Cooling fan sensor; '78 FJ40

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tls3601

tls3601

10 Year
Joined
Aug 18, 2013
Threads
234
Messages
5,364
Location
Prescott Valley, AZ
So I finally found the missing pieces. The sensor mounts on two bolts near the rear of the intake manifold on the side away from the head. My question is does the sensor itself tuck below and medial (towards the head) of the mounting point with the wire running below the sensor bracket and to the green female connector? Any pics showing someones stock setup on their '78 would help. thanks
 
Also, disconnect the neg battery connector when connecting all my plugins? Just wondering as the rig IS 36 years old....geez
 
Have you been to the library yet? So much information at your fingertips. I know that it is one simple question but so may of the masters here have typed the same answer so many times it would do best to respect them and look up what they have recently said. Particularly the most recent thread by GA Architect and the answers he has been given and the knowledge therein. Besides, I don't have one on mine so I have been lurking about these threads for answers myself. Good luck with yours.
Mike

https://forum.ih8mud.com/search/912419/?q=Cooling+fan&o=relevance&c[node]=8
 
Temp sensor mounting is pretty much what you'd think.

You really only need to disconnect your battery negative if you're going to be messing with something that is hot with the ignition off and might touch ground while you're fooling with it/around it, such as a starter cable or the dash cluster (ammeter studs). It's not a bad practice while you're doing any significant work on the truck, though, or if you're welding on the truck.

Fan Temp Sensor.webp
 
Hey spot, where does that wire come from/go? I do not have the sensor and cannot for the life of me find any stray wires or terminals? I do have the fan though.
 
It's in the same small harness on the driver's side fender that has the carb fuel solenoid and temp sensor wires and the brake pressure sender wires. Of course, it runs over to the fan controller in the passenger footwell (firewall). It's the light blue wire mated to the white wire listed as "manifold temp sensor" in the W/D.

I don't know why I can't get the 2nd photo to post upright. :^(

By the way, CA 76's at least (don't know about 77s or Fed models), had the fan sensor wire running atop the center of the head with the engine temp sender and carb solenoid wires. I don't know when that changed.

myquestoyota said:
Hey spot, where does that wire come from/go? I do not have the sensor and cannot for the life of me find any stray wires or terminals? I do have the fan though.
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Temp Sensor Wire 1.webp


Temp Sensor Wire 22.webp


Temp Sensor WD 1.webp
 
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Thanks, it's funny I can't find that because the PO pretty much left the wiring intact and I don't see where anything has been cut. Oh, by the way, I figured out what's wrong with your brakes.......:smokin:
 
Yeah, nothing actually. ;) I replaced the front calipers a while back and I just haven't had time to put things back together. I was away from home for 6 months. I don't have a tranny or transfer in it at the moment, either. :)

myquestoyota said:
Oh, by the way, I figured out what's wrong with your brakes.......:smokin:
Click to expand...
 
Did you see my "by the way" addition in post #6 above? It may be running down the top of the head.

myquestoyota said:
Thanks, it's funny I can't find that because the PO pretty much left the wiring intact and I don't see where anything has been cut.
Click to expand...
 
I have this wire that goes to a sensor by the carb but I think it is a different sensor?
carb sensor wire.webp
 
That's it. The wire with the red lug is the wire for the engine temp sensor. The small cylinder mounted on a post standing off the manifold is the fan control switch. You may even find another temp sensor up there for EGR control.

myquestoyota said:
I have this wire that goes to a sensor by the carb but I think it is a different sensor?
View attachment 940251
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That's what I was thinking but someone had led me to believe that the sensor we are looking at was the smog sensor. I might just have to go looking for that fuse in the cab, maybe that's all I need to have a working fan.
Thanks spot!
 
The fuse is taped-up in the wireway in the vicinity of the fan controller.

myquestoyota said:
That's what I was thinking but someone had led me to believe that the sensor we are looking at was the smog sensor. I might just have to go looking for that fuse in the cab, maybe that's all I need to have a working fan.
Thanks spot!
Click to expand...
 
Yeah, considering I've had the engine and tranny out twice in the past year it would have been a perfect time to get my old large frame in there and check it. Shouldn't be hard to locate. Thanks
 
spotcruiser-thanks, just what i needed! However, the PO snapped off the bolt that mounts the sensor bracket (rearward one towards firewall-the hole and threads on the mount towards the front is fine). Pilot drilled it to use easyout and snapped the easy out in there too-frustrating. Now trying to drill hole into bolt again to extract easy out. A friend suggested maybe a carbide center drill? Anyone good at getting busted off bolts out? Tips?

myguestoyota-are you a schoolteacher? Try a library......................in 2014 really??????? How often do you go to libraries for FJ40 info? I am betting mud may be the best source of info for 40's out there. I always do a search first to find info-no luck there this time. Interesting that you were looking for the same info, jumped on my thread and then acted like a douche. I think I have not upset "the masters" too much...............Most folks, but not all on here are exceptional.:rimshot:
 
spot-any ideas on alternate mounting spots if I can't extract bolt?
 
One bolt would hold the bracket just fine, especially with a little locktite. If it was me, though, I would get that other bolt out just out of stubborness. The trick is to never use an easy-out. :( With a broken bolt/screw, carefully drill right down the center with the smallest bit you can. A small bit is usually easy to keep centered. Then drill with progressively larger bits to just under the size of the stuck bolt. Usually the little bit of remaining bolt will fall out of the threads or can be pulled free after most of the bolt is gone. Sometimes it takes a tap of the correct size to get the bolt remnants to free up.

You may be able to grind down the broken easy-out with a dremel and then continue to drill out the stuck bolt.

Good luck.

tls3601 said:
spot-any ideas on alternate mounting spots if I can't extract bolt?
Click to expand...
 
spot, yes I am stubborn too and not done with this yet. Great insight, going to try that too, prob is the stuck easyout is tool steel-drilling into it is tough-right?
 
Oh yeah. Easy-outs are hard and brittle, so they break easily and are difficult to get out. :crybaby:

tls3601 said:
spot, yes I am stubborn too and not done with this yet. Great insight, going to try that too, prob is the stuck easyout is tool steel-drilling into it is tough-right?
Click to expand...
 
tls, not sure, but myquest may have been referring to the FAQs when stating 'library'. I don't think he meant it sarcastically or with malice...just my thoughts.
Hope you get that easy out extracted. I try to never use those things for that reason. I do like spot says...and you will get good at it, it's a constant occurrence with these ol' rust traps. Sometimes a bolt will break off a little above surface, that's a good thing! I try to lock on to it with vise-grips, use a propane torch to heat it up and then spray it with penetrating oil, they usually come out fairly easy that way. I replace everything I can with stainless. Things I took apart and re-built/replaced/restored 16 years ago come apart with no issues now...no rusted bolts. Good luck!

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