Slappy3243

Hey Guys,

So this is interesting to me. I did a search but really didn't come up with much. I live in Florida it finally started to cool down the last week or so. Most of my driving is on the highway, 7th gear, 75-80 MPH. We all love the feature on the tachometer that has the small yellow bars disappearing as the car warms up. My issue is that while driving on the highway, the yellow bars come back to about 5500 RPM. If I get on the car a bit more, they will go away again, but then pop up after cruising. They never go low like when first starting the car.

Anybody else experience this? I just don't want this to be indicative of a problem like a stuck thermostat or something.

Thanks.

davepl

That's because the Z06 is notorious for underheating when not driven on the track.

Slappy3243

I don't have a Z06. Sorry if I missed something but that went right over my head

mschuyler

You might want to stick the speedo on the option that shows actual oil and water temps on the right side. That would give you a better idea of the temps you are running. Mine on the highway are usually over 200 but can be in the 190s on a cool day. The bar goes up within 2 miles of starting out from bone cold, so about 170-180 or so IIRC. These cars run a little hot compared to what I'm used to, but am told this is normal.

hangman

Same exact behavior as my 2016 base. I don’t worry about it too much. I have a thread on here about it and a video as well.

VNAMVET

....you're so bad............funny too!

NSC5

Sounds like your thermostat is sticking in the open position after initial warm up. The engine temperature should definitely not drop back to the point where the "cold RPM" limits are displayed again after it initially reaches normal operating temperature.

Slappy3243

Can you post a link to your thread? I would like to read it. Have you discussed it with the dealer or elsewhere?

Thanks

This was my initial thought although my oil temps seem to be lower too. Around town driving this doesn't occur; only on the highway trips. Fans kick on as normal when at stop lights and such.

Are there any other symptoms of a stuck thermostat I should check?

Thanks

NSC5

The oil temperature will also run cooler since it uses an oil to engine coolant heat exchanger and normally the oil will track within a few degrees of the engine coolant temperature; often slightly lower since the oil cooler is fed from the cooled side of the radiator while the engine temperature gauge measures the coolant temperature before it leaves the top end of the engine.

Around town driving with stop and go traffic will heat the engine more than highway cruising so unless the outside temperature is quite cool the thermostat will be fully, or nearly fully open, in around town driving.

You should still be in warranty so I would get it to the dealer before it starts setting nuisance codes from the lower than normal operating temperature.

davepl

Just an attempt at humor... there was a while where every second thread was about Z06s overheating at the track, so I figured if you're under-hearting, it must be from a lack of tracking it... but if not a Z06, it made no sense, sorry!

Nonetheless, I don't think your car has an issue...

BELVIN20

My 2016 Z does exactly the same thing, glad to hear I am not the only one that has seen this happen. I have had the display that shows the digital temps, no more than 5 degree change in coolant temp, so I don't think that is enough to trigger the yellow 5500 rpm tach. I have also noticed that the heads up tach does not change its RPM red line when the dash tach does its thing. The chance of getting the car do this condition at the dealer is slim, never can tell how far you have to drive it for the yellow bar to show up.

Slappy3243

No warranty here unless it considered powertrain. I have a 2014 Z51 with 55,000 miles or so. Thank you for the information. Seems like this is happening to others as well.

I will check the coolant temps with the digital readout. I will also keep an eye on my head's up display to see if the changes on the DIC are reflected there as well.

Yeah, reproducing this would be difficult. We would need to go take a cruise on the highway in 6th or 7th gear for a ways.

Thanks.

NSC5

You should be covered under powertrain, excerpted from the Chevrolet warranty page on engine coverage: "Coverage on the engine cooling system begins at the inlet to the water pump and ends with the thermostat housing and/or outlet that attaches to the return hose."

Your thermostat should be within that covered "loop" of parts.

Slappy3243

Good to know! Thanks.

Gearhead Jim

Speaking of the extra yellow and red arcs on the tach, are they controlled by oil temperature or coolant temperature or some combination?

And what temperature(s?) does it take for them to completely disappear?

When they first disappear, both my coolant and oil are seriously cooler than I would want for full throttle/full rpm use.

Slappy3243

Apparently my 2014 model year car only had the analog read-out for coolant temperature. I tried messing around to get a digital reading but couldn't find it anywhere. Same issue on my way home as expected. I will try to bring the car in. I took some pictures of it too.

NSC5

I rarely use that screen but I think you need to have the display set to touring mode and then go into the information DIC menu to get the digital readouts.

JerryU

In 3 1/2 years my yellow outer rings never went back on my Z51 nor does it now on my Grand Sport.

First cool day today, it was 61 when I traveled 16 miles back from town on Interstate in 7th gear with cruise control set at 78 mph. Temp stayed at ~200.

dmhines

Never heard of this issue .. never happened on my 2014 or 2017 and drove to work in GA on many cool days. I drove to work this morning .. it was 42 degrees .. once warm it stayed warm ... 17 highway miles.

NSC5

The only vehicles I have ever owned that would cool excessively after initial warmup have been two diesel pickups when driven in very cold weather without grill covers in place. Because diesels have no air throttle and very little fuel is injected under light load they can cool excessively through the amount of fresh air ingested (similar to how Cadillac allowed their Northstar V8 to run in "camel mode" which allowed operation at reduced power after cooling system failure via shutting off fuel to alternate cylinders while allowing intake air to cool them).

My Z06 stays at normal operating temperature even when I was driving it in the mountains using engine braking on long downhill runs. It shouldn't have any problem maintaining normal temperature (at least staying warm enough) once initial heating has occurred.