Water temp gauge

Believe it or not, I don't have a water temp gauge in my ITA 240SX. The stock gauge seems to go straight to the hot mark. I don't know if it's the sender or the gauge. The only thing that seems to work on the stock gauge cluster is the tach and that is suspect so I would guess it's the gauge. In any case I want to put in an aftermarket gauge that is actually acurate.

My question is can I just get an electrical water temp gauge and splice into the wires coming from the stock sender (assuming it's good) or do I need to put in an entirely different sender? I would guess it depends on whether the signal coming from the stock sender matches the range the gauge is expecting, but I'm not sure if there's some sort of standard for this or how I can tell if they match. If I do need to put in a new sender, where's the best place to do it? Can I pull out the stock unit and put in the new one or does the ECU need the signal? Is there some place that's really easy or is it pretty much a custom job based on where you want it?

Thanks.

David

Did some searching and it looks like I can't use the stock sender with an aftermarket gauge. So I need to replace the stock sender with the new one or plumb the new one in somewhere. So does the ECU need the water temp signal? I'll dig through the service manual when I get home, but I figure somebody probably knows off the top of their head.

David

Off the top of my head, I'd bet that the ECU needs a coolant temp value, and you'll need to put in the sender (if you insist on using an electric gauge) somewhere else.

My engine doesn't have an ECU, so I'm just guessing...

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Ty Till
#16 ITS
Rocky Mountain Division

David,
The ECU does need the coolant temp sensor. It picks it up from a small, single wire sensor located in the front water port on top of the intake manifold (IIRC-its been a couple of years). I had a Moroso Hose adapter which had a drain petcock in it. I removed the petcock, and put the temp sensor in its place. Not 100% accurate, but it was close enough that I would know it if ran hotter than normal.

Jim

You can get a simple hose adapter from Nissport:

Nissport adapter

That way you can just leave the stock one in place for the ECU.

joe

[edit: getting link to work]

[This message has been edited by jamsilvia (edited June 14, 2005).]

David, I just "tapped" out the existing sender location with the appropriate size and thread, and attached both wires. Works fine.

oh, and I think Bob took the gauge out cause he was tired of looking at the high water temps we all run. Out of sight ,out of mind! ha
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Tristan Smith
Buffalo's Southwest Cafe
ITA Nissan 240sx #56

[This message has been edited by Tristan Smith (edited June 14, 2005).]

I think Bob was more concerned with a sudden loss of coolant pressure. Isn't there a coolant pressure idiot light still on the car? That can have catastrophic results also. My water temps were always decent(around 180-185 IIRC) once I moved the oil cooler off the radiator. I really had to work to get the oil temps down though.

Jim

Originally posted by its66:
I think Bob was more concerned with a sudden loss of coolant pressure. Isn't there a coolant pressure idiot light still on the car?

Click to expand...

I don't think there's one on my 1992 240SX. At the SP 12 hours, a crack in the radiator appeared - not enough to completely dump coolant, but it held no pressure. No lights on the dash.

Tho, with an AL radiator, I usually run in the sub-200 temps. At the 12, swapping back to a stock radiator - and running with interior heat on HIGH (ugh!)....it'd still creap up over 220....

So what kind of oil temps are people seeing? I haven't hooked up my oil temp gauge yet, because I'm afraid to know....

joe

[edit: stock, not sock!]



[This message has been edited by jamsilvia (edited June 14, 2005).]

The coolant pressure light was something that Bob added several years ago. It was not factory.

Once I got mine sorted out, my oil temps were 225-235. That is in Florida heat with a max of 90 minutes at a time on track. This compares to my first time out with the car when I saw water temps of almost 240, and oil temps in the 280 range.

FWIW, the car had a large aluminum radiator, and a big Setrab oil cooler. I did run it with a 170* thermostat.

Some guys runs a oil to water heat exchanger instead of, or even in addition the standard oil cooler.

Jim

Turns out there are separate sensors for the ECU and temp gauge so I think I'll just remove the stock temp gauge sensor like Tristan suggested.

Bob didn't mention a coolant pressure light. I'll poke around and see if I can find one and maybe give him a call. I did notice that there appears to be an extra sender location next to the existing two sensors on the thermostat housing. It's got a plug screwed into it currently so maybe something was there and he took it out.

What kind of water temps should I be expecting? How high is high? I've got an oil pressure gauge and I think I'm just going to match it with the water temp gauge. I can get a 120-240 or 140-280. I didn't think I'd need over 240, but now I'm wondering. I was thinking anything above 220-230 is too hot and would indicate a problem. Does that sound right? For reference, I've got a monster radiator that was shoe-horned in with an oil cooler in front of it.

Thanks for the replies.

David

Not sure if it was added by Bob Stretch or by the subsequent owner - my 240sx came with a water pressure gauge. I monitor it much more closely than my temp guage, saved me when the aluminum radiator developed a small leak.

The new build will definitely have coolant pressure guage again.

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Ed.
240SX ITA

I regularly see oil temps in the 240 range, but that is pre-cooler. I assume that the oil temp going back in the motor is closer to 200. Water temps vary according to weather and if I am in clean air or not, but around 200 - 210 is not uncommon on a hottter day.

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Tristan Smith
Buffalo's Southwest Cafe
ITA Nissan 240sx #56

Somebody help me out with the advantage of a water pressure sensor. If water pressure falls shouldn't you see a rise in temperature as well? So couldn't you just key off the temperature rise that you have a problem?

I did some poking around on the web and only found a water pressure gauge from Autometer. It goes from 0-35 PSI. I'm guessing you could use an oil pressure gauge for the same function if you wanted, but it would probably go all the way up to 100 PSI. I did find a couple warning lights that you could have trigger if pressure goes below 15 PSI. Is our water pressure normally above 15 PSI?

I guess I'm somewhat confused as to the lack of instrumentation if water pressure is that important.

David

A loss of coolant can sometimes go undetected by a temp gauge. If the coolant level drops below the sender the rise in temp will not show on the gauge, sometimes the gauge may even go cold. I think I would use a coolant pressure idiot light instead of a pressure gauge just so I didn't have another gauge to watch,

V-dub is absolutely right. If you use an oil pressure light sending unit that triggers at about 5 psi, that will alert you immediately to blown head gasket, torn or loose hose, etc. The pressure drop will be indicated long before the temperature increases to a level that would get your attention. Bob S told me about loosing an engine due to coolant loss within one or two laps(IIRC). It just seems like cheap insurance to me.