3FE temp gauge not working

[LS1FJ40]

1992 FJ80 233k.

Did my weekly winter power washing of my truck the other day. It was a balmy 46 degrees out. On Thursday I noticed my temp gauge hadn't moved from Cold. I don't always drive far enough to get fully up to temp so I don't pay attention on my 1 mile trip to work. On Thursday it was 0 degrees out so I started my truck and let her warm up for about 20 minutes before I left and drove her around for another 15 to get her nice and toasty. Temp gauge didn't move. Today (Friday) it is 12 degrees out and did the same thing. Still no movement. Could I have knocked something loose?

Water temp sender is still there. Wire looks ok. Checked relays and fuses. All seem good. What am I missing? Could the sender have just gone bad? I mean, it's original and 22 years old with 233k on it. I just get surprised when something stops working.

 

[jonheld]

Low on coolant? Does the heat still work?
Pull the sender wire and reseat. Sender wire is the lowest one on the left side of the lower housing.

 

[LS1FJ40]

Yeah, heat was still blowing hot. I checked coolant reservoir and it was low. I have a small leak in a hose where I've been losing coolant. Not much but I guess it's been a while. I filled the reservoir this morning. I checked it after school today and the reservoir is low again. Going to have to dig in to this this weekend. Ugh.

Thanks.

 

[LS1FJ40]

Have a more significant leak than before. Saw a small puddle below the bottom inlet on the radiator. Doesn't appear to be that hose but one above it somewhere. Will check it out tomorrow. She sits for the night...

 

[jonheld]

Have a more significant leak than before. Saw a small puddle below the bottom inlet on the radiator. Doesn't appear to be that hose but one above it somewhere. Will check it out tomorrow. She sits for the night...

It is difficult at best to find a coolant leak with a cold motor. The system needs to pressurize. Once it does, it should be fairly obvious.
Also, the level in the overflow will rise and fall with engine temp and coolant pressure. Make sure you're not being fooled by that. Always check level with a cold engine.

 

[Golgo13]

I almost hate to post this because it seems so basic and might make me look like an idiot, but if someone is willing to teach me something new, at least I won't be ignorant on the topic...I'm weighing in because my temp gauge also doesn't work. I'd like to join @LS1FJ40 on the subject.

I have never owned a vehicle where there is normally coolant in the overflow tank. My current '92 overflow tank has been bone dry since I got it, but the radiator is full enough that the bottom of the radiator cap is always wet. How important is it(and why?) To have coolant in the overflow tank?

 

[LS1FJ40]

Going to dig in to this when I get home. It does NOT leak when not running. Leaks substantially when running. Gauge doesn't move at all even when adding fluid to overflow while running.

Going to check sender wire when I get home and see if I'm getting power to it.

Ironically, my high blower speed quit working the other day. It had quit before. I keep spare 90987-02004 relays in my truck so I swapped Ty out and it works fine now. Still no temp gauge though...

 

[jonheld]

I almost hate to post this because it seems so basic and might make me look like an idiot, but if someone is willing to teach me something new, at least I won't be ignorant on the topic...I'm weighing in because my temp gauge also doesn't work. I'd like to join @LS1FJ40 on the subject.

I have never owned a vehicle where there is normally coolant in the overflow tank. My current '92 overflow tank has been bone dry since I got it, but the radiator is full enough that the bottom of the radiator cap is always wet. How important is it(and why?) To have coolant in the overflow tank?

Every vehicle with an overflow tank should have some coolant in it.
Start with a cold engine, a full to the top radiator (up to the top of the filler neck) and about 1/3 full of the overflow reservoir.
As the coolant heats, it expands and pressure builds in the system until it reaches the limit of the radiator cap. The cap then allows excess coolant/pressure to bleed off into the overflow tank and the level rises.
When the motor cools down, the cooling system pressure goes negative and draws coolant back into the system from the reservoir and the level falls.
This process allows the system to pressurize and maintain a constant coolant level in the system.
If the overflow is empty, you're sucking air into the radiator not coolant. However it is important to start with a full radiator, right up the filler neck.

 

[LS1FJ40]

Found the leak. Bottom inlet hose.

Now to figure out the temp gauge...

If I can't figure it out it really doesn't matter much. I'm adding an inline sending unit with digital gauge anyway.

 

[jonheld]

It does NOT leak when not running. Leaks substantially when running. Gauge doesn't move at all even when adding fluid to overflow while running.

Then it should be easy to find the problem.
Adding coolant to the overflow with the engine running will do nothing other than fill the bottle. It does not add coolant to the radiator. In your case with a substantial leak, you are loosing coolant when pressurized and sucking air back into the system when the motor cools.

 

[LS1FJ40]

Picked up an aftermarket hose today. (Rebuilding the motor in the spring when school is out so I will buy OEM then.)

I have a question. This may seem silly. I just flushed my cooling system about a month ago (maybe 300 miles). Can I "catch" the coolant when I take the hose off and reuse it or should I just bite the bullet and buy new?

 

[Golgo13]

thanks, @jonheld !

 

[4G63 POWER]

WHat color is your coolant?

 

[LS1FJ40]

WHat color is your coolant?

Not Toyota Red...