ok so I have a 98 Tacoma 2wd reg cab 2.4l with electric fan, headers, new exhaust and cold air intake. The truck has 220xxx miles on it. now to the story, coming up the pass in the mountains noticed she was getting warm so i hit the heater and she dropped back down, took the very next exit and wired my fan up bypassing the thermostat i have installed for it. back on the road and the temp is fine till the next hill, then temp shoots up again. I stop and let it cool but i had no signs of and actual overheat. temp gauge was pegged hot. got it into town and replaces the obvious t-stat and still same prob. hooked it up to the scan tool and the ecm or ecu whatever, showed that the temp was perfect. therefore temp sending unit for gauge. I replaced that and still the same problem. so then i got a aftermarket temp gauge and wired it to my new sending unit. it reads about 240 when cool. using a manual type temp gauge stuck in the radiator cap it reads a normal temp (about 190-195).


so now that ive filled in on the last few days. what do i do to get a reliable reading. i know the cooling system is fine. every aspect of it. so short of hacking the radiator hose and plumbing an adapter for a manual type gauge. What is there to do.

i dont know what to do i dont want to risk an actual overheat due to an inaccurate gauge.

 

Radiator temps are typically 20 to 30 degrees cooler than block temps. Sounds like you have poor circulation. How is the flow through the radiator? Have you pressure tested the cap ?

 

yes and yes. the cooling system is good. the truck is not hot at all. the issue is with the electric im guessing but i dont get why a brand new sending unit is giving me bad readings. im going to see if i can get a new new one tomorrow. this truck has never had overheating issues and still isnt.

 

currently its about 66 degrees outside and the truck is cool. has been sitting for a few hours and is close to ambient temperature and the gauge is reading 160. hope that helps describe the situation a bit more

 

The obvious conclusion is, if it's not the sending unit, it must be the gauge. The FSM for my 4Runner has a test procedure for the gauge in the Body Electric section under Combination Meter. I'm guessing one exists for your rig, too.

 

link to downloadable FSM's

 

tried that

 

If something is blocking the flow to your radiator you could have a temp. reading of 190 for the radiator and still have a higher temp at the sending unit in the block. I would think that the radiator temp would vary quite a bit though, and I don't know how the flow could be blocked.

But, thinking about it I remember having a lower radiator hose that separated and would collapse inside. This caused a heating issue that was corrected with a new hose. Maybe a long shot but could be worth a try.