jimbo74

my truck seems to be overheating... i say seems to, but it doesnt ever actually get to the overheated part...... anyways, here is what is going on, the tstat, cap, radiator, and coolant, and hoses are pretty new... it isnt dripping any water out..... today out of nowhere, im driving along like normal, look at the cluster and am like oh crap! the needle is almost on the hot area of the guage... right on the white line below hot..... i turn on the heater ... no change..... well i get to where im going..... go to leave, start it up, and within a block, its at halfway.... get to where im going, shut down.... well i get in it to leave again, and things are like a normal truck, start it up, it stays cold for a few minutes, then eventually works it way to midway... doesnt go past midway on that trip..... get to leave again, start it up, its at midway... start driving, its at hot again... heater turning on does nothing or so it seems... if i start babying the truck while its in the hot position, it seems to drop to midway! wtf! is going on? i have the single stage thermostat in it..... maybe the sensor is starting to go bad?

Glenn

How about the fan clutch? I had mine go bad on me, and it would almost get to overheating. It would run in the hot half of the guage. If you are sure your fan clutch is OK, when was the last time you flushed the system out and cleaned off the front and back of the radiator? Good luck.

SoCal4Running

Just a thought, maybe its not overheating and just a faulty guage or sender.

jimbo74

im leaning more towards the sensor or guage being fualty or starting to be... it doesnt always do it... sometimes its ok....... and it does it intermittently..... the fan if the clutch failed would just sieze and always be on robbing me of power..... but in that case, it would over cool the truck and make it run cold.... hmmmmmm

Glenn

...or fail to come on at the right time and actually block air flow to the radiator.

TACOMANATOR

I vote for the sensor since everything else is fairly new. If that doesn't work I would try the thermostat again, since they are inexpensive.
Good luck
If you have acsess or are inclined to buy one of thoe infrared thermometers you can obtain areading off your block when your guage is reading high. That would verify if its your sensor.

jimbo74

bnthe fan is behind the radiator, so forward momentum would still push air through the radiator....

SoCal4Running

The stock guage on my runner never worked right, even after disconnecting and cutting the end off of the wire so it wouldnt ground out on the engie the stupid thing still sometimes will show a temperature on the dash. Figure that one out.

Anyway I installed this and now I can watch when the thermostat opens and closes. Very acurate.

jimbo74

what is that guage wired to? ddi you jsut use the stock sensor? or instal an aftermarket one? or did it come with one? im not happy about mounting aux guages, however, if i have to, i will.... also, my speedo doesnt work, and i will soon be getting gps.... so..... i might jsut find a way to get a guage for the fuel as well, and jsut dump the whole cluster.....

SoCal4Running

Its all made by VDO.

The guage, sender, mouting cup are all separate items. They dont offer a package deal or anything. The sender was the only real PITA, the stock sender will not work because it will read WAY wrong, the VDO sender has reguar pipe threads which means that you have to very carfully re-tap the original sender threads in the intake maniforld. It was very un-nerving doing this because the VDO sender is just alittle bigger in diameter that the Toy sender, basically you are just moving the threads alittle and not really cutting new ones.

The guage works frikking awsome thought, well worth it.

Your spedo should be an easy fix unless its inside the cluster itself but I doubt it would be.

jimbo74

the speedo isnt broken at the cluster, the cable doesnt spin at all, its in the tranny, and as far as that goes, i have a stock 3.07 rear end gear ratio, but i also have a 5speed (whereas my trucks vin plkate says it is a 4 speed) and 31" tires..... so unless the inside speedometer gears are redone to be properly set, and i have no idea what i would need, other than the new gear, but rather the tooth count... i have no clue on that

leebee

sounds like what used to happen with my 86, drive along and everything was fine and all of a sudden the heat would shoot up to the hot mark. turns out, there was a small air pocket in the system that would get so far in the system and cause the gage to show hot. take the cap off, start it up and let the truck come up to operating temp to work the bubble out. that should clear up the problem. hope this helps.

lee

Plays_with_Toys

And make sure you have the system topped off. If mine gets even a little low it will run much hotter than normal.

Also, what t-stat are you running? I had a 195 and it ran at abou half way up the gauge, I switched down to a 180 and that really helped. I run cooler and in the same range as the rest of my family's yotas (1/4 -3/8 up the gauge).

jimbo74

i have the stock replacement single stage thermostat for my truck... i dont plan on modifying it to run a 180* thermostat... the thermostat is genuine toyota and less than a month old... the system is bled properly... i am starting to wonder if its my fan..... thinking about switching to a flexalite fan... not an electric one, but a replacement one thats always on...... i guess at speed the blades flex and allow it to not cause as much parasitic drag when its not needed

kyle_22r

you do know that a clutch fan will work better than a flex fan right? it's not spinning as much at high rpms as a flex fan would, the fluid clutch lets it slip. the only thing you can really get that's better than that setup is an electric fan.

i'd say your problem is most likely the sensor. i think they're about $12 at most parts stores

bike4miles

Did it seem like it was hot under the hood? Was the oustid of the radiator broiling or did it seem more like normal? Take note of this next time so you can get a better idea if your gauge is bad. I overheated my runner once and it shot steam out of the overflow hose. Also, make sure you don't have too much water mixed with the coolant.

jimbo74

coolant mix is good, its probably actually closer to 65% coolant and the rest water.....

no steam present.... underhood the radiator seemd warm, however no boiling over in the reservoir... i have had this happen before on another vehicle that never completely overheated, the belt fell off and didnt spin anything, but i let it cool down in steps... cold, drive it, let it sit, drive it, let it sit... so on......

could very well be the sensor... but i would rather be safe than sorry..... i know a new fan clutch is expensive..... also what about using a new fan clutch/ or the current one, along with a flex a lite fan?

frost203

I had some similar problems over the years, seemed to heat up out of no where. I used a coolant pressure tester to check for leaks. you can find even small leaks when it's pressurized. The last time I had that problem it turned out to be the most smallest head gasket leak. pressure seemed stable for basic coolant leak test. Out of frustation I left it pressurized for several 6 hr periods and had a 1 lb. pressure drop. so I did a cylinder leak down test. I heard the faintest noise so I pulled the water pump and what do you know I could hear the air hiss from the number 1 cylinder to the water jacket.

Plays_with_Toys

There would be no point to this. Flexalite fans are an upgrade because it takes all the weight from the heavy clutch off of the engine. The blades bend at higher RPMs to reduce drag, since air should be getting fed to the radiator because you are traveling forward. I think the plastic fan is also lighter than the flexalite one, so it would make the clutch combo even heavier.

jimbo74

that wasnt what i was refering to, there are flexalite made fans, that are just plastic.... arent the flex fans but appear to be made out of high impact plastic like the regular fan... im guessing they are jsut replacement fans then and not the actual ones that flex.... form everything people here sound liek they are saying... is the clutch is better than a flex fan... i dont see why? the flex fan is a lot lighter and felxes at speed becasue it doesnt need to deliver constant air....