This isn't a question. It's notes about my 99 Trooper overheating problems, the ultimate cause, how I found it, and how I resolved it. Hopefully it saves someone some time/money.
My trooper was overheating. I have a nice OBD-II-to-Bluetooth adapter that lets me view precise coolant temperature on my cell phone. It would climb regularly WELL over 100C.
My temporary fix for my overheating problem was to turn the engine off as I was cresting a hill, and allow the coolant in the radiator to drop a few degrees on the way down. I would then turn on the engine to climb the next hill or maintain a reasonable highway speed on a flat area. Incidentally, I tried this once in my 98 Rodeo and it was a bit unpleasant. With the engine off at speed, a loud ratcheting noise could be heard.
QUESTION :?: : Could the loud ratcheting noise be a functioning fan clutch being torn between a still engine and a fan that is being forced by the wind to turn?
A trick I've used in the past on my Rodeo during overheating at stop lights was to put it in neutral and rev the engine to 3500 or so to get the fan to spin faster. This trick wasn't working on the Trooper. That should have given me a clue as to the real problem. But it didn't at the time.
I needed a permanent fix and assumed it was the thermostat. The thermostat on the V6 (3.2 and 3.5) is underneath the intake plenum ('common chamber'). This makes it hard to reach. If you do it, you might as well replace your intake manifold gaskets at the same time. They get very brittle with age, and if you miraculously manage to avoid cracking them while replacing your thermostat, you will still surely shorten their lifespan. Incidentally, I've replaced these gaskets three times on my isuzus and have still never cracked open the common chamber to replace the paper gasket in the middle. (So now I have three of the gaskets laying around from the sets I've bought.)
After replacing the thermostat, the overheating problem remained. I assumed the duralast thermostat was junk. So I did it AGAIN. (this time with a more expensive thermostat, and this time completely removing the intake manifold and replacing all injector O-rings as well.)
After the second thermostat, the overheating problem remained. I assumed the remaining possible solutions were: Blocked radiator, bad water pump, or bad fan clutch. I am not sure how to test a radiator's flow, but filling the cooling system went pretty quickly, so I assume no blockages. I wasn't sure how to test the pump either. But a little searching led me to a test for the fan clutch. Get the car up to temperature (or overheating
) and turn off the engine. Now try turning the cooling fan by hand. There should be resistance. Another test is audible. When you start up the car cold, rev it to 3500 or so. Make a mental note of the noise level. Now let it idle until hot. Rev it to the same rpm, and compare sound. If the fan is not obviously LOUD compared to cold, then the clutch isn't working.
My fan was not resistant to hand-turning after warm-up. The noise wasn't there. My new diagnosis was a bad fan clutch.
I ordered a fan clutch on clearance like this one. It isn't here yet but I need to drive the car without turning off the engine every 30 seconds, so I needed a hack to get it working. So I 'bypassed' the fan clutch. How?
The plastic fan is mounted to the output side of the fan clutch with four 10mm nuts. The input side of the fan clutch is mounted to a pulley on the engine with four 12mm nuts. I took the clutch off of the engine, (a long screwdriver or breaker bar holds it in place when breaking the nuts loose) and the plastic fan off of the clutch. I then took some plumber tape (roll of .75" soft metal strip) and trimmed off two equal lengths with tin snips. I attached one end of each strip to two of the clutch's four studs to which the plastic fan mounts. I then mounted the plastic fan back onto the clutch, on top of the strips. The other end of each strip was mounted to the front of the pulley, between the pulley and the clutch. I had to drill out the holes in the strip for the 12mm studs.
The basic idea was to use anything available to keep the front of the clutch from turning independently of the back of the clutch. Using wire, strap, cord, or whatever to connect a front mounting point to a back mounting point seemed the logical way to go. I put two straps in (on opposite sides) for symmetry and strength. I assume you could use one strong strap or 4 straps and have the same result. If you can limp to a hardware store or a Wal-Mart you can probably find something usable.
The only danger I can imagine this might introduce would be if the plumber strap failed and damaged your serpentine belt or fan blades.
So now no matter what the temperature, when I rev the engine the fan is forced to turn and roars. After finally hearing it again, I'm shocked that I ever forgot to expect that sound.
Again, this is temporary; once the clutch arrives I'll fix it for good.
plumbers tape
My trooper was overheating. I have a nice OBD-II-to-Bluetooth adapter that lets me view precise coolant temperature on my cell phone. It would climb regularly WELL over 100C.
My temporary fix for my overheating problem was to turn the engine off as I was cresting a hill, and allow the coolant in the radiator to drop a few degrees on the way down. I would then turn on the engine to climb the next hill or maintain a reasonable highway speed on a flat area. Incidentally, I tried this once in my 98 Rodeo and it was a bit unpleasant. With the engine off at speed, a loud ratcheting noise could be heard.
QUESTION :?: : Could the loud ratcheting noise be a functioning fan clutch being torn between a still engine and a fan that is being forced by the wind to turn?
A trick I've used in the past on my Rodeo during overheating at stop lights was to put it in neutral and rev the engine to 3500 or so to get the fan to spin faster. This trick wasn't working on the Trooper. That should have given me a clue as to the real problem. But it didn't at the time.
I needed a permanent fix and assumed it was the thermostat. The thermostat on the V6 (3.2 and 3.5) is underneath the intake plenum ('common chamber'). This makes it hard to reach. If you do it, you might as well replace your intake manifold gaskets at the same time. They get very brittle with age, and if you miraculously manage to avoid cracking them while replacing your thermostat, you will still surely shorten their lifespan. Incidentally, I've replaced these gaskets three times on my isuzus and have still never cracked open the common chamber to replace the paper gasket in the middle. (So now I have three of the gaskets laying around from the sets I've bought.)
After replacing the thermostat, the overheating problem remained. I assumed the duralast thermostat was junk. So I did it AGAIN. (this time with a more expensive thermostat, and this time completely removing the intake manifold and replacing all injector O-rings as well.)
After the second thermostat, the overheating problem remained. I assumed the remaining possible solutions were: Blocked radiator, bad water pump, or bad fan clutch. I am not sure how to test a radiator's flow, but filling the cooling system went pretty quickly, so I assume no blockages. I wasn't sure how to test the pump either. But a little searching led me to a test for the fan clutch. Get the car up to temperature (or overheating
) and turn off the engine. Now try turning the cooling fan by hand. There should be resistance. Another test is audible. When you start up the car cold, rev it to 3500 or so. Make a mental note of the noise level. Now let it idle until hot. Rev it to the same rpm, and compare sound. If the fan is not obviously LOUD compared to cold, then the clutch isn't working.My fan was not resistant to hand-turning after warm-up. The noise wasn't there. My new diagnosis was a bad fan clutch.
I ordered a fan clutch on clearance like this one. It isn't here yet but I need to drive the car without turning off the engine every 30 seconds, so I needed a hack to get it working. So I 'bypassed' the fan clutch. How?
The plastic fan is mounted to the output side of the fan clutch with four 10mm nuts. The input side of the fan clutch is mounted to a pulley on the engine with four 12mm nuts. I took the clutch off of the engine, (a long screwdriver or breaker bar holds it in place when breaking the nuts loose) and the plastic fan off of the clutch. I then took some plumber tape (roll of .75" soft metal strip) and trimmed off two equal lengths with tin snips. I attached one end of each strip to two of the clutch's four studs to which the plastic fan mounts. I then mounted the plastic fan back onto the clutch, on top of the strips. The other end of each strip was mounted to the front of the pulley, between the pulley and the clutch. I had to drill out the holes in the strip for the 12mm studs.
The basic idea was to use anything available to keep the front of the clutch from turning independently of the back of the clutch. Using wire, strap, cord, or whatever to connect a front mounting point to a back mounting point seemed the logical way to go. I put two straps in (on opposite sides) for symmetry and strength. I assume you could use one strong strap or 4 straps and have the same result. If you can limp to a hardware store or a Wal-Mart you can probably find something usable.
The only danger I can imagine this might introduce would be if the plumber strap failed and damaged your serpentine belt or fan blades.
So now no matter what the temperature, when I rev the engine the fan is forced to turn and roars. After finally hearing it again, I'm shocked that I ever forgot to expect that sound.
Again, this is temporary; once the clutch arrives I'll fix it for good.
plumbers tape
