vze2jshn

Since replacing top of engine wiring harnes my US '78 5 speed temp gauge reads at and a little above the second white line. I have IR gunned it and all temps are normal with electric fan coming on at the correct temps. I repaced the temp sensor and it still reads consistently at the second white line even now with ambient temps in NY and Jersey declining. Is the temp gauge in my '78 adjustable--I would like to get it to read where it did prior to wiring harness replacement which was at or a little above halfway between first and second white marks.

karl ruiter

My '79 is running over the 2nd white line on hills. I suspect it is running lean.

vze2jshn

Also checked and adjusted A/F to richer side of specs. That's why I am wondering if any one knows if temp gauge's calibration is adjustable.

karl ruiter

You could certainly check the calibration of the gauge by putting a resistor in place of the sensor. I have not looked at the temp gauge but the voltage gauge has an adjustment pot. It is a fragile open frame thing and I kind of suspect that failure of these is what makes all 928 voltmeters (that I have seen) read low.

vze2jshn

Thanks Karl, can you explain the procedure? I don't have a clue.

mark kibort

lean wont do squat. just lean of stoich is the coolest your engine will run actually, and gets cooler as it gets leaner actually. stoich, is the only area where you get high heat, but our cars jog btween full lean and full rich for an aveage of a stoich ratio (for economy) 2nd white line means something is wrong with cooling or gauge.

mark kibort

the fans should come on just after the halfway mark on the gauge. if they come on at the white line, the gauge is probably off a little.

jwillman

Update.

Today I tested the electric fan with power off the jump post. The fan runs when jumped. I reconnected the fan and ran the car with the reservoir cap off.

The coolant light was on when I started the car and the reservoir had about an inch of coolant in the bottom. As the car warmed the reservoir level increased to about half full. The temp needle rose to about a needle width below the upper white line and the electric fan was not running. I shut the car off and coolant immediately started boiling over allot. Electric fan never kicked in and belt driven fan clutch felt firmer when warm versus when cold, still turned by hand but would not spin freely for what that is worth. BTW system is serviced with GO-5 coolant (until it boiled out).

Now I am concerned. Do I have a plugged radiator, bad thermostadt, bad water pump?

Mrmerlin

-you need an IR gun to check the temps of the hoses, by feel wont do it.
From the post info it sounds like a closed thermostat or a bad water pump

Landseer

I back suck-flushed the radiator on one car.
Shop vac on the inlet hose.
Water hose on inside the outlet hose.
A shot of Cascade during collection of every cansister (16 gal)
Collected a fair amount of grit.


Silicon fan fill is pretty important, too.
Takes patience.
Next time I'll heat the fluid like a baby bottle in hot water.

So long as its not bubbling due to head gasket failure you should find a solution (or set of them) pretty quickly. I've got a camry here that, once it heats up, boils over quickly due to direct injection of combustion gas into the water channels in the head.

vze2jshn

Hope it ain't a bad head gasket.

tlsmith1999

If the electric fan is not coming on, isn't there a sensor, fuse and/or relay that could be bad? If I remember correctly, I had to replace a relay and fuse to get mine working. (But I have ad to do that for a few problems, so I might be confused.

Also, the wiring connectors on my temp sensor were pretty badly corroded, so cleaning them might have helped.

jwillman

Thanks all.

I have new gaskets for the water gallery and oil filler housing as well as a new thermostadt on the way. Guess I will pull all that and the radiator and check all those. Any tips or secrets on radiator removal and reinstall?

I also have a new fan switch coming as well that I will replace while I have the radiator out.

There is a fuse and a relay that I will check. Looks like I should be able to jump the relay to check the wiring.

I did some general research and saw that a head gasket could cause this issue as well Wouldn't I have oil in the coolant or vice a versa? Whats the best /easiest way to check the head gasket.

Remember I had the reservoir cap off as I was trying to make sure I did not have air trapped in the system. Could that be a factor?

jpitman2

If you dont have oil in the water or water in the oil I think your head gasket is OK. The temp sensor in the front of the radiator is not well placed to sense the temp for control purposes IMHO. Remember to counter hold the oil cooler connections when you disconnect the hoses from the coolers - with a catch pan underneath, disconnect the bottom first so they drain before you lift the rad out and spread oil everywhere. Your problem sounds a bit like either lack of circulation, or a stuck thermo.
Interested to hear what you find.
jp 83 Euro S AT 52k

Landseer

My electric fans almost never come on.
I think the car should run moderately cool without them in the weather Texas has right now.

Concentrate on circulation. Didn't you do the WP/TB on this car?