Has the coolant reservoir overflowed? Is there oil in your coolant? What does the bottom of the radiator cap look like? I live in the AZ desert and my 3fe will only get to 220 F when doing long grades in the heat. 3FE tip for you new guys, Put your cruiser in low range when pulling steep long grades and keep the rpm's at 3000 rpm or higher even this will not hurt the mighty 3fe. My cruiser is cooler when moving than when idling. Keep those rpm's up when climbing, down shift early.
BUMP 3fe cooling system/ Bypass question
- Thread starter TOYTACO11
- Start date
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I don't think your rig is overheating dude. It takes alot for the 3FE to overheat and certainly it wont be on your driveway trying to simulate load. If all your cooling parts are new, then maybe the only thing i can think of is that you have installed the thermostat incorrectly. There is a way to orient the thermostat and gasket so do a search. I have had my rig for almost the past decade and i have had my fair share of overheating problems. None of which were stem from driving in the City. If you are overheating or on the verge of overheating, your AC will first cut off @ 225 or so....cant remember the exact number off top of my head. but your AC will stop. then you will see coolant dumping from the overflow almost 99% of the time. Your engine is trying to shed excess heat and this is how it is designed....Get yourself a real time coolant temp gauge to monitor your cooling system and TBH, this is the only way to tell if your engine is overheating or not. The stock gauge is useless.
PS. a faulty fan clutch will always point to stop and go traffic resulting in overheating, but not in highway speed.
If you feel the rig is overheating, the 1st thing you should do is to blast full heat, keep the RPM up 2-3k and let the fan clutch do its job to cool the engine....
If you are trying to overheat the engine when parked and have the RPM up 2-3k. with a working fan clutch, you are just preventing the engine from overheating instead. Quite the opposite really. If you are able to overheat your truck by keeping the RPM up like you have described. your fan cluch is certainly not working....
Hope this helps.
PS. a faulty fan clutch will always point to stop and go traffic resulting in overheating, but not in highway speed.
If you feel the rig is overheating, the 1st thing you should do is to blast full heat, keep the RPM up 2-3k and let the fan clutch do its job to cool the engine....
If you are trying to overheat the engine when parked and have the RPM up 2-3k. with a working fan clutch, you are just preventing the engine from overheating instead. Quite the opposite really. If you are able to overheat your truck by keeping the RPM up like you have described. your fan cluch is certainly not working....
Hope this helps.
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100% - Low range will keep the RPM up and let the fan clutch do its job, however, low range will also drive your tranny temp up when your crawling in 90 degree heat. It is a tradeoff. Hot tranny oil will be hard to cool back to normal compared to water, so your coolant temp is affected as well.
A failing fan clutch can cause overheating both in traffic and at highway speeds.
The front of the 80 is as aerodynamic as a brick. The fan has to create negative pressure behind the radiator in order to draw air through as opposed to around. Can't get away from that pesky physics.
I had this exact issue with my 91.
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- Thread starter
- #46
Has not overflowed gotten to the top of the reservoir, coolant looks fine and so dies oil, I live in texas the biggest hill is an overpass,
To clear a couple things up
Only overheating when driving doesnt matter what speed, the fan is working sounds like a plane taking off plus can hear it speed up and slow down with temp
It will idle all day without getting above 180-190 with ac on full blast so I believe the thermostat is installed correctly plus there was no change with it removed.
I have a aux temp gauge installed thats how I know exact temps + verified temps with ir gun
- Thread starter
- #47
Ive tried three different fan clutches none of them made any difference
- Thread starter
- #48
Im sure it would overflow however I have not let the engine get that hot for it to do it. The heat on full blast helps but still temp rises so skmething is definitely not right whatever it might be.
I ditched my fan clutch, went with full electric and never looked back. couldn't be happier.
Whatever floats your boat. I've never had an issue keeping those 155 bone crushing horses cool with the OEM system, assuming all the parts were working as they should. Drove from Jersey to Moab and back twice pulling my M416 up and over the Rockies and she was a daily driver for the better part of 30 years.
I am at a loss as to why the OP can't stay cool. The only possibilities I can think of are a partially blocked radiator, or poor coolant flow, or poor air flow. If the AC condenser fins are severely bent or clogged with debris, that would block air flow regardless of how much air the fan is trying to move.
Like I said previously, on startup, the fan should be able to hold a small cat to the grill.
@Marco Lau brought up a good point about transmission temps. If your torque converter is not locking up properly, your tranny temps will certainly be a factor.
My cooling has
Bypass the radiator and see if the engine temp stabilized. The tranny should be able to maintain 180F with just the factory cooler if your rig equipped with one.
- Thread starter
- #53
Im at a loss as well Im still thinking it is the radiator neck that got sligtly bent during shipping causing the cap to not seat properly.. I need to look a little closer but ive watched the coolant overflow when cold and hot it seems to fluctuate but its not consistant times it has been empty when hot and other times 3/4 same when cold however could also be my brain playing trucks on me since ive looked at every component so many times its hard to remember I need to write these things down lol….Also ive let it sit for a couple days and opened the radiator cap still pressurized.
Just wondering would any vacuum lines not properly routed cause any overheating?
What about IAC or tps causing this?
I will try bypassing radiator and run to an aux cooler I have used before on it…. However I feel like it may not help only because I dont see my trans fluid getting that hot after driving for 10-15 min going 50 mph max but im going to give it a try at this point ill try just about anything….
your coolant in the overflow tank tells you alot obout the cooling system. It should not fluctuate like that. You might be burning coolant else where if no leaks.
- Thread starter
- #55
I need to pay closer attention but last time i drove it it was about 1/4 full coolant reservoir cold and when i got home it was probably 3/4 full… Ill run it again tomorrow evening when I get home and verify.
Also got a question when radiator cap is removed and engine running thermostat open should I beable to see coolant is flowing pretty quickly or a more subtle movement?
The level in the reservoir should rise and fall with engine temp. As the coolant heats and expands, the radiator cap should allow coolant to flow into the overflow when the system pressure gets higher than the rating on the cap (13 psi). As the system cools and goes negative, the cap allows coolant from the overflow to be drawn back into the radiator keeping the level full.
This only works with a functional radiator cap and a full cooling system with no leaks. With a cold non-running engine, the radiator should be filled to the small port on the filler neck and the overflow bottle should be filled to the FULL line.
If you open the radiator cap with a cold non running engine and start it, as the coolant warms, it will overflow out of the filler neck and make a mess.
If you open the radiator cap with a hot engine, you will go to the emergency room. It's printed on the cap "NEVER OPEN WHEN HOT".
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- Thread starter
- #57
gotcha when i take my coolant cap off cold its usually under pressure still not alot but does have some and fluid level is toThe top and usually spills out some.. when vehicle running and cap off it does indeed overflow and makes a mess its not excessive overflowing just a steady flow
I know better then to remove the cap when engine is hot…..
- Thread starter
- #58
Still having issues with overheating I went back through the entire system flushing it out multiple times.
Did the fan clutch mod fan is definately working like it should.
Replaced thermostat made sure it is installed correctly with seal on top of it.
Tried two different radiators no change,
Did a complete tune up new plugs timing and valves adjusted per FSM
Compression test was good and even did a leak down test which passed as well. Eng oil looks fine
The one thing I am not 100% sure is how much movement should I see looking into the radiator with cap removed with thermostat open?
My water pump is like 3 yrs old and there is movement but feel like it should be more…
I have all new Hoses on the way to replace in case one of them is collapsing internally…
Also ordered a new Aisin water pump just in case…
Any suggestions would be greatly appreciated and thanks in advance.
Did the fan clutch mod fan is definately working like it should.
Replaced thermostat made sure it is installed correctly with seal on top of it.
Tried two different radiators no change,
Did a complete tune up new plugs timing and valves adjusted per FSM
Compression test was good and even did a leak down test which passed as well. Eng oil looks fine
The one thing I am not 100% sure is how much movement should I see looking into the radiator with cap removed with thermostat open?
My water pump is like 3 yrs old and there is movement but feel like it should be more…
I have all new Hoses on the way to replace in case one of them is collapsing internally…
Also ordered a new Aisin water pump just in case…
Any suggestions would be greatly appreciated and thanks in advance.
- Thread starter
- #59
So one thing I might of figured out today while trying different things warmed up the engine with radiator cap removed there didint seem to be much movement of the fluid so I figured the coolant was just bypassing so I pinched off the bypass hose and almost immediately got a ton of bubbles and coolant lowered topped it back off a couple times until no more bubbles left the bypass hose pinch off and I could not get the engine to overheat at all.
I know the thermostat is supposed to direct the coolant to bypass or not is there anything else that could cause it to keep bypassing
Thermostat is new installed correctly with gasket on top made sure of that? Could those air bubbles be the reason why it was bypassing?
Need to run engine some more tomorrow didnt get a chance to test drive it yet... wanted to get some input from others
thanks again Mike.
I know the thermostat is supposed to direct the coolant to bypass or not is there anything else that could cause it to keep bypassing
Thermostat is new installed correctly with gasket on top made sure of that? Could those air bubbles be the reason why it was bypassing?
Need to run engine some more tomorrow didnt get a chance to test drive it yet... wanted to get some input from others
thanks again Mike.
After having the complete cooling system opened on both the 3FE and 1FZ, both systems self bleed unless there is a blockage.
I have seen many threads where folks say to elevate the front, run without the cap, stand on one leg while swinging a chicken over your head, etc. The same for the power steering system. Both systems self bleed.
My procedure for filling the cooling system once opened and drained:
Fill the radiator to the top of the fill neck, fill the overflow bottle to the full line, open the heater valve fully, run the engine up to temp.
Allow to cool overnight. Check coolant level in radiator. If there was any air in the system, it should have been forced out and the radiator cap should have allowed coolant from the overflow to be drawn back in.
Fill both as needed. Carry on with your day.
After 1 or 2 drive cycles, the levels stabilize.
>>>>>This assumes a functional radiator cap and a completely sealed system.<<<<<
During normal operation, the level in the overflow should rise and fall with engine temp. There should ALWAYS be coolant in the overflow. If the overflow is getting sucked dry, then you have a leak in the system and are losing coolant under pressure.
