Build Project 2027: 1977 FJ40 Rebuild

Member Build Threads

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

waiting for time said:
Have you tried vacuum filling the cooling system?
Click to expand...
Actually I hadn’t even thought about it. It would certainly take care of any air in the system. I just ordered the vacuum kit. Fingers are crossed that between replacing the fan clutch and vacuum filling the system my overheating issue will go away. Thanks for the recommendation.
 
Fan clutch looks like the easiest and least expensive option to swap out and test. Yes it should get much harder to turn when hot. As for lack of high jackstands, Is there a Prius you could pull the front wheels up on the hood to get the height?
 
Dunbar said:
Fan clutch looks like the easiest and least expensive option to swap out and test. Yes it should get much harder to turn when hot. As for lack of high jackstands, Is there a Prius you could pull the front wheels up on the hood to get the height?
Click to expand...
Don’t for a minute doubt that I haven’t already thought about that! 😂

I definitely think the fan clutch is the most likely problem. There’s little or no difference in how hard it is to turn cold or hot.
 
You said you verified temp with a ir gun. What is the temp your reading when the motor is hottest on their gun? A fan clutch only cools at lower speeds. If it's getting hot at higher engine speeds like 50mph then you probably need more radiator. You said you had the old radiator repaired with a new core. But what kind of core is pretty critical. That to me seems like it's likely your issue. The core in the radiator is not sufficient. That's my opinion anyway.
 
White Stripe said:
You said you verified temp with a ir gun. What is the temp your reading when the motor is hottest on their gun? A fan clutch only cools at lower speeds. If it's getting hot at higher engine speeds like 50mph then you probably need more radiator. You said you had the old radiator repaired with a new core. But what kind of core is pretty critical. That to me seems like it's likely your issue. The core in the radiator is not sufficient. That's my opinion anyway.
Click to expand...
I misspoke. I had the radiator rodded, not cored. It’s original in every way. I had zero overheating issues before the tear down. I’m on the road for the next few days so I don’t have the temp numbers with me. Legitimately the only component in the cooling system that hasn’t been replaced with new or overhauled, is the fan clutch. I’ve ordered a new one along with a vacuum filler to avoid any air in the system when I re-flush and fill. Basically try to eliminate both those possibilities at once.

When I drain the system, I’ll open up the thermostat and triple check orientation and seal placement. I’m confident that all is well there.

Correct me if I’m wrong here but I was under the impression as the clutch heats up, it spins faster to further increase airflow through the radiator regardless of vehicle speed. An engine at high RPM will always produce more heat due to increased friction and increased combustion rates. If the fan clutch isn’t engaging as required and relative to temp, the airflow will be greatly reduced.

I have a pretty comprehensive background in aerodynamics and I do know if a propeller (radiator fan) isn’t at least at a speed which would allow it to grab the air in front of it and push it out the back at a rate equal to the speed of the vehicle, it will always create drag. In other words, the air drives the fan, not the other way around. If the fan clutch isn’t speeding things up as intended, it would actually slow air transfer through the radiator. The faster one drives, the more pronounced the airflow disruption and drag would become. Anyways, it’s all a fascinating discussion, but I’m led to believe it’s either air trapped in the system or an airflow issue. The clutch is definitely not changing resistance as it should. I’ll keep after it until I have it figured out. Lord knows it’s not getting any cooler in Houston.
 
Last edited:
Just got home from Idaho today and had these waiting for me. I’ll get to work tomorrow replacing the fan clutch, flushing the coolant system and refilling. Hoping this takes care of my overheating issue. The new fan clutch is substantially harder to rotate than what I have on there now so I believe I’ve found the issue.
5EABA843-93E6-48E3-BC7A-46E1A7DEB641.webp
D5F2C265-9384-4294-8438-C04EF28DF0F5.webp


I’m starting to get to the point with this 40 that I’ll have all the necessary tools to open a legit repair shop!
 
Jetlander said:
Just got home from Idaho today and had these waiting for me. I’ll get to work tomorrow replacing the fan clutch, flushing the coolant system and refilling. Hoping this takes care of my overheating issue. The new fan clutch is substantially harder to rotate than what I have on there now so I believe I’ve found the issue. View attachment 2739565View attachment 2739566

I’m starting to get to the point with this 40 that I’ll have all the necessary tools to open a legit repair shop!
Click to expand...
That is how it works if you want to do it right.😉
 
Overheating problem fixed! Replaced the fan clutch and flushed the system again. I vacuum filled the coolant and put in exactly what I drained out so I’m pretty sure I didn’t have air in the system. Put 75 miles on it at all speeds to include the normal stop and go Houston traffic with a heat index of 108°.
D6D8C317-0DB5-4FA8-88A5-B920AAB7E97C.webp
90E28A6C-C888-4AC0-A869-36DED47642ED.webp
 
Kind of a personal update but my family and I have decided to move to Idaho. Just accepted a job offer and will be heading back to the Northwest in a month. I moved to Houston from eastern Washington 9 years ago for a job. My heart never left the northwest and I’ve longed to go back to God’s country. Now is the time.

So if you see a sweet looking grey FJ40 cruising the backroads, wave! Cruisers are better suited for the Idaho backcountry versus the endless traffic on Houston interstates anyways.
 
Jetlander said:
Kind of a personal update but my family and I have decided to move to Idaho. Just accepted a job offer and will be heading back to the Northwest in a month. I moved to Houston from eastern Washington 9 years ago for a job. My heart never left the northwest and I’ve longed to go back to God’s country. Now is the time.

So if you see a sweet looking grey FJ40 cruising the backroads, wave! Cruisers are better suited for the Idaho backcountry versus the endless traffic on Houston interstates anyways.
Click to expand...
Awesome.

I sat in Dallas traffic for years, always longing to get back to Colorado. Finally made the return in 2019 and it was the best thing I ever did.

Congratulations. We only live once.
 
With my pending move to Idaho at what elevation should I consider running high altitude jets in the carb? The town I’ll be living in is at 4000’ but I’ll be spending considerable time at much higher elevations while exploring.

Hoping I’ll find a middle ground versus having to change them out each time I head to the mountains.
 
Took a few motnh hiatus from mud while work consumed my life! Build is rolling along awesome! Any final work on the rear bench seats? You gonna try for 3pt belts ?
 
Jetlander said:
With my pending move to Idaho at what elevation should I consider running high altitude jets in the carb? The town I’ll be living in is at 4000’ but I’ll be spending considerable time at much higher elevations while exploring.

Hoping I’ll find a middle ground versus having to change them out each time I head to the mountains.
Click to expand...
If you can find it in your heart, being that you will be going between elevations quite often, EFI might be a good solution? Just say'n.... :hillbilly:
 
GA Architect said:
If you can find it in your heart, being that you will be going between elevations quite often, EFI might be a good solution? Just say'n.... :hillbilly:
Click to expand...
Definitely not something I’m opposed to. I’m interested in the elevation ranges for each set of jets. 4000’ will be most of the time with occasional (hunting) trips. I’m thinking 4000’ is probably the lower range for high altitude jets so it may be worth putting them in and getting the timing and mixture right. I could easily enough adjust the mixture for mountain driving.
 
How did you secure the shoulders belts for the rear? I need to get on this in the winter as my girls wont be needing car seats anymore and i want them facing forward. @Jetlander
 
You must log in or register to reply here.

Share this page

Back
Top Bottom