After a coolant change my 4runner has been running "cold"(temp gauge about 1/8 to maybe 1/4 way up)... Ive noticed the exhaust smelling rich. Besides the poor gas mileage I've read that this can damage the motor.

Im pretty sure Ive got all the air out of the system.. BUT, if there is still air in cooling system- would it cause these symptoms?

I DMMed what I think is the thermo switch/ or sensor(not sure which one, probably sensor)--- the green one in front of the motor next to the brown one.
it was within spec.

Im thinking it might be the temp SENDER(on top of thermostat housing)... looked on my PDF 85 4runner FSM but can't find how to test it. I know its in there somewhere, its on the comp. so I can't thumb thru pages, hard to find scrolling thru 1k pages on a laptop. SO, anyone have the specs for the temp sender?(or what page in the 85 FSM?, or worse, what section?)

how many temp sensors(cooling system) of any kind are on this 85 22re? I know of 2 only.

is the TEMP SENDER only for the dashboard readout?(does not effect EFI at all?)

and the thermo sensor/switch works with the efi to tweak settings?

any ideas/suggestions would be appreciated
everything was fine before the coolant change....

last time I had air in my cooling system, the truck would surge-"misfire" etc..... none of that right now, just cold.

1985 4runner 22re, 250K,

 

did you replace a thermostat? or remove one? the single wire sensor is just a sending unit for the guage.

 

I replaced a thermostat after this started happening... thought the thermostat might be jammed open(due to debris from flush).

there is a wire/sensor?which is on the thermostat housing, I thought this was the "sender" to the gauge.... its not. I unplugged it, gauge still worked. WTH is this for?(the wire/sensor on top of thermostat)

I did find the temp sender/wire. Unplugged it and gauge didn't work.

Im certain the gauge is reading correctly and Im in fact running "cold".(I can smell my exhaust, and know its not right)

 

just got back from a drive. still same.


not sure how to diagnose this???(or efficient steps to take, w/o throwing parts at it)

can thermostat be flowing too fast?

while idling(for 15 min, already warmed up), the temp still stays low. had the cap of radiator, and water wasn't flowing. surged up and down once in a while, would flow for a second(5 seconds?), overflow a little. if it was flowing fast 24/7, I could see how Ive been running cold. what Im seeing, seems like it should be on the hot side.

exactly how bad is it to drive with the motor on the "cold side"? (about 1/8th way up, nasty rich exhaust) this is a DD, am I screwed til I fix it?

 

I believe razed is correct. Best answer to temp sensor/switch location I've seen comes from GrimReaper ( https://www.yotatech.com/forums/f116...o-power-96417/ ; reply#6). My understanding is that the issue is with the gauge (in the instrument panel) itself. The gauge is not linear in response in early 4runners. The factory put resistors in the circuit to dampen the needle (I think to deal with the "temp overshoot" issue, but I could be wrong) so the needle stays in the "cold to normal" range most (too much) of the time. So, at least in older gauges, the needle shoots to low normal and stays there until the engine is on the verge of overheating, then shoots to hot (fried). With mine, if I hit the dash when its cold, it will sometimes drop to dead cold then rise "normally", sometimes this doesn't work. Unplugging the lead to the sender in the manifold on my 22re does not affect this cold, but will keep the gauge from going to "full" normal when the engine is warm. I do not believe the sender is the problem.
There are threads on various forums (maybe YotaTech, I don't remember) to modify the dash gauge to make it more linear. I plan to just get an aftermarket gauge; there apparently a boss (on some early 22re's) on the side of the manifold just below the stock sender location where another sender or the stock one could be mounted if you want to go w/ 2 gauges.
Regarding your symptoms, do you have access to an exhaust gas analyzer or can you read the output of your O2 sensor to see if it is running rich too much of the time? 22re's are notoriously difficult to "burp", so you could have air. I've read you need to sometimes have the front of the truck on an hill and let it run w/ rad cap off til the stat opens. But this isn't the most likely cause of your gauge issue (in my experience; other members may have better ideas).

 

haven't checked back here for a while........

I bought a new thermostat, and the temp is back to normal-ish.

. Drives fine for now, kind of.

after a long freeway drive(around 65mph), it will surge at low RPMs once I get back on the regular streets..