code under the Engine Diagnostic>DTC tab. Turn the code to #3 with no report.

If the ECM does not see at least 167* over a certain duration it triggers that code and turns the coolant gauge offon the cluster.

[Silver09GT]

YOu have to edit the P0128 code under the Engine Diagnostic>DTC tab. Turn the code to #3 with no report.

If the ECM does not see at least 167* over a certain duration it triggers that code and turns the coolant gauge offon the cluster.

Thanks Sneaky, I found the logic behind how the code was set, couldn't find any parameters to adjust the set temp,,, and was about to ask if disabling the code was what you all were doing to get around that code. Thanks again for the help,, I appreciate it!!!!!

[Sneakyws6]

No problem, dealt with it on my TBSS and my G8 GXP so I already knew about the issue.

[Rockrz]

What's the benefit of running a 160 degree t-stat?

I always heard it makes the ECM advance the timing...but
if that is true, why can't the timing be advanced using
HP Tuners?

[Silver09GT]

What's the benefit of running a 160 degree t-stat?

I always heard it makes the ECM advance the timing...but
if that is true, why can't the timing be advanced using
HP Tuners?

On the G8,, it doesn't do much for you. It looks like I can run about 3* more timing when it's around the 160 temps (which didn't make much performance difference considering where I had the timing to begin with). Since you can't drop the fan setting under 192* with the standard HPT software,,,,, once you hit a little stop and go traffic, your saturated coolant temps end up being no lower than the factory thermostat (with the same fan setting).

So,, in my opinion,, for what that's worth,,, unless you have a long stretch to cruise so the coolant temps can drop below the fan setting,,, and keep you hovering around 160,, I'd say the 160 stat for the G8 is more suited for the guys taking their cars to the track on a fairly regular basis - so they can manage coolant temps better. In fact,,, I'm seriously considering putting the 187* stat back in the car.

You might want to visit a specific forum for your vehicle and do a search,, if its a fairly popular board,, this question will probably been beaten to death. I know some vehicles come with a 195 stat,,, if so,,, I'd have to get that out of there for a 180 though.

[Rockrz]

OK, so what do you do in the winter time when you need
the coolant to warm up enough for your heater to work?

[Sneakyws6]

While some of what Silver is saying I agree with there are some other points to running a 160* stat.

My car was running around 195* with the factory stat, now it runs around 170-175* all the time. I can run more timing, there is less knock recorded by the computer and the IAT temps are reduced as well.

I run a 160* stat in all of my performance cars and always will.

[Rockrz]

Does it not get cold enough in the winter where you
are that you have to use your heater?

I've heard of guys putting in the higher t-stat in
the winter, but changing this out seems like a PITA

Maybe they will come out with an electronic t-stat
so you can dial in what you need from inside the vehicle.

That's be c00L, or warm in the winter

[RWTD]

What's the benefit of running a 160 degree t-stat?

I always heard it makes the ECM advance the timing...but
if that is true, why can't the timing be advanced using
HP Tuners?

I've found zero benefit to a cooler stat like this, both on the street, strip, and on my Dynojet 224xLC (Eddy Current Load Control). The LSx based engines make their most power, and consistently, in the 19x range. More timing does NOT equal more power (yes, believe it or not!).

I'll be more than happy to prove to someone that with a proper tune you'll make more power in the 19x range. Hell, I do it all the time anyway, so no need to make my point.

[Silver09GT]

I've found zero benefit to a cooler stat like this, both on the street, strip, and on my Dynojet 224xLC (Eddy Current Load Control). The LSx based engines make their most power, and consistently, in the 19x range. More timing does NOT equal more power (yes, believe it or not!).

I'll be more than happy to prove to someone that with a proper tune you'll make more power in the 19x range. Hell, I do it all the time anyway, so no need to make my point.

Yep,,, no need to prove it by me. I wasn't having any spark knock under WOT to begin with and adding an extra three degrees with the cooler stat didn't do a thing to WOT 0-60 times.

My normal drive allows me to be moving enough to keep temps 170 - 160 degrees and it seems like it might be a fraction more peppy in that range as far as light and moderate throttle with a slightly more aggressive timing map. However,, it takes a while to get past 131-degrees when cold,,, and it looks like my gas mileage has dropped about a MPG on my daily drive because of it. It's not like these G8s are lacking on pep with a tune and the stock stat,, so I'm swapping back to the 187* stat. Man,, I hate redoing crap.

[Sneakyws6]

I Am Sorry But The Stock Stat Might Be A 186° But They Consistantly Run In The 210°+ Range On The Street And Can Get Even Higher Once 100°+ Weather Gets Here Like We Are Having In Oklahoma Right Now.

The Hotter It Gets Outside, The Hotter The Radiator Gets Then The Less The Ac Works As It Is Dealing With Hotter Temps From The Radiator.

I Have Noticed A Difference In How Cool My Ac Can Get Before And After My Thermostat Change And My Mileage Has Stayed The Same With Either Stat As I Average Manually At Each Fill Up.

[RWTD]

When I'm cruising, whether it's in 95 to 100 degree Alabama high humidity heat, the temps are around 199 range consistently. In Colorado's 90+ dry heat, the temps are around the same. The stock radiator does a great job at keeping the temps at bay.

As for the fan, they don't work past a certain mph anyway, so use them to your advantage at idle and low speeds. Yes, at idle, my temps get to around 208 on average in either of those two places in the conditions I posted, and I have seen 210. However, once moving, they cool down within a reasonable time.

As for the stock stat, it doesn't open fully at 187. It gradually opens. Now, I have no beef with purchasing a stat that is around the same temp as that, but opens fully, or taking and modifying the factory one to do such.

In regards to mileage, 2 of my customers who have switched to the 160 stat have complained of a decrease in economy. And, Silver09GT is right, the vehicle takes too long to warm up with the 160 stat in. I have made back to back pulls on the dyno with several Z06s showing that at 160, then 170, then 180, then 19x range, even testing around with varying spark ranges, that they end up making more power with each pull, and make the most consistently and smoothest power at 19x range.

[Sneakyws6]

Little Opposite Of What I Saw Here In Oklahoma When It Was 100° Out A Couple Of Weeks Ago.

Mine Made Less Power As The Vehicle Got Hot To The Point Of Having 5+ Loss In Power As It Got Hot Out Versus The Original Pull While It Was At The Operating Temps Of 175° When I Rolled Into The Shop And Got On The Dyno. Once Mine Got Over 195° It Made Less Power.

Of Course Oklahoma Is Hot As Hell Right Now It Seems.

[Silver09GT]

I appreciate the replies to this post from both Sneaky and RWTD,, they just may have saved me from putting the stock stat back in and pulling it back out!!

I didn’t do much data logging with the stock stat and what I did was late at night with outside temps in the 70s. I never saw the coolant temp get over 196* (long idle), and would see it drop fairly quickly to 188 degrees when rolling. It makes sense if the stock stat isn’t fully open at 186*,, and in peak day heat (near 100* temps here in Mississippi also) that the coolant temperature would get over what my limited data logging with the stock stat showed.

Sneaky,, you are right about the air conditioner – thanks for allowing the light bulb to come on!!! I didn’t drive the car a lot with the stock stat,, but do remember thinking the air conditioner on my 12-year old POS worked better than the G8’s. I was hoping it was because we were having uncommonly hot weather (plus it was sitting outside in the heat all day),,, and not the car’s fault (per say). However,,, temps are not much cooler,,, and the air conditioner is cooling a good bit better now - I actually have no complaint. That alone might be worth disabling the P0128 code and the drop in fuel mileage,,, which is probably related to my short daily drives and the percentage of time it spends under 131-degrees.

[04blackgmc]

i like my 160* car seems to run better and my MPG has not gone down...