1998 sr5 overheat 3.4, where to start?
04-28-2014, 07:41 AM
#1
1998 sr5 overheat 3.4, where to start?
My 1998 t4r sr5 (170,000), started to get hot while wheeling on Saturday. I know there are threads on this, but I wanted to briefly explain the situation and ask the forum for advice on where to start.
Drove one hour out to Stokes Forest (NJ) for some mild to moderate trail riding.
Temp was normal upon arrival. Drove about 10 minutes up trail consisting of steep dirt road with gullies and small to mid sized rocks. Noticed temp was above normal. I turned back down the mountain and 5 minutes later it was normal. I figured maybe this was nothing and began to head back up. The truck started to get above normal (not into the red, but obviously above middle- which is where it always sits-perfectly center). I checked the coolant and the reservoir (actually looked a bit higher than usual) and radiator were both full. Oil and trans oil looked good as well.
I then drove home and the temp was normal the entire way (1 hr highway drive). Drove the truck on streets yesterday and temp stayed normal. This morning (when cold) coolant looked about an inch under full in the reservoir.
Does anyone have advice on where to start? I found it surprising that it only got above normal temp heading up the trail-and was fine for the long drive home.
Note: new radiator six months ago (preventative maintenance, TB and water pump done at 150k), new fan blade 3 months ago after broken blade)
Drove one hour out to Stokes Forest (NJ) for some mild to moderate trail riding.
Temp was normal upon arrival. Drove about 10 minutes up trail consisting of steep dirt road with gullies and small to mid sized rocks. Noticed temp was above normal. I turned back down the mountain and 5 minutes later it was normal. I figured maybe this was nothing and began to head back up. The truck started to get above normal (not into the red, but obviously above middle- which is where it always sits-perfectly center). I checked the coolant and the reservoir (actually looked a bit higher than usual) and radiator were both full. Oil and trans oil looked good as well.
I then drove home and the temp was normal the entire way (1 hr highway drive). Drove the truck on streets yesterday and temp stayed normal. This morning (when cold) coolant looked about an inch under full in the reservoir.
Does anyone have advice on where to start? I found it surprising that it only got above normal temp heading up the trail-and was fine for the long drive home.
Note: new radiator six months ago (preventative maintenance, TB and water pump done at 150k), new fan blade 3 months ago after broken blade)
04-28-2014, 07:59 AM
#2
Registered User
Since it didn't overheat on the drive home, that sort of helps rule out a thermostat problem - if it could stay cool while putting out a lot of heat for a sustained period, it's likely not a coolant flow issue.
Could be an air flow issue - perhaps the fan clutch isn't working properly?
Also, check the radiator cap, the only two times I've ever seen my wife's 4Runner show any signs of overheating, it was the cap. Both times out in Colorado going up mountains. I'd have sworn that there was some other underlying issue, but the cap cured the overheating 100% both times, even when going up mountains out in Utah in 105 degree heat with the A/C blasting. The first time we replaced the original cap with an Autozone aftermarket (small town, only store open), it only lasted a year before failing, the second time we got an OEM cap from a dealer.
The center section of the cap is spring loaded - that spring tension pressurizes the system. Both times, the cap had failed so that center section was no longer spring loaded, which left the system unpressurized. It still worked fine 98% of the time, until you worked it extra hard, then it would heat up and boil over.
Could be an air flow issue - perhaps the fan clutch isn't working properly?
Also, check the radiator cap, the only two times I've ever seen my wife's 4Runner show any signs of overheating, it was the cap. Both times out in Colorado going up mountains. I'd have sworn that there was some other underlying issue, but the cap cured the overheating 100% both times, even when going up mountains out in Utah in 105 degree heat with the A/C blasting. The first time we replaced the original cap with an Autozone aftermarket (small town, only store open), it only lasted a year before failing, the second time we got an OEM cap from a dealer.
The center section of the cap is spring loaded - that spring tension pressurizes the system. Both times, the cap had failed so that center section was no longer spring loaded, which left the system unpressurized. It still worked fine 98% of the time, until you worked it extra hard, then it would heat up and boil over.
04-28-2014, 08:40 AM
#3
Thanks JOMOKA. It would be awesome if it is just a radiator cap issue. Is there any way to test it?
The fan clutch option makes sense too, I ran it unbalanced for some time before I replaced the broken fan blade. Do you know if there is a way to test this as well?
I use the truck as a DD and weekend trail driving. Therefore, I would like to feel confident that if I drive an hour out to the trails, I do not begin overheating and need to head home again-pretty much a wasted day- and I work six days a week so that's a whole weekend for me.
If anyone else has ideas, please feel free to comment.
The fan clutch option makes sense too, I ran it unbalanced for some time before I replaced the broken fan blade. Do you know if there is a way to test this as well?
I use the truck as a DD and weekend trail driving. Therefore, I would like to feel confident that if I drive an hour out to the trails, I do not begin overheating and need to head home again-pretty much a wasted day- and I work six days a week so that's a whole weekend for me.
If anyone else has ideas, please feel free to comment.
04-28-2014, 09:10 AM
#4
Registered User
When the engine is cold, take off the cap. There is an outer seal that stops coolatn from leaking out. Then a middle ring that is strongly spring loaded inward/downward - that's what sets the system pressure. Too much pressure and that part pushes open and allows coolant to flow into the overflow tank. Then the center section, which is lightly sprung in the opposite direction (up) - this is supposed to stay closed when the system is under pressure, but fairly easily allow coolant to be pulled back into the radiator when the engine cools down.
The first time a cap failed on ours the plastic had cracked and the whole center section was separated, and stayed in the neck of the radiator when the cap came off. The second time when the cheap aftermarket cap failed it was a bit more subtle - but the weak spring holding the center section up/shut had failed, so it just dangled, and the system never built pressure.
I'm not sure of a good way to test the fan. It's supposed to get much stiffer when it gets hot. I know mine roars for about 20 seconds after I start driving it from a cold stop, and it will do it a bit longer after starting off from a hot stop (like a gas station) on a hot day. Maybe just compare that sound (engine revved up, loud fan noise) to what it's doing when the engine is getting too hot. The fan should kick in hard and roar when the engine revs if it's hot. If it stays quiet like it does on a cold engine (after that first 20 - 30 seconds) then maybe it isn't locking up like it should.
The first time a cap failed on ours the plastic had cracked and the whole center section was separated, and stayed in the neck of the radiator when the cap came off. The second time when the cheap aftermarket cap failed it was a bit more subtle - but the weak spring holding the center section up/shut had failed, so it just dangled, and the system never built pressure.
I'm not sure of a good way to test the fan. It's supposed to get much stiffer when it gets hot. I know mine roars for about 20 seconds after I start driving it from a cold stop, and it will do it a bit longer after starting off from a hot stop (like a gas station) on a hot day. Maybe just compare that sound (engine revved up, loud fan noise) to what it's doing when the engine is getting too hot. The fan should kick in hard and roar when the engine revs if it's hot. If it stays quiet like it does on a cold engine (after that first 20 - 30 seconds) then maybe it isn't locking up like it should.
04-29-2014, 09:34 AM
#5
I checked the fan today. No play in it. When cold (with engine off) if I spin the fan it stops almost immediately. I was under the impression that after a long drive, if I killed the engine and checked the fan, it would not spin (locked up). I checked after a drive last night and after driving it seemed to be spinning very easily. Not locked up at all, does that indicate a bad clutch?
04-29-2014, 12:46 PM
#6
Registered User
I checked the fan today. No play in it. When cold (with engine off) if I spin the fan it stops almost immediately. I was under the impression that after a long drive, if I killed the engine and checked the fan, it would not spin (locked up). I checked after a drive last night and after driving it seemed to be spinning very easily. Not locked up at all, does that indicate a bad clutch?
Testing the fan clutch:
If you have reason to suspect that the fan clutch is defective, here is the recommended procedure to verify the condition of the fan clutch.
1. Start the car (cold) with the hood open and note if the fan is turning, increase the engine RPM and note if the fan turns faster and the noise increases, if it does, first good indication, if it does not increase speed/noise, clutch is bad and needs to be replaced. (Remember, this must be tested after the car has been off for and extended period, over night etc.)
2. Leave engine running and note if the fan starts to slow down after 2-5 minutes, speed/noise should diminish and even raising the RPM, the fan should not make as much noise as when first starting, if it does slow, this is the second good indication. If speed/noise does not decrease, clutch may be “frozen” and should be replaced.
3. Leave the engine idle and watch the temperature indicator. When normal operating temperature has been reached, some increase in fan speed/noise should be noted, in particular when the RPM is increased. If temperature is fairly stable and the fan noise/speed increases or cycles, third good indication. If temperature indication continues to increase, with no increase in fan noise/speed, clutch is defective and should be replaced.
4. After the engine is at normal operating temperature or above, is the only time that the “rolled up newspaper” test that many people talk about should be performed! Take some newspaper and roll it up into a long narrow tube. Be careful, keep hands and fingers away from the fan while performing this test! With the engine at full operating temperature and idling, take the rolled up paper and insert it on the back side of the fan and try to reach the hub of the fan avoiding the blades until close to the hub. Push the rolled paper at the fan increasing the friction to the hub area of the fan. If the fan can not be stopped easily this is the fourth good indication, if it can be stopped the clutch is defective and should be replaced. Again, this test can only be performed when the engine is at or above full operating temperature.
Testing can be performed in any order but just make sure the conditions during testing are those that are specified for that specific test.
Do not continue to operate the engine if the temperature continues to rise and certainly stop if the temperature approaches “redline”.
If you have reason to suspect that the fan clutch is defective, here is the recommended procedure to verify the condition of the fan clutch.
1. Start the car (cold) with the hood open and note if the fan is turning, increase the engine RPM and note if the fan turns faster and the noise increases, if it does, first good indication, if it does not increase speed/noise, clutch is bad and needs to be replaced. (Remember, this must be tested after the car has been off for and extended period, over night etc.)
2. Leave engine running and note if the fan starts to slow down after 2-5 minutes, speed/noise should diminish and even raising the RPM, the fan should not make as much noise as when first starting, if it does slow, this is the second good indication. If speed/noise does not decrease, clutch may be “frozen” and should be replaced.
3. Leave the engine idle and watch the temperature indicator. When normal operating temperature has been reached, some increase in fan speed/noise should be noted, in particular when the RPM is increased. If temperature is fairly stable and the fan noise/speed increases or cycles, third good indication. If temperature indication continues to increase, with no increase in fan noise/speed, clutch is defective and should be replaced.
4. After the engine is at normal operating temperature or above, is the only time that the “rolled up newspaper” test that many people talk about should be performed! Take some newspaper and roll it up into a long narrow tube. Be careful, keep hands and fingers away from the fan while performing this test! With the engine at full operating temperature and idling, take the rolled up paper and insert it on the back side of the fan and try to reach the hub of the fan avoiding the blades until close to the hub. Push the rolled paper at the fan increasing the friction to the hub area of the fan. If the fan can not be stopped easily this is the fourth good indication, if it can be stopped the clutch is defective and should be replaced. Again, this test can only be performed when the engine is at or above full operating temperature.
Testing can be performed in any order but just make sure the conditions during testing are those that are specified for that specific test.
Do not continue to operate the engine if the temperature continues to rise and certainly stop if the temperature approaches “redline”.
Last edited by TheDurk; 04-29-2014 at 01:24 PM.
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