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Temp Gauge is Posessed.
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Posted by: DeckSetter

Yep, that's right, the temp gauge in my '86 Celica (which can still beat Mike's v6 stang) appears to be posessed. Well, either that or something else is janktified, which is much more likely.

Sometimes I'll just be driving down the road and the temp gauge will just bury the needle back down like the motor's turned off, the needle sits clear over on the "C".

So first I thought the coolant might be low......and it was!!! Added some, filled 'er up, still does it. That was a couple of weeks ago. At that point, if I dropped it out of gear and revved it up to 4 grand or so the gauge would read the normal running temperature and stay that way for a while.

Well, it's getting progressively worse. At first it didn't do this all that often, now it does it over half the time. Also, when I rev it, it doesn't go back to normal anymore.

The hoses look ok, what else should I check for? I thought it might be an electrical short or something, but if it was electrical I wouldn't think revving the motor up would make it go back to normal. The temp gauge is electrical and the coolant system isn't pressurized.

Thanks in advance, etc.

--D/S

Posted by: VETTKLR

Go ahead and check the wiring that connects the sending unit to the gauge. Sounds to me like that revving up the motor created enough vibration to rattle that connection around enough to make it work. Check for a loose connection or some deposits on an electrical connection.

If that's all good to go, then I'd spend the $5-10 on a new sending unit.

Posted by: DeckSetter

Wiring looks ok, the connection had a little corrosion on it so I scraped it a little and it's working better. Still bounces around a bit but not as much. I drove it about 12 miles to my softball game and when I revved it up it pegged at cold, it'd never done that before when I revved it. Finally I revved the piss outta that thing and got it over 6 grand (redline) and it hardly bounced at all on the way home.

Thanks

Posted by: StoneFox

Get you a cheep after market mechanical gauge. Problem solved

Posted by: Volvord 784VC

These engines are prone to vapour locks. You mention that the coolant was down and you added some, it is important to bleed the cooling system whenever there is a loss of coolant. What is happening is when you rev it up the coolant will circulate, but at lower rpm's the trapped air will collect at the highest point (often near the temp sending unit) and the symptoms you describe will result.

There should be a coolant bleed port on top of the intake manifold, if not just loosen a hose that is at the highest point with the engine idling to bleed off any air

Posted by: DeckSetter

ah HA! that makes sense, I'll go bleed it and if I don't post anything else, no news is good news.

Thanks y'all....

Posted by: Mr. P

Quote:

Originally Posted by Volvord 784VC


	These engines are prone to vapour locks. You mention that the coolant was down and you added some, it is important to bleed the cooling system whenever there is a loss of coolant. What is happening is when you rev it up the coolant will circulate, but at lower rpm's the trapped air will collect at the highest point (often near the temp sending unit) and the symptoms you describe will result. There should be a coolant bleed port on top of the intake manifold, if not just loosen a hose that is at the highest point with the engine idling to bleed off any air

I believe Volvord nailed it. Sounds like an air bubble.
Mr. P

Posted by: 86pushrod

could be a weak alternator..

i have one on my 00' chevy.

car will have 1/4 tank of gas it will read bone empty.
once the r's have been over 3k for a min and the system charges the needle will creep back up to the correct reading.

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