Mazda temp gauge, overheating, temp sending unit issues....

you didnt answer me...

I haven't done a flow test so I can't verify the radiator is 100% but shouldn't matter. Even with a plugged radiator it would act the same. The temp gauge is showing real hot before the thermostat even opens.

did your gas mileage increase at all since the gauge has been reading hot?

Hmmm, no clue on the gas mileage. I rarely drive the truck and don't keep track. But I'm gonna guess if anything it went down.

DOn't take this the wrong way guys but is this really all the advice anyone has? Radiator cap, sending unit, and radiator? These are basic first steps for any temp troubleshooting.

And I don't think the engine is actually overheating. What I really want to find out is what ohms the temp sender should be reading at normal operating temp.

Twisted: post a photo showing exactly where this is located, or a real good description, and I'll provide the ohms resistance on my '88 B2200 within a few days. I don't have the time right now to hunt for the sensor. You want the readings with the wire unplugged, the resistance changes with temperature. Are you in U.S.? Here's what my '88 factory manual states (Chapter 15): at 176 degrees F (80 C), the resistance of the sender should be 53.5 +/- 4.2 ohms; they show it being tested by removing it, suspending it over a temperature-measured beaker of hot water (but with the sending portion in the hot water) and reading the resistance. The manual details two types of gauges, a swivel needle (like mine has) and a "bar" type. For the swivel needle type, 233 ohms is the "C" reading and 16.1 ohms is "H". For the bar type, 134.6 ohms for "C" and 13.0 ohms for "H" (229.1 ohms and 18.3 ohms for Canada, don't know why that would be different). So you may not need my information: with wire unplugged check your sensor ohms at ambient/cold temperature, should be somewhat near or higher than stated, then get the engine hot and remeasure. Let me know.

when your temp goes up gas mileage does too, trying to narrow it down..

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no offense taken but, theres not a whole that can be wrong when having over heating issues.. we are all trying to narrow it down by eliminating possibilities, not being there we all have to give the most open thought on the subject, hope yuo figure it out bro

just a word of caution, before i went out & bought a laser temp gun, i'd check it all out, if the over heating prob. still exist, it could be that the head is cracked, and the $$ for the laser gun could be used to get a new head....

Thanks for the info guys. I'm beginning to think that most the service manuals are wrong or just unsure.

What I do know is that in the service manual I had looked in today it shows 320 ohms for running temp which is way off.

In the picture catalogue at NAPA it shows a different unit for the 87 and the 88. The 88 says running temp is 48ohms but it doesn't give a rating for the 87.

If I test mine with the wire unplugged it gets to about 21ohms and holds it steady right there.

I'm solving it tonight by installing an Autometer temp gauge and sender just to diagnose and insure I'm not hurting it till I can figure it out and make the factory gauge work. I'll keep everyone updated.