Stumped on hot temp gauge reading
 

Hey guys,

I have an LS3 with an Entropy radiator in my 68 Camaro. When I bring the car up to temp the gauge keeps steadily climbing to almost 250 degrees however when I use my infrared temp gun on the upper hose it reads approx 150 degrees and the lower hose is right around 110 degrees. I replaced the thermostat this morning hoping it was that but its still doing it.

What's weird is I've cruised it around the neighborhood and it doesn't show any symptoms of overheating, no leaking coolant, hot smell, etc. but still shows almost 250 on the gauge.

Anyone have any ideas on what to check next? Could it be a miscalibrated gauge?

Where did you put the temp sensor? Is it close to ambient air temp after the car sits over night or does it read way off when looking at the ECM data with scan tool? If you put the gauge sending unit in the passenger side rear of the head then it's going to read higher than the driver side front of the head.

Mine is on the radiator passenger side right below the steam and radiator out. Is this what you're talking about? Sorry the pic keeps uploading upside down.

Move it to the passanger head on the rear. Also hook up a scan tool if the temp still shows a variation and read what the ecu is seeing. Pretty simple

I have the same setup- factory sensor in the drivers head, entropy sensor in radiator. I have found that there is about a 10 degree difference between the two. Is your radiator filled to capacity? It sounds like you have air in the system.

I don't think there is air in the system. I filled it up, ran the car and kept topping it off until it stabilized and couldn't see anymore air coming up.

Are you saying you have two sensors? One in the radiator and one in the head?

The steam is likely causing you the issue. I don't like the location for actual engine temperature either. You want to know how hot the coolant is in the engine, not after being cooled by the radiator.

That temperature sensor is for the fan controller. His temperature gauge is likely on the driver side head.

Pretty sure you have air trapped in the system based on your description of how you filled your system. You did not burp it....

Don

Any chance you have part numbers to make it work on the block? I tried searching but get overwhelmed with all the different answers. I found the correct M12- 1.5 thread with 1/8th NPT but when I screw in the sensor it doesn't come all the way out the other side which I assume means it wouldn't get a good reading?

That's not the how I interpreted above...

First off, thank you guys for helping me with all this. I'm new to all this so it's a learning process.

Here is a pic of the drivers side, is that also a temp sensor?

Yes it is and I’m pretty sure that is for your ECM and most likely your gauges are using it also. The one in the radiator is for the fan controller. Do you have an Entropy fan controller? Dakota Digital gauges with BIM module on the bus for the gauges?

Don

Honestly I don't know if I have Entropy's fan controller. I had a builder install the motor, ecu, etc. but he's no longer in business and we've parted ways. I'm actually running New Vintage gauges that I had custom made to fit in the Gen 5 Camaro console.

Ok then maybe your gauges are using that sender which would be wrong location for a gauge sender and should certainly not be reading 250 degrees if that is the case.

Maybe post some pics of your controllers etc. Entropy fan controller looks like this. Looking at your sender it is not the Entropy sender.

Have your gauges ever read lower or always 250?

Don

Nu Vintage temperature sender

You were right! I was wrong!

Don

It will read fine. Certainly better than in the radiator. But if it is reading 250 in the radiator then simply moving it will not fix that. Something else is wrong imho.

You should get a code reader for the bus and see what the ECM is reading for temperature as suggested earlier.

Don

The Nu Vintage sender is definitely what I have and it's shallow so when placed in the M12 -1.5 it never comes out the other side. Is that fine, or does it need to extend outward past the tip to read properly?

And the gauge has always read that high since I had it up and running.

Where do you live? Maybe some one local can help

Is your IR temperature meter reading Celsius? Probably a dumb question but....

Don

Thanks for everyone's help. I think it's time to find a shop to take a look.

It will work fine not sticking out.

Don

You gave up too easy. This is an opportunity for you to learn what you have...

Don

You're right Don. I went ahead and install the sensor in the rear of the head, fill her back up and got all the air out of the system and she's maintaining 185ish!!

I'm gonna drive it around the block once the weather cools down a bit here and I'll keep you posted.

Am I crazy to think that maybe having the sensor right below the steam return would mean steam was going over the sensor and making it read that high?

Maybe. I have to admit I don’t know and I would not have expected moving it to work that well. Good job!

Owning these cars is an exercise in learning. It’s part of the fun imho.

Don

Welp, I took her out once the sun went down and it's still climbing towards 250 degrees. Ugh, thought moving that sensor helped but I guess not. Gonna see tomorrow if maybe I've got air in the system.

How are you filling the engine/radiator? There are a couple of different techniques for helping avoid the "trapped" air issue. I have had good luck with filling the engine through the upper hose in addition to filling the radiator method before connecting that hose to the radiator. Keep adding it slowly until it is totally filled, you might encounter some air bubbles, but keep going until they are gone. You can also either raise the front (or rear, cant remember which one) while running will also help burp the system while running.

Thanks for the advice! I'll try those methods today.

Raise the front as high as you can.

I have good luck keeping air out of the system filling it with one of these:

https://www.ebay.com/itm/New-Lisle-2....c100005.m1851

Don

Alright maybe there is a blockage? I brought it up to temp this morning with the front end raised really high to try and bleed some air but I also put a thermometer in the radiator to see what the temps were. Whats odd is that the temp in the radiator never climbed and stayed around 80 degrees but I can fill heat in the top hose and the gauge is reading around 250.

I've ordered a new thermostat from Summit to try that option and I'm not sure the one I got locally was the right one.

Just so I can get confirmation, I have the hoses going the the right inlets right? The top one goes in, well the top one, and the bottom returns back to the lower radiator.

It sounds like your thermostat is not opening or you have an air pocket. I can’t remember if you can install an LS thermostat backwards but if you can maybe that is what is going on...

Hoses are correct.

Don

Did you just start having this issue or is this the first start up and break in? Does the lower hose ever get hot?

It's been doing this since I got it up and running. I'm going to install the correct thermostat tomorrow and see if that helps, If not, I'm going to run some food coloring through the system and see if the water is actually circulating through the motor. I figure that will be a good indicator if the water pump might be bad. Just trying to eliminate all the possibilities one by one.

Ok so how many miles have you really driven it? Start the engine and make sure the bottom Hose gets hot. If it doesn’t the engine isn’t to operating temp or the thermostat hasn’t opened. The boring gauge will read that the engine is hot but until the thermostat opens up and the system bleeds you won’t get a accurate reading.

Again where do you live ?

Sorry missed that question earlier, I live in Los Angeles.The motor was from a 2012 Camaro with around 19k miles and I've probably put right around 500 miles on the car since I've had it up and running.

Alright installed the correct thermostat, put it all back together and filled the coolant through the top hose slowly until it ran out the top of the radiator and with the car elevated. Turned on the car and let it warm up for a good 10-5 minutes and the gauge still climbs all the way to 250. The fans come on around 220 which I think is too late and the bottom hose was col the entire time so I'm assuming the thermostat never opened up. I let it run showing 250 for a good 5 minutes before shutting it off to be safe. Should I try to let it run for longer and see if the thermostat does open up? I just don't want to overheat the engine.

Oh, also I'm running Vintage Air's frontrunner setup and it's all brand new including the water pump and radiator. The 500 miles or so I've put on the setup has been with all new parts.

Keep letting it run. The lower hose needs to get hot. Have the heater running as well

Alright, I'll try again this evening. I can't run the heater as I don't have the actual vintage air system hooked up yet.

Ok, ran the car for over 20 mins and it never seemed like the thermostat opened up because the lower hose still never really got hot while the top one did. The lower one seemed to slowly start warming but not sure if thats just the residual fluid in the radiator mixing from the top to the bottom and not circulating through.

I feel like running it for 20 mins should be long enough for it to come up to temp all around and kick open the thermostat, am I wrong?

Thanks everyone for their patience as well. By now I've drained and filled the radiator about 10 times. LOL.

Put a manual temp sensor in it to verify. Maybe you’re chasing your tail.