1985 22r, the temp needle has always been rock solid at about 1/3 up the gauge. Noticed it climbed to about 2/3rds on my last trip coming over some mountain passes. Checked it out when I got home, some fluid from the weep hole on the water pump, so replaced it. The needle still rises higher than it used to, approaching red now when the engine is working hard. It can idle all day and the needle never moves beyond base, drive around town and seldom moves, but gun it up a hill and the needle creeps up. Had the radiator cleaned, new thermostat, borrowed a fan clutch from a buddy that I knew worked, no difference. Did a check for exhaust gasses in the coolant, negative. Bout the only thing left is the temp gauge/sender. Searched and found that there is little confidence in our toyota temp gauge. For grins, I unplugged the sensor at the block and took it for a drive. Guess what!!! The gauge acts just the same, holds steady at idle, and rises going up a hill. So, is it the sender? the gauge? Am I overheating at all? Is there somewhere else the gauge is getting temperature information? I may replace the sensor, its pretty cheap. Guess I need to hook up a different gauge and see what that tells me, anyone with tips on a replacement gauge? Do I tap into the existing sensor, or is there another way to monitor temp? I may spring for an infra red thermo to do some testing to try and determine the engine blocks' actual temp. Thanks for any help, this site and your combined knowledge have helped me keep this truck running.

Try replacing the sending unit, they can go bad. when i got my truck the temperature gauge would always read just above cold even when it was at normal operating temperature, i had already replaced the radiator and thermostat, so i replaced the sending unit and that fixed the problem.

How many miles on the radiator?

About 50,000 on the rad, and its a 3 row.

I doubt that it's your gauge/sender.. You can do the "feel" test - you'll be able to tell the difference between 1/3 the way up the scale and 2/3 up the scale.

Checked your plugs? Detonating at all?
Outside of that - have you added anything (like a winch) that would block flow to the radiator?
Running a fan shroud?

Guess what? That is simply not possible if you unplugged the correct sending unit,unless there is some other wireing defect. Without the sending unit connected, your gauge will not move since it has no ground path.

There are several coolant temp senders. Not sure which one is for the temp gauge on an 85, but the FSM should have the info.

Dave

What is the ratio of the coolant/water that you put back into the system? If you have more coolant than water, the engine will run hotter. Coolant does not absorb the heat as fast a water, but running plain water will tend to rust the inside of the engine and not lube the water pump as well. Try a 50-50 mix and see if the temp goes down at all. maybe try some water wetter too.

There is a clue there. Does it over heat when you gun it down a hill or on flat ground?

That sounds like trapped air to me. Take the cap off and if you can park the truck with the top of the radiator higher than the dash(i.e facing up a hill) and start the engine and let it warm up enough to see the water flowing sideways across the radiator. As soon as you start the engine turn your heater on full heat/ full blast and watch the radiator; add water as needed; and squeeze all 5 hoses: upper, lower, timing cover to lower part of block and both heater core hoses.

Sounds like overkill for "burping" the cooling system but you know i have never had a problem with a cooling system other than total failure, like having the HG blow or the clutch fan driven an inch in to the radiator, fun stuff like that.
I also have never had a customer come back after doing something in the cooling system(and dont ever do a heater core on a ford <img src="/forums/images/graemlins/evil.gif" alt="" /> or a shrocco <img src="/forums/images/graemlins/barf.gif" alt="" /> (or however its spelled, damn german Ford <img src="/forums/images/graemlins/notooth.gif" alt="" />). They are the absolute worst part to fix ever, and with the help of the parts house take two months to finish.

Thanks for all the suggestions, work took me out of town for a few days, so I am just getting back to working on this. I have a 50-50 mix, shroud in place, well burped several times, (got a T in the heater line to help) plugs look good, timing is on at 0 with distributor lines plugged, HAC systems bumps it to 12 BTDC when plugged in. Vacum pump on the distributor line moves the advance when I test it. Have had the distributor out, but can't imagine it would even run if I was a tooth off. It is not getting into the red, but does run higher (2/3 to 3/4) than it used to when it is working hard. If I engine brake going down a hill, the needle will rise. If I let it coast, needle plummets to 1/3 quickly. At idle or around town it will hold at 1/2 all day. I am thinking about dcg9381's suggestion re detonation. Its got me thinking I need to maybe check out the EGR system. I think I have eliminated everything in the coolant system and need to start thinking about other causes. One scary thought is a possible coolant or oil passage is plugged in the block? Soon as I get some free time (and after it cools off a bit, 95 degrees today) I will be back in diagnostic mode. Whew, long post, thanks again for the suggestions. <img src="/forums/images/graemlins/cheers.gif" alt="" />

It sounds like trapped air to me also, since it used to happen to me.

What I did was replace the thermostat. The replacement thermostat had a tiny hole and valve thing on it. I just snapped off the valve thing, leaving the tiny hole clear. No more temp excusions.

Now, the only time the temp gauge climbs is when it IS hot outside, like driving up out of Death Valley to Beatty, NV and it's 127 degrees outside. That's hot.

Good luck.

Al