Coolant Temp Gauge

Is there a mod to make the coolant temp sensor dynamic? Toyota made it so it just sits in the center and once it reaches a certain temp, BAM! You ran your truck till it overheated. Something about people being afraid that the temp sensor moving made them think that was smart. Is there a different resistor or motor that I could put in to make the temp sensor actually show me how hot the coolant is?

 

Scan tools and gauges tell actual coolant temp

 

That would be a way, but I was really hoping there is a way to make the factory gauge work how it should

 

I mean, I suppose you could, but it'd require reprogramming the ECU.

That said, that IS how it *should* work. It's purposefully dumbed down. The reason it doesn't show "real" temps is because people would see that, and freak out.

I see it all the time. People install a scanguage or whatever and within 15 minutes they're on TW asking if a 5 degree temp swing is "normal". (hint: yes)

IMO, unless you are trying to diagnose a specific cooling issue, it's not all that necessary to know the "actual" temp anyway. When/if the temp gauge starts rising, that means it's gone above some threshold that Toyota engineers decided was a "warning" level.

I have one of those blue tooth OBDII readers and Torque Pro on my phone. I played around with tracking temps for a while on my '17 4Runner (for trans temp) just to see how much hotter it got when I was towing my travel trailer. In the end, I never got any warning lights, and never cooked the trans fluid (smells fresh), even with the temps reaching 230ish. I've since put over 10k miles of towing on it.

 

Dang, I was hoping it was separate from the ecu, there is only one temp wire for the cluster and it is separate from the temp sensors that go to the ecu. Is it a separate ecu for the cluster?

 

That I can't say. I just remember some similar discussions coming up over the years. Never paid that close attention to the specifics, or committed them to memory, lol. IIRC, the solution was usually either an external analog gauge, scangauge, or OBDII scanner.

 

It would come down to finding a gauge and sending unit that are paired together.

Then installing the gauge in the cluster

The sending unit just changes resistance as the coolant temperature increases

 

Hmmmm. The sensor is already sending the complete data to the ECU as an analog voltage. If someone were sufficiently motivated, they could disconnect the gauge from the ECU and then drive the gauge with a separate device after splitting off the signal going to the ECU.

The trick would be figuring out the correct specs for driving the gauge, calibrating it to the input signal, and not disturbing the signal going to the ECU.


I think its doable. Might be a fun winter project if I came across a instrument cluster to experiment with.

 

Don't quote me but I believe there are two different senders. COLONEL SENDERS AND OJ SENDERSON!!! Just playing but for real I believe there are two different senders. The one by the timing cover is the one that feeds info to ECU. The dash gauge is fed by another sender. I respectfully disagree with JBrandt on this one. Running the OBD2 with real time info on a phone or tablet will show you temperature variance or temperature behavior. Yea, it's not that you need to know that you're always running 190 in heat or whatever but in an instance where something has failed you would see the number start to climb in an adverse setting (situation you wouldn't normally see temp rise). This would have alerted you WAY before the needle starts to move at 220!!!! Those heads are done at that point. Knowing trans temp just possibly saved me my trans at 293,000.... They are $25. I'm a high information person. I want all the information all the time. Depends on what type of person you are I guess and what you use your truck for. I personally think they are worth their weight in gold.

 

There is a single wire that feeds the gauge cluster wire from the lower intake manifold, its the only wire I missed when doing my head gasket. That is why I would think this is possible. Does anyone have the wiring diagram for the gauge/ sender

 

I used the hole for the temp sending unit to run my after market temp gauge it does not effect anything but the temperature gauge

Why I said the sending unit and the gauge need to be a matched set

No clue why so many seem confused between the sending unit and the coolant temp sensor

It should be the Yellow/Red wire

 

My answer is related to 2.7 engine. V6 might be different. The coolant temp gauge is quite sensitive shows the temperatures between 150F and 200+. Anything less than 150 is below the scale, 190 is at the center and over 220 is over the top of the scale. So it shows the normal operating temperatures with anything higher than 200F is Hot, anything below 160 is Cold. This is the test I did after replacing my sender:

https://www.tacomaworld.com/threads...k-or-rysium-build.457350/page-8#post-20756897

Now keep in mind that the gauge will not show the failures in time. It shows the engine temperature when everything is working, and simply saying it will worn you if you tow a trailer uphill in Death Valley with AC on, or will tell you that it is pointless to turn your cabin heater on in cold Minnesota winter before the needle goes above the L mark. But if you burst the lower radiator hose it may not even show anything wrong, even there is no coolant in the engine at all. If your water pump belt brakes it may rise a bit to the hot site but only after your engine is done and coolant turns to vapor. Unfortunately there is no real "engine temperature" gauge, that will warn you right away when engine starts overheating - for that it would have to have a sensor in the block or the head.

Very same apply to ECT sensor - it is in different spot, it feeds the ECU but it depends on the coolant being present and circulating properly. And it is dedicated really to tell ECU about the engine state for EFI end EVAP control. It is not to tell you about the engine health.

Sorry.

 

Even with an accurate temp gauge, most folks don't monitor their gauges constantly. A broken belt or hose can cause the engine to overheat in no time.

If you want to know when your engine is getting to close to overheating, the Ultragauge has an option for audible alarms (not just for coolant temp, but for almost any parameter you care to monitor). I find this feature very useful, it certainly gives me a peace of mind .

 

Thanks for the suggestion. I'll be looking into that and a possible analog gauge. kinda swamped with life right now though.