thoughts 3fe cooling system (2 Viewers)

[TOYTACO11]

Alright so my 1992 fj80 3fe 111,000 original miles is overheating and trying to figure out what it is and need some opinions...

First off Radiator is less then a year old, Has new shroud, fan clutch (green), water pump is maybe 1.5yr old bought from rock auto (aisin), coolant has been flushed but a little concerned (checked reservoir today and found black flakes all in it) thermostat is 3 months old (190deg), new 13psi radiator cap (tried a couple different ones no difference.)

New spark plugs, timing slightly advanced but made no difference when retarding it slightly per FSM, compression good and valves adjusted to spec. checked coolant for combustion gases all good, system has been burped of air.

So it seems like every few months the cruiser will start to overheat last time I swapped out thermostat and it worked fine for a few months now doing same thing again and is kinda frustrating. So today I sat in drive way put ac on high and held rpms at 2500 to get it to overheat took about 15-20 minutes while taking temps at various areas verifying it actually is overheating. the fan clutch seems to be working speeding up and slowing down with temp. with radiator cap off it doesnt seem like there is much movement when thermostat is supposed to be open but hard to tell.

these are the temps that i recorded


Top area of thermostat - 200deg would of got higher but didnt allow it to. BTW will idle all day long without overheating.. only overheats under load
water pump housing - 130-160 f
upper radiator hose - 190-200 f
lower radiator hose - 150-165 f

From looking at those temps it seems to me that the thermostat is not opening again... What are your thoughts?

Ive attached a pic for reference of where i was taking measurements highlighted temp with highlighted area on engine if that makes sense. thanks in advance. Mike

 

[TOYTACO11]

Anyone?

 

[Irish Reiver]

Can you explain why you think it is overheating? Water boils at 212f. Coolant changes that and a pressurized system changes it even more. How are you measuring the overheating?

 

[NeilC]

Your thermostat doesnt even open until the coolant gets to 190 degrees. Is 200 too high?

 

[TOYTACO11]

Your thermostat doesnt even open until the coolant gets to 190 degrees. Is 200 too

Alright those numbers are just the ones I got while trying to diagnose the issue in the driveway I did not want it to go any higher for obvious reasons……

the tempuratures go much higher gauge on dash goes to red and my aux gauge I have reads around 220deg that is to hot and not normal. As to why Im lookikg for some assistance

 

[TOYTACO11]

Can you explain why you think it is overheating? Water boils at 212f. Coolant changes that and a pressurized system changes it even more. How are you measuring the overheating?

Well three different ways Infrared gun, guage on cluster wnd aux gauge I have plumbed into the thermostat housing cluster gauge reads right below red and will go higher but never let it, aux gauge reads above 220deg, and ir gun verifyed that temp is correct

 

[thabruiser]

For giggly-poo's, remove your thermostat, and re-assess. If it is not the thermostat, it should still overheat. If it is the thermostat, it will not. In theory.

 

[flintknapper]

Alright those numbers are just the ones I got while trying to diagnose the issue in the driveway I did not want it to go any higher for obvious reasons……

the tempuratures go much higher gauge on dash goes to red and my aux gauge I have reads around 220deg that is to hot and not normal. As to why Im lookikg for some assistance

Yes, 220°f in your driveway is too hot for the ambient temps this time of year. It probably hasn't gotten over 80° in Cedar Park yet, but warmer weather is just around the corner.

What radiator do you have?

Does your fan clutch move air from the moment the engine starts?

OEM radiator cap?

 

[TOYTACO11]

Yes, 220°f in your driveway is too hot for the ambient temps this time of year. It probably hasn't gotten over 80° in Cedar Park yet, but warmer weather is just around the corner.

What radiator do you have?

Does your fan clutch move air from the moment the engine starts?

OEM radiator cap?

Dont recall what brand radiator but it worked just fine the last 6 months since I installed it. Purchased it off rock auto….

Fan moves air can even hear it picking up speed and slowing down with temps.

Oem radiator cap tried three different ones all same results.

This happened id say three months ago and I swapped out thermostat and all has been good until now… it doesnt take very long to get the temps that high either.

I think Im going to remove thermostat and try and run it that way and see what happens if still overheating Im going to flush the system as I did notice some debris in the reservoir perhaps I got a clogged line or something stuck in the water pump. Or these afternarket water pumps dont last as long as before its about 2 years old. However Ive only put 6000miles on the cruiser since then…

 

[TOYTACO11]

For giggly-poo's, remove your thermostat, and re-assess. If it is not the thermostat, it should still overheat. If it is the thermostat, it will not. In theory.

Thats my plan tonight when i get home from work

 

[flintknapper]

Dont recall what brand radiator but it worked just fine the last 6 months since I installed it. Purchased it off rock auto….

Fan moves air can even hear it picking up speed and slowing down with temps.

Oem radiator cap tried three different ones all same results.

I ask about the radiator.....wondering if you put in the all metal (CSF) Brass/Copper unit?

I have one in my '97 and it runs fine....but others (in recent years) have had cooling issues with that radiator. Most were resolved by going to a good quality Aluminum radiator. OEM cap is the 'best' so you are good there.

Fan clutch should be moving air with authority, sounds like yours is doing OK.

So logically.....you would want to look at your thermostat next. Let us know what you find.

 

[TOYTACO11]

I ask about the radiator.....wondering if you put in the all metal (CSF) Brass/Copper unit?

I have one in my '97 and it runs fine....but others (in recent years) have had cooling issues with that radiator. Most were resolved by going to a good quality Aluminum radiator. OEM cap is the 'best' so you are good there.

Fan clutch should be moving air with authority, sounds like yours is doing OK.

So logically.....you would want to look at your thermostat next. Let us know what you find.

So drained coolant this evening removed thermostat flushed out system with water hose put thermostat housing back together without the thermostat added distilled water and some vinegar started truck let it warm up couldnt get it to overheat in driveway like before temps stayed around 170-190 however Took it out for a quick spin make it about 2 miles and it climbed to a little over 200deg not sure if it did rhat due to only having water in System or if i still have a problem…

not sure which way to go now. Besides draining system install new thermostat and gasket and try again i guess…

 

[TOYTACO11]

I ask about the radiator.....wondering if you put in the all metal (CSF) Brass/Copper unit?

I have one in my '97 and it runs fine....but others (in recent years) have had cooling issues with that radiator. Most were resolved by going to a good quality Aluminum radiator. OEM cap is the 'best' so you are good there.

Fan clutch should be moving air with authority, sounds like yours is doing OK.

So logically.....you would want to look at your thermostat next. Let us know what you find.

Radiator i installed is not all aluminum its mostly plastic i believe its a csf radiator and I used to have a liland aliminum one but I was having similar issues using that one as well…

Also I did notice that when i first start the truck now the fan doesnt sound like a jet taking off like it used to but i can definately tell when its working

 

[flintknapper]

So drained coolant this evening removed thermostat flushed out system with water hose put thermostat housing back together without the thermostat added distilled water and some vinegar started truck let it warm up couldnt get it to overheat in driveway like before temps stayed around 170-190 however Took it out for a quick spin make it about 2 miles and it climbed to a little over 200deg not sure if it did rhat due to only having water in System or if i still have a problem…

not sure which way to go now. Besides draining system install new thermostat and gasket and try again i guess…

No....not related to the coolant mix (water only in this case). Pure water offers the best heat transfer to be had actually.

You can test the T-stat outside the vehicle by applying heat to it either in a pan of heated water or even using a hair dyer. Watch to see that it fully opens. IF it does then put it back in the vehicle, fill cooling system (be sure to 'burp' it fully).

Then repeat your previous 'driveway' testing. As soon as you see the temperature reach/exceed 200°F use a garden hose and 'mist' the radiator straight through the front grill. IF the temperature comes down rapidly (10-20 degrees within a couple of minutes) then I'd say you have an airflow issue and I'd be inclined to replace the fan clutch or do a fan clutch 'mod' with heavier CST silicone fluid.

Warmer weather is coming and if you drive hwy 183 out of Cedar Park into Austin you'll be in stop and go traffic at some point. So you'll want that cooling system working as well as it can, especially when running the A/C.

 

[jonheld]

Also I did notice that when i first start the truck now the fan doesnt sound like a jet taking off like it used to but i can definately tell when its working

From a cold start the fan should sound like a DC10 taking off in your driveway and should be able to hold a small cat to the front of the truck.
Change the fan clutch. You want an AISIN FCT-049 for the 3FE.

Make sure the fan shroud is in place and tight to the radiator. It will never cool properly without the shroud. I used thin adhesive closed cell foam on the shroud to make sure it seals to the radiator. Did this on the 3FE and the 1FZ.

Make sure the foam that should have come with the new radiator is in place on top and bottom. This helps to keep the airflow where it belongs.

 

[TOYTACO11]

No....not related to the coolant mix (water only in this case). Pure water offers the best heat transfer to be had actually.

You can test the T-stat outside the vehicle by applying heat to it either in a pan of heated water or even using a hair dyer. Watch to see that it fully opens. IF it does then put it back in the vehicle, fill cooling system (be sure to 'burp' it fully).

Then repeat your previous 'driveway' testing. As soon as you see the temperature reach/exceed 200°F use a garden hose and 'mist' the radiator straight through the front grill. IF the temperature comes down rapidly (10-20 degrees within a couple of minutes) then I'd say you have an airflow issue and I'd be inclined to replace the fan clutch or do a fan clutch 'mod' with heavier CST silicone fluid.

Warmer weather is coming and if you drive hwy 183 out of Cedar Park into Austin you'll be in stop and go traffic at some point. So you'll want that cooling system working as well as it can, especially when running the A/C.

I try to stay off of 183 especially now with all the construction luckily I work in round rock so I take 45 costs a couple bucks but its well worth it.

As for the thermostat I heated it up and it didnt fully open until almost 220deg and never fully closed until it got down to 150deg to me that doesnt seem right when its supposed to be 180 fully open… I ordered a new one along with gaskets just in case should be here next week.

I also have one of my old fans taken apart and draining oil out of to do the fan mod on..
What weight CST do you recommend replacing it with and do you happen to know how much is supposed to be in there?

 

[TOYTACO11]

From a cold start the fan should sound like a DC10 taking off in your driveway and should be able to hold a small cat to the front of the truck.
Change the fan clutch. You want an AISIN FCT-049.
Make sure the fan shroud is in place and tight to the radiator. It will never cool properly without the shroud. I used thin adhesive some closed cell foam on the shroud to make sure it seals to the radiator. Did this on the 3FE and the 1FZ.

The shroud is brand new and nice and secure was working fine before..

The fan I have is a AISIN FCT-049 ill have to find a stray cat and verify the fan is working…. (JK) But this is my third fan clutch ive tried all of them the FCT-049 they seem to work a while then just crap out.

 

[jonheld]

The shroud is brand new and nice and secure was working fine before..

The fan I have is a AISIN FCT-049 ill have to find a stray cat and verify the fan is working…. (JK) But this is my third fan clutch ive tried all of them the FCT-049 they seem to work a while then just crap out.

The thermostat should be installed as shown below and must have the O-ring on top of the stat.
Thermostat 90916-03052
O-ring 90430-43002
Gasket 16341-61030

 

[thabruiser]

FWIW, my "running fine" LX450 will get to 205* F on the OBD2 readout pretty quickly. From what I have searched (you can do some too, if you are so inclined!) around 200* operating temp is not uncommon running temp on these. I do have a 1FZ, just thought about that. I wouldn't think the 3FE would be much different but I am not as familiar with them.

 

[flintknapper]

I also have one of my old fans taken apart and draining oil out of to do the fan mod on..
What weight CST do you recommend replacing it with and do you happen to know how much is supposed to be in there?

I run 15K in a blue hub fan clutch. We are subject to the same Texas Heat (except its more humid where I am).

https://www.amazon.com/ASSOCIATED-5447-Silicone-Fluid-000cST/dp/B00WOZH7D2/ref=sr_1_1?dib=eyJ2IjoiMSJ9.5D75iffc_wIRgiXxawJV8kzo_ViR0IJ7O2EcHBLVFTk.RDvqHM9NDNVtaVQzqo0QvGkGDR5yHgw_0kl0ODRwZqo&dib_tag=se&keywords=15000+cst+silicone&qid=1710424977&sr=8-1

Drain out the old fan clutch (let it drain overnight) and roughly measure the amount. Replace with the same amount of new fluid. One bottle should be more than enough.

You'll get that 'start up' roar again and the fan clutch will be more aggressive....but not overly so IMO.

Be careful not to damage the O-ring seal on the fan clutch....you will be reusing it.

I'm thinking new (working) T-stat and modified fan clutch will put you back in good shape.

Clearly you are a capable person with respect to mechanics, so should be easy for you.