Temp probe goes in the inlet or outlet of rad?

[T-rev]

I would figure I want the temperate sensor telling me the temp of the coolant coming out of the motor (inlet of rad) but I started second guessing after I saw a picture of someone with their temp probe in the lower rad hose. The instructions for the gauges are all in japanese so they're no help. Can anyone confirm this for me?

[gumby74]

I have my gauge (AutoMeter Sport Comp) hooked up to the upper hose. It reads at about the same rate as the dash gauge. In that I mean it starts showing temp. a couple of minutes after startup.I don't know if this is right or not, but the lower hose took several minutes to show temp, and was never quite consistent.

[AZhitman]

Temp probe needs to go in the lower hose.

[onecrazyfoo4u]

Why would it need to go in the lower hose? I've always seen them hooked up to the upper hose, that's where mine is too....I'm no expert on it, just curious if mines in the right spot too!

[ZiG]

The stock temp sensors go on the connection to the upper hose. What does that tell you?

[AZhitman]

That's because they're reporting to the ECU.

Hot coolant enters the radiator by the upper radiator hose when the temperature of the coolant reaches the opening rating of the thermostat.

If you want to determine whether your car is operating TOO hot, you want to measure the temp at which it RETURNS to the engine, thereby telling you if your radiator is sufficiently cooling the coolant.

The water in the upper hose will always be relatively constant in the absence of an overheating problem.

[onecrazyfoo4u]

Thanks alot for the good info. Because everytime my stock temp gauge goes to Hot, like its overheating, my gauge is always reading about 190, but never over 200 deg. F. I didn't think that was too hot at all, just thought my dash gauge sender was broken or worn out. I'll have to move it to the lower hose, hopefully I haven't been overheating for real all of these times!!! As long as it's under say 210, it should be alright correct? Thanks again!

[AZhitman]

Don't rely on the stock gauge, it's notoriously crap.

And after some further research, I have found pros and cons of placing the temp gauge sensor in the upper hose - I still prefer the lower hose arrangement, but I'd be open to have my opinion corrected by someone more knowledgeable.

[Florida240sx]

Ignore all guages, Shut the laptop, WARNING DANGER TO RADIATOR HOSE the hose clamps will pop off

[ZiG]

D I still prefer the lower hose arrangement, but I'd be open to have my opinion corrected by someone more knowledgeable.

Can I give it a quick shot?

Ok, I learned all about control systems in my engineering courses, and we did go over stuff similar to this. The only real difference is that we were usually talking about a process (like heating beer as it is being made or something like that).

Anyway, the thing we want to know is the temperature of the engine, not the temperature of the radiator. For our purposes, we shouldn't really care what temperature the coolant is coming into the engine at, only what it is leaving at, since THAT will be what temp the engine is actually running at. If you're having some huge problem with the engine and it is generating way too much heat (say, leaning out or something) then the coolant coming out of it is gonna be hotter. If the coolant then goes into the rad and is cooled down just as much as normal, to whatever minimum temp it can, then your gauge mounted in the return hose would read that minimum temp, and you may be oblivious to a problem.

Errr.. hope that makes sense. I just woke up a few minutes ago...

[onecrazyfoo4u]

I got to thinking about it, and that makes more sense in the upper hose ZiG. That way you're monitoring how well your engine is performing/ heating up. If you want to know how well the radiator and thermo are performing, you would mount it in the lower hose.

I think that's why I mounted mine in the upper hose in the 1st place, I wanted to make sure the engine was running at normal temps. Does that all sound correct?