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Hey guys,

Recently i bought my first trooper and I have been working on it for a few months( I am not a mechanic, total noob). Recently I've started to have an overheating issue, especially at lower speeds. Got a new radiator, new hoses, changed the fan to an electric fan, new overflow tank, had the cooling system flushed (A bunch of crap came out since it sat for at least 15 years, new injectors, alternator, A/C compressor but AC doesnt work yet, new fuel system... I'm stumped.. Everything else seems to run well besides a small steady tranny leak. I was told to change the water pump but i can see its moving water when the tstat opens up. Any tips? someone also brought up that maybe the fan (proform 14in electric fan 1650 CFM) is not strong enough... i truly have no clue. Any insight would be welcome.
 

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Your fan just might not be moving enough air. I think most automotive mechanical clutch fans pull 2000 CFM or more. Might want to research it though. If you still have the clutch fan, you can try sticking it back on there with a new clutch and they typically work fine unless you're sitting at idle in traffic.
 

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1989 Trooper R/S
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On the 2.6 cooling is critical. I don't know if the 2.8 is as critical but will just add to turnerd's post that a fan shroud is important and even positioning of the fan in relation to the shroud matters when cooling is marginal. And just maybe, if the water pump vanes are corroded there not moving as much water as a new one would. Even timing, although remote, can have an effect on engine temp.

Motor vehicle Vehicle Automotive design Car Automotive fuel system
 

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been there with my 1990 v6 trooper, and I have designed cooling systems for manufacturers so may b able to help.
first off, I doubt your electic fan will move enough air and I would go back to mechanical fan....but first I would get a new one. the OE fans have a hydraulic clutch that may have failed so the fan speed may not have increased with temperature.

overheating on a 50/50 antifreeze takes places at about 250f with stock 16 psi cap but lower temps if caps old and less pressure. change it out. check oil for any moisture to be sure you don't have internal leak and losing pressure (check for moisture on inside of oil fill cap). if you changed your coolant just prior to problem, likely got air in system so burp it.

check radiator shroud for any gaps and seal with RTV or similar....air takes patch of least resistance and could be sucking air around the radiator rather than through.
if you haven't changed thermostat, do it.
I would also check if temp gauge is accurate using a cheap IR thermometer.

another suggestion while troubling shooting is use water instead of antifreeze....it's easier and cheaper to drain and replace while trying different components....it will also cool a bit better than antifreeze so reference this when taking temps.
 

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On the OE fan. You want to be sure you have the CORRECT fan. Isuzu 2.8 fans are getting hard to come by. There is a GM fan that fits, but it is wrong because GM made these engines with fans that turned clockwise, and fans that turned counterclockwise. The wrong fan pushes air forward through the radiator, this cools them when they are idling, but when you start driving, the fan is fighting the incoming air and the radiator doesn't get sufficient air. Know this from experience (Chevy Blazers - same basic engine). Dennis
 

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Discussion Starter · #9 ·
been there with my 1990 v6 trooper, and I have designed cooling systems for manufacturers so may b able to help.
first off, I doubt your electic fan will move enough air and I would go back to mechanical fan....but first I would get a new one. the OE fans have a hydraulic clutch that may have failed so the fan speed may not have increased with temperature.

overheating on a 50/50 antifreeze takes places at about 250f with stock 16 psi cap but lower temps if caps old and less pressure. change it out. check oil for any moisture to be sure you don't have internal leak and losing pressure (check for moisture on inside of oil fill cap). if you changed your coolant just prior to problem, likely got air in system so burp it.

check radiator shroud for any gaps and seal with RTV or similar....air takes patch of least resistance and could be sucking air around the radiator rather than through.
if you haven't changed thermostat, do it.
I would also check if temp gauge is accurate using a cheap IR thermometer.

another suggestion while troubling shooting is use water instead of antifreeze....it's easier and cheaper to drain and replace while trying different components....it will also cool a bit better than antifreeze so reference this when taking temps.
Any suggestions on which mechanical fan and clutch to buy? When i got the trooper the fan had 1 that didnt get eaten by rodents so i just threw the whole thing away. My Shroud is the OEM shroud but i do believe there are gaps between the radiator and the shroud. I did have to replace the overflow tank because it had a huge hole was just dumping coolant. New tank is holding but still got hot. Radiator cap is brand new as well and new thermostat as well. I really appreciate yalls feedback on this! ive had 0 luck with help anywhere else. You guys are awesome!
 

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Ya, glad I may be able to help. Rockauto has new clutches for less than $50 but the fan blade itself is only OEM now. I would post on the site if someone has one for cheap (get the mounting bolts as well.. IF the radiator is already been cleaned, I would seal the gaps with shroud. Cooling systems solutions are often multiple little fixes. If you get an IR thermometer you may be able to isolate the issues a bit as well as confirm temp gauge is accurate. But again, really be sure there is no air in the system ….. this may save you a lot of time and $. Steam in system will also cause gauge to read high….. simply remove the cap when cold and run engine and look for air bubbles. Remember that the system is not pressured so only get it to temp when thermostat opens ( you’ll notice the flow). If you raise front of car a bit it will expedite process a bit.

you may be able to fix the expansion tank hole with some 2 part epoxy like jb weld. There’s no pressure in tank, but it will get hot.

be sure there is no water in oil…that’s bad but won’t usually cause your issues unless really extreme.

let us know how it goes.
 

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I always go for Aisin or Denso on stuff like that since they are OE suppliers. Four seasons is usually a solid option for cooling and A/C parts as well
 
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The fan would have to be one to fit 1989-1991 2.8 Trooper, 1991-1992 3.1 Rodeo, 1990(?) - 1994 3.1 pickup. They are hard to come by. Dennis
 
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1990 trooper 2, 76 Datsun 620
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Years ago I had to ditch my belt driven fan because it was cracked. It still kept temps in check but I could tell it was wobbly when speeds increased. I put in a flex-a-lite black magic intended for a mustang or maybe it was just the universal 15” I believe. It pulls about 2200 cfm and cools the 2.8 like nobody’s business. It was about $150-180 back then.
There’s that write up on “how to corral more horses from your 2.8” and the guy goes over how to install it. Even GeoffinBC does a nice electric fan install. If you can’t get the belt driven fan, stay electric but just get what I got or what he got. Solid choices whichever way you go, belt driven OEM or sufficient electric.
Change the temp sensor sender.
 

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I tried using an electric fan on my 1990 trooper with the 3.4L conversion…..it struggled during summer and in the thin air of the Rockies it ran close to red mark on gauge and I sometimes had to pull over going up hill to cool it down. I gave the original fan away so I had to find and buy another, but bought a new four seasons brand clutch to start from scratch. I still have gaps between shroud and radiator that I need to fill up but it runs at normal temps now.

an interesting point about car temp gauges…..many car manufacturers program the gauge needle to read at 12 o’clock/center even if the actual temp is much higher or lower. They do this for marketing as back in the old days car often overheated and it was a buyers concern and a car that held a standard constant temp ment to Many as a point of quality. On my Chevy, the gauge stays dead center, or about 210F, on gauge regardless if OBD reader indicates up to 15F higher before it starts to move or actual coolant temp using IR gun to compare. Point is, don’t trust dashboard gauges when troubleshooting coolant issues.

the temp sensor is a simple variable resistor and the service manual will indicate what temp should be indicated using a multimeter. They do go bad, but best way to check is using a cheap IR thermometer and compare coolant temps at pump or coolant hose leaving engine once thermostat is open. Also, you can compare delta of hose entering radiator vs returning to engine. With fan on, ambient air in 70s, I would expect to see at
about a 15F delta, if less than 10F I would look for issues with radiator efficiency.

hope this helps.
 

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1990 trooper 2, 76 Datsun 620
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Like someone mentioned earlier, if you go electric, you need a powerful fan. Like 2000cfm minimum. Mine sounds like a hurricane when it comes on, but I haven’t mated the incoming 3.4/3500 hybrid to the trooper yet so only time will tell how the flex a lite does.
 

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Discussion Starter · #16 ·
Ya, glad I may be able to help. Rockauto has new clutches for less than $50 but the fan blade itself is only OEM now. I would post on the site if someone has one for cheap (get the mounting bolts as well.. IF the radiator is already been cleaned, I would seal the gaps with shroud. Cooling systems solutions are often multiple little fixes. If you get an IR thermometer you may be able to isolate the issues a bit as well as confirm temp gauge is accurate. But again, really be sure there is no air in the system ….. this may save you a lot of time and $. Steam in system will also cause gauge to read high….. simply remove the cap when cold and run engine and look for air bubbles. Remember that the system is not pressured so only get it to temp when thermostat opens ( you’ll notice the flow). If you raise front of car a bit it will expedite process a bit.

you may be able to fix the expansion tank hole with some 2 part epoxy like jb weld. There’s no pressure in tank, but it will get hot.

be sure there is no water in oil…that’s bad but won’t usually cause your issues unless really extreme.

let us know how it goes.
You guys are amazing!!! put a fan with a much higher CMF rating and all overheating issues are gone! Now i just gotta figure out why it stops shifting after running a little while and fix the transmission leak. THANK YOU GUYS SOOO MUCH!!! Also i checked and there seems to be no moisture in the in the oil.
 
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